Power for me is always an issue when doing more than a day trip, especially if I do something silly like forgetting to put the bung in. This happened recently when I was 5 k's offshore and suddenly realised I hadn't put the bung in.
Lucky I have an electric bilge pump on board and was able to empty the hull in a few minutes and head back to shore. The downside of this was that by lunchtime I was down on battery power which runs my gps and sounder.
I run a completely waterproof battery box system which drops into the rear hatch and sits on a couple of foam guides.
I will show you what I have and go from there. Firstly I made up a fully waterproof battery box with a lighter socket to recharge it with. The whole system drops into the rear hatch and gives me a very slight bit of nose up which I wanted anyway.
Now for the solar panel, the type I purchased was a 80 wat 12 volt system and a regulator. All up in cost $100 AUD and the parts are from Jaycar.
The panel itself simply lays on the tramp and is help in place with the standard shock cord that you use to tie the tramp up when rolled. I have another bit of shock cord running to the rear of the tramp to stop is flapping around.
I have fitted a waterproof electrical connector to the wall just behind the seat and wired it to the battery box with another waterproof connector. The regulator fits into the water proof box and I have added a shut off switch for when I am manually charging the battery at home.
here's the system rigged up. I have used it 5 times and I do not drain any power from the main battery. I have been out for 3 days in a row without having to charge and now I can go away for extended camping trips without having to worry about power.