Is There A Maximum Length Of Wire That Can Be Ran With A Solar Panel?
May 24th, 2009 by BobI would like to put a solar panel on my boat house to charge the boat batteries. The roof is about 8 feet high and the wires that are provided with most personal solar panels are only about a foot long. Will there be any loss of energy etc running a 8ᆞft wire from that solar panel?
Thanks!
May 24th, 2009
There are two issues that affect the maximum length of a wire that can be used. The first is the gauge of the wire and the second is the current that is being used.
If the resistance of a length of wire is 100 ohms and the current that is going down the wire is 1 amp then V=IR, so the voltage drop on the wire is 100 volts. If the resistance is 50 ohms and the current is 1 amp then the voltage drop is 50 volts. Your resistance and current are no where near those values. When making calculations you have to remember the length has to include from the panel to the battery and back from the battery to the panel.
I have included the a web site that will allow you to calculate the voltage drop on the loop. The other thing to remember is that as the battery charges and the voltage in the battery increases then the current decreases, which also means that the voltage drop in the wires decrease as well.
Using the calculator, a 20 foot piece of wire with a current of .25 amps, will produce a voltage drop of 0.0518 in the wires, using 20 gauge wire, which is a lot smaller than the 14 guage wire that is in your house electrical system. If you used 2 conductor 14 gauge wire the voltage drop would be 0.0129 over the 20 foot loop between the panel and the battery, this should not be significant.
Put the maximum current provided by the panel and then you can calculate the gauge of wire that you would need to use.