10s battery question.

[mr watts]

Hi,I just need a little advice,please.
I've acquired 50 brand new Samsung high drain cells and I want to make a 10s5p pack.
I have a spot welder and will be fitting a BMS.
10 of the cells are 1500mah and 30 are 2000mah they all have resistance around 25mo.
My question is,can I mix these cells ok in parallel strings of 5 cequal capacities?

Thanks,in advance

 

[Nealh]

10 + 30 = 40 so 10s 4p so you are 10 cells missing.
Do the cells have the same current discharge ? If not again one has to work to the lowest discharge denominator.
You could do, the 1500 mah cells are the lowest denominator so any P group will only be xxx X 1500mah for capacity. Tbh it is far simpler to use cells all the same.

 

[matthewslack]

Hi,I just need a little advice,please.
I've acquired 50 brand new Samsung high drain cells and I want to make a 10s5p pack.
I have a spot welder and will be fitting a BMS.
10 of the cells are 1500mah and 30 are 2000mah they all have resistance around 25mo.
My question is,can I mix these cells ok in parallel strings of 5 cequal capacities?

Thanks,in advance

Each string of 10s must be 10 cells of the same capacity, not some 1500 and some 2000mAh. If you mix cell capacities within a string the smaller ones will be flat first, and a good BMS will then turn off the battery, which means the extra capacity of the larger cells is not used. It also means the smaller cells are run flat every cycle, shortening their life.

You could put strings of 10s 1500mAh in parallel with strings of 10s 2000mAh, but unless they have identical discharge curves, there will be currents flowing 'sideways' between the big and little cells in each cell block every time a heavy current is drawn. Magnitude of current depends on degree of mismatch between the cells. Might not be a big issue, but could shorten pack life.

 

[mr watts]

Hi,thanks for your reply it makes good sense.
If I made 2 packs of identical cells both with a bms,and charged them separately.
Then discharged them both in parallel,could that work?
If not I'll source more same cells.
Cheers.