Peak-Power Characteristics of Improved Electric-Vehicle Batteries

The technique used for measuring peak power available from a battery during a discharge sustained for a limited duration of time is developed and presented. In tests performed on nickel/ iron, nickel/zinc, and lead-acid electric-vehicle batteries at the National Battery Test Laboratory, it was shown that available peak power decreases with increasing depth-of-discharge (DOD). Most batteries tested deliver between 70 W/kg and 130 W/kg at 50% DOD but produce these peak powers with currents on the order of 700 A--a current well above the capability of most state-of-the-art electric-vehicle propulsion systems.