I'm no expert, but I can offer a couple of tips:
- The solar charge controller needs to be isolated from the feeds to the Inverter and Trailer, or else the power from the solar will not charge the batteries when the system has any draw.
If you are using any power off the system when the sun is shining some of that power is going to go to that load. Whether it comes from the Solar Panels or from the batteries is immaterial. Power is supplied by the solar panels to the batteries and any load. The only way to ONLY CHARGE the batteries is to disconnect ALL LOADS and connect ONLY to the batteries. If the solar panels can supply more power that the load requires the batteries will charge. If the load draws more current than the solar panels supply the batteries will discharge.
- The batteries need to be isolated to prevent them from simply discharging each other http://vandwellers.org/isolator/index.html
A isolator is required if one battery is wired to the vehicle starter and ignition to prevent you from discharging all the batteries in a worse case situation. If you run down the starter battery you can't get get the rig running and can't get home. If you have each battery on an isolator then you will have multiple batteries, and the batteries can't share the load between them. Only the battery for the vehicle starter needs to be isolated...
- The Trailer and Inverter need to be connected at the same point in the chain, and also isolated to prevent them from competing for the current - a distribution panel is the best option there.
A distribution panel is a good idea because it gives you a common point where you can easily disconnect power from the loads. It has a safety function. The trailer and the inverter ARE connected at the same point - across the 12V battery bank.
- Check to ensure that all of the batteries are deep cycle. If you mix deep cycle and non deep-cycle then you will wear out the batteries much faster, and will only get 20% of the rated time as the non deep-cycle batteries will give out of power and break the circuit, becoming resistors.
Only suggestion that make sense. Different battery types have different behaviour as they discharge. Best to have all batteries of the same type and same age.
Reference http://analoglogic.net/projects/solar_charger/solar_charger_system_diagram.png- treat the battery band as a single unit battery once you have each battery connected in parallel and isolated.