You don't really need this, if you have an EV with V2X technology. There's already charging products that work seamlessly: https://www.youtube.com/watch?v=H0WGl_U5azs and you have 100kWh of capacity, so you could sit out an outage for a long time. You can also configure the % cut off for the EV, so you still have enough left to drive if you need to leave.

EV battery degradation from this use case is irrelevant. EVs are consistently hitting 300,000 miles with 90% capacity, so let's not belabor this point.