With all of this experimentation you do, you are becoming the de-facto go to guy for batterys, and solar in general, you show your success's and your failures, and for this I trust your results and have been able to replicate them myself, my JK bms DIY battery remains balanced week after week, glad I chose it to manage my battery. Cheers :)
Thanks a lot for your kind feedback. The JK is truly the BMS where the battery needs the least amount of maintenance over a long period of time. I really hope for the new JK to arrive soon...
@@OffGridGarageAustralia Didn't you use 304 Ah cells on the middle shelf, and 280 Ah on the other two? I used the JK BMS on both my batteries, and they are always well balanced. I have two batteries, at first the two BMS's SOC and the shunt were all the same (well very close together), then battery B always read less than Battery A SOC and the shunt, now all three are back in sync again, and I didn't change anything, weird. I do need to sort out my heating for the winter, as its fast approaching.
@@TheRonskiman the 304Ah cells are at the top. Yeah, you won't have a problem with the JK BMS. The more shunts you have the more different your results are. You have to pick one and make it your point of truth. Don't look at the other ones any more...😁
@@OffGridGarageAustralia I go by the Victron SOC, but I have the little display on the BMS, and it's just odd how those two drift out over time, then come back together again.
Very interesting video with very valuable informations, as always. I like many tests comparing different solar devices with in-depth analysis and testing them on their limits and I like the battle of different BMS where I enjoy the commentary with explanations and conclusions. This is what makes your content in your videos unique, keep it up. Every time I finish watching a new video I can't wait for the next one.
Andy, I discovered you have been correct on this issue all along. Purchased one active balancer and placed it on one of my batteries. And it did the job within a 24-hour's. I plan to move it to the next battery pack to balance that one as well. Then like you I will wait to see if the batteries maintain their balance. Thanks for another great video. I wish the BMS manufacturers would get this done. We pay a lot of money on our DIY systems to have an issue like this.
Yes, I have now several batteries where the balance cables are installed and I can just install the active balancer whenever necessary. I hope the new JK will fix that...
Hey Andy, thanks for sharing your valued info. I recently set up a bank of Lifepo4 cells on my shouse. Thanks to your videos I went with the JK with 2A balancing. I'm super impressed with how it's working out. I didn't top balance my cells when I installed them. Instead I've set my charge voltage to 3.5v and float to 3.41v I found at this voltage once it hits float it gently tops off the cells with a few amps giving the BMS plenty of time to top balance without turning off the charging from the cells peaking.
Hello Andy - great job as always with your explanations, screenshots, split screens and overall ALL of it! :) Let's sway BMS's with the banks! I am willing to think that the high charging will follow the JK BMS to the different battery bank! Yay! PS - I need to see if you sell t-shirts! LOL
So clever the double terminal and helpful!!!🧐👀👏👏 Hi Andy from Greece 🇬🇷!!🙋 I like allot your videos and the way you explain them!!😍 I am an e-scooter chunky...🤪 And helps me very much your BMS and active balancer videos to make my batteries packs (lion batteries) work as better they could!!😘 Thank you!!🙏🙋
Really excellent test. It looks like the problem is being caused by the low cells. There is something seriously odd about those numbers. It might not be the cells themselves, but the voltage sensing of the BMS(es). Looking at the individual cells starting roughly at 8:24, for the Heltec, the first 10 cells are all exactly where I would expect them to be, in the 3.54V-3.57V range. But why the heck are cells 11-16 ALL running in the 3.42V range. I mean, all six are basically at the same low voltage. And then the overkill rack at 9:32, we see roughly the same thing. Cells 1-10 are 3.55V+ but cells 11-16 are ALL roughly 3.42V. (I would argue that in 1-10 seeing some cells at 3.65V is not the problem, they overcharged because too many other cells in 11-16 were low). Why the heck are the numbers so uniform for cells 1-10, and then again uniformly too low for 11-16? that's the question. -- The deviation becomes irrelevant once the cells 1-10 get overcharged due to the low cells. Or at least, you have to discount the high-side contribution to the deviation and just look at the low-side. Its clearly the low cells that are causing the problem. Ideally when we start to see some cells hitting 3.55V, we really really want to see the lowest cell at 3.50V or higher. Why did racks #1 and #3 still uniformly have cells 11-16 at 3.42V? That just can't be right. I wonder if there is an issue with the voltage sensing. In fact... hmm. I wonder if those BMS's are using the same analog mux for all 16 cells or if they are using two different analog muxes to measure the two groups (1-10 vs 11-16). Before you do the active balancer, I'd recommend looking at the cell voltages when the rack hit their low-voltage cut-off. It is possible that the low-voltage cut-off might be set too low. Well, I guess the real question is... did any of the racks even hit the low voltage cut-off during discharge during the multi-week test? But my bet is that the voltage sensing of the BMSs is split into two analog muxes and improperly calibrated by the BMS maker. There is no other good explanation for why cell group 1-10 are one voltage, and cell group 11-16 is another. -- Oh ho! Back to 9:28. Add up those individual cell voltages and compare against the 56.7V whole-pack voltage. They add up to 56.262V. That is way too much of a difference... 0.438V. If you take cells 11-16 (6 cells) and assign the difference to those. 0.438V / 6 = 0.073V. Then 3.42V/cell (roughly) + 0.073V = 3.493.V for the possible real values for 11-16. (Or take 1-10 assume they are reading high, and subtract as an alternative). Maybe you can do the passive balancer test again until you see the weird cell 1-10 vs 11-16 deviation, and then measure the actual cell voltages for all 16 cells to see if the cell readings by the BMS are accurate or not. -Matt
Thanks Matt, we see the same 'result' with cell 1-10 in both banks because the Heltec balancer was in the bottom shelf first and I believe it has caused this 'imbalance' over time. I then swapped the Heltec and Overkill to see if it causes the same pattern in the top battery, which was perfectly balanced. Yes, it did! And the Overkill is not able to re-balance the 'damage' the Heltec did. The overall battery voltage will lower once OVP is reached and the BMS turns off the battery. Hence we see a far lower voltage with the BMS which have turned off, than in the JK-battery which stayed connected all the time and shows the real charge/absorption voltage. The other two BMS are still balancing so overall voltage will go down until they turn on FETs again and get another big push until a cell hits 3.65V again. If all BMS are connected, the voltages they show are pretty close together.
@@OffGridGarageAustralia Makes sense. Now that you have the active balancer setup, it will be interesting to see if the passive balancers are able to maintain the balance at a 3.55V target, once the active balancer has cleaned up the cells. 0.25A passive balancing current / (imbalance in Ah)... call it 30Ah just guestimate = 120 hours to correct a 30Ah imbalance. 2 hours a day of absorbption... 60 days. That would be pretty nasty to try to correct with a passive balancer.
@@junkerzn7312 And this would be under ideal conditions with a constant voltage applied to the packs and no charge/discharge current, so a real 'maintenance mode'. Crazy when a simple active balancer can sort this out in minutes when used frequently.
@@OffGridGarageAustraliaI totally agree, and could not be much happier with my JK BMSs, although the “battery state of charge” is useless- thank goodness for the Victron BMV. (When the batteries are both full, one JK says just 63% and the other says maybe 85%. I just ignore that. 🤣
Hi Andy, just as a sneaky suspicion, I believe the middle shelf is doing more of the daily heavy lifting than the other packs - since it's better balanced, the cells are all "fuller" at the end of charging and keep the pack voltage higher under load, discharging more with your shallow cycling - remember that when the charge mosfets switch off, no "absorbing" is happening for the top and bottom batteries, while the middle pack can absorb since it never reaches a protection point. Easiest way to confirm would have been before you used the active balancers, to do a quick discharge test and graph the current from each pack. Now that they've been better balanced, we expect the packs to share current better, you'll see this immediately today/tomorrow whenever you do your next full charge.
I really cannot see that the middle battery does more work than the others. I'll have to watch it again under different load conditions. I also don't discharge the battery that low that the pack voltage would be a bit higher because of better balanced cells. If that would be true, this effect would have been gone now after top balancing the other two banks, but it's not... Taking the graph of each bank is not that easy as this is my production battery. I cannot just turn it off and discharge it. I believe it has something to do with the overall internal resistance of each battery including their BMS. The middle battery must have a lower resistance than the other two. I'll test...
Another great video Andy!! I can’t wait to see the results after 2 weeks. We are definitely seeing that BMS does not stand for “Balance Management System”!! 😉
Thanks Andy, as always love ❤️ your work! 👍 PURELY on your recommendation, I bought the JK BMSs and have never looked back. As long as I do a reasonably regular full charge to 3.45v per cell, I very often see a differential of just a few mV between high and low when absorption is almost finished. Absolutely worst case : if they haven’t been up near full charge in quite some time to allow enough time for some balancing, I just turn one bank off and keep the voltage up at 3.45v per cell with my power supply. Easy 👍
You cannot go wrong with the JK. Even you had a faulty one to start with, you now see the 'magic' of it. I still don't understand why other manufacturers don't follow this path🤷♂️
@@OffGridGarageAustralia Couldn’t agree more. (And my faulty one was replaced without any argument. As you may remember, it was on my caravan 4s battery and they knew what the problem was. They even told me how I could fix it but I didn’t have the necessary soldering equipment and/or skills.)
Need to get a good DMM which is calibrated, use it to check and verify if your BMMs reads voltage correctly. Found on my SOK 24V 100Ah batteries, individual cells when read with my Keithley 6 1/2 digit DMM6500 multimeter, the BMS can have a +/- 25mV delta V from the from the multimeter. Therefore there can be voltage calibration errors on the BMS, this can confuse the true state of battery balance levels.
Hi Andi, your battery bank with the JK is lagging behind the other two banks so it’s actually worse than the other two. We saw that the top and bottom shelf banks where in the 1 digit current area while the JK was over 90A and that should only be possible if the other two are already full and the JK is now catching up. I can see a similar thing with my two banks. The two packs are parts wise completely identical, 18s EVE280k, JK-BMS, cabling and so on, the only difference is, one was build in Sep. 2022 and one this June. When the batteries are discharged from 100% the new one is always delivering halve the current than the new one. This changes when the old one is at about 70% than the new one will deliver more current than the old. When charging, the old one will always be full first and then the new one is catching up. So I guess there is some difference in the resistance of the individual packs and thats probably the case with your JK bank.
I think it's the opposite. If the JK battery takes longer to charge, it must be on a lower SOC. So it must have been discharging faster at some stage than the other two batteries. This is only possible if the internal resistance of this JK-bank is lower than in the other two. I'll test this theory.
Thank you for all the videos you made, I learnt a lot from them and just finished my first 4S battery that will go in my camper van with off-course a JK-BMS. Due to space my setup is A bit different with the 4 batterys short side to each other making it a box of 80cm by 13cm. If you want to I can send some pictures and you can make A video commenting on pictures from viewers sending you there setups ? I would like to see what others made and what you think of it.
Very interesting results. Maybe the BMS on the middle shelf is also better at charging and discharging. You could swap it with the BMS of the least performing shelf to see if the faster charge and discharge follows or stays with the cells and aluminium bus bars. But let's wait and see if the passive loadbalancers can at least keep the achieved balance first. I think they will both lose balance over time, but do suspect there will be a clear winner between the two passive balancers after two weeks.
The BMS should have no influence on he charging or discharging process of the battery. At least not in such a way what I'm seeing here. Yeah, the winner is already in the middle shelf 😄
@@OffGridGarageAustralia So the theory is that the middle shelf just has lower resistance, leading to a higher current than the other two shelves during charge and discharge, right? And the BMS itself should not introduce any noticable resistance, therefore making the cells or the bus bars the limiting factor?
Hi Andy Thanks for yet another video. Waiting patiently on your test of the new JK BMS. Hoping that this BMS is a need to have rater than nice to have. I know you are saying copper busbars, but I think they are plated brass busbars. Yes, they have higher resistance than your aluminum busbars. Clean copper would be even better. Sorry if not accurate numbers, source is Google and usually reliable. Copper = 0,01724 x 10-6 Ω·mm2/m at 20 degrees C. Aluminum = 0,0282 x 10-6 Ω·mm2/m at 20 degrees C. Brass = 0,059 x 10-6 to 0,071 x 10-6 Ω·mm2/m at 20 degrees C. depending on Cu content in the alloy. Brass has 3,5-4 times higher resistance than clean copper. That might be one reason for the higher charge/discharge on the JK battery. Cross section on your aluminum busbars is bigger than the rest. But what about internal resistance in the BMS. A test for this would be to measure voltage drop across BMS on high A that will give an easy to measure result of the internal resistance.
