A universal battery charger for cellular telephones and other battery operated devices. It also may be used to power a battery operated device when there are no batteries in the device. It can charge a battery from power sources having different voltages (e.g., a 12 volt car cigarette lighter, or a 110 or 120 volt wall outlet) and can charge a battery when no external power source is available. It has a built in battery pack, using a no-memory battery, that can be charged from any of the power sources. The battery pack can hold a charge and be discharged only upon demand. The preferred embodiment includes a 110/220 AC plug, and male and female 12 volt cigarette lighter plugs. Optionally, a DC to DC converter or similar device may be incorporated, so that the invention can recharge batteries requiring different voltages (e.g. 6 and 12 volt batteries).