LiFePO4 battery w/o a BMS: Top or Bottom Balance? Mismatched Cells? 

This is an old video when we ran packs without bms. Nowadays, you just slap a bms on the cells and it's good to go. It will top balance your pack and you don't need to think about anything. So don't worry about top or bottom balancing. Use a BMS and you are set. ~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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

I have been living off-grid since 2013. I'm the first person in the Caribbean to use lifepo4 batteries for solar storage. I have to say your videos are the best I have ever come across with respect to solar and lifepo4 information. Keep up the magnificent work bro!

Yes that answered my exact question! No filler, straight to the point, and yes I've watched your other videos. My number one trusted sources for education on this new fascinating hobby of mine!

Starting with a newer video, I've been drawing from your cell of knowledge. Consistent, Impressive presentation technique, Straight to the point, no annoying music... Bravo sir! I know it's not a grand prize or anything, but you've earned a spot in my subscription list, which is limited to 10 channels at any given time.

I usually don't comment, but that all REALLY made sense! Not only do I understand the necessary adjustments, but this is the first time I've really grasped the point of top/bottom balance. I knew it needed to be done, but now I understand why.

I do understand what you said in your video its a great help and I wrote it down so I know what I should set my charging limit to, to be in a safe zone and to promote long life of the batteries. Great video and you touched on things that are right on time with what I need to know. Thanks.

A lot of the time I don't know what he's talking about but I listen anyway

Excellent Will thankyou. I'm using cells for car audio sound quality build. Since they will never see low voltage and run around 14v, but your right, top balancing is most certainly the way to go, and again your right it is way better to bottom balance if at all possible

Thanks for a clear description of the benefits of bottom balancing and the risks associated with inexpensive BMS units. Many of us understand what we are doing, but for the noobies it is critically important that they get good information correctly presented - as you said, it is easy to get burned - these cells contain a lot of energy, which is why we use them...

Explained it good Will , been studying up on lipo batteries hopefully within 6 months will have in place

Thanks for making this video! It makes perfect sense!

Very insightful. Thanks for sharing. I use recycled 18650's to make my own batteries and this is a recurring thought for me. It was good to hear your thoughts on the matter. I do not use a Battery management system but I do use a batter monitoring device. It cost less than $20 but it displays the individual cell levels and the total battery voltage so if anything goes out of balance by too much then I can make adjustments as desired.

You are an excellent teacher!

excellent points! Hopefully it reaches the people that need to know to watch out for mismatched cells. :)

Thanks for the guard rails 👀.You pack a lot of very useful info Appreciate it

Great job . This is a new topic for me and i found your explanation to be very easy to understand. thank you!

Nice and clear video about the differences between top and bottom balancing. I saw your video about loose cells are losing the attraction where complete rack mounted systems are becoming more popular, but for me here in The Netherlands, options for affordable rack mounted batteries are very little.

Excellent work on your information, thank you.

Great video Will. Thanks.

congrats on 60k subs!

Great vid and sweet haircut will 😁👍👍👍

Great information! Thanks. My prismatic cells are charging evenly. They do seem to stop charging at 13.3v whether solar or plugin lead acid charger. So I guess that’s ok.

Perfect. Thank you.

Another very informative video ✌... what about one on victron battery protect?

good explanation, this myth around balancers and botton or top balancing, great!

Great news 100 points for sure.

Excellent explanation. Between you and Jehu I think I get it. Debating whether to build my own battery for an ebike, still not sure. Vortecks is wrapping up a 20kw project, but I was thinking maybe 2500 lol. My need for speed is not like his.

The choice of top/bottom balancing also depends on the application. In my case, my system is designed for solar backup and the cells are kept at approximately 90%. Since no lithium based cell tolerates constant trickle charging, my controller tops off the battery bank once a week while the BMS top balances. Even though there is a +- 4 Ah cell variation across the 600Ah pack, the cells stay well matched. 24 hours after top off the 16 cells are within 4-6mV and from 48 hours until the next top off, they stay within 2mV. It has operated this way for over a year now. To avoid bottom voltage issues and to extend battery life, the BMS will disconnect the pack at 15-20% state of charge although I have not encountered this case yet. This system gives me 3 days to either get solar back (snow melts) or start the generator. I don't have to bite my nails hoping one of the cells doesn't under voltage. Peace of mind is my goal.

Good stuff, theory of battery balancing is even true in photography equipment!!! Great video Will, love you, keep it going :)Big thumbs up.

Will, great job on the solar videos but I also miss your vlogs or just sit down videos with storytimes!

I always know what your saying, you use English. But I wish you'd talk longer. So I could keep listening. Your rambling is awesome.

