jonescg wrote: ↑
Mar 14, 2018 12:14 am
Any battery will prefer to spend its life at 25'C. Charging at 2C is no different to discharging at 2C - the heat is mainly coming from I^2R losses in the current collectors. The degradation is quicker at high states of charge too - more reactive species present.
I agree, the heat dissipated will be the same in situations of charging vs discharging. But discharging cells at say 2C, especially those that are not power tool grade cells would kill them pretty fast. CC/CV of 2C is terrible for these types of cells. CC/CV of 2C to 4V and then like 0.2C from 4v to 4.2v would be much better for the cell.
Heat is not the only factor to consider. Li-ion's just do not like high charging currents at high voltage levels. Even if you managed to keep the cell at 25C, charging at 2C to 100% DOD would be terrible. 70-80% DOD charging at 2C while keeping the cell cool, with optional slow charging from 70-100% DOD would be much better for the cell. This is what Tesla does.