Charging LiFePO4 with different currents - Efficiency INSANE!
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- เผยแพร่เมื่อ 8 ก.ค. 2021
- In today's battery test we will charge the 100Ah LioFePO4 cell with different charging speeds and see what the efficiency is, when we discharge it again.
Will the efficiency decrease with higher charging current? Will the charge time half with double charge current?
I also show you the efficiency of my battery since I installed it back in January.
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Wow! I am so glad I stumbled across your channel. You explain things so well and I have learned more from watching just a few of your videos than I have in weeks of research. Thank you so much!
Thanls for doing what you do. Our diy community needs more people like you. Thanks for sure
Great test, and interesting results, thank you for taking the time to do this for us.
Thank you!
Thank you Love your complete experiments, takes alot of time.
I've been watching right from the start and I must say the information your providing is top notch and very informative to people building their own batteries. The "bank" pun intended of knowledge being formed is very impressive.
Thank you so much, what a kind comment 😊
I'm so glad I'm following your adventures Andy. Keep it going. I am very much a "I wonder if I did this, what the results would be" kind of thinker. You never really know until you try! And I appreciate you actually doing it! I'm sure I'm not the only one learning from your videos. Keep them coming!
Thank you so much Tyler!
Love watching your channel Andy always informative and very entertaining 👍
Thanks, David, much appreciated!
Respect ! Many thanks for your time....
Thank you.
Yes! Very nice use of your tools. I like tests when the proper equipment can verify. A+
Thank you, Chris.
Andy, you have now been elevated to my favorite professor. Great lab work! Your testing is adding to the collective knowledge and understanding of battery physics for Humanity. Thank you!
Thank you very much, what a nice feedback!
@@OffGridGarageAustralia hi, have you ever try to charge lifepo4 with led power supply? It can be 40A or more but the price is very low.
@@przemek_kw No, I haven't tried that yet, but have seen these power supplies with CC and was wondering if that would work. I may give this a try actually...
These Efficiency's Are Amazing
Andy, Good testing... I realize this took you many hours but as a researcher, I would have repeated this testing for 3-4 weeks inorder to get conclusive data, especially at 27C. That said, you provide a great service and your videos are far more enjoyable than our research papers, just don't tell my partner that! All the best, Andy2
By far and hands down the the best solar channel.
You deserve a thumbs up! Well done ! and thanks for your dedication. Hope you enjoyed your beer afterwards.
Amazing Content..... and the Guitar Sound is always so soothing 😀
Very Very Informative and well put together Video and amazing editing as well
Thanks a lot Bruce!
I have been waiting for this one.
I've got your suggestion and request here too. Coming soon...
Wow, another great video. Love that you're saving all that info to your site. Long term it will be interesting to see the amount of capacity lost from aging. Since your usage over time of that test cell, you aren't really cycling the battery that much so the aging of LifePO4 will be more obvious. They are supposed to lose some capacity per year just from aging so curious what the number is. So with that tester in the future, if you do tests again like a year from now will be interesting to see if you lose a few percent per year.
Yeah, that will be interesting. I did a full cycle test right at the beginning when the cell was new, so let's repeat that once a year to see what's happening with this poor cell.
Great question! Thumbs up and subscribed!
Love your work Andy! Fascinating! (I’m behind on your videos, have been “off grid” and mostly out of phone/internet coverage in our caravan for weeks.)
From my experience I THINK the efficiency goes downhill significantly at higher rates of discharge due to voltage drop.
Welcome back, Dave! We will see, more tests will follow....
Fantastic job work done by yousir... Impressive I could not think about extremely high efficiency 99% of such Lifphos battery.. good representation...hats off to you Sir keep it up.
Thank you very much!
Thanks Andy, Good Test
Thanks Wayne!
I'm excited for the 0.5C, 1.0C, and 2.0C charge tests!
Coming soon... 😉
Thanks
Great test Andy! This confirms my suspicion that the charge rate doesn’t really effect the capacity
Does not seem so. And 0.4C is quite a lot with these batteries. That's 2.5kW on my 50V battery.
great tests...great info. i have recrntly upgraded my garage solar from 170ah batt and 20a charge controller to a 400ah batt and 30a charge controller and was wondering if the increase in charge amps would affect battery performance....now thanks to your test i am feeling good about my upgrade. Thanks Andy
Thank you Arnold. A 400Ah battery and 30A charging is super cool, no issues with that.
