This is a 10 watt photovoltaic charger with a 12 Ah battery. It is based on a Popular Science DIY article from July of 2008. Here are the specs:
10-watt photovoltaic (PV, aka solar-electric) panel:
Voltage: max. power 17.6V, open circuit 21.6V
Current: max. power 0.57A, short circuit 0.61A.
Pop Sci used a 5-watt panel, probably to keep costs down, but if I'm bothering to build it, I want to get more out of it! The charge controller can handle an even bigger panel, too.
Battery:: 12 amp-hours
4 amp charge controller:
Here is the spec sheet from the manufacturer: http://www.vellemanusa.com/downloads/6/sol4ucn2gbnlfresdpl.pdf. The charge controller keeps the battery from overcharging or discharging too deeply, both of which can ruin the battery.
Meter: The Pop Sci article used a 10A meter.
