Taper Charge Method for a Nickel-Cadmium Electric Vehicle Traction Battery

Saft STM 5.140 nickel cadmium batteries were evaluated at the UMASS Lowell Battery Evaluation Laboratory. These were tested using charge algorithms such as one step constant current, two-step constant current, constant current-constant voltage, and the taper method, which is the subject of this paper. The discharge was generally done at constant current, however a realistic electric vehicle test could also be used in which the response of the battery to an actual electric vehicle load profile is measured. This method was shown to increase the round trip efficiency of the battery test cycle. It was implemented on nickel cadmium electric vehicle batteries and may be applicable to other types in order to increase efficiency thereby reducing temperature and possibly increasing cycle life.