i have two 90ah life04 batteries and want to add two 100ah in parallel to obtain 390ah is this ok to mix different ah life04 batteries
asked
mixing Life04 batteries 90ah and 100ah
As there are differences in the cells (resistor wise) and electronics (for balancing for example) a mix/match is not a good idea. Mainly as there will be substantial unbalance.
Thankyou will not mix as that i believe will cause long term damage
Even cells of the same capacity are sometimes worse than a flea circus when you try to keep them in balance. (Or if you replace a bad cell with a new one... you have to take great care so this new cell does not get damaged by over or undervoltage).
That being said - and in full agreement with Johannes - there is actually one way to mix cells of various capacities. Provided you have the same amount of each capacity.
Say in your case you would have 8 pcs. 90Ah and 8 pcs. 100Ah => then you could form a 190Ah 24V battery bank by pairing 8 x [90+100] and putting these pairs in series. Of course
a) the 90Ah "as a group" and the 100Ah "as a group" would need to be of similar quality/age
b) without BMS still a no go, but the BMS could be used to monitor these virtual 190Ah cells.
So it almost looks like that is what you did want to do in the first place, although I do not understand the amounts. You say you have 2 + 2 cells? What I described, that's only (with keeping sanity) possible if you would build up a 6.4V system with 190Ah capacity.
Putting them as 4 cells in parallel... and getting just one cell would by the way give you 380Ah - not 390Ah - and would too be possible, but then you would have a 380Ah 3.2V "virtual cell".
Putting these 4 cells in series is an absolute no go, with or without BMS, they would sooner or later look like The Three Graces from Peter Paul Rubens.
