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. ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Does off-grid solar confuse you? Check out my DIY friendly website for solar system packages and product recommendations, and so much more! www.mobile-solarpower.com Join our DIY solar community! #1 largest solar forum on the internet for beginners and professionals alike: www.diysolarforum.com Check out my best-selling, beginner-friendly 12V off-grid solar book (affiliate link): amzn.to/2Aj4dX4 If DIY is not for you, but you love solar and need an offgrid system, check out Tesla Solar. Low prices and great warranty, and they can take your entire house offgrid with their new Powerwalls: ts.la/william57509 ~~~~~~~~~~~~~~~~~~~~~~~~~ My solar equipment recommendations (Constantly updated! Check here first): 12V/48V Lithium Batteries: www.mobile-solarpower.com/solar-batteries.html Solar System Component Directory: www.mobile-solarpower.com/solarcomponents.html Plug-N-Play Systems: www.mobile-solarpower.com/full-size-systems.html Complete 48V System Kits: www.mobile-solarpower.com/complete-48v-solar-kits.html DIY Friendly Air Conditioner/ Heat Pumps: www.mobile-solarpower.com/solar-friendly-air-conditioners.html Complete 48V System Blueprint: www.mobile-solarpower.com/48v-complete-system-blueprint.html ~~~~~~~~~~~~~~~~~~~~~~~~~~ My Favorite Online Stores for DIY Solar and Coupon Codes: -Current Connected: SOK, Victron and High Quality Components. Best prices and warranty around: currentconnected.com/?ref=wp -Signature Solar: Cheap Server Rack Batteries and Large Solar Panels: www.signaturesolar.com/?ref=h-cvbzfahsek -Ecoflow Delta Official Site: My favorite plug-n-play solar generator: us.ecoflow.com/?aff=7 -AmpereTime: Cheapest 12V batteries around: amperetime.com/products/ampere-time-12v-100ah-lithium-lifepo4-battery?ref=h-cvbzfahsek -Rich Solar: Mega site and cheaper prices than renogy! Check them out: richsolar.com/?ref=h-cvbzfahsek -Shop Solar Kits: Huge site with every solar kit you can imagine! Check it out: shopsolarkits.com/?ref=will-p -Battery Hookup: Cheap cell deals bit.ly/2mIxSqt 10% off code: diysolar -Watts 24/7: Best deals on all-in-one solar power systems, with customer support and distribution here in the USA: watts247.com/?wpam_id=3 ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Contact Information: I am NOT available for personal solar system consult! If you wish to contact me, this is my direct email: williamprowsediysolar@gmail.com Join the forum at diysolarforum.com/ if you wish to hang out with myself and others and talk about solar FTC Disclosure Statement and Disclaimers: Every video includes some form of paid promotion or sponsorship. Some links on this youtube channel may be affiliate links. We may get paid if you buy something or take an action after clicking one of these. My videos are for educational purposes only. Information is subject to change/update at any time. Electricity is DANGEROUS and can kill. Be smart and use common sense :) DIY Solar Power with Will Prowse is a participant in the Amazon Services LLC Associates Program, An affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com
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.
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
@@BlazeByte21 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.......
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
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.
@@gkeith4120 yes, this would be slightly better. I would connect the + on the first cell and the - on the last cell. This way the total buss bar length (+ & - together) is the same for each cell.
Great video. We too figured you just put the new cells in and the bms takes care of everything. We bought 8 cells to replace bad 100ah ANC cells. Our sample size is 1 so we can't make any statistical judgements but we still don't recommend neata batteries, anc cells or seplos bms (doesn't balance cells well or at all). We got a black LONGWEI that otherwise looks just like Will's power supply. We only received (as expected) 8 bus bars with our 8 cells. We drilled holes in aluminum yards sticks for on-the-cheap bus bars to balance. We put an extra new battery in the group in case one of older ones doesn't charge up to 3.6. We are currently at 3.8a and 3.353V. We have 9 more 5kWh (server rack) packs so this is going to be a long process.
