I’m going on a photo expedition into the jungle of Guyana up the Rewa river. I’m planning on bringing my Nikon D800 camera and the D300 as a backup. In order to be able to recharge the batteries, I had to come up with a solar solution since there is not going to be any electricity. Therefore I purchased the waterproof and flexible solarpanel CHEPRE by SIStech Switzerland. It weights only 530gr, but is powerful enough to recharge both batteries, the EN-EL15 for the Nikon D800 and the EN-EL3e for the Nikon D300.
Solar panels produce only direct current (DC), but the standard battery chargers expect alternating current (AC), so no luck using the standard chargers that come with the camera. Furthermore, both camera use a different type of battery, which would mean to bring two cradles, one for each. Fortunately, there is a smart solution of a universal battery charger with exchangeable plates which can be connected directly to the panel or to any standard 12v cigarette lighter plug. It is advisable though to use a powertank as a buffer to be independent of sunlight.
I successfully loaded both batteries within a few hours even on slightly over casted days. I was also capable of charging the Ultrabook ASUS Zenbook UX31A via the powertank.