Somewhat self-correcting as a cell with lower internal resistance will charge & discharge at higher current than others - thus getting aged faster and catching up to its peers. As the cells age, their internal resistances get progressively less matched. When cells in parallel are new and well-matched, they balance well. Advice about tradeoffs in using much larger cell sizes rather than parallel small cells welcome. Specifically LiFePO4 in form factor of cylindrical 18650 or 26650. Note: NOT asking about other lithium chemistries such as lithium polymer. If it's not safe to wire that many directly together, would it be safe if current limiting components or fuse/polyswitch were added between parallel cells? Or is it better to architect a large pack in strings of at most 3P x (however many) in series? Would it be possible to get to 10, 20, 30 cells in parallel with this chemistry? The completed pack would drive a DC motor. Is it also safe to add more cells in parallel? The most I've seen discussed for other chemistries is around 3 cells in parallel. This chemistry is supposed to be much safer than other lithium chemistries, as it doesn't catch fire even when punctured. Precautions taken would include ensuring they're brand new cells from the same manufacturer lot, at about the same state of charge, and letting them rest for a day to equalize before charging or discharging the pack.
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