Can I use different capacity cells

[soyachips]

Hi everyone,

I didn’t plan it this way but I’ve ended up with 22 x 10Ah Headways and 22 x 15Ah Headways.

Can I put all the 10Ah cells together in series to make 72V and the same with the 15Ah cells, then put these together in parallel to make s bigger capacity 72V pack?

Thanks!

[antiscab]

Yep, that'll work fine. If you want to save on bms, you can parrallel individuallly 10Ah and 15Ah to make 25Ah then put in series. Might be a little awkward in layout though

[soyachips]

Thanks that’s good news but I’m curious why the 10Ah cells don’t run out of energy first and hit low voltage before the 15Ah cells?

[antiscab]

Currents flows proportional to the inverse of resistance. The smaller cells generally have higher resistance, and don't put out as many amps in parrallel as the larger cells. It all evens out

[soyachips]

Got it, thanks.

Also by paralleling each 10Ah and 15Ah together first they can be monitored as one “cell” and I only need 1/2 the number of BMS?

[coulomb]

by paralleling each 10Ah and 15Ah together first they can be monitored as one “cell” and I only need 1/2 the number of BMS?

Yes.

[soyachips]

Excellent, thanks for the help ... now have to work out how to arrange different size cells together into a pack!