I meant copper busbars. The ones which are coming with the cells usually are tinned copper, not brass. And these aluminium bus bars from Power Paul have a lower resistance than these copper busbars due to the dimensions. Have a look at the linked video in the description where I have tested them.
@@OffGridGarageAustralia There is some talk about brass busbars on the web, and I can see why someone is tempted to deliver brass instead of copper, material price of copper to double up compared to brass. My cells are from QSO and seems also copper. I can see on you video that the aluminum busbars also are with the “long” bolt hole version, that would also have been a concern for me, long hole / welded studs = small contact area, tight fit round hole must be better. I am intending to make my own cobber busbars from a 3x30mm piece of cobber with tight fit bolt holes. I am making a bend up and down again to try to relieve stress on terminals. First test bend is done with a 3d printed template (PETG) for the bend and it actually worked, the 3 bends are with a nice radius on corners just need to figure out some better guide for the jig, my ocd does not allow the bend to be not perfect 90deg across the busbar. (3x30mm busbars VS 95mm2 wire from battery to MP2) I still think you should measure voltage drop across BMS on a specific A, for all 3 BMS both in charge and discharge to see if the difference is inside the BMS itself.
@@lkjaerThe smaller contact area is actually a big advantage of these welded studs. You apply the same torque on a smaller area. It gives the perfect connection. Better than any other terminals I have ever tested (flat terminals or even the double hole busbars). All tested here on the channel: th-cam.com/video/VPQvs-2YYzA/w-d-xo.html
It would be interesting to see what would happen if the balancer in the JK-BMS was off for 2-3 weeks. Would the JK be just as bad/good as the other 2? 🤔🤨🧐😅
Moin Andy. First at all, really enjoy your art of testing, improve and troubleshooting the world of solar and LiFePo4. Especially I like your selfmade batteryshelf with a lot detailed workmanship. One question follows me ,after all videos I saw, related to this batterybanks,: why do you not replace the Heltec, JB and the Overkill BMS´ses with an Gobel, Pace or Seplos instead?. We saw the improvement of all these enterprise BMS´ses and the new features about handling and security. So, from Andy to Andy: I´ll really exited about this video, when you´ll rip these "RV-BMS´ses" out and build an homogen habit for your batteries with the same BMS 🙂 Have a good week and don´t forget the cooling process ;-) Regards AJ
I suspect the BMS over the bus bars, for the middle battery...Which should be easy to test for, with a BMS swap..But, just a hunch, could be the bus bars, I don't know...I certainly expect the top and bottom battery to be out of balance again very quickly...Very Interesting...
I was hoping some of this experimentation Andy was doing with the battery shelf and balancing would help me understand what is happening with my small battery. I have a 4S3P system that I built with Headway 15Ah cells. Total capacity is around 50 Ah (which is greater than the 45Ah "marked" on the batteries). It uses an Overkill BMS. So I'm a bit confused... With 100% SOC, my cell delta is 5mV- great! Cells are around 3.34V. After partial discharge, then a recharge, they all come up evenly in voltage... until.... Cell 4 reaches around 3.45V. The other 3 cells keep going up to 3.65V and the passive balancer attempts to bring Cell 4 up, but never does. If I let the pack charge up to the point where overvoltage protection kicks in, then disconnect charging, eventually they all settle down to around 3.34V. Before I assembled this pack in its 4S3P config, I had all the batteries in parallel and top balanced them. So what's going on here? Why is cell 4 (which is made up of 3 batteries) only able to get to 3.45V? It seems that below 3.45V all the cells stay balanced. It is only Cell 4 that cannot go above 3.45V. Is it the battery? Loose connection (they all seem tight to me... I can't find a torque spec for these cells)? Do I have a bad cell? I have also checked the voltage reading on each cell with a calibrated Fluke meter and the BMS readings are right on the money, +/- 1mV. So I know the voltage readings are correct.
Below 3.45 you probably won't see much difference in differential - it is only going to show up higher voltages than that . See Andy's video where he explains the charge curve of LiFePo4 cells. It could be that the one cell is under charged or weak . Ideally you would want to do manual balance of your low cells to bring them up to same as others. Andy has a video on how to do this.
So, to begin with, to see the full voltage delta, you need to charge the battery until one cells hits 3.65V and the BMS turns off. Then you have your highest and lowest cell in the pack. The passive balancer will not be enough to balance your cells quick enough. You need to keep the battery at 13.8V and let it sit with this voltage for quite a while to let the BMS balance. Make sure, the battery is not in use and Charge Balance is turned off.
@@OffGridGarageAustralia right... got it. I think that may be the issue. I am letting it get to 3.65 and it shuts down charging... but that doesn't let the lowest cell continue to charge. I'll just leave it at 13.8 for awhile and see how it does. Thanks!!!!!!!
@@marlomontanaro3233or get one of these active balancers and do a full top balance. That is much quicker. Balancing by leaving the power supply on 13.8V could take a very long time. I mean, very very long. Weeks...
Andy I leave my 5 amp active balancer connected all the time to my RV 304 AH pack - The active balancer seems to stop balancing at about 10mV and then the passive balancers hone it down to 2 or 3mV - I have not experienced any deviation during discharge high enough for active balancer to kick in substantially and if it did its fairly efficient at shuffling the Joules around - in contrast to passive balancing which just burns it off - as for your middle shelf its a conundrum - The copper bus bars are nickel coated which is not a great conductor, how pure is the copper underneath? In the real world, pure aluminum will never have less resistance than pure de-oxygenated copper like- for - like - Thinner bus bars will always give higher resistance than thick for higher currents so you're comparing apples with oranges - I use 300amp copper laminated flexible bus bars they will take some beating. Hugs from Wales UK
Thanks Trevor. I have not noticed that these balancer ever stop working. Even the smallest difference makes them balancing. It will be in the next video again. I charged a battery to 80% and let it sit there for 2 weeks with an active balancer connected. It was fully top balanced before (over 3.6V with 5mV deviation). Fully charged again yesterday and the top balancing done before was totally gone. Could not charge higher than 54.5V before the first cell hit 3.65V. That is exactly the problem with these balancers, they won't stop. This is not so much of a problem when you fully charge the battery every single day. Watch the video in the description where the balancing function is explained. Also the video where I did the calculation about aluminium vs copper bars.
Perfectly top-balanced my 16s pack with 2A JK and afterwards switched off balancing. Pack is charged in everyday-life up to 3,47V per cell. Why i switched off balacing? Because that balancing far away from 3,65V top will theoretically destroy the top-balanced state... Still under surveillance, but looks pretty nice so far - 0.003V deviation after weeks.
Yep, great test. Let us know after a few weeks. I expect, the battery will be imbalanced again as it always needs a bit of balancing with every single charge.
I’m with Andy- keep the balancing off below say 3.43v and you won’t have issues. I’ve been running my cells at 3.45v absorption and balancing starting at 3.43v with the JK BMSs for many months, and my balance is almost always within just 2mV.
During the last months i did several tests - always beginning with top-balanced state: 1.) B Start @ 3.45V, Charge up to 3,47V -> pretty quickly visible deviation 2.) B Start @ 3.47V, charge up to 3,47V -> deviation visible after some days Thought: Any balancing after top-balancing WILL destroy the top-balanced state. And that led me to the comment above. 3.) Perfectly top balanced. Switched off balancing alltogether. Everyday charge up to 3,47V. Experiment with 2 different batteries: a) 14,4kWh EVE LF280K, JK 2A b) 1,92kWh Winston, 123smart BMS Experiment running since about 4, 5, 6? weeks. Almost no deviation. Expectation: After some months (spring?) there might be a deviation again which then calls for another top-balancing cycle with balancing switched on from 3,5V, charge up to 3,62-3,65V.
JK is good in balancing but very bad when measuring current and calculating SOC. I have their new version bms on order hopefully it works better. They also have a copy of the Smart Shunt (Victron) now.
With the aluminum busbars the current has no potential jump to an other metal, cause the battery terminals are also aluminum. The voltages in the electrochemical voltages series of copper and aluminum are quite different. This potential jump leads to more resistance without additional heating, but the current choose always the way of the lowest resistance, so the middle rack with the aluminum busbars is prefered. I think this potential jumps have the bigger effect than the slight differences in ohmic resistance.
@@OffGridGarageAustralia I Totally agree Andy. (I guess it’s maybe “old thinking” from before the days of LFP, with a very different voltage curve?) I do absorption @ 3.45v per cell, and as long as it’s fully charged reasonably regularly, the JK handles it perfectly. I very often see just 2mV variation.
I got my pack for 3 years and bought one of the first jikong/jkbms and already at this time I knew that it was the way to go. People that have done their homework know what to buy. What I meant is that it's not something new, passive balancing waste energy anyway and clearly can't meet the performance of a smart active balancer for the time needed to balance a pack.
@FutureSystem738 I charge to 3.37V and absorbtion to 3.4V, I'm something like 95% SOC, no problem since 3 years. My cells are gently charged, there is no need to go to 99 or 100% SOC
I wonder if the JK BMS internal balancer is using enough energy to keep it at a lower SOC than the other two, which means it's taking longer to fully charge. The Balancer circuit may not be as efficient as we think, so perhaps it's wasting 0.5A while it's balancing at 2.0A due to losses. This means over 10 hours it could be 5Ah behind the others. These are made up figures to demonstrate the point, and possibly difficult to actually measure, but worth a thought. It might also be interesting to get an IR measurement of each battery, both with and without the BMS to see if there's much difference. But again it's hard to know if this will create much difference because in reality I haven't seen a direct relationship between IR and battery efficiency. Still loving these tests that you do to get to the nitty gritty of battery building, they all help put the pieces of the puzzle together for everyone.
Thanks a lot, Paul. Your aluminium bus bars are still holding up well, without issues. Madi did such a test a while back and left some of her banks balancing with the JK. She set different activation voltages for each bank. Some of the cells were discharged to low SOC due to the power the JK consumed. Usually the balancer only activates when the battery is full and we have enough surplus power, so it's not an issue. With the NEEY, for example, I could never measure a self consumption but again it's hard to tell when the balancer is actually active... I'll do an resistance/impedance test for all three banks and see if the JK bank has an overall lower resistance than the other banks.
Good point. My diy with jk active balance sits with lower SOC after some hours of balance than other with passive ones. Will check again that after making all of then with the same cable cross.
Good evening Dear friend Andy. This is George.🙂 I would like to ask you if you can enlighten me on the question I have. I would like to build a system by stepping up the DC voltage further to 72 or 96 volts, with three or four 24 volt lifepo4 batteries in series. I would like to ask you, what's the best way to charge them, given that each 24 volt battery has an independent bms so it won't stop charging the whole system, if one of them reaches full charge first. My purpose is to use lower capacity and higher voltage, so that I use smaller cross-section wires and less system pieces. Also, is it possible to use a 24V charger with parallel wiring on all 24 volt batteries, regardless if the inverter gets the total voltage from the 96 volt batteries in series? ?Thanks in advance and congratulations on your work.
The bust bars can influence the total resistance of the pack, but there shouldn't be that high of a difference. I'm observing differences in my parallel packs also. The 100Ah one draws and charges up to 40% of the total compared to the 60% for 300Ah one, at least from some quick observations I made.
I would need to install a voltage trigger as well then for the MS. It cannot stay connected all the time. From previous testing, we know the balancers are working great and I don't need another comparison. This is more about how the passive balancers deal with the situation as some viewers suggested.
