DIY LiFePO4 24-volt 1088Ah battery build (32 cell Lishen 272Ah)

michael d

Solar Addict
Joined
Dec 15, 2019
Messages
384
Presently in the design /acquisition phase:
32 272AH Lishen cells here now.
waiting on bus bar cell interconnects. likely make some myself.

design subject to change!

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Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Joined
Oct 29, 2019
Messages
5,408
Location
Rural NE Ontario Canada
Be aware that each cell weighs approximately 5kg/11lbs X32 that is HEAVY !
Precharge "Top Charge" and Top Balance each cell before final assembly.
As these are NOT Matched Cells - they are Bulk Commodity cells. Try to do a full capacity test on each cell, once all are complete try to match identical cells together, ideally by capacity and IR (Internal Resistance) so that the sets perform as closely together as possible.

NORMALLY it is not advised to parallel unmatched cells as various issues can occur and there is no "fine monitoring" of each individual cells as you only see the average of the "set". This also includes the Voltage & IR (which the BMS' will use) of the collective "set". The 3 cells will appear as one to the BMS. That CAN hide a failing cell, or one over charged or discharged within the set.

EV's use Paralleled cells BUT they are all perfectly matched, batched & binned to be exactly identical throughout their full operating ranges. They are also each lower capacity than these big honking 272AH cells, which makes their internal management & balancing quite different. They are NOT comparable to big LFP.
"21700 cells start around 3.0Ah (3000mAh) and go up to 4.0Ah (4000mAh)"
"18650 cells typically range from around 2.3AH (2300 mAh) to a maximum of 3.6AH (3600 mAh)."
 
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