A vehicle storage battery is monitored to determine battery capacity, state of charge and certain fault conditions. The ambient temperature, battery voltage alternator/regulator output voltage and current to and from the battery are continuously measured. Current voltage (I-V) data is analyzed to determine the internal resistance and polarization of the battery. A determination is made regarding state of charge and fault conditions produced by corroded terminals and low electrolyte level. The low temperature starting limit is determined by comparing the battery's power output capability with starting power requirements of the vehicle. Data produced by the comparison are indicated on the dashboard of the vehicle.