Because it's reaching a fuller state of charge because it's much better balanced/at a higher voltage and has lower resistance so gives up its charge easier. Might be worth an individual shelf capacity test when in the standard state where top & bottom shelves are not top balanced properly
Even if the passive balancer does work, why stress the cells to such a high state of charge and for such an extended length of time. With a JK bms, Neey or Heltec + voltage detection control relay, the problem is solved with no stress. With an active balancer you can use the battery in real world situations, no need for networking to inverter and only occasional venturing into absorption voltages with minimal time to maintain the top balance. I think your original thinking of 55.2 volts is the winner. I can’t help but think how many rack systems out there are not operating at peak efficiency because of high cell disconnect or are degraded by high state of charge. Keep up the good work Andy, I think I know where this one is going.
There were people commenting saying that Andy was not giving the passive balancers enough voltage to work with, basically, the voltage was too low for the passive balancers to work with, so, he has been doing a test for the past few weeks too see if the commentors comments had any merit, I had one bloke vermently arguing with me that both he and I, and the manufacturer of particularly my batteries was wrong about charging methods and voltages, and that both Andy and mysekf are wrong.....
@@GapRecordingsNamibia Yes passive will work BUT, it has to have enough balance current, well matched cells, initial top balance, enough time above balance voltage and frequent enough cycles up at that range as to not let the balance go awry to get unmanageable. So many built systems have weak passives balancers and rely on a networked approach to hold absorption voltages high until it fixes it which could be a very long time. I consider that a patch of a problem that won’t get better in the future. The interesting trend of better batteries is looking at the lower bulk or absorption voltage recommendations. This usually means that it has a better balancer.
Yes, I understand that, and know that, and agree, my two enerSol packs (15S) that I've had for over a year now has seen one pack consistently run away at the steep end of the curve, charging to 3.5V / per cell, my absorption was set to 2 hrs and in a year it did nit come down with even 1mV..... I opened it up 2 weeks back and used a set of light bulbs to manually bring down the high cells...... The two packs are now within 20mV of one another and both are at around 30mV cell difference have set absorption down to 30 minutes will keep watching it now, this is today is week 3........
@@GapRecordingsNamibia Andy has a great video “Automate your active balancer to become a Neey (almost)”. Probably the best/least expensive way to upgrade an existing bms.
Hola Andy , tu problema son los bms diferentes, yo tengo ese mismo problema y mis baterías si tienen los mismos bus bar ,ya pedí un juego de bms de las misma marca para corregir esto ya hacer que una batería trabaje más fuerte que otra es un desastre al final.
Where is your positive lead and negative lead connected to your bus bar? The closer the wire connection is to whatever cell pack is, the cells that will get more power sooner, hence why one bank fills faster than the other.
I was really surprised when some time ago you presented us with the unbalanced cells figures Andy, I am new to the game, as you know, and while I'm testing my new 16 x 304Ah cells for my first self-built battery storage, in order to kick my system into action, I purchased an Odipie 5Kw rack-mounted battery, a totally unknown quantity to me, however after weeks of usage, the max voltage differential amongst the cells is only 10ma. Am I just a lucky bunny or are off-the-shelf batteries known to be that good? Thanks for the share, we keep on following you 🙏
Thanks for your feedback and sharing. It depends to what voltage the battery charges to. 55V is when the cells start spreading apart and the deviation will start to be visible. I have seen some manufacturers only charge to 54.8V. This will hide any cell imbalance.
@@OffGridGarageAustralia Hi, thanks for your kind reply, I see what you mean however for almost three months I've been charging this battery unit to 3.45v per cell initially and for the last week up to 3.55v (56.8v) I only checked the cell's voltages after a full charge so I'm not aware at what state they were when it arrived, the total voltage was 53.42V. I shall update should anything change.
My experience shows me, the internal balancer is not able to hold the cells in balance after discharging and charging again... I'm looking forward to your next test, but I think I'll be right! 😅 Greetings from Germany
It has never worked for me in any battery I have built or tested. After some time, they always need some sort of maintenance... unless they have an active balancer built-in.
With regular solar charging and discharge loads - I set my Pace bms on jakipers to OVP at 3.52 and reset at 3.45 with absorb voltage of 56.6 and 1 hour absorb time. I think it has helped some - at least the differentials on one are 70 mv at worse and others are less than 60mv. Maybe over time they will come down more and if they do I will raise the OVP up higher. But now I am pretty sure the differential will be pretty good if I go back to 3.45v absorb.
5am it is when the video goes online 😉 I've checked all cells through the BMS in different state of charges and could not see a cell being low. This would also be visible again when we fully charge with such a high current.
My JK BMS always had my cells around. .008V deviation. I switched to Seplos for the Mason cases, and so far the balance has been ok. Around 80mv worse case. Not as good as JK, but the JK's did not support parallel comms between each other, so I could not use Solar Assistant to monitor them all. It works well with the Seplos BMS's. I can always just add a heltec balancer in the Masons.
JK recently started selling the industrial variant of its bms with inverter comms and parallel comms. Andy has it on his website already 😉 In September that bms was in presale yet, but I hope soon we will see video about it (keeps the fingers crossed)
Thanks Andy. It's nice to see the improvements you get. 💪 I have two SEPLOS batteries and I added an active balancer to each one and one came out defective, unbalancing. After a year of operation, I saw the difference between the cells. I have always worked at 54.8v. We will increase the voltage to 56.8 to see the improvement difference. I have never seen my Victron inverter go floating. I assume it will be the vconfigure setting or the dvcc parameter in cervo gx. How do you have it configured so that it enters float? Can you send me the Victron configuration file by email? Greetings
Charging to 54.8V only will hide the voltage delta of tour cells. This is not high enough to get them out of the flat part of the charge curve and they all look the same voltage. 56.8V will definitely open your eyes and gives you a better picture across your cells. The Multiplus has a charger tab and I entered the same parameters as in my solar charge controllers: Absorption 56.8V, 1h absorption time, float voltage at 55.2V (these are just test parameters and a lot higher than I usually charge). This is only of interest if you actually charge through the MP, either through the grid or any connected PV-Inverters.
Wow, that is insane difference in current, I did have, but it is not like this difference when I used to discharge batteries with 120 amps the two 105s gives 60 and the 280 gives the other 60 now after replacing the bad cells and balance problems and tightening the busbars, these cells are affected by temprature more than lithium ion cells. The bloated cells I had they were though to balance but when I managed to balance them they just drop down again. By the way I didn't charge them past 54.6 unless I want to balance. but charging this high voltage the big 280 ah keeps charging but the 105 tah batteries stop taking large current at 54.8 and the 280ah takes more and it is JK also.
Yeah, if you have different capacities, these results can show but in my case, I have 304Ah and two 280ah banks. The middle one with the JK is one of the 280Ah banks. It can only be that the overall resistance including BMS is lower in this bank.
You should do the test with matching busbar types. The higher charge rate of the JK BMS will also likely cause greater cell imbalance. Certainly, with my JK at higher charge rates, i see more cell imbalance.
Each battery banks has the same bus bars. The banks with the JK uses aluminium bars (with lower resistance) and despite charging faster than the other two banks when full, the deviation is lower.
@OffGridGarageAustralia I see that, but for the sake of comparison, you have another variable in there. Would have been interesting if the aluminium busbar would have been on one of the passive balanced banks
@@timevans8223Ah, I see what you mean. I'll measure the overall impedance of the banks first and compare them. I have the suspicion, that the middle battery has a lower overall resistance and hence discharges a bit faster as well. More to come...
@OffGridGarageAustralia for equal cross-section, aluminium has 56% more resistance than copper. the middle shelf in your pack must have a higher resistance with those busbar unless they are a lot thicker
Looks like the TLDR of battery balancing is that passive balancers are shit and active balancing is the way to go. Thank you for sharing the experience of charging to a higher voltage to see if the passive balancers would work.
Yeah, these 100-200mA passive balancing is certainly something off the past. They work with Li-ion where we can start balancing very early but this concept does not work with LiFePO4 any more and their falt charge curve.
Is it possible to install an active bms to a wallmounted powerbank lifepo4 ?? And may be install a switch when the user want to use the active balancer
Do you get a victron “high dc ripple warning” when doing these tests? That’s what happens to mine whenever a cell reaches the high voltage cutoff and the BMS starts to cycle charge current on/off.
No, never had this warning or problem with my gear. As long as there is a load connected and the solar power is sufficient, it keeps the system running.
Why it's flowing in the jkbms at the end... while 2 other bms have stopped (I suppose parameters are strictly the same) 1- could be that runners in this pack are slower runners than in the other 2 packs 2- could be that jk as delayed those runners start by doing a better job at balancing 3- could be that the jkbms voltage sensor on cells is aiming lower then the other 2 4- could be that there is more resistance on the circuit to this pack vs the others, less power in this pack in same amount of time...
If you are charging at tens of amps, the 150 mA balance current is a miniscule proportion of that. For example, with a 50 amp charge current, 150 mA is 0.3% of the charge current. It may take hundreds of charge cycles to see any effect at all. It's all a matter of proportion. I have 450 AH of batteries on my boat using four Overkill BMSs. I stop my 50 amp shore charger at 3.45 volts/cell with a tail current cut-off of 12 amps, and continue charging the bank to 3.55 volts/cell with a 5 amp charger (0.01C) in parallel with the 50 amp charger, to balance the cells. The 5 amp charger is set to stop charging with a tail current of 4 amps. I have the Overkills set to begin balancing at 3.30 volts/cell, and by using this method, I've had no trouble maintaining a balance of 10 mV. Assuming a balance current of 150mA per BMS, the balance current of the four BMSs is 4 X 0.150 amp = 0.6 amps. 12% of the charge current.
Andy was testing some claims that people were making on previous videos saying he was charging at too low a voltage for the passive balancers to work at, this was the culmination of 4 weeks worth of testing at a higher voltage to see if the claims had any merit.
I put a voltage operated relay. It turns the balancers on at 27 volts and off at 26.4 volts. power by the voltage sence. They have a 2 pole relay si 2 batteries for one device.
If you do a capacity test, on a known dodgy cell. With a month/week inbetween charging and discharging. This will show the self discharge rate, and indicate what balance current is required. Have you done this before? If not, what a stonking episode that would be! I would do it, but have no capacity tester...
@@tryingtosucceed No, I haven't done this test before. I actually may have a dodgy cell in the bottom shelf (cell 15 which is low again even after the recent top balance). I'll put your suggestion on my list of future videos. Thanks for that.
I made a 24v 16cell battery from used Calb cells. The capacity of the cells varies from 88ah to 99ah so does internal resistance. The BMS is an Ant. I top balanced the battery before using it and never had an active balancer. After almost a year I still don't have much deviation (around 0,04v max) at 3,55 cell voltage. Maybe active balancers are guilty to those deviations when you use them from the start?
It would take a lot longer. The NEEY balances only on cell at a time while this active balancer balances all the cells at the same time. See Stuart's video in the description.
Hello, i have car with LiFePo4 battery, have access to OBD and shocked when loocked charging process from 99 to 100% where diviation reaches 300-350 milivolts, recently seen disassemble video of that car battery and there is passive balancing in it`s BMS (2 resistors 10 ohm on each mosfet probably in parralel) how to reduce that diviation ? I can`t set current less then 6 amps for AC charging , and battery management dumb - it`s not reducing current and finishes charging when highgest voltage cell reaches 3.752 v at same current rate that it started - 2.6 amps (6a for 230v AC charging)
Hello I was wondering if you may know the answer to a JK Bms probably im having as iv emailed jk and unfortunately had no response from them . My Bms is new and all working but when I try to change parameters in Basic or advanced settings it says …… sending failure, the bms beeps when you hit parameter ok button so it’s getting that command ok but a send failure warning comes up on screen . Iv double checked everything and watched your set up videos again but this is a odd one , any help would be great thank you.
ALU oxide is a super isolator. So: what I think the internal DC resistance of the battery is higher than the other two. Personally I would NEVER use ALU for the bars as it is an inferior material to use for that purpose. ALU oxide forms very quickly again after it is removed.
This battery proves the opposite. The battery performs better then the other two, it seems. Also, all battery terminals of these prismatic cells are made from aluminium. Since I stopped using any contact grease, I have no problems with connections any more.
@@niktak1114 Yeah, you need to set the other parameters for high charge warning and the recovery voltages accordingly and logically, so alarm needs to be under the protection. But it may be too high for a 200A BMS... It's not ideal and I don't know why they used the alarm/2 for setting the charge current limit. They fixed that in V3.0 of their BMS.
