Overcoming the battery-busbar problem (for now). Here is what I found!
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- เผยแพร่เมื่อ 12 มี.ค. 2022
- As you know me, I did some more testing to find the cause of the hot terminals and busbars from the last video. What I found was not nice. It seems the aluminium busbars are not 100% flat. Because they don't bend as much as the thinner copper busbars when screwing them down, the contact area was just too small and the contacts overheated at larger currents.
I also found a way to overcome this problem. The question is, will this last though or are we whack-a-mole situation here?
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Thanks so much for the in depth work on this Andy. It's the ultimate point of your channel, so show people not only what you're doing, but how and why. Rarely do we see people go into such detail especially in todays throw away culture.
It's quite surprising to see the amount of people saying "use copper", who have either forgotten or neglected to look at your previous experiences with copper and tinned copper. There are pro's and con's of both materials, in my case I've decided to stick with Aluminium and the approx. 2000 bars I've sold so far have all been working well as far as I know. This extra preparation information will be included with future bus bar sales as a bonus. I might even consider a small sachet of Alminox (the paste I use now) in bus bar sales.
While the product is vastly different, the underlying formula is the same as if we bought seeds to grow a plant from a shop. If we buy the seeds, drop them on the ground and walk away, we will probably find that in 3 weeks it's still a seed sitting on the ground doing nothing. However if we ensure the soil is appropriate, dig the hole, add the right amount of water, and bury it as prescribed, we come back to a sprouting plant. Preparing bus bars, doing nuts to the right torque, properly crimping lugs, and much more, is all part of the process of a DIY battery. This is the stuff we don't usually see behind the scenes in factories making these by the thousands.
Good find with the raised edges too, even though the outside edge hangs just over the diameter of the battery terminal, the inside edge would likely affect the contact patch. So ensuring the surface is flat is a worthwhile step, and it's also something anyone can do with no special tools.
For people who use the various pastes, be wary of what is used to apply the paste to the bus bar or to any surface. Using a cue tip needs to be done VERY carefully, because the fibres can easily dislodge and remain on the surface. If you're doing a lot of them, you can go to your local crafts store or pharmacy and get a similar looking item but it has a foam end on it (often used for applying face paint or make-up too), and this avoids the fibre issue. For larger areas, there are things called a "dabbing sponge" that would be ideal. Or as Andy uses, a clean rag can be easy for the bus bars, but tricky to use on battery terminals with studs.
And finally for the people who still didn't see the info about the bars, they are made from 5005 sheet (not extrusion), laser cut (not stamped), and are 20 x 4mm. The current carrying ability is well above what Andy requires for this application. I use them on batteries that I allow up to 250A current drain.
Paul, 5005 is a relatively high tensile Aluminium alloy, something akin to what street signs would be made from. I'm no electrical engineer, but my understanding is that pure aluminium is the best conductor of electricity (of the various aluminium alloys) and it is also much softer than a 5000 series alloy and would conform better when tightened down to the battery post. Even with Andy's sanding, there will be all sorts of other variables like small variations in height of the different cell terminals, slight variations of the angle of the cells as they sit for example and so I think any bus bar needs to be flexible in order to have a good connection to the battery post. Copper can be thinner for the same current carrying capacity, is very soft when annealed and does not have as bad a problem with the oxide layer being such a good insulator. It has much to recommend it. For those with deep pockets, silver plated copper would be even better LOL.
@@Ropetangler Have a look at Andy's previous videos (I did mention that above), he's had experience with various bus bars, and these have been the best yet. You're free to use whatever you prefer, just as I am, and everyone is. The results of these are proven, as are the results for some others. I'm not saying there's a right or wrong, this is what I use, this is what Andy is using at the moment, and it's what many others use too. Just because you disagree with something, doesn't make it wrong.
Thanks a lot Paul. I've pinned your comment to the top of the list.
Would 1099 (commercially pure aluminum) make better bus bars? Softer, and higher conductivity. Or would an 8xxx alloy (good conductivity, higher corrosion resistance, excellent creep resistance) be better?
Hi.
20x4 mm is good for 64 amps, according to online calculators.
Trying to learn, why do you say it's good for 250A batteries?
Thanks in advance.
I'd still ditch them. Aluminum is a terrible choice for DIY packs. Managing the oxide is a neverending task and copper or nickel is an infinitely better choice, especially in a pack that is functionally outdoors (no climate control). You won't win this fight against chemistry. That's my advice as a professional electrical engineer.
We will find out over time. It's an experiment! Like many others we do here on the channel 😉
@@OffGridGarageAustralia an experiment is fine, but over time, likely sooner than later, the daily heat cycle and load/idle heat cycling will have those bus bars moving a lot and wiping away the No-ox-id, and you’ll be back to candle connections. I’d hate for one to go critical overnight. I’d strongly recommend a change soon to nickel plated bus bars, either aluminum or copper core, or solid copper bus bars. There’s a reason they’re standard in every commercial battery bank.
@@mausball I'm not expecting them to move actually. If they don't heat up, there is no expansion.
@@OffGridGarageAustralia Mausball's comments match my experience and I have the same concern about the connection failing in the future. It is too easy to eliminate even the possibility. And the consequences are overheated terminals and damaged cells. Would not be worth the risk for me.
@@OffGridGarageAustralia they’re aluminum. Day to night temps will make them move a few thousandths twice a day minimum.
What I have learned is that aluminum should be used for containers of Spat but not busbars.
David…. 🤪🤪🤪🤪🤪 that was the funniest ! That statement made me laugh aloud…. Affirmative… no Al any where near passage of EMF. Thanks and 73s…
Aluminum is good to make kid's toys so they can be broken between Xmas and New Years.
