Mastervolt BI 1203-S IsolatorBI 1203 S Isolator Onboard systems usually consist of two or more batteries that function independently when powering the 12 or 24V consumers. These batteries require independent charging with reliable battery isolators or battery combiners. Mastervolt offers several intelligent solutions: Battery isolators that divide your charge current with a minimum energy loss. The Charge Mate for connecting and or disconnecting two batteries. Battery Watch for