Started wiring the the split charging on my work van today. In the back of the van I have a 120ah battery that came out of my brother in laws boat. The battery is in a box with an accessory socket on the top and a few power pole connectors.
The battery can be removed from the van for portable use but when it is in the van it powers my 600 watt inverter and used for charging various other things.
I have a voltage sensing relay rated at 140 amps that controls charging and when the engine is running but also gives me another 100 ah if I am working the inverter hard with some power tools.