For old EV batteries where the only reason they need replacement is reduced capacity I wonder if they might be useful in some stationary applications? I'd love to have a whole-house battery backup system for the occasional power outage, but systems with new batteries are too expensive.
An 80 kWh battery, say, that has lost half its capacity would have been enough to get me through most outages I've seen since moving into my current house 15 years ago without me having to even try to reduce power during the outage. The one or two outages where that would not have been enough, it would have been sufficient to just dress warmer, turn the thermostat down a little, and avoid doing laundry.
I'd be interested in this as long as the price per kWh of the degraded battery is significantly lower than the price for a new battery with the same capacity. The degraded battery is going to be good for much less cycles than a new battery of the same capacity, so it should cost less.
I'm not very knowledgeable about this, but don't think they fail this gracefully.
I thought that a lot of the battery failures in EVs was due to the failures of individual cells (like AA batteries) within modules, which make it impossible for the BMS to balance power between modules. There was a recent youtube video where an old Model S had its range dramatically reduced to less than 25% because a module had 2 bad cells. The cells were replaced, and the car works as normal now. There was a debate about how long-term that fix would be (eg, would the same thing happen soon, as other cells die).
My LEAF had that repair done under warranty (cell #17 was dramatically weaker than the rest, resulting in the pack suddenly having around 33% range and 50% power). Repair was disassemble, change module #9 (cells 17&18), reassemble but took about 2 calendar weeks for parts and trained labor reasons (repair itself was done in a single day).
3.25 years later there is no evidence of recurrence/spread and battery diagnostics are all good. That’s an N of 1, but I don’t see any structural reason to think my battery would now be any different than the sibling car’s battery that was next off the production line (assuming there was no additional fault introduced during service).
This couple used Leaf modules to create a 48v pack for their vintage bus. 3 years later their bus construction is done and they're on the road, and the batteries are doing fine.
An 80 kWh battery, say, that has lost half its capacity would have been enough to get me through most outages I've seen since moving into my current house 15 years ago without me having to even try to reduce power during the outage. The one or two outages where that would not have been enough, it would have been sufficient to just dress warmer, turn the thermostat down a little, and avoid doing laundry.
I'd be interested in this as long as the price per kWh of the degraded battery is significantly lower than the price for a new battery with the same capacity. The degraded battery is going to be good for much less cycles than a new battery of the same capacity, so it should cost less.