Well, they work on my battery now as well. Let's see and learn (long term experiment 😉)
The terminals of the batteries are aluminium anyway.
This has probably already been said but you should use a flexible bus bar or cable for terminal connection. The subtle expansion and contraction during charging and discharging could cause terminal failure over time.
To tell the truth, I have never trusted aluminum in electrical applications. As a professional electrician, I have always used Ideal NOALOX Anti-Oxidant Compound to coat aluminum connections. Having maintained a number of 40 to 250 hp 480-277 volt and 208-120 volt 3 phase irrigation pumps I can tell you the connections would not last a season without anti-oxidant paste. I also used to recoat the connections on these high amp applications once a year but never let them go more than two seasons without a recoat.
With aluminum, there is one other worry. The expansion rate is so great, the connection tends to move and wear off minute amounts of aluminum causing the connection to loosen and arc. The expansion also seems to change the shape of the connection almost as if someone hammered the wire and connection thinner.
Finally, are you absolutely certain that the bus bars are actually heavy enough to carry the load? I would take a cross sectional area of the bus bars and compare it to the cross sectional area of the nearest wire gauge to determine the load capacity.
Good luck with the aluminum. It has been my experience that no matter what, at least a certain percentage of connections always end up being trouble over time. Sorry, I should have said something sometime ago about my apprehension, but you seemed so sure of what you were doing.
Also, how did you cure the stripped threads on cell #6 (I think)?
The terminals of the batteries are aluminium.
@@OffGridGarageAustralia Yes. I know that. I have considered these types of cells for myself. To be sure, most of the connections in the big units that I used to maintain were Al to Al or Al to Cu rated. Still, the big problem in my opinion was distortion of the connection brought about by heat expansion. That is why I took them apart on a periodic basis to see what kind of damage was being done and to recoat any bare metal. Some of those big motors were running as high as 400 amps. IE, so much that they had be started by a remote 120V circuit. What is your amp demand?
@@josepeixoto3384 Yes. Have you ever worked around crop circle, AKA center pivot, wells? Some draw down as far as 900 feet with many at 400 to 500 feet. The demand for water per acre can be as high as 6500 to 7000 gallons per acre per day at 0.25 inches per day. That works out to about 117GPM on 10 acres. A 1/4-mile circle that covers around 125 acres will demand around 1400 to 1500GPM at 80% efficiency on a 12-hour cycle. All of that depends on the crop being irrigated.
Using very rough and average calculations because each well, and its applications, is always very different from all others, the horsepower demand will of course depend on depth of well and psi to be maintained. Well head pressure maintained at 160 to 170 PSI will require up to 200HP while 50 to 60PSI will require around 80HP, and none of that involves the free water surface depth in the well. These examples are of pumping out of a surface tank, a ditch, or a pond. There are also considerations for frictional loss in the main line and how many towers are actually in the pivot, adding length to the pivot, all of which requires the addition of PSI to maintain pressure at the end of the pivot.
A 200 HP pump can use nearly 150,000 no load watts which comes out to be about 416 amps in a 120-volt line to neutral 208V three phase system or 180 amps in a 277 line to neutral voltage in a 480Volt system (with a neutral in a modified or Star Delta). Use a PF of 1 just for simplicity's sake. In my area, there are many wells that are very much larger than this example.
Very interesting indeed, I’ve ordered flexible copper busbars in hope I don’t have too many issues. I was watching one of your videos yesterday while waiting to pick up the kids and I did have to chuckle as you said at the end of the video you sometimes sit for hours watching your bms, that’s exactly what I do. My wife thinks I’m mad. Was a fascinating video about adding a battery in parallel with a lower state of charge.
There was a bit of a fiasco in the 1970’s in the USA and Canada where new homes were being wired with aluminum wiring instead of copper.
The connections in the various boxes were having heat issues much as you were having.
There were untold numbers of homes that had to be re-wired due to fires and the threat of fire. Some electricians stated “oh we’ll just coat the connections with anti-oxidation paste and that will solve the issue”. It didn’t. The houses got re-wired with copper.
So… I just stick with good ol’ plated copper bus bars and not worry.
Really appreciate the work you’ve put in to your videos!
Change the busbars to COPPER, IMO; experience taught me just that. Keep up the good work.
Thanks, yeah, it might be better in the long run but lets see how the al bars last over time now. We all want to learn here 😉
Copper and aluminium react. Would need an appropriate electrical joint paste
The cells terminals are aluminium. If you join a copper busbar to an alu cell terminal, it will be worse than what he has now.
@@danielardelian2 How so? I can put a temperature probe on all of my copper busbars and they are ambient temperature, no heat whatsoever. The batteries live in totes on my back porch in a high humidity location. 18 months with no problem at all....yet.
Aluminum is a contact disaster.
I always sand the busbars with WD40 so they don't corrode again.
Then I apply noalox to the busbars and screw the whole thing together.
Since then it's been quiet.
Grinding alone only improved it for a few weeks.
Greetings from bavaria =)
Great Video. This video and the last video should be a must-view for anyone building a battery. The high currents we deal with require special attention to all connections.
A few points:
* No-oxide is to prevent oxidation but will not remove oxidation.
* That was a great discovery about the raised lip around the edge of the busbar. When the busbars were cut (or stamped), it probably raised the edges around the cuts.
* You may want to hit the cell terminals with a wire brush right before you install the busbars.
* That is a good point about the aluminum bus bars not bending as easily as the copper.... Another reason to use copper.
