"This software enables EV battery packs to be used for stationary storage. It achieves this by converting the EV battery CAN data into a brand battery format that solar inverters can understand. This makes it extremely cheap and easy to use large EV batteries in a true plug'n'play fashion!..."
https://github.com/dalathegreat/Battery-Emulator
A video of someone who has done this and now has 120kW.h (IIRC) of battery on hand: