PV Gap

Ruth Said:

What to do with a solar panel?

We Answered:

Hey AJ, Tom is quite right, a panel that size is a great trickle charger at 1.2 amps. If you have a good sized 12 volt battery, like from a truck, or for a boat trolling motor (it should be at least 60 amp hours) you can hook it to the battery and it will charge it slowly anytime the sun shines. Don't worry about the voltage, most 12 volt nominal volt panels are wired for 18 - 19 volts, and if you hook them to a battery, the panel voltage comes right down to the batteries charging curve voltage anyway, they are designed for that. What you do need is a diode. A diode is an electrical check valve, allowing current to flow in one direction, but not the other. This will prevent the battery from discharging through the panel at night. Many panels today come with diodes inside the junction box on the back of the panel. If yours does not have any, go to Radio Shack, look for a 6 amp silicone diode, usually around75 cents. Put it in series between the panel and the battery, then, while you have a voltmeter hooked to the battery, connect the panel/diode to the battery and see if the voltage goes up slightly. If it does, you're all set. If not, turn the diode around and try it again. It has to be connected into the circuit the correct direction. Many people will state that you need a charge controller, but this is not necessary if your panels max current, ISC is less than 2% of your batterys amp hour capacity. In your case, if you have a 60 AH or larger battery, skip the controller. There is a great discussion about this in Richard Perez's book, I will list it below.

If you want to learn more about these devices, there is a great magazine that gets into the nuts and bolts of renewable energy, it's called Home Power Magazine, the link is below. We started by hooking a slightly larger panel to some golf cart batteries 12 years ago, reading that magazine and going to some energy fairs. Today our home is completely powered by the wind and sun. Check it out sometime. Take care, Rudydoo