Yes, absolutely. It's still the best out there. I hope the new JK will bring some additional features as well as the communication for parallel batteries.
I have 2 identical 105Ah batteries, with same BMS, cable lenght, fuses, everything is the same but one discharge more than the other, I assume that is because of total internal resistance of cells plus resistance of fuses and holders also bms should count but at the end of day I have 15% difference in SOC. You middle shelf has a much big difference I don't believe that is only because of bus bars, the A are much higher compare to others so total internal resistance has to be very different and for that I blame the 2 other BMS and difference in cells, my 32 are from same batch and yours are from different orders. You test hardware if everything was the same probably you should be doing something wrong. I came here everyday with the hope of see your review of the JKBMS :o)
Thanks a lot. That is exactly my suspicion as well: the overall resistance of the battery including the BMS. It can be true for my setup as I use three different BMS. More testing coming.
The passive balancers are a pure resistive load. There is no way that a voltage increase of 3% will make a big difference in the balancing current, which your test confirms.
It's not so much about the voltage increase but more about that the charge curve gets way steeper at a higher voltage which is in favour of the passive balancer. Yes, and the 3% makes a huge difference exactly at this 3.45V point.
passive balancers taper and cut current near OVP,and active balancers do not,thats how they are designed to function, "thats the answer they give me when i ask about that to Pace Bms vendor" i'm not sure about overkill and heltec though
These active balancers are coming from the Li-ion area where it made sense to start balancing early. This concept doe snot work with LiFePO4 due to the very flat curves these batteries have. They can effectively only balance at 3.45V and above.
Hallo Andy: Messe doch mal den (gesamt) Innenwiderstand aller drei Batterieregale. Meine Theorie: Alu ohne Kontaktoberfläche ist auf Dauer als Busbar problematisch. Es bildet sich eine hart Qxidschicht welche von den Schrauben nicht duchgedrückt werden kann. Dies ist mit einem Zinnplating jedoch gut möglich (wie bei Deinen Cu-Busbars). Daher: Immer auf eine Verzinnung achten als top-layer (Standard in der Automobilindustrie - Direktes Kontaktieren auf Alu ist dort verboten).
Yes, I can do that, good tip. The battery terminals are made of aluminium as well. How do you deal with that when connecting the copper bus bars? I have stopped using grease between the contacts as they cause trouble over time. I had the best results with no grease at all.
@@OffGridGarageAustralia If there is a tin layer, which is soft, the contact area is protected from getting oxided also on the aluminium side (microscop level - A-spots). But if you have on both sides aluminium - it´s quite bad. Best solution would be Sn/Sn on both side - but I think the cell manufactures decided for Al out of cost reasons (not Sn coated) + mech stability. I use for the cells the standatd bus bars (I think they are quite good) + Al contact paste to reduce the resitsance and protection from oxidation over time. Screwing must be good - sensor cables should not be on the cell terminals but in the middle of the bus bar seperately. works good since ~1 year.
@@markmark9532Well, the middle battery has aluminium on both sides (no contact grease) and performs better than the other two banks from what I can see... against all odds and explanation. I believe the BMS has a far lower resistance than the other two BMS and therefor the overall resistance of the bank including the BMS is lower compared to the other two battery banks.
weird on the middle shelf, you would have thought any difference in discharge would rebalance on charge so as to all 3 batteries to hit full together. Odd, needs sleeping on and thinking about. Although are they the 304's and top/bottom are 280's ?
It is in deed weird.... The 304Ah bank is at the top. I can only think about an overall difference in resistance between the packs which makes this possible.
@@OffGridGarageAustralia The three batteries are loaded differently, if I remember correctly the plus and minus cables are at the top of your large busbar in your cabinet, maybe try moving the minus to achieve an equal load during charging and discharging.
Very much possible. I have 3 batteries in parallel, and only one has JK BMS. And guess what? I have similar picture. It discharges more and charges with bigger current after.
Does the active balancer not have a much higher efficiency than the passive balancer of the other two banks? I think more of the JK BMS may have a lower resistance than the other two BMS.
In my case it may also be caused by another reason. The battery with JK bms is connected to the bus bar with 50mm2 cable, while the others with 16mm2. I'm going to replace all of them with 25mm2 soon and see. They are all 100ah 15S so its enough. And JK bms battery is DIY, while two others - factory made, and I didn't opened them yet to see what's inside My struggle to make the communication to the inverter ended up with nothing by the way. Now I have Solar Assistant in between and it works like charm. It sees batteries via rs232, rs485 with no issues. But back to jk active balance - its way more effective than two others passive. And the factory settings in two factory bms are too conservative I think. They have 3.55 as high voltage alarm and this triggers charge shutdown till the cell goes down at 3.45.
6:55 Hmmm... THIS is interesting. At this point, all 3 batteries have almost same "min-max" voltages. 9:15 At this point there are several "Opinions" can be made (not necessary accurate): 1. "Oh yeah, JK suck! it is not charging the cells correctly; proof it is the last to get fully charged." 2. "WOW! JK rock! It was the last to give up!" / "JK has smallest delta among the pack. it is doing the job right!" 3. "I am not convinced! middle battery has better cell conditions, if JK is the better BMS, put it at the top or bottom." 12:28 with 100ma balancing current.... give these two 3 more days to balance it.
As per my experience, these passive balancer will only balance if the battery is disconnected and not in use, slap a power supply on it for constant voltage and then let the balancer work. And yes, it can take days...
I wonder if on top of the aluminum bus bars contributing, that the JK bms has a lower resistance across its mosfets (or may be higher). Id say there is a bit too it, maybe even the internal resistance on the cells potentially contributing
You are a legend andy, taking the time to respond to people. I love your videos too (secretly i think my partener does as well)@@OffGridGarageAustralia
@@BadIdea1123 I'm always here for everyone. Making videos is on think but you also need to be part of the community and provide help and feedback. Thank you for your kind words.
I said it in the initial video, it's bad to aim for 100%SOC... I charge at something like 95%SOC (3.37V, absorb 3.4V). Sometimes it goes to 20mV deviation, 90% of the time I'm under 8mV deviation, pack charge between 90A and 5A. I can't see no reason to try to go further, you will only find problems there.
Your videos often contain some level of head-scratching (on my side), especially when you clearly show what's going on and what needs further investigations. Having seen quite a few of your video's so far but definitely not all yet (you've published 465x, I believe) I believe that perhaps your challenges and findings are more than 1x thing in this particular situation; perhaps the passive balancer is thrown off a wee bit, as its algorithm might expect lower internal resistances from the LiFePO4 cells? (far fetched perhaps but maybe the aluminum busbars create a galvanic difference between it and the battery-terminals?) Where I assume all the cells of the middle battery-bank are quite similar, no Frankensteining, no B-quality (although I don't believe that would make much difference, as you have shown in other videos). I also believe that the passive balancing algorithms might be a wee bit different between your 3x BMS, if I take into account how huge some of the measurements are. (where active balancers are often capacitive and passive balancers are often resistive, i.e. bleeding the voltages in the latter rather than storing the voltages into capacitors as is the case in active balancers) And I also understand an active balancer works independently from the BMS, and therefore reacts faster (to imbalances) compared to a passive balancer. The passive balancing requires the BMS.
IMHO The super low balance current is just simply not enough for batteries of this size with anything other than the JK BMS. A few hundred milliamps just doesn’t do it! I have two banks, each with a JK BMS, and have no issues with difference between high and low cell typically just 2mV at the end of the one hour absorption phase.
mmm...I have same JK Bms. I think the difference are the different cell battery pack.....you should try to swap Bms ..put Jk Bms in the pack with more V deviation. Ps:JK Bms work very good with my shi..y, unbalanced 200A 16S cell pack,but LCD display stop working after 6 month,buy new Lcd and stop working after 7 month..The seller say LCD is not in guarantee!!!!
There are runners in each pack.... they just can't keep up with their friends, they are the weak links. 1- top balancing correctly 2- charge and increase voltage slowly (low Amp, 10A) then observe at which voltage first runners start to climb, you hit 50mV deviation.... Stop here, you are not far from the voltage you should use as absorbtion. Use a little les as charging voltage cause high Amp will push those runners to start To run even earlier then they should do. I got 3 years of precise statistics on my pack, each time deviation is higher then 20mV I store the cell which got min voltage and the one that got highest voltage... then a graph show me the pack health. At first I was having many 20mV+ hits, I reduced charge/absorbtion voltage till I nearly got none.
With all of this experimentation you do, you are becoming the de-facto go to guy for batterys, and solar in general, you show your success's and your failures, and for this I trust your results and have been able to replicate them myself, my JK bms DIY battery remains balanced week after week, glad I chose it to manage my battery. Cheers :)
Thanks a lot for your kind feedback. The JK is truly the BMS where the battery needs the least amount of maintenance over a long period of time.
I really hope for the new JK to arrive soon...
@@OffGridGarageAustralia Didn't you use 304 Ah cells on the middle shelf, and 280 Ah on the other two? I used the JK BMS on both my batteries, and they are always well balanced. I have two batteries, at first the two BMS's SOC and the shunt were all the same (well very close together), then battery B always read less than Battery A SOC and the shunt, now all three are back in sync again, and I didn't change anything, weird. I do need to sort out my heating for the winter, as its fast approaching.
@@TheRonskiman the 304Ah cells are at the top.
Yeah, you won't have a problem with the JK BMS. The more shunts you have the more different your results are. You have to pick one and make it your point of truth. Don't look at the other ones any more...😁
@@OffGridGarageAustralia I go by the Victron SOC, but I have the little display on the BMS, and it's just odd how those two drift out over time, then come back together again.
Very interesting video with very valuable informations, as always. I like many tests comparing different solar devices with in-depth analysis and testing them on their limits and I like the battle of different BMS where I enjoy the commentary with explanations and conclusions. This is what makes your content in your videos unique, keep it up. Every time I finish watching a new video I can't wait for the next one.
Thanks a lot for your feedback and kind words. Heaps more to come!
Andy, I discovered you have been correct on this issue all along. Purchased one active balancer and placed it on one of my batteries. And it did the job within a 24-hour's. I plan to move it to the next battery pack to balance that one as well. Then like you I will wait to see if the batteries maintain their balance. Thanks for another great video. I wish the BMS manufacturers would get this done. We pay a lot of money on our DIY systems to have an issue like this.
Yes, I have now several batteries where the balance cables are installed and I can just install the active balancer whenever necessary.
I hope the new JK will fix that...
Hey Andy, thanks for sharing your valued info.
I recently set up a bank of Lifepo4 cells on my shouse. Thanks to your videos I went with the JK with 2A balancing.
I'm super impressed with how it's working out. I didn't top balance my cells when I installed them. Instead I've set my charge voltage to 3.5v and float to 3.41v I found at this voltage once it hits float it gently tops off the cells with a few amps giving the BMS plenty of time to top balance without turning off the charging from the cells peaking.
Thanks for sharing. The JK is certainly a very good BMS and you don't need anything else. I hope the new JK will be as great as the old model...
Imagine the new JK BMSes having enabled communication between themselves as parallel banks and with the Victron system. It'll be a dream come true...
Hello Andy - great job as always with your explanations, screenshots, split screens and overall ALL of it! :) Let's sway BMS's with the banks! I am willing to think that the high charging will follow the JK BMS to the different battery bank! Yay! PS - I need to see if you sell t-shirts! LOL
So clever the double terminal and helpful!!!🧐👀👏👏
Hi Andy from Greece 🇬🇷!!🙋
I like allot your videos and the way you explain them!!😍
I am an e-scooter chunky...🤪 And helps me very much your BMS and active balancer videos to make my batteries packs (lion batteries) work as better they could!!😘
Thank you!!🙏🙋
Awesome! Thank you!
Really excellent test. It looks like the problem is being caused by the low cells. There is something seriously odd about those numbers. It might not be the cells themselves, but the voltage sensing of the BMS(es).
Looking at the individual cells starting roughly at 8:24, for the Heltec, the first 10 cells are all exactly where I would expect them to be, in the 3.54V-3.57V range. But why the heck are cells 11-16 ALL running in the 3.42V range. I mean, all six are basically at the same low voltage.
