The build and travels of a Mercedes Unimog U1300L camper/expedition vehicle. For Sale.

First of all it should be noted that there are three separate electrical systems at work on the Unimog, these are:

The Unimogs own 24v DC system that operates all the vehicles running electrics such as headlights, starting motor, de-misters etc. This feeds power through a split charge system into the batteries in the living module.
The living module is fitted with a petrol generator providing 5kva of 240v AC. This is used for charging batteries, 3 pin 240v sockets, hot water and hot air. There's a shore/caravan type hookup at the rear for 240v in and out.
The 12v DC system within the living module that controls and provides the power for all the systems eg. fridge, lights, heating system etc.

The 24v and 240v systems were already on the vehicle when I bought it. I installed the 12v system so that's what I'm going to describe here.

First of all I needed to list all the components that would need to draw power from the 12v system, and these are:

12v compressor fridge.
Eberspacher hydronic operating system.
Water pump.
LED lights.
Oven (light and ignition)
Hob (ignition)
Water tank level indicator.
Thermometer.
Thetford toilet.

The most energy demanding component here is the Waeco compressor fridge consuming an average of 45watts. This is how I work out the amperage consumption for a days use:

Bearing in mind that this will be the greatest draw, the other use will seem insignificant but lets assume we will use a further 10 amps on top of this in a 24hr period (over estimating) giving us a need of 100amps per day. It's desirable to have at least 2 days of power from the batteries so we need at least 200amps of battery power. To prolong the life of the battery cycles it's advised that they are not discharged more that 50% leaving us with a total need of at least 400amps battery power. I decided to use AGM type batteries as they are totally sealed maintenance free, can take a rough life and last for more cycles than standard lead acid batteries. I chose to have four separate cells of 110amp capacity giving us a total of 440amp/hrs.

Once I'd established the battery capacity, the next step is to decide on the most effective way to recharge the cells. As we have quite a large battery capacity and the fridge uses a lot of power we need high output charging systems. The first and most obvious is to take power from the base vehicle 24v system. The power comes from the alternator and can only be utilised when the engine is running. For this I used a Waeco 40amp 24v - 12v charger that I can switch on from the drivers seat when the engine is running. The second method is to use a 240v charger that will come on every time the generator is running or we have an electric hook up. For this I use a Waeco 25amp 240v - 12v charger. The third method is to harness the natural energy from the sun using solar panels. I have installed a Sunware Fox solar regulator that can control solar panels up to 350w. I plan to have between 200w - 250w of solar panels on the roof that should replace most of the energy we use every day.

Most of the electrics have been installed together underneath the lounge in front of the water tank. The pictures below show them being installed...