The battery in an electric vehicle (EV) faces serious performance demands every time the driver steps on the accelerator or the brake. So after a number of years, when its capacity has dropped 20 to 30 per cent, it gets replaced.

But that retired battery can still function well in less demanding applications — like stationary energy storage systems of microgrids — where the fluctuations in power/energy and charge are much smaller.

Because the sun doesn’t always shine and the wind doesn’t always…