How to Top Balance LiFePO4 Battery Cells Quickly (and when you need to do it)
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- Опубликовано: 30 июн 2024
- Do not adjust the voltage of the power supply after you connect it to your cells!! You should do as I did in the video and set it to 3.6V, then attach the leads second. Do not adjust the voltage when the leads are connected to the cells!!
If you have new/high quality cells, and you pull full capacity with normal BMS, no real need to top balance.
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2:27 for Step by step top balancing instructions
If you buy quality new cells, you can use BMS to top balance, then capacity test in a few cycles. That's the easiest way.
Ian made a great point of using a blocking diode so you won't burn up the power supply. Smart idea.
If you are quick charging, current sharing is an issue and you need to attach the positive and negative leads at opposite ends of the battery. In this video we are balancing and topping off at very low currents, so you can attach the leads anywhere. If it makes you feel better to attach at opposite ends, go for it. .1A on a 150A bus bar is not going to cause a current sharing problem.
~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Can I do this top balancing at a higher amperage, say 3.6V @50A?
DIY Solar Power with Will Prowse Do you ever resale any of the cells you test?
Wanting to build a battery for a small camper project. Just thought I’d ask. And thanks for all the info in your videos.
@@tevincampbell1735 Sure as long as you don't exceed the c rate of the battery
Hello is it okay to top balance cell 4 cell, parallel 2 cell at a time ? and another 2 after, because i only have 3 busbar but i need atleast 6 busbar to parallel all 4 cell at the same time. thanks
@@panthergaming732 I would think you could balance 2 pairs and then balace the two balanced pairs. But Iif I read your question correctly, you'd eventually have to connect all 4 to balance them equally. You need 6 busbars to do that. If you have some copper pipe you can make great busbars with a hacksaw, a hammer, and a drill for the lug holes. Cut the pipe into the correct length, ,smash the pipe flat with the hammer, and drill the correct spaced and sized holes. You don't have to have commercial busbars.......
Finally, a clear, concise, rational explanation. Tons of half-assed information on RUclips.
Thanks Will. The charge profiles confirm that numbers I came up with recently after days of testing and checking sources for my own build...
Fantastic video. A proper initial balance will ensure the longest life and best capacity. I can’t wait to see you build a system with those cells.
Nicely done, thank you for doing this video! Straight to the point, accurate, and very helpful for those looking to put together packs.
Just came across this video. I had eight fortune cells I ordered last year and am just getting around to putting the system together. This totally takes the mystery out of top balancing. These things are expensive and I was sweating this aspect of the build.
Hi Will, nice vid! Only one small advice: connect the batteries like you did but connect the power supply diagonal. In other words, put one of the wires on the right side of the pack. If done so the current goes thru as many busbars for each cell. Like you did, the current has to travel via ALL busbars for the right cel while the left cell gets it direct from the charger. I know, if you leave this setup stand for a while it will balance eventually but it can be done a little quicker the diagonal way.
Hi Rik, any chance you could elaborate a bit more on how to do this please? cheers
@@finnskellig7422 Simple,just connect the + wire (from the power supply) at one end of the 16 cells, 16P, and the -- wire to the OTHER end; the way he did it makes no sense, it's a beginner mistake;
The difference here, with a SMALL power supply, is negligible; BUT it CANNOT be tolerated on large (100 Amperes +) power supplies/chargers!
There are many conflicting theories about this subject including the long bus bars on battery rack units and I would agree in principle, however, if the resistance of the bus material is negligible, I would assume the current to be equally distributed across the array. Having said so, I would prefer to individually charge each battery up to its max capacity before installation but then again I'm no expert in this area (yet 😍). Thanks for your input 🙏
Great video! Thanks. I didn't realize balancing with such a simple thing it sounded complicated until this video. I had one cell that was charging higher than the others and BMS over voltage protection was making the charge bang on and off repeatedly. I took my pack apart and strap them all in parallel and they top balanced themselves in a couple hours. Now the system charges quickly and without any banging on and off. The only thing I don't understand is why the BMS didn't do this automatically. Thank you sir!