Well done on the testing, I think a 1C (100amp charge and discharge) would be interesting too.
Just commissioning a 16s2p 280ah eve battery system now. Used Batrium BMS and all Victron gear. Quattro 10kva and Smart MPPT 450/100 and very happy so far.
Nice!
Good work
you are really lithium battery university. world gets lot of information which every one can't offered.Thanks
Great vid contain as always.. 👍💪💪
Appreciate it!
Well i managed to cut my charge time in half but I did find a problem. Nice thing about testing the limits of your setup, if it is flawed any error you made will become apparent. I checked the cables for heat every half hour, on the third hour i noticed the first 9 inch cable coming off my battery's terminal fuse in-between a kill switch was starting to get very warm. There is another 9 inch cable running from that switch to a bus bar, the bus bar side was cool. I have made the determination i sized the fuse too large on this battery. 300amps is too big for 2 awg cable, the other battery has a 225 amp fuse and remains cool. I just purchased two 175 amp terminal fuses, If the first 175 amp fuse i test on the main battery works well i will also replace the 225 amp fuse with the other 175 amp and use the 225 as a backup. I will be returning the 300 amp fuse as it does not even make a suitable backup. I made the mistake of trying to fuse for my inverter than fusing for my cables.
Super Video 👍
Thank you very much!
boy that is good . using your solar panel alignment tool for multi purpose tool👍😊
didnt know that 2 years ago spat used to calibrate your projects
Could you use this battery tester to top up your battery bank (8S 272ah cells) with a diesel generator when needed, or could you recommend a good battery charger for me, my components are Epever and not sure if Victron would work with my system?
I really enjoy your videos. Here is a question for you. When charging from solar panels, is it more efficient with higher voltage household/domestic panels into a charge controller OR the 12v (12v-19v) panels into a charge controller.
From what I know the domestic panels are around 38v and just added in series to get higher DC voltage. Doesn't matter is you series link 18v panels or 38v so long as your voltage is higher than the battery pack.
Advantage of a mppt charge controller is less loss plus can handle high vdc in so thinner wires needed from panels to charge controller
You want to keep the solar voltage as high as possible to have a low current running so you can use thinner and less cabling (less $$$). The solar charge controller converts this high voltage/low current in the battery voltage with higher current (amps are what is charging your battery). The power (W) is almost the same though.
@@OffGridGarageAustralia Thank you for you reply. I am struggling to find an MPPT charge controller that will run my 2x400w solar panels ( Imp: 9.42A
, Vmp: 32.91V, Voc: 40.25V ) to charge my 12V 400Ah LiofePo4 battery. This solar set up will be going on my van build.
@@drewhodge3820 Victron recommends this controller for your setup: amzn.to/3khDmDY
Have a play here with their online calculator: www.victronenergy.com/mppt-calculator
Great!!
Great test! These batteries are even better knowing this information. One thing I did notice Andy... It seems dark in the OGG when at night there. It is very dark! lol no winter power. This gave me an Idea and something else I have researched a bit. How about integrating a micro turbine for battery charging in the winter? I'm not sure what kind of winds you get but it's a viable solution in parts of the U.S. Just a thought . Ah, now after watching this video I feel very thirsty for some reason.. : )
I'm looking into a small wind turbine for a while. They are not expensive and could add some additional energy. As we live in a valley, it's not super ideal for that but these small 2kW turbines start at around 2m/s so that could actually work...
Very interesting test! Don't understand, why you don't have around 100k subscribers already. You're doing great!
Efficiency should be calculated with Wh not Ah i think. Looks more like 93-96% efficiency. Interesting though that the smartshunt measures such a high efficiency with Wh.
It confuses me, that the smartshunt only shows 8 charge cycles when the charged energy is almost 375 kWh. I assumed 26 charge cycles with your rated battery capacity of about 14,3 kWh.
Greetings from Germany
Thanks Lukas (mein Sohn hat den gleichen Namen 💪).
It will come over time, more and more people will be interested in this DIY battery solar tech.
But you're right, Wh should be the way to go as it includes the voltage as well.
