A method for estimating the capacity of a battery, including the following steps: estimation of a steady-state voltage U.sub.R, an internal resistance R.sub.1 and an internal voltage drop U.sub.K of the battery, caused by a density difference in the battery acid; initialization of a model describing the battery in order to estimate the capacity, using estimated values U.sub.R, R.sub.1 and U.sub.K ; stimulation of the initialized model with predefined load current characteristic I.sub.Batt,stim, in particular a simulated load current characteristic of a consumer in operative connection with the battery, in order to obtain a voltage response U.sub.Batt,pred of the model, representing the battery voltage given the predefined load current characteristic; comparison of the voltage response U.sub.Batt,pred of the model with a predefinable, minimal battery voltage U.sub.Batt,limit, and estimation of the capacity of the battery by comparing U.sub.Batt,pred and U.sub.batt,limit.