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

Finally, a clear, concise, rational explanation. Tons of half-assed information on UKposts.

Thanks Will. The charge profiles confirm that numbers I came up with recently after days of testing and checking sources for my own build...

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.

Nicely done, thank you for doing this video! Straight to the point, accurate, and very helpful for those looking to put together packs.

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.

This should be the first video anyone watches before building a battery bank. Wish I'd seen it much sooner!

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.

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 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!

Manual top balance, gold nuggets, thanks! Been watching your videos since before you got an RV! Now look at you!

Great info and timing for my project, appreciate it Will.

Thanks Will for giving us interesting and informative uploads. You make lockdown easier. 👍

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!

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.

Will thanks for keeping it simple. I just received my 271ah cells and will apply this method to top balancing them.

You just keep coming with these tutorials! Wow!

Fantastic, thank you for taking the time to explain this process, Will!

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

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.

Thanks Will. Great tips. Thanks for your insight.

I referenced this vid on Off Grid Garage's current (Jul 2021) discussion of balancing. Keep the good info coming!

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%.

Will, l think your a great teacher-Solar Guru🇦🇺

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

Using the same power supply today as is in the video lol. It's great!

as usual, first rate work! clear, to the point and smart science!

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

best solar channel by far, thanks

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.

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 nice to be around this cude dude ;)

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

👍Great precise basic information! Thank you!

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...

Always learn more when I watch your videos! Thanks, J

Oh thank you so mucu, your information is gold!

Always great videos/information....and great eye candy :)

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.

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.

Another great video Will!

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.

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?

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!

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.

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.

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.

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

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

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.

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?

Thank you for the video. At what Nm should those prismatic cells be tightened?

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!

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, how long do you let them set after top balancing and what is the expected resting voltage after this process?

Man i loved this video, thank you

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! 🙏

Thanks Wil

Thanks Will.

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

Thank you! (again)

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 ...

Thanks for sharing Will. May I know why we have used 16 LFP cells to make 48V pack instead 15?

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 ?

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.

great video, just one question used the LIFePO4cells without a BMS what could be the end results thanks.

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!!

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

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 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

Good info.

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?

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 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...

Thats alot of money for your vids. All these lifep04 batteries🙌🏽

Awesome Video!

Will this work on nihm batteries? I want to balance my Prius cells and would like to recondition them as well by using an inverter to discharge them . Thanks

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.

Hello. When do you will test the new Yinlong LTO battery? Thanks. Good 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.

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.

Will @3:40 you indicate to create 4s packs and then charge with a traditional 12V charger to avoid long waits top balancing. I have two questions: 1) I do not own a 12V charger, but was wondering if I could use the power supply in this video and what settings would be used? 2) Do the 4s batteries need the BMS attached when doing this?

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?

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?

You the man will

Excellent. Ty.

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.

Hi. I have new eve 280Ah cells. I have had them on a dc power supply to try and top balance. Been sat at 3.65v for 3 days. Not dropping below 2.6amps. If I disconnect the power. Bat at 3.35v ??

I have 2 BYD batteries 24V 260Ah, I got one of them almost fully discharged, I realigned cell voltage with a power supply, thus all cells were more or less aligned to 3.25V. Then, I put both batteries in serie and charged with solar MPPT 1100 W or 0.05C charging current, adding around 120 Ah. Battery 1 cells voltage went up to 3.65 while battery 2 cells voltage remaind around 3.45V. Then, BMS switched off both batteries. After disconnect, one battery voltage stabilized to 28V and other battery voltage to 26.8V Can I set my 2 batteries in parrallel in order to align both voltages ? Any precaution is needed for doing this, in order to avoid excessive current Amp between both batteries ? Thanks for your valuable informative videos.

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.

Thank You

Cool!...thanks budy!

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

I picked up a Valence U27-12XP do I need to add a BMS to use in my camping trailer with a PD9140A - 40 Amp Electronic Power Converter with wizzard and an MPPT solar charger set for gel cells. I am a little confused.

Aliexpress does not have these, please advise on where to purchase these batteries! Great job on the vids Will I grabbed your book too!

Hi Will - at minute 3:41 (et seq.) you discuss making 4s, 12v batteries and charging them up quickly with a TRADITIONAL 12 charger, did you mean like a normal charger for a LiFEP04 12 battery, or some sort of BMS setup? Thanks again - I'm using your links to buy stuff :)

if you have a pack with 4p 24s can the busbars joining the parallel cells be thinner (for lack of a better word) than the ones connecting the series

Hello Will, If I do not have a charger like yours can I use a power supply like the one you show in your DIY Milk Crate Generator Videos that is the one I purchased where you can adjust the voltage. Not sure if it will keep sending amps when charged or drop to zero like the one you are showing. I do have a amp meter so can check amp loads?