That's what the Sunsei Solar Charger SE-6000 is all about.

You're running a serious RV or boat, so your energy needs cannot be compromised. That's why we engineered the SE-6000. This baby delivers 6 amps of charging current, enough to run multiple batteries at the same time. Designed to be compatible with your vehicle or cabin's electrical system. Just expose this weatherproof solar panel to daylight and you have peace of mind. Yeah, that easy. Clean, green noiseless energy - a great alternative to a rumbling fume-spewing generator. (Cough, cough). The SE-6000 lets you enjoy the fresh heavenly air in your corner of Nirvana.