A charging process of a rechargeable lighting device is controlled by a software algorithm and a microcontroller configured within the rechargeable lighting device which has first and the second charging contacts located on its exterior and the charging circuit is turned on when a cradle detection circuit detects that at least one of the charging contacts engages an electrical contact when the rechargeable lighting device is inserted into a charging cradle. The charging process begins with a charge-current which is constant and a battery charge-voltage which rises up to a nominal battery charge-voltage. The rechargeable lighting device recovers to a preselected condition through use of a power interruption avoidance algorithm configured within the microcontroller when there is a loss of power to the microcontroller of less than a preselected amount of time.