The DDC-12/24 offers the smartest system yet for current and voltage controlled charging between the house and starting batteries eliminating the need for an isolator or battery switches.During charging, the Duo Charge monitors voltage at the house battery. When voltage exceeds the set minimum (typically 13V in a 12-volt system and 26V in a 24-volt system), the Duo Charge automatically engages, providing up to 30 amps to the starting battery. When no charge source is present, the Duo Charge separates the batteries, so the starting battery won't be accidentally discharged. 4 program presets: (Gel, AGM, Std. Fld., FDC)