And then the overkill rack at 9:32, we see roughly the same thing. Cells 1-10 are 3.55V+ but cells 11-16 are ALL roughly 3.42V. (I would argue that in 1-10 seeing some cells at 3.65V is not the problem, they overcharged because too many other cells in 11-16 were low).
Why the heck are the numbers so uniform for cells 1-10, and then again uniformly too low for 11-16? that's the question.
--
The deviation becomes irrelevant once the cells 1-10 get overcharged due to the low cells. Or at least, you have to discount the high-side contribution to the deviation and just look at the low-side. Its clearly the low cells that are causing the problem. Ideally when we start to see some cells hitting 3.55V, we really really want to see the lowest cell at 3.50V or higher. Why did racks #1 and #3 still uniformly have cells 11-16 at 3.42V? That just can't be right.
I wonder if there is an issue with the voltage sensing. In fact... hmm. I wonder if those BMS's are using the same analog mux for all 16 cells or if they are using two different analog muxes to measure the two groups (1-10 vs 11-16).
Before you do the active balancer, I'd recommend looking at the cell voltages when the rack hit their low-voltage cut-off. It is possible that the low-voltage cut-off might be set too low. Well, I guess the real question is... did any of the racks even hit the low voltage cut-off during discharge during the multi-week test?
But my bet is that the voltage sensing of the BMSs is split into two analog muxes and improperly calibrated by the BMS maker. There is no other good explanation for why cell group 1-10 are one voltage, and cell group 11-16 is another.
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Oh ho! Back to 9:28. Add up those individual cell voltages and compare against the 56.7V whole-pack voltage. They add up to 56.262V. That is way too much of a difference... 0.438V. If you take cells 11-16 (6 cells) and assign the difference to those. 0.438V / 6 = 0.073V. Then 3.42V/cell (roughly) + 0.073V = 3.493.V for the possible real values for 11-16. (Or take 1-10 assume they are reading high, and subtract as an alternative).
Maybe you can do the passive balancer test again until you see the weird cell 1-10 vs 11-16 deviation, and then measure the actual cell voltages for all 16 cells to see if the cell readings by the BMS are accurate or not.
-Matt
Thanks Matt,
we see the same 'result' with cell 1-10 in both banks because the Heltec balancer was in the bottom shelf first and I believe it has caused this 'imbalance' over time. I then swapped the Heltec and Overkill to see if it causes the same pattern in the top battery, which was perfectly balanced. Yes, it did!
And the Overkill is not able to re-balance the 'damage' the Heltec did.
The overall battery voltage will lower once OVP is reached and the BMS turns off the battery. Hence we see a far lower voltage with the BMS which have turned off, than in the JK-battery which stayed connected all the time and shows the real charge/absorption voltage.
The other two BMS are still balancing so overall voltage will go down until they turn on FETs again and get another big push until a cell hits 3.65V again.
If all BMS are connected, the voltages they show are pretty close together.
@@OffGridGarageAustralia Makes sense. Now that you have the active balancer setup, it will be interesting to see if the passive balancers are able to maintain the balance at a 3.55V target, once the active balancer has cleaned up the cells.
0.25A passive balancing current / (imbalance in Ah)... call it 30Ah just guestimate = 120 hours to correct a 30Ah imbalance. 2 hours a day of absorbption... 60 days. That would be pretty nasty to try to correct with a passive balancer.
@@junkerzn7312 And this would be under ideal conditions with a constant voltage applied to the packs and no charge/discharge current, so a real 'maintenance mode'. Crazy when a simple active balancer can sort this out in minutes when used frequently.
From all I can comprehend, using an Active Balance/JK BMS is the answer. I have been watching my JK BMS units working well.
Yes, absolutely. The JK is still king under all BMS.
@@OffGridGarageAustraliaI totally agree, and could not be much happier with my JK BMSs, although the “battery state of charge” is useless- thank goodness for the Victron BMV. (When the batteries are both full, one JK says just 63% and the other says maybe 85%. I just ignore that. 🤣
Hi Andy, just as a sneaky suspicion, I believe the middle shelf is doing more of the daily heavy lifting than the other packs - since it's better balanced, the cells are all "fuller" at the end of charging and keep the pack voltage higher under load, discharging more with your shallow cycling - remember that when the charge mosfets switch off, no "absorbing" is happening for the top and bottom batteries, while the middle pack can absorb since it never reaches a protection point.
Easiest way to confirm would have been before you used the active balancers, to do a quick discharge test and graph the current from each pack.
Now that they've been better balanced, we expect the packs to share current better, you'll see this immediately today/tomorrow whenever you do your next full charge.
I really cannot see that the middle battery does more work than the others. I'll have to watch it again under different load conditions. I also don't discharge the battery that low that the pack voltage would be a bit higher because of better balanced cells. If that would be true, this effect would have been gone now after top balancing the other two banks, but it's not...
Taking the graph of each bank is not that easy as this is my production battery. I cannot just turn it off and discharge it.
I believe it has something to do with the overall internal resistance of each battery including their BMS. The middle battery must have a lower resistance than the other two. I'll test...
AB has one job and does it very well. Cool
Hey great video 🎉
Why has aluminum lower resistance compared to copper? Is it a special mix? Isnt copper the best conductor (besides gold)? 😏
Another great video Andy!! I can’t wait to see the results after 2 weeks. We are definitely seeing that BMS does not stand for “Balance Management System”!! 😉
Hahaha, no, passive balancing is not the way to go forward here...😁
Thanks Andy, as always love ❤️ your work! 👍
PURELY on your recommendation, I bought the JK BMSs and have never looked back. As long as I do a reasonably regular full charge to 3.45v per cell, I very often see a differential of just a few mV between high and low when absorption is almost finished.
Absolutely worst case : if they haven’t been up near full charge in quite some time to allow enough time for some balancing, I just turn one bank off and keep the voltage up at 3.45v per cell with my power supply. Easy 👍
You cannot go wrong with the JK. Even you had a faulty one to start with, you now see the 'magic' of it. I still don't understand why other manufacturers don't follow this path🤷♂️
@@OffGridGarageAustralia Couldn’t agree more. (And my faulty one was replaced without any argument. As you may remember, it was on my caravan 4s battery and they knew what the problem was. They even told me how I could fix it but I didn’t have the necessary soldering equipment and/or skills.)
Need to get a good DMM which is calibrated, use it to check and verify if your BMMs reads voltage correctly.
Found on my SOK 24V 100Ah batteries, individual cells when read with my Keithley 6 1/2 digit DMM6500 multimeter, the BMS can have a +/- 25mV delta V from the from the multimeter.
Therefore there can be voltage calibration errors on the BMS, this can confuse the true state of battery balance levels.
Top quality content 👍
maybe need that middle batter meed to replace 😮 thank you Andy
Hi Andi,
your battery bank with the JK is lagging behind the other two banks so it’s actually worse than the other two.
We saw that the top and bottom shelf banks where in the 1 digit current area while the JK was over 90A and that should only be possible if the other two are already full and the JK is now catching up.
I can see a similar thing with my two banks.
The two packs are parts wise completely identical, 18s EVE280k, JK-BMS, cabling and so on, the only difference is, one was build in Sep. 2022 and one this June.
When the batteries are discharged from 100% the new one is always delivering halve the current than the new one. This changes when the old one is at about 70% than the new one will deliver more current than the old. When charging, the old one will always be full first and then the new one is catching up.
So I guess there is some difference in the resistance of the individual packs and thats probably the case with your JK bank.
I think it's the opposite. If the JK battery takes longer to charge, it must be on a lower SOC. So it must have been discharging faster at some stage than the other two batteries. This is only possible if the internal resistance of this JK-bank is lower than in the other two. I'll test this theory.
Looking forward seeing the video and thanks for all your work!
Great video
Thank you for all the videos you made, I learnt a lot from them and just finished my first 4S battery that will go in my camper van with off-course a JK-BMS. Due to space my setup is A bit different with the 4 batterys short side to each other making it a box of 80cm by 13cm. If you want to I can send some pictures and you can make A video commenting on pictures from viewers sending you there setups ? I would like to see what others made and what you think of it.
Thanks for sharing, I have a friend who built exactly such a battery for his vehicle as well. Looks weird but works the same way...
Very interesting results. Maybe the BMS on the middle shelf is also better at charging and discharging. You could swap it with the BMS of the least performing shelf to see if the faster charge and discharge follows or stays with the cells and aluminium bus bars.
But let's wait and see if the passive loadbalancers can at least keep the achieved balance first. I think they will both lose balance over time, but do suspect there will be a clear winner between the two passive balancers after two weeks.
The BMS should have no influence on he charging or discharging process of the battery. At least not in such a way what I'm seeing here.
Yeah, the winner is already in the middle shelf 😄
@@OffGridGarageAustralia So the theory is that the middle shelf just has lower resistance, leading to a higher current than the other two shelves during charge and discharge, right?
And the BMS itself should not introduce any noticable resistance, therefore making the cells or the bus bars the limiting factor?
Hi Andy
Thanks for yet another video. Waiting patiently on your test of the new JK BMS. Hoping that this BMS is a need to have rater than nice to have.
I know you are saying copper busbars, but I think they are plated brass busbars. Yes, they have higher resistance than your aluminum busbars. Clean copper would be even better.
Sorry if not accurate numbers, source is Google and usually reliable.
Copper = 0,01724 x 10-6 Ω·mm2/m at 20 degrees C.
Aluminum = 0,0282 x 10-6 Ω·mm2/m at 20 degrees C.
Brass = 0,059 x 10-6 to 0,071 x 10-6 Ω·mm2/m at 20 degrees C. depending on Cu content in the alloy.
Brass has 3,5-4 times higher resistance than clean copper. That might be one reason for the higher charge/discharge on the JK battery. Cross section on your aluminum busbars is bigger than the rest. But what about internal resistance in the BMS. A test for this would be to measure voltage drop across BMS on high A that will give an easy to measure result of the internal resistance.
I meant copper busbars. The ones which are coming with the cells usually are tinned copper, not brass.
And these aluminium bus bars from Power Paul have a lower resistance than these copper busbars due to the dimensions. Have a look at the linked video in the description where I have tested them.
@@OffGridGarageAustralia There is some talk about brass busbars on the web, and I can see why someone is tempted to deliver brass instead of copper, material price of copper to double up compared to brass. My cells are from QSO and seems also copper.
I can see on you video that the aluminum busbars also are with the “long” bolt hole version, that would also have been a concern for me, long hole / welded studs = small contact area, tight fit round hole must be better.
I am intending to make my own cobber busbars from a 3x30mm piece of cobber with tight fit bolt holes. I am making a bend up and down again to try to relieve stress on terminals. First test bend is done with a 3d printed template (PETG) for the bend and it actually worked, the 3 bends are with a nice radius on corners just need to figure out some better guide for the jig, my ocd does not allow the bend to be not perfect 90deg across the busbar. (3x30mm busbars VS 95mm2 wire from battery to MP2)
I still think you should measure voltage drop across BMS on a specific A, for all 3 BMS both in charge and discharge to see if the difference is inside the BMS itself.
@@lkjaerThe smaller contact area is actually a big advantage of these welded studs. You apply the same torque on a smaller area. It gives the perfect connection. Better than any other terminals I have ever tested (flat terminals or even the double hole busbars).
All tested here on the channel: th-cam.com/video/VPQvs-2YYzA/w-d-xo.html
It would be interesting to see what would happen if the balancer in the JK-BMS was off for 2-3 weeks. Would the JK be just as bad/good as the other 2? 🤔🤨🧐😅
verry good question 👍
I'll do it once we finished this test... thanks for your suggestion.
Moin Andy. First at all, really enjoy your art of testing, improve and troubleshooting the world of solar and LiFePo4. Especially I like your selfmade batteryshelf with a lot detailed workmanship. One question follows me ,after all videos I saw, related to this batterybanks,:
why do you not replace the Heltec, JB and the Overkill BMS´ses with an Gobel, Pace or Seplos instead?.
We saw the improvement of all these enterprise BMS´ses and the new features about handling and security.
