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October 2016

Solar panel power point

Two of the most important specifications in a solar panel are the open circuit voltage (VOC) and the maximum power. A solar panel’s VOC can be checked by using a multi-tester or a voltmeter. The two test probes of the multi-tester are connected to the two terminals of the solar panel and the voltage will be displayed. If there is no voltage or there is no display, there must be something wrong with the solar panel. Most solar panels from 20W to 100W have an open circuit voltage VOC of between 18-22V. Then the 60cell panels that are from 250W to 265W have a VOC of 36-38V. The bigger 300W+ panels have a VOC of around 45V.

It is important also to note that VOC is the voltage when the solar panel has no load. In such case, the current flowing through it is zero. So it’s perfectly safe to measure the voltage of a solar panel under the heat of the sun. Just make sure the terminals are not shorted together or they can form a path through you and you can get electrocuted. The voltage is effectively potential energy. VOC is the maximum voltage that the solar panel can give.

Once the solar panel is loaded, for example it gets connected to a charge controller or grid-tie inverter, the voltage drops by 10-20% and it begins to deliver its maximum current. When the solar panel delivers it maximum voltage and its maximum current, that’s when it’s operating at its maximum power point. The job of ensuring that the solar panel operates in this region falls on the grid-tie inverter and some MPPT charge controllers. Even a few tenths of a volt (0.5V) difference from this maximum power point can cause the power of the solar panel to drop by 50%.

For more information on solar panels and how it can yield its maximum power, you can attend any of our seminars this coming November.Click the link button below for the details of seminar.

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