To be honest this , this is EXCELLENT !!! I am one of those guys out there that have a mismatch batteries and this is a good solutions for that. BMS is just wasted of money. Yeah I have BMS but on this tutorial this gave me a lot more safer than BMS. BMS is just for lazy people how dont know a little math!!!

Thanks, it makes a lot of sense. A cheap bms on a under stressed lifepo4 battery is not just a waste of money but gives the user a false sense of security.

Thank you handsome boy.. Miss you, Hope to see you soon...

You rock.. Dude, keep it up!!!

I tried to bottom balance my electric lawnmower. I am using used 18650 lithium ion cells and cycling them from 90% to 0% in one hour each week. So a much different situation than the solar you are talking about. The bottom balancing did not work for me because the self discharge is a little chaotic with the cells I have. So I need to balance the pack once a month. I don’t have any way to do that automatically when bottom balancing. Top balancing once a month is easy. I charge each cell to 4.10v and every once in a while a group will self discharge down to 4.04v which throws out the balance. So my experience is exactly what you said. The quality of the cells you have and how you use them will greatly change how you should deal with balancing. If I increase the size of my pack and only charged to 4.0 volts per cell it might not go out of balance.

Interesting. TNX. 👍🏽

Good info will....

DUDE Will YOUR A MIND READER. I was contemplating sending my cells back. I got one that fits this video unfortunately. I'm currently custom programming my TS-45 to deal with this issue. I have been manually balancing with a load tester to scrub voltage during the day on one cell. No matter what i do it just charges WAAAYYY faster then the other 3 cells. Now i gotta babysit it and set the HVD to what you said as i've been regularly hitting 4.0V on this one cell. I'm having trouble discharging as im still testing and not using it to its fullest right now but the Victron LVD is simple to change with the bluetooth model. GREAT VID WILL I'M PULLING MY HAIR OUT until this vid. Might even scrap the cell and buy a new one to compensate the loss. Really want as much capacity as possible.

Now I get it

All good was looking to only charge to 80-90% anyway for longevity. Possibly even less due to my like usage scenario. I'll adjust the charge limits when I'm going to use them and need max available power from them. But for day to day min draws, I'll let them stay in their happy place 😁

I made a few videos trying to explain series battery and supercapacitor balancing. It really is super simple to understand but hard as hell to explain in a way to make sense to someone new to charging/discharging lol. I'm annoyed that lower priced chargers rarely let you adjust the charge voltage. It's always the max voltage for equal batteries so you have literally no safety margin. Then, the li ion batteries go from 100% to 90% and stay there really quickly unless you use them right away anyways.

Perfect!

Interesting, I'm using a Zeva BMS (from Australia) which top balances (by slowly draining cells that are higher voltage). The problem with bottom balancing is my battery doesn't get to the bottom very often, while I do usually get it charged up each day. The balancer only drains milliamps, so it needs to do it often. Pretty much always something needs balancing, and it's not always the same cell series. I do have my max charge voltage lower (thanks Victron) so as you say I'm not running it at full capacity. The Zeva BMS lets me configure what voltage it starts balancing. Right now my cells have a 0.03V difference and battery is 91% charged. One cell series 3.88V, the rest 3.90 or 3.91. So it's pretty subtle, but it's a big pack (6.5Kwh). My BMS is connected to a Gigavac contactor switch so if any cell series goes too high or too low, (or if the BMS fails) it disconnects the whole battery. It should never get into that state though, as it should usually be balanced, and a battery protect should turn disable the DC power out before then, and the inverter has it's own limits too. Note my pack is Lithium Ion (not LiFePO4) so in my case it's essential to keep things balanced or big fire could happen :)

excellent

new subscriber, question where is a good place to shop for solar? (panels, charge controller, batteries, inverters)

Seeing you asked for what to talk about, I'd like your opinion on the Electrodacus chargers, they are only a little more expensive but have a bms included. The maker also believes in parallel for the panels and claims there is very little loss compared to mppt and says the transformers in them always need replacing eventually which makes his system come out in front in the long term...I'm very close to pulling the trigger on this or what you are recommending currently so keen to see your view.

This video was so simple...oh, wait, it takes someone really smart to make a tough subjects sound easy. You should write a book like Solar Power for Dummies...oh, yeah, you did! (Mobile Solar Power). :)

Nice

I think it depends on application w/out solar. For ex., junk cells used to intermittently power a fridge may be better off top balancing for fast charging. Junk cells used in a continuous manner seem better off bottom balancing to squeeze more safe power at low voltage.