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.
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.
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.
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.
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
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.
@@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 🙏
Came here to say this. Makes an even bigger difference if using smaller temporary wires instead of bus bars. The current can choose to go through a battery instead of toward the next battery, so by forcing the current to go all the way down the line to get back to the power supply, the delta V across each cell is much closer during the whole process, without relying as much on sitting for a while at the end.
Batteries wired in parallel self balance themselves. If you hook all them up in parallel and let the batteries sit for a couple days, they will self balance without hooking up any charger to it.
hi the positive and negative connections should be at opposite ends of the battery to more evenly charge the battery's else the ones closest to the charger will charge first and take a long time to distribute the charge to the cells further away
Does not matter here because at that current with these bus bars, current sharing is not an issue. If you are charging quickly, then it will matter and it needs to be at opposite ends.
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.
Shouldn't you be charging from a centerpoint? The small but still present resistance of the buss bars and connection points will create at least a .1 or .2 VDC difference from the charger connection point to the last battery. So the further downstream, you still have imbalance. Always appreciate your videos, thank you.
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.
Do you think it’s ok to use stranded 12awg wire for bus bars when top balancing? I don’t have enough bus bars and figured since it was low volts and low amps it would be fine. Does anyone know?
Is it possible to top balance 1 set ot 4 pieces then another set of 4 pieces... Once both sets are top balanced to be connected in series (8s for 24 v inverter)
Hello Sir. Can I connect them in series for example 8*3.65=29,2 in order to give 29,2 volts and 5Amps with the charger and do it faster, or I will have other issues?
Hello Will and fellow DIYers, I have 8 brand new 280Ah Lifepo4 cells that arrived balanced and a JK self balancing BMS. I also have an LV2424 but I don't have a separate 24v Lifepo4 charger. Would I be able to use the charger in the hybrid LV2424 to do my initial Top Balance? I haven't seen this done before. Thanks!
How does that bench power supply know when to stop charging? Or do you just need to monitor the voltage and stop it manually? It was my understanding overcharging LiFePO4 is very bad :)
@@WillProwse l did not do a capacity test. I'm new to this and found out how important it is to do that. Well here's the deal I have 6- 100AH batteries on a 12,000watt growatt inverter. The system has been up and running for 2 months now. In the last week I noticed that the batteries would not charge fully as they were. They now peak at 53.3 volts. I checked the screen and the voltage is off on some of the cell's. Now of course I tried to save money like most dummies and purchased the batteries from AliExpress. Also they hold up well until they hit about 49or 50 volts and then they seem to speed up discharge. But it varies on discharge. I don't work the system hard at all but I guess the capacity test will tell all. By the way the voltage different is like 3262mv and 3293 in difference. What do you think I should do.
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.
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 ?
My 20V 5A cheapo power supply won't do 3.65V at 5 amps. For some reason it drops to 1 amp 3.65 volts when I output the charge. Frustrating. what cheap power supply will output 3.65 volts at 5 amps?
Hi, thanks so much for your videos, im buying 8 Eve 280 ah cells and dont intend using them for up to 2 months so can I just connect them all in parallel and let time do its balancing for a month or two?
Should the correct way to wire the charger to the battery be to connect one lead to the front positive end and connect the other lead to the back negative lead. So one wire will be on one end of the battery pack and the other will be on the opposite end.
WHY DO YOU SAY 48V WITH 16 CELLS IN SERIES, THE NOMINAL IS 54, I DON'T KNOW WHAT THE HELL IS HAPPENING WITH MY BANK IT HAS 15S 48V, IT IS BALANCED BUT IT NEVER SHOWS MORE THAN 5O VOLTS AT THE END OF THE CHARGE, IT IS SOMETHING VERY STRANGE, BUT MAYBE THEY SOLD ME RECYCLED OR SECOND HAND?
