Solar powered battery charger
This is totally obvious, but if I'm dumb enough to not have thought of it there's a chance at least one of you out there is too. It's a solar-powered battery charger. It takes AAA, AA, C or D cells and takes 3-4 hours of full sunlight to do a full charge. £16 from Sunlight Solar.
There's a stand so you can redirect the panel to optimize sunbeam contact. It also has a blocking diode to "protect the solar cells during poor lighting conditions". If you have a battery in the charger and no power's coming in, it's possible for the battery to actually drain. Presumably this "protection" diode is intended to prevent that. If you've gotta use batteries, use rechargables, and get a solar charger like the aforementioned.
[GT]