The software on the smart shunt is... kind of smart. If I use the battery at say 60%SOC and do a 10% DoD only, doing this 10 times is not the same as a 100% DoD. It is heaps softer and counts maybe only like 1% of a cycle. Keeping the cells in the flat area of the curve and the DD low will make them last forever.
Andy,
Lithium batteries have a very high Coulombic efficiency (amps or charge in and out) but the power efficiency is lower due to the higher charge voltage and lower discharge voltage which brings the power efficiency down to around 90%.
Dan
Yeah, isn't that true for all batteries though? I have the results of the Wh as well in the video. Next time, I take this into account. Thank you.
99% is awesome! Lead is what 70% round trip especially if charged/discharged hard?
I'd like to plant a seed of an idea in your mind, Andy. It's too early for it now since you are still generating some great original information about LiFePO4 cells. But at some point, it would be cool for you to make a summary video of your key findings (e.g., connecting cells at different SOC in parallel to balance them is fine as long as the cell voltages aren't wildly different) and then a link to the video(s) that back up that finding. It would be a kind of summary and table of contents for your valuable series of videos. Someday...
That's a great suggestion. I should take some notes along the way and keep this in mind. Thank you.
A good learning test, and it won't be too long a test, about hour and half, to understand over-potential kinetic voltage due to cell current. This is kinetic energy used by cell (loss), and is addition to I^2*Rs loss. It is required to support cell current for discharge or charging and has a time delayed decay response.
Start with the 100 AH cell at about 80-85% SOC. You don't want a fully charged cell.
Make sure it is rested at this state of charge with no load for at least five minutes.
With your YR1035 battery Z meter measure cell resistance at cell terminals. Should be around 0.5 milliohms for 100AH cell.
Set your load/charge tester with following sequence. Five minutes for each test cycle with logging data.
If your tester cannot do this many sequences then drop out 10A and 30A cycles or run them as a second test sequence. With 0.5 milliohm cell resistance, 10A only has 5 mV voltage drop so accuracy will not be very good for that current anyway, but the kinetic voltage drop will be large in relation to low current load relative to higher current. This is good to know this voltage drop for low current. As current is increased the relative additional voltage drop will reduce in rate of increase.
1) Run 10A discharge .
2) Run 0A (no load)
3) Run 10A charge
4) Run 0A
5) Run 20A discharge
6) Run 0A
7) Run 20A charge
8) Run 0A
9) Run 30A discharge
10) Run 0A
11) Run 30A charge
12) Run 0A
13) Run 40A discharge
14) Run 0A
15) Run 40A charge
16) Run 0A
Measure cell resistance with meter again. If cell warmed up a little due to 40A cycle the Rs will decrease a little from initial reading.
For each charge and discharge cycle, you should first see an immediate voltage drop for discharge, or rise for charging that corresponds to current times cell resistance, followed by an addition exponential decay voltage drop (like and R-C decay) for discharge, exponential additional rise for charging. For LFP cell the exponential decay/rise should last 1-3 minutes before voltage levels out. Waiting 5 minutes is just to make sure. The level out voltage is when cell reaches equilibrium for demanded cell current.
The 0A cycle between each test is to get back to cell open circuit equilibrium voltage. It should remain the same throughout test.
The net exponential drop for each cycle should increase by the natural log of current through cell. If you were able to go above 0.5C current it would deviate from this.
Knowing the I^2*Rs loss plus the kinetic voltage * cell current loss you can compute the round trip charge-discharge efficiency accurately.
The extra kinetic over-potential drop explains why charging at greater bulk charge current results in longer absorb time as this over-potential voltage reduces as current diminishes. When charging at low bulk current there is less over-potential created so you don't need much absorb time to fully charge. You have to reach about 3.45v + over-potential to approach full charge. In the test you did for this video, by stopping charge at 3.5v you charged the cell less for higher current rates. This added some error to your results. The overpotential losses for charging increases as cell approaches full charge, so for incomplete charge you are not counting the losses by not fully charging.
For LFP, the discharge and charging over-potential should be close to same for same discharge or charge current, respectively. Reason not to start with fully charged cell is the kinetic over-potential to current relation changes between charge current and discharge current near full charge.
