Alternator Charging

These are my favorite ways to connect house batteries to the engine alternator. The reason I like these systems is because it incorporates a relay, which is an electromagnetic switch that is activated by providing 12 volts across the relay coil. When wired as shown the relay will only engage when the ignition is on and a switch controlling ground is on. This way we can decide when we want to send power to the auxiliary batteries while protecting yourself by automatically disconnect when engine is turned off.

12V Lead Acid

The reason I used the battery separator as optional is because you will have a pretty good idea when your auxiliary batteries need some extra power, long stretch of cloudy days, snow covered panels, etc. Furthermore battery separators are meant to disconnect your engine battery when your engine is off, controlling the relay with ignition power will do the same.

24V/48V Li-Ion

For a 24v or 48v lithium battery I use a very similar system but a crucial CVCC (Constant voltage constant current) boost converter will need to be installed between engine and auxiliary batteries.