Solar panel wiring
February 28, 2010
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Some may think there’s a lot to know about wiring a solar system, but the truth is the basics are pretty much the same as they were 20 years ago. Wiring solar panels is like wiring Christmas lights. There are several sites out there that show you the basics. However, it’s important to know when to use the methods discussed.
The device you use to convert your panels’ power will determine your wiring arrangement, or vice versa.
You’d need 25 * 12 Vpm solar panels in series to make 300V. Or, 5 * 60 Vpm panels. Notice how much current these inverters can handle, about 20A. They generally don’t need a lot of current at that high of a voltage.
You’d need 6 * 10 Ipm solar panels in parallel to make 60 Amps. Or, 2 * 30 Ipm panels. These charge controllers can still handle up to 150 Voc, but they’re designed to work with higher current. They generally don’t need higher voltage like solar-to-grid tie inverters. But keep in mind that the voltage should be higher than the voltage of your battery bank.
What’s your input device?
Before you buy solar panels, you need to know what you’re going to use to convert the solar power. Are you using a charge controller and/or a grid tie inverter? Here’s a couple of different things you could use (click on their description tab for details):- Kaco blue planet 1502xi Inverter
- PVPowered PVP1100-SD-120
- Morningstar TriStar TS-MPPT-45 Charge Controller
- OutBack FLEXmax 80 Charge Controller
Wiring
First, it’s important to know the basics. There are two basic ways to wire solar panels, series and parallel. Series arrangements increase the voltage of an array. Parallel arrangements increase the current of an array. Let’s use an 80 Watt, 12 Vpm, 6.6 Ipm solar panel for examples. (See my article about choosing solar panels to learn what Vpm and Ipm means.) Wiring panels in series:- +/plus/red to –/minus/black, +/red to –/black, + to –, etc.
- Three panels in series equals 36V at 6.6 Amps.
- +/plus/red to +/red to +, –/minus/black to –/black to –, etc.
- Three panels in parallel equals 12V at 19.8 Amps.
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Series vs. Parallel
These wiring arrangements, though different, generally achieve the same result in terms of power. But there are differences you should consider:| Series | Parallel | |
| Electrical focus | voltage | current (amps) |
| Wire diameter | smaller | larger |
| Physical handling | easier | harder |
| Cost per foot | less | more |
| If one panel is in the shade: | the whole string produces less power | the other panels are unaffected |
The device you use to convert your panels’ power will determine your wiring arrangement, or vice versa.
Direct Solar-to-Grid Inverters
Most high power grid tie inverters (for solar systems) will require many series connections of solar panels. If you look at the input specifications for the first two devices listed at the top, they require 120-400 VDC.You’d need 25 * 12 Vpm solar panels in series to make 300V. Or, 5 * 60 Vpm panels. Notice how much current these inverters can handle, about 20A. They generally don’t need a lot of current at that high of a voltage.
Charge Controllers
Most high power charge controllers will require more parallel connections of solar panels. If you look at the input specifications of the last two devices listed at the top, they’re good for 45 or 80 Amps DC.You’d need 6 * 10 Ipm solar panels in parallel to make 60 Amps. Or, 2 * 30 Ipm panels. These charge controllers can still handle up to 150 Voc, but they’re designed to work with higher current. They generally don’t need higher voltage like solar-to-grid tie inverters. But keep in mind that the voltage should be higher than the voltage of your battery bank.