So, from Andy to Andy: I´ll really exited about this video, when you´ll rip these "RV-BMS´ses" out and build an homogen habit for your batteries with the same BMS 🙂
Have a good week and don´t forget the cooling process ;-)
Regards AJ
I suspect the BMS over the bus bars, for the middle battery...Which should be easy to test for, with a BMS swap..But, just a hunch, could be the bus bars, I don't know...I certainly expect the top and bottom battery to be out of balance again very quickly...Very Interesting...
I think you could be right with the top and bottom battery being out of balance again soon. I think I can already see a trend after a few charges...
I was hoping some of this experimentation Andy was doing with the battery shelf and balancing would help me understand what is happening with my small battery. I have a 4S3P system that I built with Headway 15Ah cells. Total capacity is around 50 Ah (which is greater than the 45Ah "marked" on the batteries). It uses an Overkill BMS. So I'm a bit confused... With 100% SOC, my cell delta is 5mV- great! Cells are around 3.34V. After partial discharge, then a recharge, they all come up evenly in voltage... until.... Cell 4 reaches around 3.45V. The other 3 cells keep going up to 3.65V and the passive balancer attempts to bring Cell 4 up, but never does. If I let the pack charge up to the point where overvoltage protection kicks in, then disconnect charging, eventually they all settle down to around 3.34V. Before I assembled this pack in its 4S3P config, I had all the batteries in parallel and top balanced them.
So what's going on here? Why is cell 4 (which is made up of 3 batteries) only able to get to 3.45V? It seems that below 3.45V all the cells stay balanced. It is only Cell 4 that cannot go above 3.45V. Is it the battery? Loose connection (they all seem tight to me... I can't find a torque spec for these cells)? Do I have a bad cell?
I have also checked the voltage reading on each cell with a calibrated Fluke meter and the BMS readings are right on the money, +/- 1mV. So I know the voltage readings are correct.
Below 3.45 you probably won't see much difference in differential - it is only going to show up higher voltages than that . See Andy's video where he explains the charge curve of LiFePo4 cells. It could be that the one cell is under charged or weak . Ideally you would want to do manual balance of your low cells to bring them up to same as others. Andy has a video on how to do this.
So, to begin with, to see the full voltage delta, you need to charge the battery until one cells hits 3.65V and the BMS turns off. Then you have your highest and lowest cell in the pack.
The passive balancer will not be enough to balance your cells quick enough. You need to keep the battery at 13.8V and let it sit with this voltage for quite a while to let the BMS balance. Make sure, the battery is not in use and Charge Balance is turned off.
@@OffGridGarageAustralia right... got it. I think that may be the issue. I am letting it get to 3.65 and it shuts down charging... but that doesn't let the lowest cell continue to charge. I'll just leave it at 13.8 for awhile and see how it does. Thanks!!!!!!!
@@marlomontanaro3233or get one of these active balancers and do a full top balance. That is much quicker.
Balancing by leaving the power supply on 13.8V could take a very long time. I mean, very very long. Weeks...
finally diybms FTW!
Yep, it is happening...
Andy I leave my 5 amp active balancer connected all the time to my RV 304 AH pack - The active balancer seems to stop balancing at about 10mV and then the passive balancers hone it down to 2 or 3mV - I have not experienced any deviation during discharge high enough for active balancer to kick in substantially and if it did its fairly efficient at shuffling the Joules around - in contrast to passive balancing which just burns it off - as for your middle shelf its a conundrum - The copper bus bars are nickel coated which is not a great conductor, how pure is the copper underneath? In the real world, pure aluminum will never have less resistance than pure de-oxygenated copper like- for - like - Thinner bus bars will always give higher resistance than thick for higher currents so you're comparing apples with oranges - I use 300amp copper laminated flexible bus bars they will take some beating. Hugs from Wales UK
Thanks Trevor. I have not noticed that these balancer ever stop working. Even the smallest difference makes them balancing.
It will be in the next video again. I charged a battery to 80% and let it sit there for 2 weeks with an active balancer connected. It was fully top balanced before (over 3.6V with 5mV deviation). Fully charged again yesterday and the top balancing done before was totally gone. Could not charge higher than 54.5V before the first cell hit 3.65V.
That is exactly the problem with these balancers, they won't stop.
This is not so much of a problem when you fully charge the battery every single day.
Watch the video in the description where the balancing function is explained.
Also the video where I did the calculation about aluminium vs copper bars.
I have (two sets of) 4 batteries with the Overkill. Always stays between .006 to 004 balance each. 12 volt system in an RV
Depends on the voltage you charge to. Also, 12V batteries have only 4 cells and are a lot easier to maintain and balance.
Perfectly top-balanced my 16s pack with 2A JK and afterwards switched off balancing.
Pack is charged in everyday-life up to 3,47V per cell.
Why i switched off balacing? Because that balancing far away from 3,65V top will theoretically destroy the top-balanced state...
Still under surveillance, but looks pretty nice so far - 0.003V deviation after weeks.
Yep, great test. Let us know after a few weeks.
I expect, the battery will be imbalanced again as it always needs a bit of balancing with every single charge.
I’m with Andy- keep the balancing off below say 3.43v and you won’t have issues.
I’ve been running my cells at 3.45v absorption and balancing starting at 3.43v with the JK BMSs for many months, and my balance is almost always within just 2mV.
During the last months i did several tests - always beginning with top-balanced state:
1.) B Start @ 3.45V, Charge up to 3,47V -> pretty quickly visible deviation
2.) B Start @ 3.47V, charge up to 3,47V -> deviation visible after some days
Thought: Any balancing after top-balancing WILL destroy the top-balanced state. And that led me to the comment above.
3.) Perfectly top balanced. Switched off balancing alltogether. Everyday charge up to 3,47V. Experiment with 2 different batteries:
a) 14,4kWh EVE LF280K, JK 2A
b) 1,92kWh Winston, 123smart BMS
Experiment running since about 4, 5, 6? weeks. Almost no deviation.
Expectation: After some months (spring?) there might be a deviation again which then calls for another top-balancing cycle with balancing switched on from 3,5V, charge up to 3,62-3,65V.
@@OffGridGarageAustralia See my answer before. Just took another look 0.001V deviation once sun's gone.
💙👊😎
JK is good in balancing but very bad when measuring current and calculating SOC. I have their new version bms on order hopefully it works better. They also have a copy of the Smart Shunt (Victron) now.
With the aluminum busbars the current has no potential jump to an other metal, cause the battery terminals are also aluminum. The voltages in the electrochemical voltages series of copper and aluminum are quite different. This potential jump leads to more resistance without additional heating, but the current choose always the way of the lowest resistance, so the middle rack with the aluminum busbars is prefered. I think this potential jumps have the bigger effect than the slight differences in ohmic resistance.
Battery manufacturers should just make active balancers the standard
They should. So far, there is only one company which does it: JK
@@OffGridGarageAustralia I Totally agree Andy. (I guess it’s maybe “old thinking” from before the days of LFP, with a very different voltage curve?)
I do absorption @ 3.45v per cell, and as long as it’s fully charged reasonably regularly, the JK handles it perfectly. I very often see just 2mV variation.
@@FutureSystem738
2mV during absorbtion, or after the balancer has done its work?
At wich cell voltage have you configured the balancer to kick in?
I got my pack for 3 years and bought one of the first jikong/jkbms and already at this time I knew that it was the way to go. People that have done their homework know what to buy. What I meant is that it's not something new, passive balancing waste energy anyway and clearly can't meet the performance of a smart active balancer for the time needed to balance a pack.
@FutureSystem738 I charge to 3.37V and absorbtion to 3.4V, I'm something like 95% SOC, no problem since 3 years. My cells are gently charged, there is no need to go to 99 or 100% SOC
I wonder if the JK BMS internal balancer is using enough energy to keep it at a lower SOC than the other two, which means it's taking longer to fully charge. The Balancer circuit may not be as efficient as we think, so perhaps it's wasting 0.5A while it's balancing at 2.0A due to losses. This means over 10 hours it could be 5Ah behind the others. These are made up figures to demonstrate the point, and possibly difficult to actually measure, but worth a thought.
It might also be interesting to get an IR measurement of each battery, both with and without the BMS to see if there's much difference. But again it's hard to know if this will create much difference because in reality I haven't seen a direct relationship between IR and battery efficiency.
Still loving these tests that you do to get to the nitty gritty of battery building, they all help put the pieces of the puzzle together for everyone.
Thanks a lot, Paul. Your aluminium bus bars are still holding up well, without issues.
Madi did such a test a while back and left some of her banks balancing with the JK. She set different activation voltages for each bank. Some of the cells were discharged to low SOC due to the power the JK consumed.
Usually the balancer only activates when the battery is full and we have enough surplus power, so it's not an issue. With the NEEY, for example, I could never measure a self consumption but again it's hard to tell when the balancer is actually active...
I'll do an resistance/impedance test for all three banks and see if the JK bank has an overall lower resistance than the other banks.
Good point. My diy with jk active balance sits with lower SOC after some hours of balance than other with passive ones. Will check again that after making all of then with the same cable cross.
Cant you mesure the "internal" resistance of the hole pack? And compare the shelfs in that way?
Yes, that it my prediction as well! I'll do this after the two weeks are over.
Good evening Dear friend Andy. This is George.🙂 I would like to ask you if you can enlighten me on the question I have. I would like to build a system by stepping up the DC voltage further to 72 or 96 volts, with three or four 24 volt lifepo4 batteries in series. I would like to ask you, what's the best way to charge them, given that each 24 volt battery has an independent bms so it won't stop charging the whole system, if one of them reaches full charge first. My purpose is to use lower capacity and higher voltage, so that I use smaller cross-section wires and less system pieces. Also, is it possible to use a 24V charger with parallel wiring on all 24 volt batteries, regardless if the inverter gets the total voltage from the 96 volt batteries in series? ?Thanks in advance and congratulations on your work.
The bust bars can influence the total resistance of the pack, but there shouldn't be that high of a difference. I'm observing differences in my parallel packs also. The 100Ah one draws and charges up to 40% of the total compared to the 60% for 300Ah one, at least from some quick observations I made.
Why don’t you keep one active balancer in place and only revert the other back to the passive balancer to have a better comparison?
The niddle battery with the JK BMS already has a built in active balancer, hence why the other two packs were so far out ..........
I would need to install a voltage trigger as well then for the MS. It cannot stay connected all the time.
From previous testing, we know the balancers are working great and I don't need another comparison. This is more about how the passive balancers deal with the situation as some viewers suggested.
Because it's reaching a fuller state of charge because it's much better balanced/at a higher voltage and has lower resistance so gives up its charge easier. Might be worth an individual shelf capacity test when in the standard state where top & bottom shelves are not top balanced properly
I will test for internal resistance of the whole pack including the BMS. That is my suspicion as well.
Even if the passive balancer does work, why stress the cells to such a high state of charge and for such an extended length of time. With a JK bms, Neey or Heltec + voltage detection control relay, the problem is solved with no stress. With an active balancer you can use the battery in real world situations, no need for networking to inverter and only occasional venturing into absorption voltages with minimal time to maintain the top balance. I think your original thinking of 55.2 volts is the winner. I can’t help but think how many rack systems out there are not operating at peak efficiency because of high cell disconnect or are degraded by high state of charge. Keep up the good work Andy, I think I know where this one is going.
There were people commenting saying that Andy was not giving the passive balancers enough voltage to work with, basically, the voltage was too low for the passive balancers to work with, so, he has been doing a test for the past few weeks too see if the commentors comments had any merit, I had one bloke vermently arguing with me that both he and I, and the manufacturer of particularly my batteries was wrong about charging methods and voltages, and that both Andy and mysekf are wrong.....
@@GapRecordingsNamibia
Yes passive will work BUT, it has to have enough balance current, well matched cells, initial top balance, enough time above balance voltage and frequent enough cycles up at that range as to not let the balance go awry to get unmanageable. So many built systems have weak passives balancers and rely on a networked approach to hold absorption voltages high until it fixes it which could be a very long time. I consider that a patch of a problem that won’t get better in the future. The interesting trend of better batteries is looking at the lower bulk or absorption voltage recommendations. This usually means that it has a better balancer.
