Abstract: A system for supplying primary electrical power to modular components of electronic equipment. The system uses a battery power source mounted either in the module or as part of a battery pack that attaches to the module. Module circuitry supplies a recharge current to the battery power source. A charge circuit charges the batteries in a parallel and supplies power to the module by connecting the batteries in series. Circuitry also determines the amount of battery power source used for an operation of the module and sends a recharge current to the battery power source corresponding to the power consumed by the module and based on the available recharge current.