Seven years on and this is still evolving, mainly the electrics.
I added a DC-DC charger with a manual over-ride switch, I also added an OBD2 PCM for fusing and control, as I wanted the fridges to run off the feed to the rear prior to the DC-DC charger so the battery gets the full charge capacity of the charger I needed to add some relays to acheive this, I also added some relays to remove the firdges off the battery when the mains was connected.
As my fridges are 12-24v only I added a 24v power supply to the system, it simply plugs in, when mains is connected the 24v supply turns on, operates a couple of relays and viola, the fridges swap over to the 24v supply, allowing the smaller 12v charger to charge the battery without a load on it.
As this unit like the rest is all removable Anderson plugs were used to allow everything to be plug-n-play....
I added some voltmeters to the front so I can monitor what is happening in the rear as well as the over-ride switch for the DC-DC charger, the other switch is to control my dual electric fan set up...
This system worked 100% perfectly on our recent Cape trip....