A system and method for a double source battery charger of an engine-generator. The double source battery charger of the engine-generator includes an electric starter and a battery. The electric starter is selectively energized by the battery to start an engine of the engine-generator. The double source charger maintains the battery at a desired charge such that the battery has sufficient charge to energize the electric starter. The double source battery charger is selectively coupled to one of two power sources to charge the battery: an alternator of the engine-generator and an external AC source, such as a standard 120 Volt or 240 Volt wall outlet. As a result, the battery is charged by either power from a wall outlet or, if the generator is running, by power provided from the alternator.