LiFePO4 Battery Bank in Series (48V or 60V) balancer

[eabyrd]

Will a BMS work with batteries instead of individual cells? My goodness I hadn’t thought of them in that way. Of course I have the Taino balancers already so their cost is zero. Would a BMS provide additional benefits though. Could I set over and under voltage at battery levels instead of cell levels?

 

[Gadgetnerd]

A bms sees each battery as an individual cell yes. It constantly monitors the voltage of each battery and balances them individually. It also monitors the total pack voltage. I know 12V components are easier to source an all that but the ultimate goal is if you are using 120V appliances then the closer your pack voltage is to that 120V, the more efficient it is both electrically and financially (buying less copper). Same with the solar input side, four 12v panels in 48v series are way more efficient than in 12V parallel (plus you have to fuse) I'd go so far as to say the only reason you would run series strings in parallel at all is because you are limited in the voltage your charge controller will accept (which increases as you put more panels in series) Hope this helps.

 

[eabyrd]

A bms sees each battery as an individual cell yes. It constantly monitors the voltage of each battery and balances them individually. It also monitors the total pack voltage. I know 12V components are easier to source an all that but the ultimate goal is if you are using 120V appliances then the closer your pack voltage is to that 120V, the more efficient it is both electrically and financially (buying less copper). Same with the solar input side, four 12v panels in 48v series are way more efficient than in 12V parallel (plus you have to fuse) I'd go so far as to say the only reason you would run series strings in parallel at all is because you are limited in the voltage your charge controller will accept (which increases as you put more panels in series) Hope this helps.

Can you point to a 4s BMS with a range of 11v to 14.4 volts as the under / over “cell” voltage and 44v to 55v as the “battery” limits.

To restate the plan. 4x 12 volt lifepo4 batteries in series for a 48 volt nominal system. The question is how to maintain balance between the 4 series connected batteries over their life. Currently I accomplish this with my AGM bank by using Taico active balancers. It works quite well, maintaining a 20mv difference unless their is a really high charge / discharge rate

 

[Gadgetnerd]

There are hundreds on Alibaba and Amazon and ebay. Just go 12v, 4 or 8s ( allows expansion from 4 cells) and whatever amperage you want to draw at those 12V in parallel so you'll want say 200 amps for 2400 watts (200x12) and so on...my 16 cell 48v pack balances to 1mv but that will always increase when charging, discharging or when the batteries gets closer to full or empty.

 

[eabyrd]

There are hundreds on Alibaba and Amazon and ebay. Just go 12v, 4 or 8s ( allows expansion from 4 cells) and whatever amperage you want to draw at those 12V in parallel so you'll want say 200 amps for 2400 watts (200x12) and so on...my 16 cell 48v pack balances to 1mv but that will always increase when charging, discharging or when the batteries gets closer to full or empty.

Are you suggesting I break open perfectly good batteries that already have perfectly good BMS installed and install a replacement that connects to each individual cell? Kinda defeats the purpose of buying the cheap Chins style batteries. If I wanted to do that I would just buy fortune cells and build a battery

 

[Gadgetnerd]

No, the internal bms's manage the individual cells (4x3.2V or whatever) inside each battery. What I'm saying get a BMS (which is also a balancer) rather than the balancer you suggested to manage each of the 4 or 5 12V batteries in your pack.

 

[eabyrd]

I have never seen a BMS that can be programmed to a voltage range of 11 - 14 volts. I have been looking on AMZ as we went back and fourth. Would appreciate a hint as the addition of over voltage and under voltage protection has merit

 

[Gadgetnerd]

I have never seen a BMS that can be programmed to a voltage range of 11 - 14 volts. I have been looking on AMZ as we went back and fourth. Would appreciate a hint as the addition of over voltage and under voltage protection has merit

This is exactly the problem with 12V parallel systems, It's a bit of a weird ask because basically you already passively balance cells just by putting them in parallel, and also when you charge them in parallel (which I suspect is all the device you showed does if it is even an active balancer) Just watched a youtube video where a guy (apparently an aerospace engineer) built a 20kwh system with 5 parallel 400ah 12V batteries. I thought the goal was to have 20K of power not spend 20K...lol Needless to say comments were turned off. They do have commercial BMS systems for multiple 12V batteries but I doubt they're cost-effective for your application, my neighbour worked 40 years for a telecom and they had battery backup power systems configured like this, needless to say they're pretty obsolete now. I know its not helpful but I'd go series and invest in a 48V integrated charge controller/inverter and get rid of evey piece of 12V and 24V stuff while you still can IMO.

 

[eabyrd]

This is exactly the problem with 12V parallel systems, It's a bit of a weird ask because basically you already passively balance cells just by putting them in parallel, and also when you charge them in parallel (which I suspect is all the device you showed does if it is even an active balancer) Just watched a youtube video where a guy (apparently an aerospace engineer) built a 20kwh system with 5 parallel 400ah 12V batteries. I thought the goal was to have 20K of power not spend 20K...lol Needless to say comments were turned off. They do have commercial BMS systems for multiple 12V batteries but I doubt they're cost-effective for your application, my neighbour worked 40 years for a telecom and they had battery backup power systems configured like this, needless to say they're pretty obsolete now. I know its not helpful but I'd go series and invest in a 48V integrated charge controller/inverter and get rid of evey piece of 12V and 24V stuff while you still can IMO.

 

[eabyrd]

Dude, we must have a language problem, but there are no, none zilch, zero, nada parallel cells in a 48 volt system containing 4 12 volt batteries in series

thanks for trying to help though

 

[Gadgetnerd]

Dude, we must have a language problem, but there are no, none zilch, zero, nada parallel cells in a 48 volt system containing 4 12 volt batteries in series

thanks for trying to help though

 

[Gadgetnerd]

I guess what I mean is either way, (parallel or series) there's no feasible way to monitor the batteries as individual 12v "cells" in a 48v series or 12V parallel group. The tangent I went off on was about the youtube guy building a parallel 12v system of like 2000ah. It's such a dumb way to do it, what with the 1/0 gauge wire and the inverter the size of a tank because it has to handle like 400amps...lol

 

[FingerSling]

I assume you found something in the end? Not sure if links are allowed but options on Amazon and Ebay for what I think you're looking for.

For example, https://www.amazon.com/gp/product/B09GLS1DVR, https://www.ebay.com/itm/284292893212

Edit: Apologies to eabyrd as I just realized a similar link was posted earlier in the thread and I missed it when I stumbled upon this thread looking to solve the same problem. 16s would be preferred, but my mower is mechanically setup for four separate batteries and I don't want to mess with the mechanics too much.

 

[time2roll]

I assume you found something in the end? Not sure if links are allowed but options on Amazon and Ebay for what I think you're looking for.

For example, https://www.amazon.com/gp/product/B09GLS1DVR, https://www.ebay.com/itm/284292893212

Edit: Apologies to eabyrd as I just realized a similar link was posted earlier in the thread and I missed it when I stumbled upon this thread looking to solve the same problem. 16s would be preferred, but my mower is mechanically setup for four separate batteries and I don't want to mess with the mechanics too much.

I would assume either of your links will work well for what you need.