Sverige
A Brit in Sweden
Ok, this may constitute heresy even asking this question, but here goes anyway!
Given that the weakest cell in a series pack dictates the overall battery capacity (as it reaches LVC soonest), is there anything to prevent the DIY LFP battery builder balancing out cell capacities by adding small capacity LFP cells in parallel with the lowest capacity cells in a series pack?
An example - I buy an 8 cell set of 280Ah prismatic cells which are sold as matched grade A, but on initial testing I find my cells have capacities ranging from 285Ah down to 278Ah. What if anything stops me using some 2.2Ah 26650 size A123 cells (also LiFePO4 chemistry) in parallel with the weakest cells to get them all up to 285Ah so my battery maintains not only top balance, but is closely bottom balanced also?
Apart from the practical difficulties of arranging the cabling so as to avoid any shorts, etc, I can’t see a drawback. Maybe you could argue just the cost of the small cells isn’t justified by the benefit of the additional capacity to the overall pack, but if just one prismatic cell is lower than the others, then adding a few small cells in parallel might bring up the capacity of the whole pack.
Anyone care to comment on how feasible this is?
Given that the weakest cell in a series pack dictates the overall battery capacity (as it reaches LVC soonest), is there anything to prevent the DIY LFP battery builder balancing out cell capacities by adding small capacity LFP cells in parallel with the lowest capacity cells in a series pack?
An example - I buy an 8 cell set of 280Ah prismatic cells which are sold as matched grade A, but on initial testing I find my cells have capacities ranging from 285Ah down to 278Ah. What if anything stops me using some 2.2Ah 26650 size A123 cells (also LiFePO4 chemistry) in parallel with the weakest cells to get them all up to 285Ah so my battery maintains not only top balance, but is closely bottom balanced also?
Apart from the practical difficulties of arranging the cabling so as to avoid any shorts, etc, I can’t see a drawback. Maybe you could argue just the cost of the small cells isn’t justified by the benefit of the additional capacity to the overall pack, but if just one prismatic cell is lower than the others, then adding a few small cells in parallel might bring up the capacity of the whole pack.
Anyone care to comment on how feasible this is?