It's a test, Karl. Watch the video in the description, where I explained it.
Yes, I understand that, and know that, and agree, my two enerSol packs (15S) that I've had for over a year now has seen one pack consistently run away at the steep end of the curve, charging to 3.5V / per cell, my absorption was set to 2 hrs and in a year it did nit come down with even 1mV..... I opened it up 2 weeks back and used a set of light bulbs to manually bring down the high cells...... The two packs are now within 20mV of one another and both are at around 30mV cell difference have set absorption down to 30 minutes will keep watching it now, this is today is week 3........
@@GapRecordingsNamibia
Andy has a great video “Automate your active balancer to become a Neey (almost)”. Probably the best/least expensive way to upgrade an existing bms.
question for the man with a plan. What BMS, and charge controller for the sodium ion battery cells are available.
Same as for LiFePO4, I believe. Just need to set the numbers differently...
Heya, I didn't expect a differant result then what came out of the test, why, you already proved a passive can't compeet with a active balance
Hola Andy , tu problema son los bms diferentes, yo tengo ese mismo problema y mis baterías si tienen los mismos bus bar ,ya pedí un juego de bms de las misma marca para corregir esto ya hacer que una batería trabaje más fuerte que otra es un desastre al final.
Where is your positive lead and negative lead connected to your bus bar?
The closer the wire connection is to whatever cell pack is, the cells that will get more power sooner, hence why one bank fills faster than the other.
I was really surprised when some time ago you presented us with the unbalanced cells figures Andy, I am new to the game, as you know, and while I'm testing my new 16 x 304Ah cells for my first self-built battery storage, in order to kick my system into action, I purchased an Odipie 5Kw rack-mounted battery, a totally unknown quantity to me, however after weeks of usage, the max voltage differential amongst the cells is only 10ma. Am I just a lucky bunny or are off-the-shelf batteries known to be that good? Thanks for the share, we keep on following you 🙏
Thanks for your feedback and sharing.
It depends to what voltage the battery charges to. 55V is when the cells start spreading apart and the deviation will start to be visible. I have seen some manufacturers only charge to 54.8V. This will hide any cell imbalance.
@@OffGridGarageAustralia Hi, thanks for your kind reply, I see what you mean however for almost three months I've been charging this battery unit to 3.45v per cell initially and for the last week up to 3.55v (56.8v) I only checked the cell's voltages after a full charge so I'm not aware at what state they were when it arrived, the total voltage was 53.42V. I shall update should anything change.
My experience shows me, the internal balancer is not able to hold the cells in balance after discharging and charging again... I'm looking forward to your next test, but I think I'll be right! 😅
Greetings from Germany
It has never worked for me in any battery I have built or tested. After some time, they always need some sort of maintenance... unless they have an active balancer built-in.
With regular solar charging and discharge loads - I set my Pace bms on jakipers to OVP at 3.52 and reset at 3.45 with absorb voltage of 56.6 and 1 hour absorb time. I think it has helped some - at least the differentials on one are 70 mv at worse and others are less than 60mv. Maybe over time they will come down more and if they do I will raise the OVP up higher. But now I am pretty sure the differential will be pretty good if I go back to 3.45v absorb.
They may balance over time, but it can take very very long. These passive balancers are not great.
Morgen Andy ist ja ganz schön früh bei dir 6 Uhr. Zur Frage am Schluss evtl. mal die Zellen einzeln gemessen ob da eine defekt ist ?
5am it is when the video goes online 😉
I've checked all cells through the BMS in different state of charges and could not see a cell being low. This would also be visible again when we fully charge with such a high current.
Do you think it might be a firmware QC issue like with the Seplos BMS? These passive balancers are apparently doing absolutely nothing.
No, that's not a FW issue here. I believe it's related to internal resistance.
My JK BMS always had my cells around. .008V deviation. I switched to Seplos for the Mason cases, and so far the balance has been ok. Around 80mv worse case. Not as good as JK, but the JK's did not support parallel comms between each other, so I could not use Solar Assistant to monitor them all. It works well with the Seplos BMS's. I can always just add a heltec balancer in the Masons.
JK recently started selling the industrial variant of its bms with inverter comms and parallel comms. Andy has it on his website already 😉
In September that bms was in presale yet, but I hope soon we will see video about it (keeps the fingers crossed)
Apparently the new JK is almost here... I have everything prepared for the test!
@@OffGridGarageAustralia 🙏💪💪
Thanks Andy. It's nice to see the improvements you get. 💪
I have two SEPLOS batteries and I added an active balancer to each one and one came out defective, unbalancing. After a year of operation, I saw the difference between the cells. I have always worked at 54.8v. We will increase the voltage to 56.8 to see the improvement difference.
I have never seen my Victron inverter go floating. I assume it will be the vconfigure setting or the dvcc parameter in cervo gx. How do you have it configured so that it enters float? Can you send me the Victron configuration file by email?
Greetings
Charging to 54.8V only will hide the voltage delta of tour cells. This is not high enough to get them out of the flat part of the charge curve and they all look the same voltage. 56.8V will definitely open your eyes and gives you a better picture across your cells.
The Multiplus has a charger tab and I entered the same parameters as in my solar charge controllers: Absorption 56.8V, 1h absorption time, float voltage at 55.2V (these are just test parameters and a lot higher than I usually charge). This is only of interest if you actually charge through the MP, either through the grid or any connected PV-Inverters.
@@OffGridGarageAustralia We'll try it and see if.....
@@ismsanama6587 I did charge to 55.2V for over a year and it did hide the deviation. So, charging to 54.8V will even hide it more...
@@OffGridGarageAustralia ok. thank you
Wow, that is insane difference in current, I did have, but it is not like this difference when I used to discharge batteries with 120 amps the two 105s gives 60 and the 280 gives the other 60 now after replacing the bad cells and balance problems and tightening the busbars, these cells are affected by temprature more than lithium ion cells. The bloated cells I had they were though to balance but when I managed to balance them they just drop down again. By the way I didn't charge them past 54.6 unless I want to balance. but charging this high voltage the big 280 ah keeps charging but the 105 tah batteries stop taking large current at 54.8 and the 280ah takes more and it is JK also.
Yeah, if you have different capacities, these results can show but in my case, I have 304Ah and two 280ah banks. The middle one with the JK is one of the 280Ah banks. It can only be that the overall resistance including BMS is lower in this bank.
So what is the make of the active balancers?? 🙃
Heltec, NEEY...
off-grid-garage.com/battery-management-systems-bms/
You should do the test with matching busbar types. The higher charge rate of the JK BMS will also likely cause greater cell imbalance. Certainly, with my JK at higher charge rates, i see more cell imbalance.
Each battery banks has the same bus bars. The banks with the JK uses aluminium bars (with lower resistance) and despite charging faster than the other two banks when full, the deviation is lower.
@OffGridGarageAustralia I see that, but for the sake of comparison, you have another variable in there. Would have been interesting if the aluminium busbar would have been on one of the passive balanced banks
@@timevans8223Ah, I see what you mean. I'll measure the overall impedance of the banks first and compare them. I have the suspicion, that the middle battery has a lower overall resistance and hence discharges a bit faster as well. More to come...
@OffGridGarageAustralia for equal cross-section, aluminium has 56% more resistance than copper. the middle shelf in your pack must have a higher resistance with those busbar unless they are a lot thicker
@@timevans8223 You still haven't watched the video where I installed these aluminium busbars 😉
They have a lower resistance, my friend ...
Looks like the TLDR of battery balancing is that passive balancers are shit and active balancing is the way to go. Thank you for sharing the experience of charging to a higher voltage to see if the passive balancers would work.
Yeah, these 100-200mA passive balancing is certainly something off the past. They work with Li-ion where we can start balancing very early but this concept does not work with LiFePO4 any more and their falt charge curve.
Is it possible to install an active bms to a wallmounted powerbank lifepo4 ?? And may be install a switch when the user want to use the active balancer
Do you get a victron “high dc ripple warning” when doing these tests? That’s what happens to mine whenever a cell reaches the high voltage cutoff and the BMS starts to cycle charge current on/off.
No, never had this warning or problem with my gear. As long as there is a load connected and the solar power is sufficient, it keeps the system running.
Why it's flowing in the jkbms at the end... while 2 other bms have stopped (I suppose parameters are strictly the same)
1- could be that runners in this pack are slower runners than in the other 2 packs
2- could be that jk as delayed those runners start by doing a better job at balancing
3- could be that the jkbms voltage sensor on cells is aiming lower then the other 2
4- could be that there is more resistance on the circuit to this pack vs the others, less power in this pack in same amount of time...
🎉
🥈
If you are charging at tens of amps, the 150 mA balance current is a miniscule proportion of that. For example, with a 50 amp charge current, 150 mA is 0.3% of the charge current. It may take hundreds of charge cycles to see any effect at all. It's all a matter of proportion. I have 450 AH of batteries on my boat using four Overkill BMSs. I stop my 50 amp shore charger at 3.45 volts/cell with a tail current cut-off of 12 amps, and continue charging the bank to 3.55 volts/cell with a 5 amp charger (0.01C) in parallel with the 50 amp charger, to balance the cells. The 5 amp charger is set to stop charging with a tail current of 4 amps. I have the Overkills set to begin balancing at 3.30 volts/cell, and by using this method, I've had no trouble maintaining a balance of 10 mV.
Assuming a balance current of 150mA per BMS, the balance current of the four BMSs is 4 X 0.150 amp = 0.6 amps. 12% of the charge current.
Hi Andy, why not configure the active balancer to activate when the Difference is higher of 50mv.
Andy was testing some claims that people were making on previous videos saying he was charging at too low a voltage for the passive balancers to work at, this was the culmination of 4 weeks worth of testing at a higher voltage to see if the claims had any merit.
This active balancer cannot be programmed. It just runs forever when connected.
I put a voltage operated relay. It turns the balancers on at 27 volts and off at 26.4 volts. power by the voltage sence. They have a 2 pole relay si 2 batteries for one device.
@@johnpimlott1843 That is perfect. I've shown something like this here in this video: th-cam.com/video/kEeD-oM4QnY/w-d-xo.html
Do cells become unbalanced, due to different levels of self discharge?
Yes, absolutely.
If you do a capacity test, on a known dodgy cell. With a month/week inbetween charging and discharging. This will show the self discharge rate, and indicate what balance current is required. Have you done this before? If not, what a stonking episode that would be! I would do it, but have no capacity tester...
@@tryingtosucceed No, I haven't done this test before. I actually may have a dodgy cell in the bottom shelf (cell 15 which is low again even after the recent top balance). I'll put your suggestion on my list of future videos. Thanks for that.
Possible; due to the active ballance the cells are closer in charge and so draw more Amps. Amps per cell is actually small for the the capacity.
Even an imbalanced pack will draw the same power until the first cell hits 3.65V. They don't slow down.
Do you have a video on getting the cerbo gx to connect to the VRM? My viv vonect gives an error of 153 something not communicating ...
Yes, I have: th-cam.com/video/kAT5NDywgwk/w-d-xo.html
I made a 24v 16cell battery from used Calb cells. The capacity of the cells varies from 88ah to 99ah so does internal resistance. The BMS is an Ant. I top balanced the battery before using it and never had an active balancer. After almost a year I still don't have much deviation (around 0,04v max) at 3,55 cell voltage. Maybe active balancers are guilty to those deviations when you use them from the start?
Would the Neey Balancer not be better in such a case? (Fast balancing of all cells)
It would take a lot longer. The NEEY balances only on cell at a time while this active balancer balances all the cells at the same time. See Stuart's video in the description.
Hello, i have car with LiFePo4 battery, have access to OBD and shocked when loocked charging process from 99 to 100% where diviation reaches 300-350 milivolts, recently seen disassemble video of that car battery and there is passive balancing in it`s BMS (2 resistors 10 ohm on each mosfet probably in parralel) how to reduce that diviation ? I can`t set current less then 6 amps for AC charging , and battery management dumb - it`s not reducing current and finishes charging when highgest voltage cell reaches 3.752 v at same current rate that it started - 2.6 amps (6a for 230v AC charging)
Hello I was wondering if you may know the answer to a JK Bms probably im having as iv emailed jk and unfortunately had no response from them . My Bms is new and all working but when I try to change parameters in Basic or advanced settings it says …… sending failure, the bms beeps when you hit parameter ok button so it’s getting that command ok but a
send failure warning comes up on screen . Iv double checked everything and watched your set up videos again but this is a odd one , any help would be great thank you.
