What would be considered ruined Leaf EV batteries that have significant range loss (20% to 50% degradation, for a car that went around 60 miles with a full battery) are being used to cover peak load right now in California and have been used to do so for years.

https://www.youtube.com/watch?v=JqlOlqK_ot8

2nd life use cases for cheap, mass produced batteries like this are more common than you think.