Solar Panel Voltage Drop

Measuring voltage and solar panel testing.

Solar panel voltage drop.

This voltage drop calculator is a tool to help plan your wiring run and get as much production as possible from your array. Simply touch the solar panel leads with the multi meter probes matching their corresponding polarity red to red black to black. Voltages can be read on a pv module with the use of a voltmeter or multimeter. For distances at 48 volts double the 24 volt distances for a 5 percent loss figure.

As the temperature of the solar panel increases its output current increases exponentially while the voltage output is reduced linearly. Five percent is normally acceptable in low voltage systems but if you want a 2 figure divide the given distances by 2 5. This concept known as voltage drop leads to a slight production loss from your solar array. Voltage drop is more pronounced over longer distances.

In fact the voltage reduction is so predictable that it can be used to accurately measure temperature. Solar panel wattages have steadily increased over time. For a 10 loss multiply the distance by 2. This would be the view from the back of the pv module.

For 240 volt 5 loss double the 120 volt distances. As a result heat can severely reduce the solar panel s production of power. When you go solar one of the goals is to minimize voltage drop so that your system performs at peak efficiency. This would be a 0 2 ohm piece of wire you can calibrate with a power supply and ammeter with some load or sense the voltage drop from your long cable with a twisted pair and choose conductors with 50mv drop and read as 20mv per 100ma charge current then switch to read voltage with a common v.

Standard 36 cell solar panels intended for nominal 12 volt battery charging typically operate between 16 5 volts and 18 5 volts according to their stc ratings. This means your panels need to be at a substantially higher voltage than your battery bank in order to overcome this drop and still be able to store power. This concept known as voltage drop leads to a slight production loss from your solar array. What you ll see over to the right is an example of a voltmeter measuring voc with a junction box.

As recently as 2016 17 solar panels with output ratings of 250 watts were common. When current moves through an electrical circuit a small amount of voltage is lost due to resistance in the wires.