I guess for ev's it's easier to replace the not so good cells. I've got a a cell was rocketing at 3.75 while all the other where all around 3.3...basically quite discharged. We're doing some testing about rebalance but the ending will be...just replacing most probably.

Great vid. I want to take my son off the grid but he lives in Ramona, CA were it really gets hot in the summer. He has to keep his a/c on 24/7. The good news is he lives in a 20x8 foot insulated travel trailer with a small overhead Coleman a/c unit. To start the system I currently have 19 six volt deep cycle golf cart batteries and one 100 watt solar panel. So how do I calculate the remaining equipment that is required? Does one of your books cover this?

At about 4:30 you suggest that it is best to stay between 20 and 80 percent charge. That means the lifepo4 battery bank is only useing 60% of its capacity. Presumably this prolongs the life of the cells. What about in electric vehicles? Does charging a set of lifepo4 cells to 100% and then discharging it to 0% on a regular basis greatly affect its lifespan? Comparison maybe? In other words, just how badly am I hurting my lifepo4 cells in my car by doing full discharge cycling? The answer to this question helps folks decide on wether or not to use standard lithium cells or lifepo4 for their electric vehicle. Thanks for the great videos! :)

Re Venom balancer. Is it safe to open it up. I have to wack mine a few times before it reads correctly and I wonder if something is loose.

Nice haircut. You've been keeping up with your grooming since moving to San Diego.

@Will Prowse, have you ever rebuilt a battery or looked into how to do that?

Do you have to worry about top or bottom balancing and capacity testing with prebuilt batteries like the Zooms batteries for example? Thank you Will! 🙏

Good video but can you do a full practical video on how to do it?

Hi Will. Off topic. What are your thoughts regarding high Watt solar panels on rv builds. Example a single 320 watt panel connected to the EPEVER mppt 40 to 3 lithium batteries? Thanks Chris

I top balance my cells because I never get them down under 30% somehow but in summer they are always nearly full. So it depends on how you loadcycle your system. Then you must look how to balance it.

Yup I got a Rover so 14.4 for me

I’m looking at buying 3 300ah 12v drop in replacements and connecting them in parallel for 900ah capacity, is there a different way to balance these?

Hi Will, not sure if i can get an answer on this or not,, I may have asked in a previous video.. But here i learned that for solar it is better to do a bottom balance.. I will have a 13s system that i'm building using the big BMW cells, about 27Kwh. per cell. I think.. i calculated about 660Ah. and so i have learned that a BMS would be totally useless. and that bottom balancing is best.. What is the best way ( or is there a device) to bottom balance ?

I have a few packs. Hundreds of dollars worth i made for less than half because i followed these simple guideline. No Bms. Only thing to add mentally get a gauge of your average commute. Build battery accordingly. If a 10AH will drain halfway to work and back in up to few days. BUILD A DOUBLE IF POSSIBLE 15 OR 20AH. Cost is issue BUT KEY because of larger size. You never drain it maybe half. BOTTOM LINE YOUR CELLS ARE. NEVER STRESSED. STAYING BALLANCED. DONT WIMP OUT ON AMPS

i have 9=400w 51v solar&6=100w 18v so i went with(PowMr)mppt Solar charge controller

Thanks for your channel. Could be great to make a comparison between an epever 30A and a victron 100/30A MPPT

Have you tested daly bms, reasonable prices, but some look like fakes, Great vids

Subscribed! Thanks for sharing. We have battery projects like this on our new channel Lucky Dog Farms.

If we use your recommendation and set limits to high (13.3)-low(12). Should we still balance the cell? Thanks.

I bought a XZOY 24V-5120W-LiFeP04 (200-BMS) and since it comes with it's own internal BMS, and is rated for 25.6V, what should I set the lower and upper limit to in my Victron Solar Charge Controller and/or my Victron MultiPlus-1?

I use a simple $10 dollar battery charge controler to set custom charge parameters on any system. check it out might help you out. MODEL XH-M604

Love your Videos. Question: when I use a bms on my lifepo4 battery how do I protect my victron mppt charger? When the bms cut the charging and the solar panels are still putting power, how do I protect my charger? Panels still on my mppt and the bms cut, it could damage my charger right? Cheers from Germany

My problem is finding a BMS with built in bottom balancing because, as you said, I don't want to go to 100% SOC and many of them seem to balance at like 3.65v. Are there any BMSs with bluetooth where that balance point is configurable?

