My Land Rover has three separate electrical systems.
1. Vehicle operation circuit - Runs the engine, exterior lights, winch ... the usual stuff. It runs off the front car battery.
2. Rear electrics - Runs the refrigerator, water pump, both radios, various 12v outlets, clock, is in parallel with the front battery when the winch is used and all the interior lighting. This runs off a deep cycle battery which is charged by the alternator and #3. This battery runs all the parasitic electrical stuff (electrical clock & radios)
3. Mains circuit - provides 120V for the dual voltage refrigerator. There is a grounded duplex exterior type outlet mounted inside the vehicle allowing use of 12V appliances or tools with the vehicle buttoned up. There is also a permanently mounted 3 stage battery charger connected to the rear deep cycle battery. The charger first stage is 10 amps and the third stage is a trickle charger for keeping a battery topped up.
This is a genuine Land Rover power plug (water proof) for a military radio trailer. I looked closely at one on a military Land Rover during a Land Rover meet and decided that it would be just the thing I was looking for to add a 110V inlet. I bought one during a business trip to the UK and removed the plug from the housing. I replaced the original plug with a recessed male mains connector. It was a perfect fit. This allows me to plug my Land Rover to a 110V power source using an extension cord. You can also see a 12V outlet at the rear. I use this mostly for my shower pump.
If I really wanted to I could also add a trickle charger for the primary batteries. But since all the parasitic electrics are run off the secondary the primary keeps its charge for a very long time.
I tend to plug my Land Rover in if it is going to be sitting a week or longer without driving or when I'm working on my car. I can play MP3's on the radio all day and keep cold drinks in the on board fridge without worrying about running down the battery and there are 2 convenient 120V outlets for plugging tools in.
Another plus is when I'm packing to head off on a trip. I can cool down the refrigerator using 120V before loading and I can load the fridge the day before and keep everything cold without running down a battery.