* I am not very surprised about the difference in current on the lines to the BMS. The current ratio will be inversely proportional to the resistance ratio of the two lines. Just a little bit of resistance in one of the crimps or connections can throw off the ratio.
Thank you. The aluminium busbars are laser cut, not stamped, so I was surprised to find the edges been raised a bit.
@@OffGridGarageAustralia Interesting..... It must have bubbled up a tiny bit along the cut.
Very useful video.
PS: To avoid IR reflections, you can put a small patch of electrical insulating tape on the busbar and measure the temperature with the IR camera on the electrical tape
Yes, thank you, masking tape or electrical tape does the trick indeed.
What about a permanent marker?
or just a quick spray with some matt black paint
If you want to go a bit crazy on truing the surface place the sandpaper on a sheet of glass before sanding. That's what I used to do when truing CPU surfaces and heatsink surfaces before applying thermal paste.
Ah, yeah glass would be optimal. I have a mirror tile which I could use. Thanks for the tip!
you are doing all the hard work for everyone thank you !!!!
Thanks a lot for this comment!
Congratulations! You shave the problems away one by one 🙂
The bus bars that still get warm might have similar issues on the poles of the cells. They should be deoxidized as well.
BTW: You may use the sandpaper and grease at same time. Then you will have even less oxide. Proof is that you can solder aluminium foil quite well if you apply oil or grease and rub with the soldering irron.
Regarding the blue cables: Good practice will be to put one lug on bottom and one on top of the bus bar. Then they should behave symmetrically.
Thanks Johannes. The two busbars are getting 1-2° warmer than the rest at ~90A, so I'll leave it as it is for now and see how this unfolds.
Yes, sandpaper plus grease at the same time, then wipe it off with grease to exclude any air exposure.
That's a great idea with the blue cables but the black ones on the other side work just fine with the same connection method 🤷♂️
While it is true that the oxide forms very quickly, it's only the first 4 nano meter that forms almost instantaneously; the deeper oxide takes a lot longer, so adding no-oxide right after sanding is fine. Incidentally, your experience also shows the reasons to use a conductive paste such as MG847 or silver based compounds: it's to make a uniform connection between two contacts when they might not be fully 'flat'. The paste fills the 'gaps' between the two contact areas.
Thank you for substantiating the theory. I have used MG Chemical 846 C Compound in many electrical joints. But I detest the item to the hilt, due to its unauthorized spreading on digits, even though Nitrile safety gloves were used. Thanks for the similar thought. Have a nice Sunday evening. 73s…
031322/1433h PST 🇺🇸
So is it MG847 vs MG846?
@@OffGridGarageAustralia MG847. MG846 has higher resistance: 63 Ω·cm vs 23 Ω.cm. MG846 is silicone based. MG847 also doesn't 'bleed', that is, it stays put.
@@OffGridGarageAustralia By the way, don't just take my word for it. Check out Ray Builds Cool Stuff on YT, a few video's back he's trying various methods, measuring terminal resistance etc., and ultimately settles on 847 as well.
We used to have a similar problem putting epoxy coatings on lead, where an oxide coating forms instantly. The answer to apply the epoxy (or conductive paste) and then immediately scrub and massage with a metal bursh, through the unset coating. Now the metal is on bare metal, not oxide, and can be finished or bonded.
your making good points for copper busbars .....
Maybe, maybe not. I'm experimenting and learning😉
@Off-Grid Garage well Im glad mine are multi layered copper, especially in a mobile application.
Glad to see you have sorted out the issue, with lots of people calling out the use of aluminium bus bars, I have to agree. Andy you need to use pure gold bus bars, skip the tinned copper, go all in 😂. Keep up the experimentation, it would be boring if it just worked first time.
Thanks 👍 Gold, you reckon? I'll see if I can find some on AliExpress 😉
@@OffGridGarageAustralia If you can't find it on Aliexpress, A 10 oz gold bar is around 27.5K AUD at the moment from the Perth Mint, you might have to make your new bus bars a little thin 🤣 keep up the great work 👍
Depending on the type of aluminium, if it is extruded, cut from sheet, cold rolled or formed it will form an oxidised surface within 20 minutes of manufacture or working. This is well known in the marine industry where many boat hulls are made from aluminium. Also, not all aluminium is the same you need to be aware that the resistance of some aluminium is higher than other types. It is not all suitable for bus bars. The higher grades are better but not perfect. Use Copper for bus bars. Yes it is more expensive but it is also more conductive and does not have these issues.
I get soft copper tubing and smash it flat. Very inexpensive way to get all copper buss bars.
@@geraldkoth654 any issues with the bare copper to aluminium battery terminals?
They used 5005 aluminium for these busbars.
Personally I would ditch the aluminium in favour of tinned copper.
Aluminium is not a good choice for low voltage application’s unless it’s welded.
Why do you think it's not a good choice?
Because my tin plated copper bus bars were cool as cucumbers after several hours at 90-100A today.
@@OffGridGarageAustralia there’s too much chance of oxidisation on aluminium leading to high terminal resistances and temperatures, I have had nothing but problems the same as you with my battery using aluminium, changed to tinned copper and no problems.
I really appreciate, I have never thought about bus bars being flat until your issue.. very cool idea to sand them and see how flat they are. This is positive news
Abshir
Good video. I noticed years ago that modern 3 pin Australian 3 pin 240V etectrical plugs, now had pins that were stamped out of sheet and not accurately cut from engineered strip brass. The punching meant the nartow pin had a curved cross-section, and so like your busbars had a lip next to any edges. This resulted in a very narrow contact area. If the attached lead had 1 sq mm or 1.5 sq mm cable,, the heat wasnt conducted away, and pins and plug got burnt.
