A powertrain includes a motor-generator that is coupled to an engine. A starter mechanism is coupled to the engine. A first energy storage device is disposed in a parallel electrical relationship with the starter mechanism. A second energy storage device is disposed in a parallel electrical relationship with the motor-generator. The electrical circuit exhibits a first electrical resistance between the first energy storage device and the motor-generator, and a second electrical resistance between the second energy storage device and the motor-generator. The first electrical resistance is greater than the second electrical resistance so that electrical energy from the motor-generator more easily flows to the second energy storage device than the first energy storage device, and the motor-generator more easily draws electrical energy from the second energy storage device than from the first energy storage device.