Method for monitoring the functional condition of the battery by using the battery voltage during vehicle

A method for determining a functional condition of a battery, the method comprising the steps of: Measuring an initial battery voltage after a first voltage drop during a start of engine cranking phase; Monitoring a battery voltage during the remainder of the engine cranking phase; Determining a first peak voltage after the first voltage drop; Determining a lowest battery voltage during an interval between the first peak voltage and the completion of the engine cranking phase; Determining whether a voltage difference between the lowest battery voltage and the initial battery voltage is less than a voltage threshold value; and Identifying a bad battery functional state in response to the fact that the voltage difference is less than the voltage threshold.