ALU oxide is a super isolator. So: what I think the internal DC resistance of the battery is higher than the other two. Personally I would NEVER use ALU for the bars as it is an inferior material to use for that purpose. ALU oxide forms very quickly again after it is removed.
This battery proves the opposite. The battery performs better then the other two, it seems.
Also, all battery terminals of these prismatic cells are made from aluminium. Since I stopped using any contact grease, I have no problems with connections any more.
Is there a way to make the 200A seplos BMS request a charge current of more than 100A? My stack of 4 only requests 400A combined.
Set the Charging Overcurrent Warning parameter in the Seplos BMS to 400A. That will set the requested BMS current to 200A.
@@OffGridGarageAustralia Thanks! They really need to update their parameter naming/explanations lol
@@OffGridGarageAustralia actually if I try to set it to 400A I get "parameter set fail (code:e2)"
@@niktak1114 Yeah, you need to set the other parameters for high charge warning and the recovery voltages accordingly and logically, so alarm needs to be under the protection. But it may be too high for a 200A BMS... It's not ideal and I don't know why they used the alarm/2 for setting the charge current limit.
They fixed that in V3.0 of their BMS.
Have to say that investing in the JK BMS was the best investment I could have made. Cell deviation is always below 5 MVolts!
Yes, absolutely. It's still the best out there. I hope the new JK will bring some additional features as well as the communication for parallel batteries.
wont it be better to install a Neeeeeeeey 4 Amp aktive balancer to the battery and let it stay on, balancing at 3.44 and turn of at 3.40 volt ?
Well, that would not be part of the test. See the video with part 1 in the description.
I have 2 identical 105Ah batteries, with same BMS, cable lenght, fuses, everything is the same but one discharge more than the other, I assume that is because of total internal resistance of cells plus resistance of fuses and holders also bms should count but at the end of day I have 15% difference in SOC. You middle shelf has a much big difference I don't believe that is only because of bus bars, the A are much higher compare to others so total internal resistance has to be very different and for that I blame the 2 other BMS and difference in cells, my 32 are from same batch and yours are from different orders. You test hardware if everything was the same probably you should be doing something wrong. I came here everyday with the hope of see your review of the JKBMS :o)
Thanks a lot. That is exactly my suspicion as well: the overall resistance of the battery including the BMS. It can be true for my setup as I use three different BMS. More testing coming.
The passive balancers are a pure resistive load. There is no way that a voltage increase of 3% will make a big difference in the balancing current, which your test confirms.
It's not so much about the voltage increase but more about that the charge curve gets way steeper at a higher voltage which is in favour of the passive balancer. Yes, and the 3% makes a huge difference exactly at this 3.45V point.
passive balancers taper and cut current near OVP,and active balancers do not,thats how they are designed to function,
"thats the answer they give me when i ask about that to Pace Bms vendor"
i'm not sure about overkill and heltec though
These active balancers are coming from the Li-ion area where it made sense to start balancing early. This concept doe snot work with LiFePO4 due to the very flat curves these batteries have. They can effectively only balance at 3.45V and above.
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Oh...AL busbars are much thicker...less resistance eh.
Hi friends 🎉
What's up, friend?!
Hallo Andy: Messe doch mal den (gesamt) Innenwiderstand aller drei Batterieregale. Meine Theorie: Alu ohne Kontaktoberfläche ist auf Dauer als Busbar problematisch. Es bildet sich eine hart Qxidschicht welche von den Schrauben nicht duchgedrückt werden kann. Dies ist mit einem Zinnplating jedoch gut möglich (wie bei Deinen Cu-Busbars). Daher: Immer auf eine Verzinnung achten als top-layer (Standard in der Automobilindustrie - Direktes Kontaktieren auf Alu ist dort verboten).
Oder Alu-Kontaktpaste verwenden.
Yes, I can do that, good tip. The battery terminals are made of aluminium as well. How do you deal with that when connecting the copper bus bars?
I have stopped using grease between the contacts as they cause trouble over time. I had the best results with no grease at all.
@@OffGridGarageAustralia If there is a tin layer, which is soft, the contact area is protected from getting oxided also on the aluminium side (microscop level - A-spots). But if you have on both sides aluminium - it´s quite bad. Best solution would be Sn/Sn on both side - but I think the cell manufactures decided for Al out of cost reasons (not Sn coated) + mech stability. I use for the cells the standatd bus bars (I think they are quite good) + Al contact paste to reduce the resitsance and protection from oxidation over time. Screwing must be good - sensor cables should not be on the cell terminals but in the middle of the bus bar seperately. works good since ~1 year.
@@Meiestrix Die habe ich im Einsatz
@@markmark9532Well, the middle battery has aluminium on both sides (no contact grease) and performs better than the other two banks from what I can see... against all odds and explanation. I believe the BMS has a far lower resistance than the other two BMS and therefor the overall resistance of the bank including the BMS is lower compared to the other two battery banks.
weird on the middle shelf, you would have thought any difference in discharge would rebalance on charge so as to all 3 batteries to hit full together. Odd, needs sleeping on and thinking about. Although are they the 304's and top/bottom are 280's ?
It is in deed weird.... The 304Ah bank is at the top.
I can only think about an overall difference in resistance between the packs which makes this possible.
@@OffGridGarageAustralia The three batteries are loaded differently, if I remember correctly the plus and minus cables are at the top of your large busbar in your cabinet, maybe try moving the minus to achieve an equal load during charging and discharging.
Aluminum has higher resistance than copper. Dont know if its not the case for your busbars thought.
The video is in the description. If the Al busbars have a larger cross section than Cu, aluminium is better than copper.
The middle pack is behind because the efficiency loss of the active balancer
Very much possible. I have 3 batteries in parallel, and only one has JK BMS. And guess what? I have similar picture. It discharges more and charges with bigger current after.
strange, because better efficiency discharging should also have better efficiency charging so it should come back to the same level equally
Does the active balancer not have a much higher efficiency than the passive balancer of the other two banks?
I think more of the JK BMS may have a lower resistance than the other two BMS.
In my case it may also be caused by another reason. The battery with JK bms is connected to the bus bar with 50mm2 cable, while the others with 16mm2. I'm going to replace all of them with 25mm2 soon and see. They are all 100ah 15S so its enough.
And JK bms battery is DIY, while two others - factory made, and I didn't opened them yet to see what's inside
My struggle to make the communication to the inverter ended up with nothing by the way. Now I have Solar Assistant in between and it works like charm. It sees batteries via rs232, rs485 with no issues.
But back to jk active balance - its way more effective than two others passive. And the factory settings in two factory bms are too conservative I think. They have 3.55 as high voltage alarm and this triggers charge shutdown till the cell goes down at 3.45.
Aluminium oxidation will give you a thin layer high resistance contact. So its not the best idea to use aluminium.
6:55 Hmmm... THIS is interesting. At this point, all 3 batteries have almost same "min-max" voltages.
9:15 At this point there are several "Opinions" can be made (not necessary accurate):
1. "Oh yeah, JK suck! it is not charging the cells correctly; proof it is the last to get fully charged."
2. "WOW! JK rock! It was the last to give up!" / "JK has smallest delta among the pack. it is doing the job right!"
3. "I am not convinced! middle battery has better cell conditions, if JK is the better BMS, put it at the top or bottom."
12:28 with 100ma balancing current.... give these two 3 more days to balance it.
As per my experience, these passive balancer will only balance if the battery is disconnected and not in use, slap a power supply on it for constant voltage and then let the balancer work. And yes, it can take days...
Just wanted to repeat my comment, JBD BMSes exist where they will balance both while charging and while not charging.
Not all of them unfortunately. There are differences in the firmware...
I wonder if on top of the aluminum bus bars contributing, that the JK bms has a lower resistance across its mosfets (or may be higher). Id say there is a bit too it, maybe even the internal resistance on the cells potentially contributing
Yeah, I believe the overall resistance in this middle battery including BMS is lower than with the other two. I'll investigate...
You are a legend andy, taking the time to respond to people. I love your videos too (secretly i think my partener does as well)@@OffGridGarageAustralia
@@BadIdea1123 I'm always here for everyone. Making videos is on think but you also need to be part of the community and provide help and feedback.
Thank you for your kind words.
Hello!
What's up? 🤘
its October can we get a drinking song and dance
I thought we do this in December🤷♂️
I said it in the initial video, it's bad to aim for 100%SOC... I charge at something like 95%SOC (3.37V, absorb 3.4V).
Sometimes it goes to 20mV deviation, 90% of the time I'm under 8mV deviation, pack charge between 90A and 5A.
I can't see no reason to try to go further, you will only find problems there.
Your videos often contain some level of head-scratching (on my side), especially when you clearly show what's going on and what needs further investigations. Having seen quite a few of your video's so far but definitely not all yet (you've published 465x, I believe) I believe that perhaps your challenges and findings are more than 1x thing in this particular situation; perhaps the passive balancer is thrown off a wee bit, as its algorithm might expect lower internal resistances from the LiFePO4 cells? (far fetched perhaps but maybe the aluminum busbars create a galvanic difference between it and the battery-terminals?) Where I assume all the cells of the middle battery-bank are quite similar, no Frankensteining, no B-quality (although I don't believe that would make much difference, as you have shown in other videos).
I also believe that the passive balancing algorithms might be a wee bit different between your 3x BMS, if I take into account how huge some of the measurements are. (where active balancers are often capacitive and passive balancers are often resistive, i.e. bleeding the voltages in the latter rather than storing the voltages into capacitors as is the case in active balancers) And I also understand an active balancer works independently from the BMS, and therefore reacts faster (to imbalances) compared to a passive balancer. The passive balancing requires the BMS.
IMHO The super low balance current is just simply not enough for batteries of this size with anything other than the JK BMS. A few hundred milliamps just doesn’t do it!
I have two banks, each with a JK BMS, and have no issues with difference between high and low cell typically just 2mV at the end of the one hour absorption phase.
@@FutureSystem738 Thanks for the clarification, very much appreciated!
Makes sense.
Is your S.P.A.T. fridge off-grid?
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PAUL! 🙃
@@OffGridGarageAustralia IKR!!!
@@OffGridGarageAustralia if I had to guess at Cliff Notes on this, it would be to simply source/use the JK BMS?
mmm...I have same JK Bms. I think the difference are the different cell battery pack.....you should try to swap Bms ..put Jk Bms in the pack with more V deviation.
Ps:JK Bms work very good with my shi..y, unbalanced 200A 16S cell pack,but LCD display stop working after 6 month,buy new Lcd and stop working after 7 month..The seller say LCD is not in guarantee!!!!
I don't want to swap too much back and forth, it messes with the results. I have to wait and see, gaining more data.
Was you display always turned on?
There are runners in each pack.... they just can't keep up with their friends, they are the weak links.
1- top balancing correctly
2- charge and increase voltage slowly (low Amp, 10A) then observe at which voltage first runners start to climb, you hit 50mV deviation.... Stop here, you are not far from the voltage you should use as absorbtion. Use a little les as charging voltage cause high Amp will push those runners to start To run even earlier then they should do.
I got 3 years of precise statistics on my pack, each time deviation is higher then 20mV I store the cell which got min voltage and the one that got highest voltage... then a graph show me the pack health. At first I was having many 20mV+ hits, I reduced charge/absorbtion voltage till I nearly got none.
I still think this philosophy is backwards. I Bulk charge at a lower voltage and float charge at a higher voltage.
Why would that make any sense?
I will never buy a Neey. Hankzor sent me a broken one and tried to keep my money.
Thanks for sharing.
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Passive balancer is totally useless. Not worth wasting time.
I just want a BMS that works, so the jk bms or nothing, I think the 5A is even better than the 2A
New JK-BMS incoming...
@@OffGridGarageAustraliaWow, interesting Andy.
(However my 2A balancing JK’s are doing the job, so I won’t be switching any time soon.)