A degraded battery bank does not mean a bank with outright "bad" cells. The cells will probably be way more off than they used to be, but there can still be plenty of effective capacity in the bank. Heck, if space isn't an issue, it's productive as long as it isn't self-discharging too fast.

You can still have a working battery even with some "bad" (i.e., way out of spec) cells, depending on the BMS. All the thresholds are configurable, just that a regular EV setup would lean towards safety.