Anyone building a DIY battery pack should follow these instructions. The last 48V battery I put together a couple of months ago was needed for a scheduled neighborhood transformer replacement power outage and unfortunately the Chinese prismatic cells did not get delivered until late the day before. Fortunately I had the cabinet, buss bars, wiring, BMS & cell balance board ready to go so I just installed the 16 cells right out of the box and charged at 56V until one the cells started to show signs of over voltage. While the system did work and get us through the entire power outage the next day, the cells were severely out of balance and it took a couple of weeks of "screwing around" by manually connecting ceramic resistors to over charged cells and trying to individually charge low cells with a 3.6V buck charger. Should have just taken the cells out of the cabinet, put them on a bench and done what Will said.
Great advice. I would like to add something I learned. Lower quality cells can drift from one another by time (ex :when not in use) . If they are too far apart for your bms to cope with this, then I charge the individual cells (that have a lower state of charge) little by little with a 3.65v charger. They don't need to be super balanced at the end. Just enough so your bms can do the job again. Hopefully Mr Prowse agrees with this. It works for me with older sinopoly batteries from my boat, that sometimes sit idle for 6 months
Hi Henri. Do you put a load directly on a cell that is too high? And charge the low cells as you said. I have a boat and need to do this now. André in Sydney
Manual top balance, gold nuggets, thanks! Been watching your videos since before you got an RV! Now look at you!
I just wanted to tell you that I'm learning so much about solar components from you and your videos. Thanks and keep those videos coming.
You just keep coming with these tutorials! Wow!
Damn kid!
You are providing such a Wonderful service to the Solar Community at large and you Clearly enjoy what you are doing.
We can’t thank you enough for sharing your knowledge with us!
Thanks Will for giving us interesting and informative uploads. You make lockdown easier. 👍
Right now , i'm using your methode. 4 pieces 120 Ah , 3.2 V. Start charging 05/11 afternoon European Time. Four days later , Finally the end is near. i think tonight the job is done. Thank you for learning this way of topbalancing. Perfect explained . The second time i gonna place the cells first in parallel and charge up to 90%.
Great info and timing for my project, appreciate it Will.
Will thanks for keeping it simple. I just received my 271ah cells and will apply this method to top balancing them.
Thank you very important step ! Most LiFePO4 type cells I have dealt with are only charged to about 80% or so new when shipped. I like to pre test each cell first .bring up than parralo charge . takes more time but can do 4S banks get them over 90% . then let go for a day or 2 in parralo.
This should be the first video anyone watches before building a battery bank. Wish I'd seen it much sooner!
I referenced this vid on Off Grid Garage's current (Jul 2021) discussion of balancing.
Keep the good info coming!
Hello, unfortunately I don't understand English very well but I really like how you explain things. I really like to watch your videos and learn a lot from you, for that I would like to thank you very much and I hope that you continue to shoot videos. Best regards from Vienna
I've been having this problem, one of my cells run away at high voltage. I'm gonna take my bank apart again, and top balance. Thanks Will...
Did you manage to solve the problem?
Fantastic, thank you for taking the time to explain this process, Will!
Thanks Will. Great tips. Thanks for your insight.
One note that, while not too important once the current drops to a low level, to properly balance the voltage of the pack is to connect one charging lead to the right side and the other charging lead to the left side. This is to balance out the resistance in the length of the wires and buss bars. Otherwise the last cell in the string of parallel batteries may be at a slightly lower state of charge from receiving less current from a higher resistance. Connecting one on the left and another to the right balances this all out
That sounds pretty reasonable. Though we are talking about 1-2mm thick buss bars. Only pressure fit connections, but I can't imagine the resistance being significant - do you have any numbers of what kind of resistance this could be and the corresponding voltage drop/unbalancing?
I agree with you Jason. I used short pieces of small wire to top balance all my cells because I didn’t have enough bus bars and I measured 9mV drop in each cell as I got further away from the PS leads. It did finally all balance out once I switched the leads around like the you said but it probably took much longer than it should have.