I also noticed some of your thermal shots showed the nuts snd studs were the hottest parts, meaning they were the conductors. As you probably know stainless steel has only a few percent of the conductivity of copper so is not good. So any improvement in inter-cell or post connection, is worthwhile. As 25 x 6mm is a common Aluminium extrusion, and i cant see why with increased cell sizes these days, and little limitation of vertical height or space on cell tops, more robust links are not offered or manufactured. 150 sq mm is great. I made some for a 48V set of 460Ah cells i acquired a few years ago.
Once again, great work on your reports, many thanks.
Thanks a lot for your feedback and kind words.
I think the next time I'm going to build such a battery, I would go with flexible busbars. More expensive but a no brainer when it comes to small movements or unlevelled terminals. Saying that, I had no issues with the standard bus bars which come with the cells ever. Also the aluminium bars I have installed without any conductive or anti-oxidant paste as some suggested, are working perfectly fine.
Incroyable cette resistance d'oxydation et comment elle peut influé sur les cosses ainsi que sur la batterie ! merci beaucoup Andy hâte de suivre les prochains épisodes...😊
Right at the Moment I'm installing the Electrics at my RV. After your Video today I was testing my Multiplus 12/1600 with around 1200W. I did not reach 100A load on my LiFeYPo4 selfmade Battery but I right away checked all connections for any heat! And thanks to you and this Video, I found a not perfect fitting connection in my Installation! 😳... This just heated up, so I needed to clean and tighten things correctly.
In the end, I did not thought that such monor things could be so crazy bad. So Thanks!!!! It helped a lot to stay safe!
Andy..you are amazing on attention to the details. I have experience issues with busbars before and resorted to same solution as Mermaid Lady. Your test was so scientific that made me to rethink of my busbars .
Thank you very much. Don't give up and do more testing with you busbars. I'm sure you can find out what's wrong.
I vote too to change the aluminum. Aluminum is a very reactive material it oxidate instant
It seems to be fixed for now. Lets see what time does to these connections.
When I used to polish fibre optic leads, the instructions were to polish in a figure of 8. This did make a difference when using the £5000 tester for loss. Maybe its the same for busbars for uniform flatness., 👍👍
That is a pretty standard technique for lapping parts in the engineering arena.
Mostly you want random movement, a figure 8 "pattern" gets close without being tedious.
Andy, have you thought about using copper crush washers between the plate and the terminal? They use these types of washers in the automotive industry as a liquid seal (eg. oil sump bolt, banjo bolts). As the name suggests, the washer will squash down to mate up to an imperfect surface.
An item that was not looked into - how flat/smooth is the terminal face on the batteries? Making the bus-bar dead flat is great, but if it is then bolted down to an imperfect battery terminal then the hard work is lost.
Can't wait to see your fix
I make all my busbars out of 3mm copper. It's not cheap, but they barely get warm with 100amps running through them (hard to notice any additional warmth to the touch).
I got a set of buss bars from Paul. They are working great for me. Other commenters are saying ditch them. I say NO. The terminals are aluminum anyway. There is always going to be a greater chance of issues with unlike conductor minerals.
I find them great as well. Some comments here don't provide any explanation why you should not use them. I think they heard Al is not as a good conductor as Cu and therefore should not be used. They may not quite understand...
Nice spot. I'd have family telling me how they "know" it should work, but it does not, so it must be some other imaginary thing. Like they'd guess at the metal being poor quality or something.
Lots of guessing, but no actual testing. So great you actually checked, tested, and found a solution.
Leider habe ich dieses Problem vor dem Einbau meiner flexiblen Busbars auch festgestellt, da ich misstrauisch war, ob die Fläche vernünftigen Kontakt gibt. Habe ich mit diesem Sandpapier geebnet, und dabei festgestellt, das es Probleme gegeben hätte. Danke, für dieses Video, es bestätigt mein Vorgehen….. liebe Grüsse nach sunny hot Australia.
Dieses Problem hatte ich vor einem Jahr, und mein Akku funktioniert seid dem super.
Pure copper bar and make your own. My thought is that you have to make the aluminum bus bar so thick to carry the current that when you torque them down they are so stiff they can’t conform to the terminal differences between cells. Just my two cents
Pure copper would be bad on the aluminium terminals of the cells.
The thickness of the aluminium bars is certainly one problem to get them flat on the terminals. But the main problems where the ones I showed in the video.
I think you hit the nail on the head, it is a mix of three issue
1. Build up of oxide on Al.
2. Thicker Al busbar is not flexible enough to ensure good contact over whole area of battery terminal especially to over come the other problems.
3. The bussbar are not perfectly flat, this looks distortion of the flat material as the bussbars are Punched out of flat plate so a bit of local Distortion at punched edges.
I have built a 404 Ahr battery (@12v) from 202 AHr cells and used thick Al bar as busbars for our van. Busbars holes were drilled (and deburred), ends were sawn then filed. Finally I polished the bars to remove the accumulated oxide and installed (I did a bench install and a few weeks later final installed). This was then run at 90A (45A PER CELL as 4S2P) and no heating at the terminals (just the 200A switch gets warm!).
Been running for two trips of 2 weeks each and looking at BMS ((JBD 250A) all looks good. About to repeat 90A load and check no new hot spots.
So no issue using Al for busbars provided prepared right then torqued nice and tight. This not only produces a good electrical contact but also a gas tight contact to stop future oxidation at the Al to Al connection.