Andy, what is the impact of this situation on battery life? Another question is, what will the cellular voltage balance be like in the long term?
Well, we don't know the answer to these questions. In a solar setup, if you charge your batteries with 0.2C, it will be very safe and the batteries should have no problem to reach the proposed 6000 cycles.
I'll do tests with my batteries over time to gain some data.
💪🏼💪🏼💪🏼excellent video good info thanks 💪🏼💪🏼💪🏼
Thank you.
Ive dealt with lead acid since i was a kid. I remember using my dad's 100ah deep cycle to power my backyard playhouse and I could barely draw 100 watts from that thing.
And now I've got my first lifepo4 pack, only 11 pounds, that i can dump over 300 watts into and draw over 600 watts from, and the voltage drop at peak load is only about a volt. I put it in my backpack to go camping.
Of course that is coulombic efficiency. For electrical efficiency, using the watt hour readings, it looks like the efficiency is in the mid 90's. Still, very impressive!
I've got two charge controllers, each capable of 100A coupled to a 10kW array. It's summer here in the North, and 100A+ is common these days.
How many Cs are that for your battery though?
@@OffGridGarageAustralia It's a 2x 280Ah 48V setup, so if I decouple one of them (hypothetically), it can get close to 0.7C (hypothetically). In any case, it was just a response to your 100A remark :)
HELP PLEASE. I have three 12v LifePO4 Batteries. One is 50AH, two are 75AH. Should I buy a 15AMP or 25 AMP Victron Blue Charger? Which is better? Many thanks. (Andy, I love your methodical approach). Kindly consider my question. I think its relevant.
Higher capacity at the smallest charge current makes sense. At the smallest current, battery voltage drop due to internal resistance is small therefore giving enough headroom for an extra charge before hitting the cut-off voltage of 3.65V.
I Purchased four p35 LifePO chargers thinking they would be 5 amps short like the p20's i purchased. I was wrong they do produce 140 amps LOL, I have the battery's discharged right now, i believe it took 5+ hours for the P20's to bring them back after depleted. Of course i was only getting 60amps instead of the 80 i intended with the P20's. I will update with how fast it takes them to charge tomorrow with all four P35 chargers. As of now i cant put them all on the same circuit off indoor power, tripped the breaker. I will split the load so i can get some good charge time testing in. The generator i will have to split the circuits too. I am not sure But i think the single 30amp connection off my DF4500 gen will not be enough to power the fourth charger with the other three. So i will run a separate line to the 15amp circuit of the generator for the fourth charger. The 4500watt gen itself has plenty of power to accomplish the task, just a circuit balancing game.
Great test. Any idea if the rate of discharge current would also effect the efficiency?
I'm not expecting this with these LFP cells. 0.4C is already a lot of current for these large cells and unlike many people will hit this with their solar setup.
Andy, if I read the charts right, you start the discharge right after finishing the charging (you have no wait steps in between) and that might be elevating your results. I did the test according to the datasheet - with 30 minute wait time between the cycles - and I am measuring only 93% round trip efficiency. The voltage goes down a measurable amount by itself when the battery is in rest and you have this part of the discharge cycle, while I have it outside.
And actually the fact the you look at the Ah might be a problem as well because the voltage is not constant during the test. Current at higher voltage gives greater energy so comparing Ah at different voltages does not give a meaningful result. In the first test you have 107.22/109.34 == 98% in Ah but only 345.7/363.69 == 95% in Wh.
Is it better for the battery if I set it up to charge up to 90% via the BMS which has a bluetooth or leave it to charge to 100%? It will be used every day.
Can you recommend mppt voltage charging settings for 12v lifepo cells system
Yes, I will do a full series of all my settings soon here on the channel.
@@OffGridGarageAustralia Ok thank you
How many amperes need to charge a Lifepo4 24v 100AH batteries?
Andy I love to watch your videos which motivate me to built my on lifepo4 battery so I make 12.8 volt 60ah battery bank by using 40 cells with 6ah capacity of each cell ...start charging battery with 14.5 volt with 7 ampere charging current but still my battery accepting only 2.50 ampere charge current .... Why ? Please make video on this how to fast charge lifepo4 cells / battery ?
If your batteries are taking less current, they maybe getting full. It could also mean you have bad connections and a voltage drop somewhere. Very hard to tell.
