Recharge profile for spacecraft Ni/H2 batteries

Abstract

An improved method of charging a rechargeable nickel/hydrogen battery comprises the steps of applying a charging current to the battery resulting in a substantially full state of charge, then for a period up to approximately 60 minutes before the onset of discharging, applying a boost charging current at a rate in the range of approximately C to C/20 for a duration up to approximately 60 minutes. The charging of the battery before applying the boost step may include the application of a taper charging current. Also, at the end of the taper charging step and immediately prior to the boost charge, a trickle charging current may be applied at a rate in the range of approximately C/80 to C/500. In another instance, when the battery has been charged to about 70% to 95% of a full state of charge, the linearly decreasing taper charge may be applied until a final desired recharge ratio is reached. Thereafter, up to a duration of approximately 60 minutes before the onset of discharging, the boost charging current may be applied at a rate in the range of approximately C to C/20 for part of or for the entire duration. The timed sequence of the initial high rate charge, the taper charge, the trickle charge, and the boost charge, in conjunction with proper control of battery temperature and recharge ratio has been found to increase overall battery capacity by approximately 10% to 30%.