Again thanks for the videos.
Thanks for sharing your experience, Ian. Much appreciated.
I will monitor the situation over time with mine and see if the problem comes back. It did with the old battery and re-doing all busbars was ever only a temporary fix.
I love your batt box off-the-chine
Good to see you made some improvement with the sanding. I guess you'll find out in time if they hold up.
Hi Andy. Why are you stuck with aluminium. Why not copper, nickel or even appropriately sized stainless steel. I'm afraid even your perfectly sanded busbars will reoxidise again.
Horse Dead Beating
I'll copy the answer from the comment above:
To learn, to understand and to experiment.
I could have bought a ready built battery, right? It would just work.
It's a DIY channel after all, so we experiment.
Andy, I'd like to tell you that I find 4 Nm too soft adjustment for such a thick bar to make proper contact. May be increasing torque would save u time and work. Up to 8 Nm that assembly is more than safe to tight. Just a contructive opinion.
Thank You.
As I told in a comment on the last video: Do not use a washer alone, use a serrated washer, to cut through all oxides, a washer and a spring washer to keep the force constant over temperatures...
The washers are only applied from the top. I think there is a misunderstanding here: 99% of the current will flow from the busbar to the terminals directly and only a very small amount thought the actual stud. The form and type of washers will make no difference of the connection underneath.
I think a serrated washer could risk worse contact if it's not fully compressed.
@@OffGridGarageAustralia But even if the serrated washers have not much effect, the spring washer will keep the force constantly applied.
@@the78mole yes i think a spring washer is essential as alum has a fair bit of thermal expansion.
@@the78mole That's what I use the flange nuts for, right? They have the same effect.
Thank you
Essentially, the rigid busbar doesn't always make good contact due to the slight angle when tightened down. The crimp ring lugs on the other hand are independent and able to make better contact due to the flexibility. My EVO batteries came with 2 layer flexible busbars that can mate with the terminal more easily. Thicker isn't better. What the manufacturer did was use two thin layers one of top of the other to carry the amperage. They are fastened in the middle with heat shrink tube. I highly recommend this or use of the ring lug to connect your batteries.
Looking good. I sand my terminals with inox on them while I sand them.
Yes, that would be ideal and then wipe it of with Noox as well, so there is no exposure to the air.
Very interesting, thanks.
Thanks David.
This is where I would be trying copper washers!
Not only are they good conductors, they also make good gaskets which once cleaned, won't allow air to get in between the contract surfaces....
Andy, you are making me laugh!😂
Interesting. Never would have thought to much of bus bars but for sure I will be testing them when I build my first pack in a month when the batteries arrive.
I find that applying the electrical grease to the sandpaper directly. Then I wipe them off with a paper towel covered in grease so it keeps it greasy. I install them greasy and it seems to prevent oxidation since it squeezes the grease out under the contact points of the busbar. YMMV
The less exposure to the air the better, so this is a good workflow you're describing there.
7:04 - A new saying for you Andy: "It's just not cricket!"
¡Gracias!
Thank you very much, Jose! Great support!
nice info
Thanks
I saw in another video that even lugs are not straight and need to go a similar process. Basically one need to ensure planeity of the two connecting surfaces as you cannot apply enough torque to ensure initimate contact. cheers
congrats for the improvement. What is about the contact face on the poles? Are they flat enough? Remember the issues with Al wires in DDR electrical installations. The are prone to fail, especially when getting aged.
I checked the terminals in the last video. And they seem to be working fine with the copper bars coming with the cells.
Andy, it most likely does happen to a lot of people, but they probably don’t stare at their battery with a thermal camera every day to find out lol. If I say ouch when I touch them, then I know they are too hot, otherwise, I just keep sendin it.
Actually, in all honesty, I have temperature sensors every 3rd busbar connection. I check them on my phone way more times than a sane person should. But after I roasted a stainless steel washer, by putting it between two connections carrying 3-400 amps, I constantly stay worried.
Temperatur sensors at the busbars is not a bad idea actually. Could be another great project... 🤔
Another example where less is more.
Using the cheap bus bar would probably have worked out of the box, while those fancy aluminium bus bar are just a failure.
Shinny metal will reflect heat! And can show as hot in the thermal! 😎👍
I commented before about the flatness of your mating surfaces. I am curious as to why you haven't checked the factory surface of the cell terminals. Given the inflexibility of the aluminum bars, any unevenness on the call terminals will work against you as much as the bus bar irregularities.
This is a critical topic here to raise awareness, no matter the configuration. Great job Andy!
Thanks. I checked the terminals as well but as they worked with the other busbars I was more focusing on the al bars and found the light sanding seems to have removed the oxide as well as uneven areas. But there could be more and time will tell...
Try the 4 GA busbars that Maddie sent you and test them using the infrared camera. If they don't heat up, then they are plenty thick enough.
I found them a bit stiff, they push my cells apart.
