My favourite and relevant building quote is:
"I just get the bullet out of the gun and then I run after it to get it to hit the right spot"
Lloyd House - A builder featured in Lloyd Kahn's book - Builders of the Pacific Coast.
(A series of books which I highly recommend and have been a massive influence and inspiration.)
The power from the solar panels leads down to the silver box on the left. This is a charge controller. It monitors the PV (solar) power and the batteries status to deliver optimum charge characteristics and to avoid damaging over charge scenarios. It's an MPPT controller (maximum power point tracking) which basically means it optimises the PV output voltage and amperage to deliver the maximum watts (power.) They are more expensive but will give you maybe 10% or more juice from your system.
The blue box on the right is the inverter. This creates 240volts AC from the 12volts DC for running domestic appliances.
There's also an auxiliary charging circuit from the vehicles electric system. When the engine is running the auxiliary batteries in the camper unit are charged and the fridge is run. (The fridge uses a lot of electricity so when parked up camping it is run from the gas supply. Ironic, cooling from a flame... magic.) If the camper were to be in a guaranteed full summer sunny location the electric system could run the refrigeration but it would be quiet taxing.
Here is a small PV computer that's mounted externally from the electric locker. This displays all sorts of valuable information about what the system is doing. The small black switch just to the right activates the inverter. This saves having to leave it on all the time (they have a small background current drain even when there's no load being used. It's not much but it's worth turning it off. Every little helps!)
This is the utilities locker. 50litres of water, 170ah of 12volt battery storage and 7kg of butane gas all live in here. The white bucket is an emergency use sawdust compost toilet. This is only really an option in a weekend van where you have a base at home to process the waste. (Unless you want to be regularly digging large holes in the woods which is the only other ethical way to dispose of the sawdust/ waste mix. Simply dumping it is not good.) There's heaps (excuse the pun) of highly recommended information in Joeseph Jenkins book "Humanure - a guide to composting human manure."