The Enerdrive | Dometic ePOWER DC2DC 40A+ Battery Charger is a fully automatic multistage, multi input battery charger with the ability to charge from either an alternator linked to a battery; or via solar power with the in built Maximum Power Point Tracking (MPPT) Solar Controller. With two inputs available, the main/house battery will be charged from either the engine while underway, or via the solar panels when stationary. The process to choose either engine or solar is fully automatic and both functions are controlled from within the unit itself without the need for external relays.