Advice need on building a 2p 7s battery.

[PhiPhi]

Hi I'm new here and was not sure the best place for this question.

I currently have a 24v 7s 94Ah battery using Samsung SDI NMC cells, I haven't yet hooked up a my BMS but as a precaution have setup very conservative charging/discharging parameters on the MPPT/Hybrid inverter and check the cell balance every few days.

I have 7 additional matched cells on the way and wondered if it would be better parallel the cells in pairs and then put the cell pairs in series or to stick with 7s and put those 2 batteries in parallel? I foolishly purchase another 7s-16s smart bms because the cell pairing didn't occur to be at the time, anyway I would prefer the latter configuration so I can maintain cell level monitoring but not at the cost of safety or battery performance.

 

[PhiPhi]

Well I guess it wasn't as easy question as I thought.

 

[newbostonconst]

How I would do it.....but am sure other would do it different.
The new 7 cells need to be balanced and then voltage brought close (with in a hundredth of a volt preferably) of the other pack. I would then put them in parallel to the other pack.

You could run 6 jumpers between the two packs at the inner connections so that every cell is paralleled at every connection. I think there is potential to get more energy doing this because if there is a weak cell the other parallel cell in the other pack will help it out without the bms shutting down the whole pack.

 

[PhiPhi]

@newbostonconst Thank you very much! In that case I'll stick with the simpler configuration of paralleling the 2 packs rather than individual cells.