Building a 20s 14p battery - parallel two 20s 7p VS 20 series of two 7p in parallel

Batteries, Chargers, and Battery Management Systems.
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Peterfr12   100 mW

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Building a 20s 14p battery - parallel two 20s 7p VS 20 series of two 7p in parallel

Post by Peterfr12 » Apr 28 2019 5:05pm

Dear ebikers,

I am building a giant battery for my recumbent a 20s 14p, so 84V 49Ah when fully charged. I have enough space under my seat to carry it.

I ordered 40 7p NESE modules from Agnius and 290 Sanyo cells from Tumich. The NESE modules are fantastic. I am familiar with series and parallel circuit, but I wonder which setup the best is:
Setup 1 where I will parallel two 20s 7p modules
setup 1.png
setup 1.png (28.45 KiB) Viewed 219 times
Setup 2 where I will parallel two 7p modules and I will add in series 20 of them?
setup 2.png
setup 2.png (28.21 KiB) Viewed 219 times
I have not yet ordered a 20s smart bluetooth BMS (Aliexpress?) but I don’t know if when I will install a 20s BMS, one setup is better than the other for connections (setup 2 here).

Many thanks for your answers.

Best regards,
Pierre

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amberwolf   100 GW

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Re: Building a 20s 14p battery - parallel two 20s 7p VS 20 series of two 7p in parallel

Post by amberwolf » Apr 28 2019 7:33pm

If you want to use a single BMS, then 20s 14p as one block would be simpler wiring, etc. But it takes a single spot on the bike large enough for the whole thing in one box for that, or else you wind up running balance wires and main power wires between the two.


So if you need to split the pack into two blocks to fit it on the bike, two BMSs making two completely separate (but paralleled at the main outputs) 20s 7p packs would be better. (partly because if you had a problem with either half, the other half could still independently operate the bike until you could fix the problem). The only thing you have to cable between them is the main power wires. (assuming you use a common-port BMS that charges and discharges from the same port, which makes things simpler than separate ports).

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agniusm   10 MW

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Re: Building a 20s 14p battery - parallel two 20s 7p VS 20 series of two 7p in parallel

Post by agniusm » Jun 27 2019 11:36am

Better parallel then series your pack. This way your 14P group cells will be in balance to each other perfectly. You can split paralleled packs no problem, say 20 modules which would make 10s14p and then another same

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