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BMS's for higher current have a lot more FETs, and cost more. Whatever the vendor rated it for, it probably doesn't have a lot of margin. The amount of nickel welded into the pack is also based on the vendor's design. Exceeding that will increase heating in the interconnects as well as the cells and BMS. The ambient temperature becomes important, and the duration of the high current. Put a temperature probe or two against the battery and do some testing..