i love the idea, but everything i know tells me that replacing one cell in a series parallel array with a fresh one is a bad idea.

over it’s life, a battery’s capacity and internal resistance change, so it’s not only important to match batteries in a pack by exact type, but also condition. otherwise, the cells won’t charge / discharge evenly, leading to overdischarge / overcharge, or, if managed by the bms, drastically reduced performance (basically all cells are limited to the worst one’s performance).

still, the concept is fantastic, so i hope they found a way to work around this issue!