Would it make more sense during parallel topping off to put connection both on center cell?
Using the same power supply today as is in the video lol. It's great!
Thanx for this brother Will. I have a 4P4S 12v battery and one of my 4P sets were at 3.7 SOC while the other three were at 3.5 so I am following your vid...
Shalom
Will, l think your a great teacher-Solar Guru🇦🇺
Another great video Will!
You should put together some videos with your knowledge and experience and give us solutions in the Sailing world. Many sail boaters want to move away from clunky diesel engines and go electric. Your videos are of great value.
as usual, first rate work! clear, to the point and smart science!
If your power supply has an option for sense leads you can add a second pair of leads from the power supply to the battery terminals. This lets the power supply sense the voltage at the battery and any voltage drop is eliminated. This makes the top-level charge quicker without the need to boost the voltage setting.
Always learn more when I watch your videos! Thanks, J
You might have just saved me a whole bunch of $$$ and hours!. I've spent the last two weeks testing and balancing a 13s cradle system in series. Groups of 12.
Always nice to be around this cude dude ;)
Always great videos/information....and great eye candy :)
best solar channel by far, thanks
Thanks for your share. A little suggestion: connect each battery by Cement resistance at first, like 2 ohm /5W. It can avoid big current to damage battery. After all battery have be balance (with same voltage), exchange the cement resistance to copper sheet, and charge / recharge one cycle.
You should always use a blocking diode to charge batteries with a lab power supply to prevent the current from flowing back into the power supply outputs. Those power supplies usually have a crowbar circuit across the outputs that can short and cause a short circuit across the outputs. This will blow your power supply instantly.
Oh that's smart!!!! Will add that. Good point
Only needed on the + side?
Be sure and take the voltage drop across the blocking diode and subtract from your metered voltage.
Ian,
What would be looking for in the blocking diode you suggest - assuming one of the recent 24V surplus BYD packs ( like David Poz's) using a charger like Will was using? A link would be nice🙂
Thanks
What size/type it should be ?
👍Great precise basic information! Thank you!
I’ve got 3,7v lion cells with 50 A.h. Cap. Didn’t get to use power source, after I’ve watched this video I wasn’t sure about the result but here it is. Connected all cells in parallel and the result over the night exactly 9hrs30 minutes. Cells differed at around 0,5 Volt before- and after the night result -> 3,551 each cell.
Hi Will thank you so much for the information that you provide and this video. A few places that I've read on top balancing mentioned letting the pack settle for an hour or so and then check the pack voltage. Keep charging and resting the pack until the pack settles in at 3.65. Is that necessary in your opinion? Or just let the charger get to 3.65 and then reassemble the pack? Thanks again.
I am in the process of doing this to my 4S 280Ah setup. It takes forever. I'm past the 12 hr mark now and the batteries still take 4.4A at 3.65V.
A tip to consider!!
Do not place the power leads at the same end of the battery bank. The cell furthest away will not receive the same amount of charge due to the (small) voltage drop in the bus bar. Connect the leads at the opposite ends. That will give a more even charge as the current to each cell will have roughly the same length of cable/bus bar to travel through.
Funny. I just noticed another post saying the same thing.
You might wish to have the positive and negative on physically different ends of the cells so the resistance of the terminal connection is equalized the as you demonstrated the cells furthest away from the charger will have a lower voltage than the ones closest to the charger. Great production quality on your videos BTW!
ruclips.net/video/k-V8RIuyBbU/видео.html
How do u buy ur battery on Ali express. I have problems communicating with them. I need a good buyer
i had seen another popular broadcaster showing parallel charging & even though they've done it that way for years with lead acid I was doubtful. But now I'm not! Thank you.
Oh thank you so mucu, your information is gold!
Hi Will, great video as usual. I just got 16x 30ah pouch cells real cheap. I am charging them now and will capacity test each cell before I make a 2p8s 24v battery. Question-should I combine the highest and lowest capacity cells in parallel for my 2p arrangement or does it matter?
