A method for determining the amount of charge which can be drawn from a storage battery and a monitoring device are provided that measure at least one of battery currents and battery voltages at at least two points in time before or during a rise phase and during or after a decay phase of a charging or discharging operation. A characteristic variable for the amount of charge is determined. The characteristic variable is derived from the relationship of at least one battery voltage value from the rise phase with respect to at least one battery voltage value from the decay phase or from the relationship of at least one battery current value from the rise phase with respect to at least one battery current value from the decay phase.