Fast charging means you don't exceed neither the max voltage per cell nor the max current each cell can take.
I did similar test to my lifepo4 pack but if I look at the current then the efficiency is over 98% but if I look at the total power then efficiency is around 90%, I didn't get why you calculated the efficiency with current and not with power?
Hi Andy, can you show a how-to for dummies using that charger. I bought one and, of course, Chinese instructions. I have tried to understand the setup by watching you and others, but reckon I'm just plain dumb?
Isn't efficiency power in vs power out not Ah in Ah out?
Of the total system, including losses in wiring etc. - yes. If you just want to test the efficiency of the LiFePO4 cell, Ah works perfectly since it ignores those losses and only compares the Ahs going in the battery, and the ones you get out. That's also why capacity tests are done in Ah - since losses in cabling don't matter, whereas if you were to do this in Wh, they would matter (voltage drops over every connection, wire, etc.).
You can do both tests and they will show a greater loss when using Wh due to the cabling and resistance involved. This one was for the pure cell chemistry.
@@upnorthandpersonal I should imagine there's also loss in the cells which is why they often get warm when being charged. Charge rate could affect this.
@@colinhercus7765 At these rates I've never had a LiFePO4 cell get warm. In any case, those losses are very minimal since the internal resistance is so low. I still think Ah in/Ah out is a good test for the LiFePO4 chemistry without having to account for other losses. It shows the efficiency of the chemistry to absorb charge and how this changes with charge rate (i.e. almost doesn't).
very interesting test ! Amazing efficiency from the so called not so good as Made in the US batteries.
a nice OGG hoodie would be very efficient
It is cold here ❄
Is there some efficiency value for the (Charging Rate X Time to charge) ?? It doesn't seem to match the Charging Capacity AHs. (i.e. 5 amps for 22.00 hrs = 110 AH and 10 amps X 10hr.10 min = 101.6 ah [6 ah missing?])
To be more precise, I would need to repeat each test say 5 times. It just shows there is no downside when charging faster or slower (except of some small added degradation).
Andy, I'm a huge fan! I have watched hundreds of hours of your channel and learned so much. Thanks for all the hard work.
On the subject of work, I haven't figured out what you do at your day job. Is it a secret? 😉
Thank you very much, John. And I appreciate all your comments here on the channel, Always great to read them!
I'm an electrician by trade but have always worked in the ICT industry, electronics, hardware, software support, all kind of stuff. But my heart is the electrical and electronic side of things. I find really great joy in cabling stuff and creating/building things. Creating videos is on of these very satisfying things, I now do for many years. It's a s**t ton of work but the feedback is always the greatest reward. Like yours today for example 😉
Super good test! (Thanks a lot for this!!!!). Can you do the same with a lead-acid battery? Then we can also change our minds for the new technology. Grüße aus dem verregneten Sommer in Deutschland
I could do this test with the AGM batteries I have. They are limited in charging/discharging current though. I'll think about it how I could do that.
Meine Mutter hat gesagt, es is so heiss. Wohnst du wohl nicht in Nordhessen...
Out of interest I would like to see on maybe a small cell what happens if it gets overcharged. Yes it will get some damage but how will capacity fair after..
I now have 12 D-size LFP cells here but don't really want to do such testing as we all know the cells will suffer.
Eine Gegenüberstellung vom Coulomb-Wirkungsgrad und den Energy Wirkungsgrad (Wh) wäre interessant. Kannst du die daten noch liefern? Dein Gerät zeigt sie ja in Wh an. Der Energie Wirkungsgrad ist immer schlechter auf grund der Polarisierungs Aktivierung ;-). Und hier sollte der Wirkungsgrad bei größeren Strom auch schlechter werden.
Efficiency of Charging should be based on the energy,not just the current. All numbers based on that are lower.I think other factors played a role since there is no clear trend. As you mentioned battery temperature may affect your results and from my experience DC current sensors are often slightly impacted by temperature as well
If you measure in Wh, it totally depends on the connections and cables as well. This was a test considering the pure capacity which blends such other factors out. In the next test I do both but 'm expecting the results will vary as well because of different connection quality from the tester to the cell.
