I have a small marine solar panel on my boat It came with the boat. I want to make sure it is working before I connect it. With a volt meter It is only reading .2 volts dc. I would think it should be 2-5 volts?
Mark, the 2 vdc is pretty typical. Most panels for home use are set up to charge 2 volt batteries, and they are wired for an, open circuit voltage of 8 to 9 volts. This allows it to have enough voltage to feed through a few diodes, perhaps a charge controller and 30 or 40 feet of wire and still have at least 5 volts left over. Once you connect it to the battery the panel will drop to whatever the batteries charging curve voltage would be. If you have a few minutes, I would suggest getting a book at the library called, The Complete Battery Book, by Richard Perez. Just read the chapters pertaining to lead acid batteries, the other discussions on lithium, ni cads and such won't apply to your boat system. If your panel is not large, and it's short circuit current rating in amps is less than 2% of the amp hour capacity of the battery, you can even run the panel without a charge controller. The book explains this as well. There is a great magazine that gets into the nuts and bolts of this stuff, it's called Home Power, you can find it online. You might also find some info at a couple renewable energy websites, I will list them below. Panels are rated in two ways, open circuit voltage, which you measure with a multimeter while the panel is in open sun and nothing is connected to it. The other rating is short cirucuit current, which you measure with an ammeter while the panel is in the sun as well. You connect the ammeter across the output of the panel and let all the power short right through the meter, so you'll need an ammeter big enough to handle more amps than the panel puts out. A 0 amp unit will work for your boat panel. These tests won't hurt the panel, or the meters, we do it all the time in the field, and the manufacturers will tell you to do the same test if you have a problem with a panel and they want to know if it's malfunctioning. You can check one of their websites if you like. Good luck Mark, and take care, Rudydoo
If it's only reading 0.2 volts, then the panel is burned out. What you can do is look for a nameplate on the panel, then try to look it up on the internet. Hopefully that will say what the voltage is supposed to be. You are right in that a panel intended to charge a 2-volt battery should read about 8 volts open circuit out in daylight, even if it isn't pointing straight at the sun. Is it a flexible rubber panel? Those are notorious for dying after just a couple years.
It has to be facing the sun for full power U check at the battery and it should increase as the sun hits directly on it. U can't check it at the panel after the diode.
