Method and device for estimating the usable charge capacity of an electrical energy store

A method for estimating a usable charge capacity of an electrical energy store, the method comprising:

• determining a nominal initial charge capacity and a maximum initial estimation error of a new energy store or a degraded energy store;
• determining one or more nominal charge capacities and one or more maximum estimation errors for the degraded energy store;
• interpolating a characteristic of a nominal charge capacity and of maximum lower and upper estimation errors between interpolation points of the nominal initial charge capacity and the one or more nominal charge capacities, and interpolation points of the maximum initial estimation error and the one or more maximum estimation errors;
• and
• estimating a nominal state-of-charge, a current usable charge capacity with a lower estimation reserve, and a current usable charge capacity with an upper estimation reserve for a current degradation state of the electrical energy store.