This Southern California solar farm is using retired EV batteries for storing the power and then send to the grid when needed. This way the retired batteries can extend their usefulness for several…::A Southern California company is showing how repurposing EV batteries for stationary storage can extend their usefulness for several years.
In practice they’re used more as a sort of capacitor to provide voltage regulation on the grid, basically what gas is doing for reliability. Not sure how often that wouldn’t involve a full discharge, but I know most gas in this context is running way below its capability.
It sounds like this is being used for day/night storage here as opposed to spot demand, so it may be using more of the charge range.
I wonder if these batteries have reduced peak power output, can they fulfil the kind of balancing that you are suggesting? I guess if they had enough it would be fine.