DC to DC chargers, also referred to as battery to battery chargers, allow for the alternator (or generator) of a vehicle to charge the primary battery and your off-grid batteries at the same time. The CTEK DC to DC charger line also acts as an isolator for your primary battery to ensure that your starting battery is never drained. These chargers are a great option for campers, work trucks, and any other recreation vehicles with battery bank setups.