If a pure silver foil of thickness 0.3 mm is screwed between battery and copper plate bus bar will show least ohmic resistance so do it and see differences ....
looking at the marks left after sanding they look like they have been pierced and stamped out of sheet material on a press (seen this many times as a toolmaker) they should be planished after the stamping process to flatten the surfaces, looks like the planishing pressure was not high enough, even better would be to grind the faces flat and parallel on a lumsden grinder, nice job identifying the high spots giving a very small contact area.
just watching the battery install again and noticed the caption saying "Laser cut", didnt see that the first time round. must admit not seen this from laser before - every days a school day 😁
gold bus bars and your problem is solved forever 🤣
I get some out of the basement 😂
thanks tanti saluti dall'Italia👏👏👏👏👏👏👏👏
Heya well it looks like you solve the problem hope that it stay good now
Thanks Andy, Looking at the nickel plated copper busbars, these are hard drawn copper which is not soft in any way, just as an idea you could heat the copper busbar up to a high enough temperature that would anneal the copper and soften it up, similar to when you buy copper tubing in a coil that is easily bent, you wouldn't know how flat the post on the battery was either, you could even try thin annealed copper washers between the battery post and busbar, in the early days many engines had copper head gaskets that you would re-use after annealing them again over a flame
Oh, wow, now we're really getting into experimenting. I like it😁
Then cover it with tin. There will be an even more plastic layer and less corrosion in contact with Al.
I don't know if you saw my other post, I have seen a fairly good price on nickel coated copper braid flexible bus bars at £40 for 15pcs which I thought was good in comparison to the others I have seen of the same type.
"Minerals Official Store" on AliExpress have them listed as "Tin plated copper braided strap M6" with various thicknesses.
I've got exactly these bus bars incoming from the Mineral Store on Ali. I ordered only one though as they may not fit the batteries as some of their customers said.
I have also been using aluminium busbars, both on a 32 cell battery pack and with Victron batteries in a motorhome with no problem. My systems have two differences which might be significant.
1. I made my own busbars from lengths of flat bar. I did use Andy's test using fine sand paper to check flatness and they are absolutely flat so checking the source material for flatness is important.
2. So far I haven't charged or discharged faster than 50A but typically have charged and discharged for periods of over 10 hours without any appararent terminal post heating. I do not have a thermal imaging camera but as Andy demonstrates any significant heating would be discernable by touch.
The motorhome has been using lithium batteries with aluminium busbars for 3 years now and the 32 cell pack has been running for one year. Normally problems will show up within that time so it seems to me that the quality of connection is more about the specific mechanics of the materials and assembly technique rather than just chemistry.
@10:50 I would keep an eye on that, I wonder if it is due to poor crimping on the terminal or poor connection inside the BMS.
I bet it's the crimping as the P- is connected the same way on the other side and is fine.
No, it's incorrect assembly of the termination. The two wires' crimps should sandwich the terminal busbar between them so the contacts are identical. As we see them there are multiple higher resistance paths throught the terminal screw and washers and from one crimp through the other.
It would be interesting to test at 150% of normal max, or ideally 2x normal max. In other words, if your BMS limits to 100amps (fairly quickly shuts off), bypass the BMS and test for 30 minutes at 150 amps or 200 amps. Starting with the battery fully charged, a 200 Ah or greater battery should have no problem at 200 amps for 30 minutes. That will show any heating issues more quickly, and if it is good at 200%, it will be good at the normal max.
The BMS can deliver 200A constantly or 350A for a few minutes.
If I can see no more heat building up at close to 100A, that's good enough for me as I will never draw more power from these batteries. In fact with 2 more banks installed, it will be close to 40A max per bank for now.
Andy your findings are great information, and most certainly very worthwhile as a reminder for us all to be extra careful when assembling our battery packs.
However have you calculated the energy losses across your original set up, my point would be that I don't think you had a significant problem in the first place, or even a minor problem as far as energy losses are concerned, nor a long term problem either!
That is correct. I didn't have a problem with that with the old battery. And it will get better over time once we install the other batteries in the shelf. The current will split up into 3 or 4 batteries. I'll monitor it anyway, so time will tell....
Battery terminals are not all the same height, could be off just a little causing uneven contacts. Flexible connections/bus bars you don't need to worry about the difference in terminal heights
Yes, that could be the case. The aluminium bars are rock solid and won't bend at all to such tiny differences.
Thank you for your TH-cam channel. I am in Mundaring WA and have start doing things very similar to yourself with working towards a small off grid power system for a tiny house design for my future living. Question for a simple off grid would 24v be better than 48v. I have been going over pros and cons like running lighting, fridge and other things straight from battery rather than using a inverter to run everything on 240v, or would you think just going 48v and run standed equipment on 240v AC?
Don't use washer mate, really from my 22 years of being a technician in the military. I am using a straight file on my busbars, Andy.
I go with the copper camp. I also only use brass nuts, bolts, threads and washers with battery grease on all terminations. When I worked on multiple aluminium 1000A busbars we always cleaned the bars first using a wire brush and Vaseline together. Then we did a drop test across the connection using high current and checking for any potential across the joint. Any potential and we started all over again.
The best way to sand is in a "figure eight", says a retired journeyman tool and die maker. It takes a little practice, but will give you the flattest result.
I'm sorry you had a problem, but also glad. You've saved me and others because I was totally unaware solid aluminum busbars would be a problem. I haven't bought anything yet, I'm just about to, so you saved me a lot of time and frustration. How often do you think you might have to repeat this process?
It's not really a problem, it's more an experiment over time. I should be good now. Not sure if the oxide layer comes back at some stage, some say yes, some say know, so I have to find out, right?
Non-flat surface at contact area of busbars and cable lugs, no matter of its material - it is permanent pain for installation. It is a "byproduct" of its manufacturing process with pressing and cutting operations. The same problem is for power semiconductor heatsinks.
Hi off-grid garage I recommend you use aluminium foil in England this is called bacon foil at the top and underneath the link
Nice video Andy. I think it is always combination of things. What i'm worried is what will that Al busbar do over time..It is pretty critical how much you tightened it and hod plane is your busbar..S i would try to put some temperature probe on one busbar and leave it for later one and check if it will increase in temperature over time..i would go for those cables..even if you have to make your own with lets say 50mm cables ..I think this might allow flexing and also less likely Al will melt..or how is that process called as AL will usually change shape once it is under constant pressure.