@@OffGridGarageAustralia I believe that would not be the case. The connection to the cell has 4 wires - one set to deliver the high current and another set to measure the voltage at the cell terminals. Therefore the quality of the connection affects only the work the charger has to to but not the measured values.
A Watt is a Watt.. It will be the same.. Why Utilities companies use a Watt Meter...
@@WizzRacing But it's not a watt is a watt. He measured charge transfer not energy transfer.
@@ahbushnell1 You even know what a watt consist of?
It's strange that there's not a consistent trend. I know it would take too long to figure out empirically, but I suspect variables like the temperature are playing a larger role than the charge/discharge rates.
There is a lot of variations in this tests. I probably would need to do each test 5-10 times and then compare the average.
The battery was fully charged when you connected the shunt, right?
so you have consumed 10kWh more compared to charged but it still gives 96% and it is distributed over many cycles and if you were to count as you did, you should lose 1% every time you charge the battery and it is much less loss than that . Could it be that the losses increase as the extreme modes approach (that the efficiency would increase between 3.1v to 3.45v?)
Do you have any thoughts on that?
Heat loss due to internal and cable resistance has to be taken into account as well in a real scenario. This was just a pure capacity test using Ah, not Wh.
For efficiency kw-hr is what is important not the amp-hrs. In terms of energy the current makes a significant difference.
I have a 12v setup on a sail boat. The bow thruster takes 500A. So I've had to size my bank not to exceed 1C discharge. I use 272Ah cells in a 4S2P arrangement.
Yes, that will work. But this is not the only load for these batteries right? The thruster is just for docking purposes...
@@OffGridGarageAustralia Yes there are other loads. Typical 12v loads don't exceed 10 to 20A. But anchor windlass can take 100A and the inverter will regularly take 100A and can take 250A.
@@millzee60 and you charge from solar or shore power?
@@OffGridGarageAustralia Yes, both. I have two Victron 30A MPPT charge controllers, one for each of the two 370W panels I have and the Multiplus 3KVA which I limit to 60A for shore power charging. Hmm, maybe having watched your videos I should up that. But then when I'm connected to shore power it is usually overnight so there is plenty of time.
BTW, living in the UK, on occasion I've seen 400W from the 370W panels :)
Don't you have solar for charging?
ok looking for info on x3 10k solax inverter and if it is possible to use diy batteries and how. anyone with info it would be greatly appreciated if you can help.
I have some 8ah high current cells, capable of 200+ amps continuous, but funny thing, they are well used, and should be in the 6-7ah range, maybe 7.5ah, but after testing, charging at 5 amps. Discharge at 1amp sometimes less, 300-500ma or so, I'm getting 20-14+ah? How is this happening?? Is something up with my ISDT charger?? The cells are 8ah Headway LiFePo cells, is it the low current discharge ya think? Can you do a similar test? Average charge current, with very low C rate discharge.. I can only discharge at 1.5a max, but usually it's half that! Just like charge current, i can set it at 20amps, doesn't mean it will charge at 20 amps, it usually starts at set current, but drops as voltage changes, i guess it's it's the algorithm, can you run a similar test ??
Sure, I put this request on the list. Just received some new cells to test anyways ;)
@@OffGridGarageAustralia thanks!
All the week with same t-shirt, great 😂
I also sleep in it 😉
"100 Amps coming off your solar, how often do you get that?!" forward one year later "It's 250Amp weather today, it's too much, need to limit!!!" 😂
Hey, I am looking to get the fastest possible charge time to save on generator charging on poor solar days. Trying 120 amps on 400ah of LifePO4 each with 200amp bms.
Yeah, that makes sense. You don't want to run the gen for too long.
On the other hand, does it use half the fuel if it runs with half the load only? I know, there is the noise too, but just curious...
@@OffGridGarageAustralia No it won't be half, it will be less but not half. The generator will be sucking down alot of fuel with nothing connected, just with the gen running. So you have all that lost energy right off the start so i guess the point of fast charging is to minimize lost energy and as you know LifePO4 battery's charge efficiently at high amps. So if obviously you have to factor in AH, battery type, and charge rate. If i can reduce 9 hours gen run time to 2-3 hours. There is no way i can lose efficiency doing that. This is also paired with solar, The Gen and chargers are for poor solar days. Also it is a Inverter propane generator, clean signal.
