Sunbender Do-It-Yourself Solar Battery Charger Kits are a great way to start using solar energy and a fun way to teach kids about the energy source of the future (and the present!)
Similar to how an off-grid solar home works, the solar panel will charge up the batteries during the day, so you can use the power whenever you need it.
By building your own AAA solar battery charger, you can see in a hands-on way how solar works. Kit comes complete with 3.6V 100mA flexible solar panel, battery holder, blocking diode, heat shrink tubing and complete instructions. Requires soldering. For NiMH or NiCd rechargeable batteries only.
The solar panel will charge 2 AAA batteries at a 100mA charge rate in full sun. In 5 hours of full sun, you will put 500 mAh into your batteries. Weight = 0.3 oz (8.4 g)
You can add another panel below, to increase current and double the power to your batteries.