Guys,

I have a 110 amp auxiliary battery under the bonnet, and an another in a portable battery box that I use occasionally, which plugs in the back, and used if I'm camping for more than a couple of days. The Radarc solenoid is simply and works well isolating the start battery, while the alternator keeps them all charged.

Question : I'm thinking of adding a 300w solar to keep the auxiliary batteries topped up while camping for longer periods. People have suggested changing my charging system to a DC-DC charger to keep everything fully charged, and to have the advantage of the in-built solar controller.

I like simple, so the solenoid seems the best method for me, but I do like the idea of a solar panel. In my case, would it be as simple as connecting a solar panel, via a controller, to the auxiliary under the bonnet and only switching it on when camped? I don't see the need to have to working all the time, as the alternator is keeping the batteries charged.

The only disadvantage I can see is that most solar controllers need to be connected to the battery/s first so it can determine the voltage ( 12v or 24v ) before the panel is connected. So if I put a switch on the solar controller I would need to go through this procedure every time I wished to connect it.

Does this all sound right & workable?