Great video on the balancing of the cells. What info or help can you shed some light on Solar Controllers causing RFI Radio Frequency Interference
Hey Will, first off, I want to thank you for all the great videos, and for the easy to follow book too. You gave me the courage, and knowledge to get started on my first solar system.
Since it’s taking a month of Sundays to top balance my EVE LF280K cells, Is there any reason I can’t charge them first with my all in one solar power system. Then re-configure them and top balance um.
Thank you for the video. At what Nm should those prismatic cells be tightened?
The lifepo4 battery i build for my ebike lost the balancing, thanks for the video , i will top charge each serial line of the battery
Nice. A fortune cell balancing vid. Good thing I need to balance 8. Thanks Will you are the dude. So if I don't have a bench charger, I can make two 12v stacks and use a car charger?
How often should this be done with your system? Is it recommended to disassemble a 24v bank down to 12v run in parallel to ensure its balanced every couple of years?
Awesome Video!
Thanks for sharing Will. May I know why we have used 16 LFP cells to make 48V pack instead 15?
You're talking about needing a cell balancer every 6 months to a year. Can you discuss balancers that your recommend, and the steps needed to determine if it needs used and how to use it?
What is bottom balancing?
Are these balancing practices needed on pre-assembled batteries as well?
You mentioned that this is kind of unnecessary and that they balance over time, correct? What's the benefits of balancing every 6 months?
Thank you, Will! 🙏
Hi Will, how long do you let them set after top balancing and what is the expected resting voltage after this process?
So...putting together my first battery utilizing used Headway 38120 cells, cautiously. If possible, how do I figure out if a cell is bad after assembly? or, test individual cells?... Appreciate your content!!
Great video! But what kind of charger should I use to balance to 3.6v?
Will your the man! Thanx
Hi DIY Solar,
Wouldn't Bottom Balancing be a better method?
When top balancing, you measure at the steep side of the charge curve where the last 5% (or so) of the S.O.C. will be.
When bottom balancing, you discharge all the cells till 2,6 (about) and will know all the cells will be at the lower 10% of their charge
Connecting them in series and charge them with a normal charge current would result in an equal charge in each battery, specially when avoiding the upper 10% (90%S.O.C.)
I would like to hear your reason for choosing for top balancing.
Regards and keep up the good works!
Wow! I think you answered my exact question with a video! how awesome is that!? Fantastic content Will, took me from zero knowledge to acceptable moron on the subject of solar in just a few days.
Thats alot of money for your vids. All these lifep04 batteries🙌🏽
Good evening my friend, please watch your videos and everything is very nice, continue like this .... recently I made an electric scooter and put a 72volt 80 amp controller !!! the scooter is very powerful and so I bought 24cells 3.2v 50ah lifepo4 batteries ... did I do well to buy them? I had to buy something else because my bms created a problem and I took them out of a scooter .. I think it was the best for my scooter ...
Thank you! (again)
Man i loved this video, thank you
Good info.
Hi Will, ..as usual, great video. I would like to know your favorite test method for determining when a cell is heading for early failure. Is measuring the rise of internal cell resistance a good method for LiFePO4 chemistry. What and how is your method...
Good question. Should make a video on this
When I saw this vid I thought wow, Will is a mind reader 🙂. Please make that video!
Have a EVT4000 scooter that I converted to 48 volt Elite Power Li’s w/ active balancing 10-years ago. Has worked great all these years. But recently have been experiencing voltage sag with higher demand accelerations. Suspect a bad cell or two. Coincidently, I let pack sit for a long period & active balancing drew pack down to 20% above absolute zero capacity. Amazingly, on full recharge, pack was revived with very little sag. It appears that “full” discharge helped things allot. Is that possible?
Still plan on doing the manual cell balancing you outlined on this video. Will watch for your NEXT video about diagnosing bad cells!! Thanks for your highly informative channel 👍
Thanks, looking forward to your video on this often overlooked test.
Thanks Will.
great video, just one question used the LIFePO4cells without a BMS what could be the end results thanks.
