more than one cell on a single bms...

[ericfx1984]

so lets say I am building a 4s pack... and planning to build with 230ah cells... COULD I build with 8 cells, 2p on each leg of the BMS... and WOULD it balance the cells properly

basically i am asking could you build an 8 cell, 4s battery with a single 4s BMS?

 

[Horsefly]

Yes. It's done often. The two cells in each parallel group appear to the BMS as one cell. There is lots of debate about how good or bad this configuration is. Many of us (me included) say it is better to ask your BMS to manage one cell at each slot in your battery. If instead you do two 4S batteries in parallel each with its own BMS, you have some redundancy: If one battery / BMS cuts out (LVD/HVD/ or whatever) the other battery can continue to power your system.

 

[Bob B]

It would be a 2P4S pack ..... I did mine that way and have not had any problems.

Cells that are poorly matched wouldn't be ideal for this setup ..... but even if poorly matched, the only likely problem would be some capacity loss.

 

[MisterSandals]

I have been running a 2P4S 206Ah cell (412Ah 12.8V battery) in my RV for almost 2 years now. Works great, probably due to effort taken to setup properly.

I picked the best 8 cells from the 13 I ordered. I determined thru use, their capacities relative to each other (ranked). This info was key to making each of the 2P pairs combined capacities equal to the others (4 pairs).

Pairing strongest with weakest. Second strongest to second weakest…

So far it’s been trouble free, I wouldn’t change a thing. I REALLY like the idea of a single BMS in my RV (120A Overkill).

 

[JoeHam]

This dude put out a video about it :

?

 

[time2roll]

so lets say I am building a 4s pack... and planning to build with 230ah cells... COULD I build with 8 cells, 2p on each leg of the BMS... and WOULD it balance the cells properly

basically i am asking could you build an 8 cell, 4s battery with a single 4s BMS?

I have 2x 4s batteries with 8 cells each. No issues. I even skipped the top balance and just put it in service with a 5a active balancer. Works great.

 

[Steve_S]

so lets say I am building a 4s pack... and planning to build with 230ah cells... COULD I build with 8 cells, 2p on each leg of the BMS... and WOULD it balance the cells properly

basically i am asking could you build an 8 cell, 4s battery with a single 4s BMS?

Please download this resource PDF, it will save you a LOT of questions and hassles Luyuan Tech Basic Lifepo4 Assembly Guide

 

[Ole dog]

What about 2, 7s4p batteries on one bms,?

 

[Horsefly]

What about 2, 7s4p batteries on one bms,?

I'm not sure what this means. 7 cells, in series to make one pack, and then 4 of those packs in parallel to make a "thing", and then 2 more of those "things"? Please explain what you are asking.

 

[Ole dog]

I'm not sure what this means. 7 cells, in series to make one pack, and then 4 of those packs in parallel to make a "thing", and then 2 more of those "things"? Please explain what you are asking.

1 ,7s overkill bms , hooked up ,in parallel, to 2 , idetical 7s 4p compleat battery banks..

 

[time2roll]

deleted

 

[100 Proof]

so lets say I am building a 4s pack... and planning to build with 230ah cells... COULD I build with 8 cells, 2p on each leg of the BMS... and WOULD it balance the cells properly

basically i am asking could you build an 8 cell, 4s battery with a single 4s BMS?

That is EXACTLY the setup I have using EVE cells. I've only been running it for six months or so, but so far, I couldn't be happier.

 

[Horsefly]

1 ,7s overkill bms , hooked up ,in parallel, to 2 , idetical 7s 4p compleat battery banks..

Isn't that just a single 8p7s battery? If you are hooking a single BMS up to two identical 4p7s, there is a BMS balance lead shared between each set of 4p in one 7s and the corresponding 4p in the other 7s, effectively making those cells all in parallel. So you end up with 8p7s.

Edit to add: Does Overkill even sell a 7s BMS?

 

[Ole dog]

Ok... i lets start over, I have 2 batteries, 24v lion {NMC) madeup of 28 ( cells,) 3.7v each. totaling 32AH. configured as,7s4p. Now parallel these together, for 64 AH.
All right it's a JBD bms, my over sight. Now wire this(7s) JBD , 80 amp bms to control both batteries,in parallel, or can you teach me a new trick!

 

[Ole dog]

Now multiply times 5

 

[Horsefly]

Ok... i lets start over, I have 2 batteries, 24v lion {NMC) madeup of 28 ( cells,) 3.7v each. totaling 32AH. configured as,7s4p. Now parallel these together, for 64 AH.
All right it's a JBD bms, my over sight. Now wire this(7s) JBD , 80 amp bms to control both batteries,in parallel, or can you teach me a new trick!

If you really want these to operate as two separate batteries, you will need a separate BMS for each. Like I said, if you want to have one BMS manage those 56 cells, it will be in a 8p7s configuration.

I don't think you meant 7s4p, which would be 4 batteries wires as 7s. Sounds like you mean 4p7s, which is groups of 4 cells wired in parallel, and then 7 of the groups wired in series.

I don't know what the multiply times 5 comment means.

Edit: Corrected the total number of cells