This video is great, but there's no instructions for what happens after the cells hit full capacity. Can I go to sleep and let them charge overnight? Is it safe if they hit full capacity (the power supply is at 0.1A) and stay connected to the power supply for 6-8 hrs? Thanks :) .
I bought 8 LIFE PO4 12 v 200 ah with 200 BMS in it to subtitute some 12v 200 ah gel batteries I have in a solar system, Do I need to top those batteries ?
I received my CCCV charger today and began to top balance. The cells were around the 3.3V range. Upon starting the current readout was 4.2A and dropped gradually. I kept an eye on it and it got down to about 3.7A after an hour or so. However, after a couple hours I noticed that the current started to quickly bounce around 4.0-4.2A and has been hanging out there for the past hour. Is this normal activity with the charger? I am using this charger linked in the description.
Sorry for many a stupid question 🙌 ive just started watching videos like this, about battery's. And i want to learn more, i have a ebike i like to gettt Long range on (my battery is almost finish now 60v 26 amps) can you use cells like this for that?
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?
hi mr Thanks for the good information you share .. I need a 12/24V charging circuit for lifepo4 batteries to do a project, please help me if you have a map of the charging circuit. tnx
Would it be fine to balance the cells by keeping them in a string, say 4 cells in series, and charging the string to 14.4v (3.6x4)? Or is it necessary to parallel all cells and charge to the cell balance voltage (3.6)?
Hi mate I'm a little puzzled I've just bought 4 280ah cells from China set them off top balancing 3.65v the amps were at 7.5 next morning they were at 5.7amps which is OK I think by tea time I came in and amps were 10.9 and not budged over next 12 hours so turned off as don't seem right do u have any suggestions please
You should connect the charger diagonally, so positive and negative are on opposite sides of cell block, so the current is accepted equally by all cells and voltage is truly balanced. The way you have it now the cell closer to the PSU will be charged more than cell further away from PSU. Since most people don't wait until current drops all the way to zero, this could lead to less than ideal balance.
If you're charging quickly, sure. Charging .1-10A across 150A bus bars is not going to cause a current sharing issue. If you want to do that, go for it. If we were charging quickly, current sharing is concern and it needs to be diagonal.
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.
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
Just a pick at nits. I won't ever used a metal ratchet-driver without isolating one bus. I appreciate your videos and I'd like to see more so please don't replicate my error.
@@WillProwse I'll go have a watch, Thanks. Sorry for the trouble. Seems that, I'm just a little sensitive after that particular unscheduled welding event and I don't want to go shopping for underwear in the current climate.
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.
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?
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?
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?
Hi Will Enjoy your videos mate and have a quick question regarding top balancing. I have some mb31 to do and the settings i was going to use were 3.65v 40ah and was after your input on the cutoff amps you would use if any. My zke ebca40l does not seem to except above 9.99amps where i see others do, probably im missing something here. Thanks Mate
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!
my batteries has now been charging för 10 days and not reached 3,4V. I started on 3,29V and is now on 3,38V 10 days later. it started to charge at 5Amps and has dropped now to 0,8Amps as its closing in to 3.4V. But 10 days??!! can that really be as it should ? Thanks for great Video!!
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...
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 👍
I was charging my 100AH LFP battery with a 20A charger that uses 9 stages. This battery has bluetooth and was watching the charging time left. Once the battery got to 99 percent charge the time left starting slowly increasing. Was this due to the dropping level of the Amp input? I was not for sure what was happen and stopped the charging. Why was time left for full charge increasing? I was using a HTRC 20A charger.
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
Hi Will, Don't you risk destroying a bench psu by connecting it to batteries as a charger. I have always understood you should connect it through a diode? Maybe this only applies to PSUs with bipolar output devices but you would seem to be reverse biasing the output transistors.
Interesting, Thanks, So if you add a diode then I guess you need to compensate for the voltage drop across the diode and/or monitor cell with a volt meter?
Just FYI, if you are thick like me, if there are big sparks, you got it connected wrong. Tried 3 times in a row before I realized I had the cell connected wrong