Thanks Wil
As always great video :)
Just observation in this setup without any compression at 3.6v all this batteries will expend permanently i the middle on they sides ?
Hello Will, thanks for all your very helpful and well made videos about Solar and powerwall. I just receive 16 Lifepo4 280Ah cells purchased on a famous chinese market, all cells are well balanced but thanks to your advice, I start to make top balancing. All cells plugged on parallel, connected to lab power.
Lab power set up : 3,65V output and 10A (max power).
Battery pack : 3,332V.
When I plug the power lab on the battery pack, only 0.35A consume.
Is it normal? Is there something to do in order to speed up the load?
Thanks for your help
Aliexpress does not have these, please advise on where to purchase these batteries!
Great job on the vids Will I grabbed your book too!
Hello. When do you will test the new Yinlong LTO battery? Thanks. Good work.
Could you maybe look into how to connect a 3:rd party bms to victron smart bms. So one can use other Lifepo4 batteries with the victron stuff. It needs to talk canbus as far as I can see.
Daniel Evigh rec bms do that!
I watch several of your video and you have tested numerous of different types of battery power storage. Which battery would you recommend for home use?
Man I'm learning so much,I'm building a 4s6p headway bank, balance these the same? Should I install a bms,what do you recommend? Thanks will.
I always stick the red and black leads in the centre of the string of cells rather than both at one end, if you check the cell voltages they will be higher at the end nearer the leads for a good few hours. If you leave em charging for days it probably doesnt make much difference tho.
Could you do a video covering ALL steps needed? Let's say I'm replacing old 12V batteries in an RV, and I decide to order a bunch of CALB or Fortune packs. Exactly which steps should I do to rip out the old lead-acid or AGM batteries and replace them with LifePo4? Seems like there is testing the packs, top balancing (this video), grouping them by 4 to get 12V, add BMS and balancing leads etc....? Anything else I'm missing?
Hi thanks for the informative video. I'm new to this and am building headway hp battery. They are nominal at 3.2V and charging voltage 3.6. Should I top charge to 3.2 or 3.6 voltage. Thanks
Cool!...thanks budy!
I am struggling to find any info here and could use some guidance please. I am trying to build a 14s 48v battery pack from used Leaf cells. I can not find info on how you connect a BMS and the charger at the same time? Does the BMS just do its job once it is connected and act to monitor and balance the cells so they remain the same voltage per cell, and then just charge with a LiFe charger? Trying my best to understand all of this, I trust your knowledge the most Will
I working with 38120 headway cells. I put all 64 of them in P to balance for three weeks, Then I put them in 4s4p basicly made four 16 cell 12v, then I hooked a 8 amp 12v charger to it, and the charger will only charge them up to 13.3 v and stop. My question is, what is the BMS I need to put on this 64 cell 12v battery? four 12v bms? Can you point me out to one that got the battery wire already solder onto the bms, since I can't see to do that. Thanks. Keep up the great work.
Hello, thanks for explaining the procedure. I appreciate your enthusiasm. I have a small question:
Is it safe to keep them charging overnight? Technically, if I keep the supply voltage to 3.6V, then it should be safe, as once all of them charged and balanced, the input current will be o eventually, right? Just wanted to confirm from you who must have been doing this often.
I never do actually. I have a lot of my habits form charging lipoly cells for years. I try to avoid charging unattended often.
It shouldn't take more than a few hours if your cells are at high soc.
@@WillProwse Got it! Thanks :)
Excellent. Ty.
Hey! I love your channel and motivated me to build my own Lifepo4 battery. I’ve been having issue with the top balancing seems to be stuck at 3.26v and one cell at 3.24v currently charging at 3.65 and 5.9-6A and doesn’t seem to be going up. Been going for almost 20 hours? I’m using a cheap Amazon power supply with 14g alligator clamp? Could that be causing the issue. Thinking about going to 12awg with ring terminals. Thanks for the help!
