The battery charging process of the present invention uses three charging rates. The initial charge rate of C charges the battery (101) until the battery's temperature reaches a certain level (102). The charger then changes to a trickle charge rate of C/8 to finish charging the battery (103). Next, the charger reduces the charging rate to C/40 to maintain the battery's charge (105). The process then monitors the battery's voltage. If the voltage signal has a slope that indicates the battery is being used by an attached device (106), the charging rate is increased to the trickle charge rate to simultaneously power the device and charge the battery.