Method and apparatus for determining the state of health of a battery

The method involves estimating the open-circuit voltage (UR), internal resistance (RI) and internal voltage drop (UK) caused by density variations in the battery acid. A model is initialized to estimate the capacity with the estimated values. The model is stimulated using a load current characteristic of a load to obtain the battery voltage at the voltage response (Ubatt,prad) of the model. The voltage response of the model is compared with a minimum battery voltage, to estimate the capacity. An Independent claim is included for an apparatus for estimating the capacity of a battery.