I made my busbars out of the left over alloy C channel lengths and just cut them the length of the pack with a circular saw and drilled holes in the right spot then sanded them by hand and put it all together, I had none of the tools to test heating etc but two years later my system is working fine. I guess it depends on how much you want to draw from the pack at once though.
Terminal velocity!
Aluminum has an oxide form almost instantly, maybe you can find a soft stainless brush to clean the buss and terminals with, a clean one, and keep it clean with acetone, did you check the voltage drop across the terminal and buss? (I missed the last video!) But I'll watch it, soon! 😜
I didn't check the voltage drop as I cannot measure it. There is no access to the actual terminal of the cell any more. It's all covered by the busbar.
@@OffGridGarageAustralia Maybe you can get to the batt term. Since this is an experiment, how about drilling a hole in the alum bus-bar large enough to put your voltmeter probe through. If the surface area is small then it probably does not matter where the hole is located. But, I would be inclined to position the holes at the extreme end of the bus-bar. Good Luck.
Hi Andy, your journey has been an interesting one.
We are completely off the grid and have been for over 15 years. At present we are running on lead acid batteries, 880 amps at 24 volts with a victron inverter. After watching your channel and a few others, going down the lithium road will be the next step.
I'm asking out of complete ignorance, the EVE batteries have aluminium terminals with stainless studs, why is the bottom of the busbars more important than the top, where the nut and washer tighten down on the busbar and do you think over time there would be any reaction between the aluminium and the stainless.
Cheers
Drew
I find it interesting that you have used quality components and displayed excellent workmanship throughout every phase of your build, yet you insist on trying to get an inferior material to work for your bus bars. The aluminum terminals are welded, eliminating the concern over oxidation, but using the same material for bus bars has continually given you problems. There's a reason copper is the standard.
You get better results if you use common soap bar and little water to lubricate the paper (hence wet n dry paper) stops the paper clogging up
If you are interested in tin plating your copper for corrosion resistance, the channel NerdRage has the recipe. It is only tin and S. acid with thiourea from tarn-X silver polish. You just dip the copper in till you get enough in a few minutes coating it. That's it. Just don't store it, it goes bad after a month and won't work. Warmer works better too, it has crystals that need to be melted. Just watch his video, he explains in detail.
Hot tin-dipping will be better (soft layer, good cogesion) and faster.
there is a reason nobody uses aluminium for bus bars. its just not a good idea. you should use your meter to measure the voltage drop between the terminals
I can't measure the voltage drop as I don't have access to the terminals any more.
@@OffGridGarageAustralia It is a shame you cannot reach the batt terminal.. If you could reach the terminal you could measure the voltage drop and tell how good the connection is. Yes, you will have less chance of over-heating when there is less current. However, it only reduces the risk, does not eliminate the problem.
BTW. thanks for making these videos. They are a good thing for everyone considering doing the same thing or are simply interested. Please keep it up.
@@OffGridGarageAustralia just probe the nuts, they are connected to the studs and will probably give you the actual voltage
Andy Congratulations, you have found the root cause of the "candle terminal"
problem. However, a more complete solution must include the Al cell terminals
to be de-oxidized. I use a small wire wheel brush in a cordless drill followed
quickly with an application of dielectric grease.
A torque of 8 Nm is required with cells that have Al threaded terminals. 4 Nm
torque is not enough. Newer cells with laser welded-on bolts can be torqued to
10 Nm. However, laser welding bolts to cell terminals is frequently done to
cover up that they are not new cells. The amount of deception associated with
Lifep04 cells are shameful (are you listening china?).
My full year's experience with this build: PIP-8048MAX inverter, 20 Trina 405W
solar panels, JK-B2A24S20P BMS and 32 (2P16S) Lishen 272Ah cells with 20x4 mm 4
hole Cu bus-bars. I feel 2P16S build was a mistake. My next build will be
1P16S x 2 or more. The 2P configuration makes it very difficult to identify a
weak cell and/or replace it.
My early experience with this build is with 3 Daly BMS's. My experience is very
much the same as yours: They are not suitable for a solar system, plus their
marketing is suspect - I.E 100A is not equal to 50A, especially in solar systems.
The below comments probably apply to 50+ Amp charging/discharging. I don't
think these problems will exist in a 3KW or smaller solar system.
If anybody disagrees with any of my comments, I would be pleased to hear with
metrics, rationale, or experience. I can supply all of that, but it will require
a lot more text space than I have here. I welcome learning more and being wrong
about this solar system.
I have been fighting (and very frustrated) by this "candle terminal" problem for
about a year. BTW, "Ray Builds Cool Stuff" calls it a "runner", because the
symptoms are a week cell, I.E one cell will overcharge and under discharge
(with active balancing). Ray will soon have the "loose nut" problem again. I
think this is due to the side force on the terminal bolts when the cell (cells
in compression) will expand during charging. (I ruled out temperature as the
reason).
I have to loosen, then tighten terminal nuts (8 Nm) every month. Easy to spot
with a finger, because the bus-bar is not cold. I am experimenting with a
flexible Cu bus-bar. The preliminary results are good. However, they are about $7
apiece. I think cable or braided "bus-bars" will have too much resistance if
the size is practical. (AWG 0 or 1 Cu or bigger Al)
The flatness of the bus-bars, level across the cells, and Al vs Cu bus-bars are
a small part of the problem. A mirror surface on the Al might be more of a
problem than a solution because it is oxidized.