I have seen several off grid folks giving up on solar all together and just building huge 400-800ah LifePO4 banks and they pump 120+ amps into them for a hour +/- and have days of battery power. :-D My camper will have 600ah. dual system lead and lifepo4.2x200ah LifePO4 and 2x100ah lead acid. All brand new batteries, decided to go LifePO4 right after i bought new lead acid batteries. A dual system like this is perfect for me as lead acid is more reliable in a freezing climate and i plan to do winter camping. The LifePO4 will be stored in heated storage so it wont be a problem but it is nice to have the backup lead acid. After the lead acid stop holding a charge they will be replaced with more LifePO4 and probably end up with none outside on the tongue of the camper. I could install separate heaters to put them outside but why bother when i have heated storage already. With the LifePO4 i will not be powering just the DC systems but all the systems with 30amp shore power connection from the LifePO4 bank and inverter. So that will keep the lead acid topped off while using the LifePO4 as its main source of power and when they are low i will fast charge those LifePO4 off the Gen. and solar. The solar will always be charging with a 50amp victron charge controller.
I might run a tv/laptop or a small washing machine/Coffee maker.The inverter has a remote on/off switch and can crank the a/c system but most the systems i will use are the furnace and other DC based systems. If i don't need the shore power I will only use the LifePO4 to supplement the DC system and top off the lead acid bank but I will have it off about 50/50 +/- so that the inefficiency of the inverter are not compounded by running it all the time.
How do you zoom in on the tester
With the mouse, you just click and draw a rectangle...
Wouldn't it make more sense to compare the amount of energy (i.e. watt-hours instead of amp-hours) as a measurement for efficiency?
Depends what you are testing for. Wh include the voltage and are dependent on internal resistance, cabling, and contact resistance. Ah are the pure capacity. All batteries usually have the Ah as a fixed parameter to compare with other batteries.
Great Test! What kind of test could you perform that would show when the battery is full so you don't overcharge it. Say your battery has a capacity of 109 Ah. With a voltage of 3.65, what is the current when the battery hits 109Ah. That would be the point where you stop charging. You could do this at 3.6v, 3.55, and so on.
When the current goes to 0, or near 0 your battery will be at max capacity.
@@BradCagle Full charge takes place when the battery extends to the voltage limit, and the current drops to 5% of the rated current (.05C or C/20). Anything below that overcharges the battery.
@@SpeakerKevin Fully charged is when the battery stops pulling current. You cannot overcharge a lifep04 cell unless you exceed 3.65v, you just cant. You don't want to hold the voltage high (i.e. over 3.4 range) for extended periods of time, that's not good for it. I'm not sure where this misconception is coming from, but I've worked with lifep04 cells for over 10 years now.
That is correct, if you don't exceed 3.65V you don't overcharge the cell. there is no current flowing if the charge voltage is the same as the cell voltage. As Brad said, it is still not recommended to keep the cells at 3.65V for long, in fact our past testing have shown you can fully charge the cells at 3.35V without causing any stress or degradation.
@@BradCagle If the cells are fully charged when they hit 3.4V and current goes to zero, How is it that you can go to 3.65V and zero current that the cells are not over charged? The reason for the 3.65V is to speed up the charging process. Chargers generally cut off at .05C so 3.65V was selected to give you a full charge when you reach that amperage. Anything beyond that and you are overcharging your cells.
14:26 Future Andy is laughing at this! haha
13:25-13:40
How does 40A charge current equal 112A? I mean, i get the math of .4*280. But if you set your charge current to 40A, then isnt that actually .14C?
I don't know why people have a hard time understanding that a Watt is a Watt.. So your test is validated. As you used the same gear to perform the test.. So Temperature is not relevant. It's Watts in vs Watts out....
I can only imagine the temperature as the reason for the fluctuation. Internal impedance increases drastically at reduced temperature. At 20C constant I will expect over 99% efficiency based on the test I have done with different LiFePO4 cells.
Your a time traveler now !
I always was! ⏲
Good👍👍👍
Thanks
Good mate Andy, off looking for gold today. Your up early.
I can schedule videos 😃 always publishing at 5am. While I'm asleep ;)
@@OffGridGarageAustralia How do you do that mate?
