I built a small 12 volt emergency backup power generator a while ago. You can read the gory details here:

http://papoanaya.dreamwidth.org/117111.html

It was more of an experiment than anything else. This provides enough power to charge cell phones and portable LED lamps.

This is what I can tell you of that experience:

Get the largest wattage that you can get. I made this mistake with mine. I purchased a 13 Watt panel. It works well, but the wattage will dictate size of the battery. The rule of thumb is that you cannot use a battery Amp/Hr larger than 1.5 of the amount of watts. In other words, with 13 watts, the battery cannot be more than 25 Amp/Hr. If you get a 100 Watt, then you can have a 150-200 AmpHour battery (this is a boat/camper size battery).

Battery must be deep cycle batteries. Be mindful while buying them. The small ones are the ones used for alarm systems and the large ones are the marine type. There are "solar power" specialized ones. I do not know, but I am using a small deep cycle one for a scooter and it works fine.


Get a controller to make your life easier and do not burn your battery.

Good luck!