Your isolator what every dual-battery system is based on. Wire this through an adequate circuit breaker or fuse, and connect your engine's starting battery to your house battery so you can charge both while the car is running. This Blue Sea isolator is our choice because of it's automatic switching on and off depending on the voltage it is sensing on either end. It disconnects when either battery drops to 12.75v., and reconnects when it senses a charge voltage of over 13.5v. Easy enough.
From the manufacturer:
- Protects sensitive electronics by temporary isolation of house loads from engine circuit during engine cranking
- 12/24 volt auto ranging voltage input
- Hermetically sealed contacts/vaporproof
- Ignition protectedâsafe for installation aboard gasoline powered boats
- Supports high-output alternators up to 120 Amperes