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Mixed packs
#1
Hey guys i hope you can help me Big Grin i could not find the answer...i have 7s 80p packs each 200ah, now i want to expand to 14s Big Grin when i build the other 7 packs and the ah hour is higher than the original 7 packs how big of a problem will it be?
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#2
As Long as you base your load on the weakest packs its fine. But you are basically wasting the other capacity that exist due to this Smile

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#3
thanks for your answer, so the best option is buy used cells and sort them over the 14 packs
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#4
It shouldn't matter as long as the voltage is the same. Once you connect all the packs together (including the balance connectors) they will equalize to the same voltage. The voltage will remain the same while charging and discharging.
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#5
Jony, he's not connecting them in parallel, and also he doesn't mention what kind of bms he's using, if any.
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#6
(03-23-2020, 01:56 AM)Korishan Wrote: Jony, he's not connecting them in parallel, and also he doesn't mention what kind of bms he's using, if any.

i am only in the buildig fase at the moment so it's easy to change your plans Big Grin  the BMS i had in mind is a daly BMS
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#7
Are you planning to mix new a d old ? Are the old like oooold?

IF so dont do it. In series you want the same type of cells IF you can you want same amount cells, same amount lows and highs , as Close capacity as possible.
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#8
sorry, no not "new" cells other used cells Big Grin
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#9
If you have 14 battery packs wired in series and the battery packs all have different capacities, your string of batteries will only perform as good as the lowest battery pack in the string. I suggest trying to better match cell capacities next time. I'm building large packs so I just take all the cells and mix them up in a big box. If you're building smaller packs, sorting cells is much more important.

One thing you could to alleviate the problem is add a few extra cells to the packs that are testing lower.
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