How to Test the Power Output of a Solar Panel with a Multimeter

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A cottage industry has grown up around the buying and selling of used solar panels as long-time customers seek upgrades to new technologies and bargain hunters look for cheap alternatives for do-it-yourself installations. There’s also a vibrant scratch-and-dent market for aluminum-framed panels that have been bent or otherwise damaged during shipping. Buying used goods carries with it certain caveats, but with a multimeter and minimal effort, you can test a panel before any money changes hands.

Things You'll Need

  • Solar panel
  • Multimeter
  • Test the voltage of your panel in full view of the sun. The angle of the panel relative to the sun will make a difference in the output you record, so tilt the panel back so that it receives the most possible sunlight across its entire surface.

  • Remove the cover from the converter box located on the back of the panel.

  • Consult the owner’s manual for the panel, if it is available, to see the diagram of the connections in the converter box. If that is not available, look for the "+" and "-" signs next to the connections. They will usually be the two outermost screws with "+" on the left and "-" on the right.

  • Set your multimeter to DC volts at a level well in excess of the panel’s rating. For example, if the panel is rated at 22 volts, set your multimeter to "DC volts, 200." The rating should be noted on a plate or sticker right below the converter box.

  • Connect the red to the "+" connection and the black to the "-" connection. Check the reading on your multimeter to see that it is close or equal to the rating.

  • Remove the multimeter wires from the panel and switch the setting to DC amperes, again at a level well in excess of the panel's rating. It is wise to turn the panel away from the sun to measure the current as the panel is live when the sun is shining on its face. Connecting to the live junctions when testing the current can cause sparking.

  • Connect the multimeter to the shaded panel in the same way you did to measure the volts. When the connections are secure, turn the panel back to face the sun and check the reading. It’s not unheard of to get a slightly higher reading than the current rating listed on the panel, so you want to see at least a matching number. If both the voltage and amperage test properly, you’ve got a good panel that should serve you for years to come.

Tips & Warnings

  • Be wary of newer glass panels that have cracks or condensation under the glass. The conductivity is likely compromised, meaning you can probably leave your multimeter in your pocket.

References

  • Photo Credit Jupiterimages/Photos.com/Getty Images
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