Last year I bought a set of 16 LiFePO4 280AH batteries to build a 48V system. After setting idle for a year they had an initial voltage of 3.16V per cell. I used a lead acid battery charger to bring 4 sets of 4 cells up to near 3.4V per cell which is where the lead acid chargers stopped charging. I top balanced 2 sets of 4 batteries wired in parallel at 3.65V with a 30V 10A power supply set at 3.65V and 10A. The power supply is struggling to charge the 3rd & 4th sets above 3.34V with the power supply set at 3.65V. Should I turn up the voltage a few notches and keep a watch on the batteries to insure they don't rise above 3.65V?
All the cells will have slightly different impedance. If they are closely matched, they will stay in balance for a large number of cycles. If they are not closely matched they will drift out of balance relatively quickly. For LiFePO4 cells independent cell passive top balancing circuits will keep individual cells from overcharging and the pack BMS from prematurely shutting off or the charging circuit from thinking the pack has full charge when it doesn’t. If you’re a hobbyist and you like messing with this stuff all the time to keep it working, you don’t need the expense. However if you just want it to work and you don’t want to screw with it all the time, pay the money.
I used to have a ‘66 Mustang that I was always working on and I loved it... until I got older and making more money. I ended up getting a BMW M5 and paying someone to work on it when it infrequently needed it.
by connecting the power supply to the first cell, it will be a higher voltage than the cell on the far right due to the resistance off the busbars and the connections between them. Better would be positive from charger to the left positive terminal and negative from the charger to the right negative terminal
Hey Will, Just for clarification can you explain the reason & importance of wearing safety glasses when touching batter terminals.
Not Will here :) The reason is for protection of your eye in the event there is a short while working on the battery sparks could easily fly into the eye
another question - - - can you use a good 12 volt car charger to bring up 4 sells in series before charging all the batteries in parallel
Hi! Thanks for this video! I was wondering, how do you know when you have a bad cell in your pack? I have 8 cells...24v, when put a high load on it (80 amps) i see one cell that drops a lot in voltage, while the other cells do not drop that much. Is that a sign for a bad cell? I can charge it back up to 3.55V and my BMS does get all 8 cells balanced with a 5mV difference.
Check your connections as a degraded busbar connection can cause this behavior.
Good question. How do you know if a cell is Bad?
I’m in the process of switching from lead acid batteries to Lifepo4. I got 4 12v, 200 ah Ampere time batteries that will be connected in series and parallel for a 24 volt system.
My first question is, what charger did you use? I looked on Amazon for the one you had, but couldn’t find it.
My second question is, do I need a BMS with a Victron 150v, 100a charge controller?
Thanks for all you do. Your tutorials enabled me to set up our off grid solar.
My solar setup is about complete, just waiting to see if Battleborn is ever going to release the new batteries there was rumor of. Could you build and balance and slap a bms on one of these and I purchase it through your store?
Hi I am one of your subscribers I really like the great things you are to us.please I am from Ghana but staying Italy. I really want to talk to you for the project I want to do
Him - "You can't screw this up" Me - "Hold my beer"
Will, I have been watching your videos for awhile now and I’m starting to kinda sorta understand electricity a little bit. I have a question, which doesn’t really apply to this video. I just recently got a Z2 Auto CPAP machine and I have a AC to DC plug for it. I have a 44000mah Aimtom portable battery which is available on Amazon. Is there a way I can use a DC to DC wire to connect the two? Or do I need some kind of converter thingie to make it run?
if the voltage in both equipment are the same, don`t see why can not being use. just make sure machine and charger are the same voltage and that the amps you got in the batteries, is enough for holding the machine on the whole night, i do use a CPAP machine from Phillips, it do have his own Li-on battery good for one night.
So if I buy 4x 3.2V brand new cells, I can just buy a decent 4S 12V 60A (say) BMS, wire up the balance cables, and that's that? Let the BMS top balance the cells for me, then do a few discharge capacity tests? I'm slowly learning more and more about this stuff. The biggest scary part is the initial balancing - top balancing, bottom balancing, it becomes a lot of info to process. Thanks so much for your videos, I'm learning a lot!