@@chuxxsss You schedule your video. It's a setting in TH-cam...
Man das wird jedesmal spannender.
Ich hab Joe schon geschrieben..
Andy du muss sie auf den Kopf stellen und noch bisl rechts und links drücken.. Dann kommen auch 3 oder 4 Ampere raus 😎😋🤣😂 nein nur Spaß..
Ps die Verhandlungen mit oettinger laufen. 😜🍻
Die Verhandlungen.......!? Man das wird ja immer spannender!
ha,ha, thanks mate testing looks nice but it eating energy and time just for a question.
A basic coulombic efficiency test where the number of decimal points in the calculation are important
You have just measured coluombs, not wattage. Actually, the coloumetric efficiency should be close to 100% with LiFePO. Measuring errors might occur due to temperature differences, shifting the voltage levels that the meter uses for decision when to start/stop charging/discharging. Could you check the actual wattage with your device? A rough estimate would be to check voltages at 50% SOC for charging and discharging with different currents and then multiply this with the Ah readings from your previous measurement. This shouldn't take too long and will result in a table with actual efficiencies for different charging/discharging rates.
Now do theses tests 4 000 times each to know how it affects battery life lol !
"Many Years Later" lol
For the voiceless.... Here is my like button press
Tests are at too low of current rate to see much difference in efficiency..
You will begin to see more degradation above 0.5C charge and discharge rates. About 95-96% roundtrip for 0.5C, 90-91% for 1C.
Consider what these losses do to battery heating. A couple watts loss has little effect on cell heating. 10-25 watts of loss will heat up cell.
I now have some smaller cells to test with.
I am disappointed with viewers. If you watch the video that is obviously excellent content why not take 3/8ths of a second to hit the like button? Thank you for taking almost an entire week to running this test for a viewer. They are insanly efficient batteries!
🤗👍👍👍👍👍🖖
I think its Not correct. You have to Use the Energy ( Wh ) because you have a Higher Vorlage while charging and and a lower Vorlage at the Same SOC while discharging. For the 5A Test ist about 95% efficency
You beat me to it. I was about to make that point :-). LiFePO4 is one of the most efficient chemistries available with its low internal resistance, but it isn't 99%. Even 95% requires near perfect conditions and not charging or discharging all the way.
-Matt
You can use either, depending of what you want to test. Here, this is a pure capacity test in Ah. All batteries are been compared with their capacity, not Wh. If you measure Wh, it would take other factors into account like cabling, internal resistance, resistance between terminal and busbar,... and is hard to repeat. The tester alone connects differently to the terminal every time, so resistance is changing and therefore the results. Ah are more consistent in this case.
@@OffGridGarageAustralia Ah is a reasonable parameter for this type of testing. However, you can't use Ah data alone to calculate round-trip efficiency. Amps alone is not a measure of energy.
-Matt
Nice test, but - to be honest - there is no significant result at all! Its all in the range of accuracy of meters, cable-connections e.g. For the battery its always better to charge slowly and you get the most capacity also by discharging slowly.
Where is that 1C test
Coming!
Really I want a like 3 or 5C but I mean 1C is generally what they are rated for
@@james10739 I've got some smaller cells here which can do 5C continues discharge 😉
Don't use the Ah/Capacity measuring for calculating the efficiency. Use the Wh/Energy measuring. Doing so, you get results 2%-5% less, but more accurate for what you want to do. Don't drink beer, before working/Wh in terms of physics is understood and done. ;-)
In regards to your estimated efficiency of your running system: 99% of loading/unloading efficiency is just not possible, and a great indicator of a failure in your/the devices measurement. Be honest with yourself, please.
BUT... Wh are so dependent on you connections, cables and other factors. Ah are not...
The efficiency is surely very high in my battery. I have very shallow discharge/charge DoDs which makes that so high. * cycles all in total.
Capacity is measured in Ah not A. Better in Wh, unless you are very inexperienced battery user.
missed a key stoke, thanks for pointing that out. but i am inexperienced and want to keep the math simple my monitor shows amps but not watts so i use that.....30 amps in an hour (30ah)in from my charge controller to my 400 ah rated battery. as i become more comfortable with this tech i may become a more refined user but for now i enjoy using solar created electricity