I would add a disconnect on the solar PV (+) side. It’ll make maintenance easier.
Yeah, looks good. I’d add a switch to disconnect the panels and another to disconnect the batteries altogether.
Also, do you not have an inverter? 400Ahrs is a massive amount of battery for a non-inverter setup. The DC things are typically pretty small loads so it would be hard to use a real amount of that energy. Especially considering you have 500W watts of solar.
We have a 21’ TT with 200Ahrs of capacity and 600w of solar. In a normal night we’ll use at most 20Ahrs. This is easily recharged within an hour of sunrise in full sun and even is a forest with spotty direct sun we’ll easily recover our daily usage.
you should double the panels – otherwise you’re not going to be able to charge that 400ah of batteries a lot of days
Your wire gauges look light, but it depends on the length of the wire runs. For instance the 6mm from the panels to the controller I’d up to 10mm if the distance is more than 3m (total of the positive and negative lines). The 10mm it also depends, if the controller is right next to the battery it’s fine, if it’s across the RV need to check the distance.
Starting at the panels, 3 is really awkward as parallel isn’t a great choice but usually necessary with an odd number like that paired with that controller. I would try and fit 4 smaller panels and wire them in 2s2p. Get your voltage up so you can charge earlier and later in the day will make a big difference with some shade tolerance.
All that battery and no inverter is a huge waste. If you don’t want an inverter you may as well just throw one 200 watt panel on the roof and use one 100 ah lithium battery. The house DC load will not be very demanding.
We used to full time in a 25ft Sprinter chassis class c as well and we had 400 watts of solar (two 200 watt panels in series) and 200 ah of lithium batteries and a cheap 2000 watt CNBOU inverter and it powered everything for us including laptops and tv watching in the evening. Only needed the generator after a few cloudy days.
The best advice I can give is to get a Victron battery shunt and Victron charge controller. Knowing exactly how many watts you are harvesting and how much you use your battery in amps just by looking at your phone is a game changer.
As for the cabling, I have no idea what AWG translate to MM, but you will want a solar disconnect and if you add an inverter you’ll want a battery disconnect before that inverter. If you stick with that awkward parallel solar setup you shouldn’t need inline fuses for the panels due to the low voltages you will be using.