Hi Will and all together, have I understand right, that I can top balancing my cells with 13.4v with my solar charger? With or without the BMS? And is that right that I don't need a extra Lithium battery charger to balance the cells? It would be great to get a answer from someone! 🙏🙏🙏😊

I think he just called me a dumbass because I have no idea what he was talkin about LOL I'll try harder next time

i have 6x50a&3x130a&1x270amp cell top balance=960ah x4=set at14.1v for my solar it works good .I got the batteries over time what do you say is this good

Do you have a video explaining BMS size parameters. Example: if I have a bank of four 3.6v 280 ah cells what size BMS do I need?

How critical is balancing the liFePo batteries? And initial individually full charge before hooking up? I have (8) 12v 100ah chins in a 4s2p config for my 5000w 48v phocos. I have about 2000w pv input. Seems like they are not lasting long as they should.

If I build a 48v bank for a bike, would you recommend rebalancing the cells every 6 months or a year? Just to be safe?

Do I need to balance my Lion Energy battery bank? I individually charged each battery (4) I haven't connected them together yet. I am running a 24V bank, 2 pairs of 12V batteries. Since the batteries have BMS, is it unnecessary for me to balance them? Will they do it on their own in time? I am probably over thinking this, but hoping you can help me out.

Please let me know if I can use my Progressive Dynamics Industry Converter (PDI) (60amp- PD9260) to charge LiFeP04 12v solar battery system with correct BMS and controller.

Why do you show a renogy charge controller and state you can't adjust the charge voltage? It's pretty easy with the computer software. Done mine many times....

Does the inverter matter ? I want to use a 2000watt inverter and then ultimately install solar on my roof. I don’t want to buy the wrong inverter and then have to change it when I install solar. The controller etc does matter correct? They need to be solar oriented. Correct??? I am so confused 🤷‍♂️ Please reply. Thanks Will

OK so if you limit the charge voltage you can get the desired %? Like 60 - 70- or 80?

Wouldn't a diode between the charger drop the voltage to the battery for chargers with set voltages ?

I am purchasing two separate LiFeP04 batteries from different manufacturers, because they are sized to fit in different foot-prints. Is it dangerous to pair two dissimilar battery manufacturers in parallel?

Hi i have 4 x 210Ah Cells, 4S 12V. 2 x Cells at 3.33, 1 Cell at 3.25 and 1 Cell at 3.28. Maybe sound crazy, but is there a way to balance the cells by drawing current via a 3V Motor, to manually bring down each cell so they all have matching voltages, using a multi meter in the process. I have a Victron IP22 charger, so no good to top balance, and i don't want to buy another charger to top balance. The string will have a JBD BMS but I want to balance the cells before installing the BMS. Many thanks

Well, leave comments or questions. Hmm My 8 year old Trogen L-16 battery system is connected with 16 new LI-iron 280ah good quality top balanced batteries. I cycle between 12.4 vdc and 13.4 vdc on my 12 solar panels here in Montana. I will have to turn off the li-iron when the temp drops below 35 degrees in my shed. I eventually will phase out the Trogen batteries and get another 16 Li-Iron. About 3 months the system is off during the darkest part of winter, on trickle charge ANY SUGGESTIONS, Please reply, Thank You.

I have a question , if I change lifepo4 to 3.65 how long do I need to wait till it balance? I'm building 24v 8cell pack when parallel battery pack hits 3.65v I disconnect chage and check voltage tow cells in 3.64 and all other in 3.65 - grade A new cells (sorry about my English)

Will I just got 8 3.2v 120ah grade A cells all the cells read exactly the same 3.29v is it safe to go ahead install a 8S bms and start using them ??

Juicy Battery Couture. Was the e-book I sent you of any value?

So if the LIFePO4 says it is 12.8 v 100Ah What is the Top and Bottom settings that I have to set my contoller at?

How to change the upper voltage limit. In the bms I have set the upper voltage to 3.4 volt. The cells are not good quality ones. It is getting disconnected before complete charge. Please help.

Are there LiPOs that have the BMS integrated into the battery. (12 volts @ 10AH.)

bro can you make a video about mixing different brand of lifepo4 batteries in series ? like I have 12v 100ah plus another 12v 138ah and 12v 40ah batteries in series ?

Just wondering if you have used single cell balancing modules that limit the voltage for any module to about 3.5V. These self balance without a BMS and only cost $5 each.

Active balancing ftw :)

Did you move your bottom balancing video with the digital battery meter to private??? I need that video.

Assume I have several 12v (4S) Batteries with their own 4S-BMS. Assume also I have an Inverter that takes in 48VDC. Q1: Will it work if I connect 4 of my 12V batteries in series to my 48V Inverter? Q2: Can I connect the Inverter to the Batteries CAN port and get battery readings?

Why can't I hook a 20 amp power sourc to my 20 amp solar charger, to have all the settings I need? or can I?