Some people believe a warm terminal is not a problem because the voltage drop is
very small compared to the 54 Volts of the battery. That is true, but the
voltage drop from a warm bus-bar/terminal really screws up active balancing (see
below).
I found that a high 50 mV cell difference should be set to trigger the
balancing. Balancing in the middle of the charge cycle can actually unbalance
the cells. This setting will achieve a top balance (it would be nice if the BMS
could turn off the bottom balance).
A conductive grease is not as conductive as solid Al or Cu. Oxidation is the
real culprit. I am surprised how small the apparent contact surface area can
be. I guess a few molecules of Cu or Al do not have much resistance - which
suggests the pressure of the contact surface is more important. My measurements
of two 20 mm wide bus-bars connected together with a 6 mm SS bolt/nut have a
resistance about proportional to the torque up to about 4 Nm. After that, the
resistance falls to about 25 u-Ohms. The 70 mm long bus-bars themselves have
about 20 to 70 u-Ohms resistance. I have seen a shiny but oxidized Al connection
to have 500 u-Ohms. That produces a bus-bar dissipating 10 Watts @ 100A with a
voltage drop of 100 mV between cells. That voltage drop will confuse a BMS a
profound amount and heat the bus-bars. BTW, I found a washer and a more
conductive bolt than SS will not be a significant help. It is the pressure of the
connection and lack of oxidation that is significant.
These comments are from my many hours of experimentation/frustration using
professional quality test instruments. I.E. I can measure down to a micro-Ohm
accuracy and a 0.1 u-Ohm resolution of a terminal connection.
Thank you Andy for your honesty and willingness to share your mistakes. That
makes you unique in the TH-cam world. Please avoid the temptation to edit that
out. Your mistakes make me feel I am not so dumb. -doug
As a future builder (waiting for stuff to arrive) and avid learner, I find your description, method and reasoning amazing.
Thank you for the effort you put in the text above.
Do you regularly share your thoughts on any forum?
Would love to go by your opinions, thoughts, doubts, etc.
Again, thanks for your above comment!
Also, one question: you mention you have to re torque your bus bars once a month for optimal performance. My battery is meant to be in a closed metal box (fire security) in an RV, so a.much more harsh environment.
Is there a way to mitigate the need of re torquing?
Thanks in advance
I always use copper bus bars we live off grid and run 80 nickle iron batterys.
The problem with those bus bars you can get thermal runaway and cook your batterys.
Hi Andy, which thermal camera are you using please
The unbalanced current in the BMS cabling is likely due to incorrect assembly of the termination. The two wires' crimps should sandwich the terminal busbar between them so the contacts are identical.
As we see them there are multiple higher resistance paths through the terminal screw and washers and from one crimp through the other.
On the other side of the terminal, the crimp should be under the terminal busbar to keep it level.
Hi Andy. Would be very interested in seeing you compare aluminium and copper resistance.
Thanks
Try to find older Andy's video.
@@lubomirremiar8952 I have seen all his videos...
The Aluminium bar has a lower resistance: th-cam.com/video/mdr5HZZRaTc/w-d-xo.html
@@OffGridGarageAustralia thanks. Could not remember this one. Seems like I have not looked well enough... Will see this again.
Thanks you very much sir!
Keep'em coming!!!
@@ricardomarcelino8388 Thank you!
Stick sandpaper flat to surface pkate and sand in a figure 8 pattern for and even result.
I was thinking you could put one of the BMS voltage input (blue) cables on the bottom of that little bus bar and the other on top. That way they both have the same contact surface on that little bus bar. And, add/move washers appropriately on the other side of that bus bar to make sure the little bus bar is level.
I can try but I think it the crimp of the ring terminal. I don't have the issue on the other side with the same connection method.
I was impressed with those busbars so I tried to order some of them for my project. PowerPaul won't ship to the USA :
Maybe not any more, this was a while back when I showed these bus bars. He said something about complications to send them overseas...
Maybe a softer metal washer that acts like a gasktet ...like copper in between the battery terminals and busbar might help?
Measuring the voltage across the buss bar would work too. Measure the voltage drop between cells.
I'm pretty sure that I am about to buy the exact same kit of batteries except with their choice of BMS and balancers... It looks a lot more involved wiring it up than expected but possibly that's just because of your choice of BMS....
The bars are probably uneven from the hole being drilled into them, I always use a counter sinker to clean up all of my holes when I drill holes at work in aluminum... Nice monitoring with the heat gun though. That has me worried that I should also have one as I am firing up my solar system for the very first time soon.
Heck get some 2 gauge cable, silver solder the ends hammer and sand flat drill a hole for the terminal, it should be a perfect buss!
I would not do that, far too much work. I would rather use the copper bars coming with the cells.
Just go copper bus bar Andy and be done with it. 👍
But what would we learn? You may know, I never go the straight way 😉
@@OffGridGarageAustralia yep you’re right, I’ll keep watching from Sunny dry South Australia. 👍
You should do this on a thick piece of glass, also use a full sheet of wet and dry and do the entire surface, move it in a figure 8, that removes the metal evenly. Better still do not use alloy for this job! Good luck. Edit, a good glass is an old oven door glass. Also much better to use some lubricant, a mild dishwashing detergent in a spray bottle to keep things moving nicely would suffice, when doing steel use DWF.
I'm wondering if the bus bar ends are pressed, to assure flatness, sanded, cleaned with acetone, then greased, if that would make any difference. Might want to consider sanding the terminal bases with 800 grit. It appears the circular sanding did the trick.
So far so good. Lets see if it lasts.