Abstract: A power supply system that allows a user to standardize on one or two battery types and use these supported types to power electronic devices designed to use other, non-supported battery types. A battery sleeve is provided to convert the form factor of one battery to that of another battery. The system may also include a battery pack assembly that allows batteries of a supported type to be used to power electronic devices designed to use a conventional, proprietary battery pack design. Such battery pack assemblies allow dedicated, single use battery chargers sold with a given electronic device to be used to charge consumer capped batteries that may be used in other electronic devices. A universal charger/power supply unit may be provided that can used to charge a variety of rechargeable batteries and provide power to a variety of electronic devices.