Solar Panel Minimum Voltage Calculator – Why it’s important
With a solar power system it’s important that the solar panels match the electrical characteristics of the solar inverter or charge controller that they’re connected to. One of these characteristics that’s very important is the minimum voltage the solar inverter or controller can handle. If the voltage supplied from the solar panels is too low it won’t be able to convert the power from the solar panels into useful energy – and that’d be a waste of time!
The voltage that solar panels produce when exposed to sunlight changes depending on the temperature of the panel, and despite what you may think hotter is not better! The hotter the solar panel is operating at the lower the voltage produced by the panel. This is known as the temperature coefficient, and for polycrystalline and monocrystalline solar panels this is always a negative percentage per degree above 25oC.
Note: This page deals specifically with the minimum voltages a solar power system will produce. Check out our solar panel voltage calculator page here for a calculator that covers both high and low solar panel voltage calculations.
Let’s have a look at what’s required to calculate the minimum solar panel voltage.
Solar Panel Minimum Voltage Calculator – Information you need to know
REC TwinPeak 295W solar panel data sheet with specs highlighted that are required for the solar panel minimum voltage calculator. Click on image to view full size image.
Working out the minimum voltage that your solar power system will reach is not a straight forward thing as it requires information from the solar panel data sheet and some site-specific information be entered into our solar panel minimum voltage calculator. Specifically, the following is required:
Maximum site temperature. This is the maximum ambient temperature that can be expected at the site. Our calculator adds 35oC to this to allow for the additional temperature that can be expected at the solar cells above ambient.
Solar panel Mpp Voltage at STC. This is the voltage you can expect the solar panel to work at under Standard Test Conditions (STC). STC conditions are with the solar cell temperature at 25oC. This figure can be found on your solar panel data sheet.
Solar panel Temperature Coefficient of PMpp. This is the percentage of change in the voltage that the solar panel produces per degree over the STC cell temperature of 25oC. This isn’t technically the correct data to use for this calculation however it’s close enough to provide a relatively accurate result. The correct data would be the VMpp temperature coefficient however this is not usually shown on a solar panel data sheet. The temperature coefficient of PMpp can be found on the solar panel data sheet.
Number of Solar Panels in a Series String. This is the number of solar panels connected in series, or positive to negative in your solar panel array. This figure is up to your design requirements and may need to be adjusted to suit the input voltage range of your solar panel charge controller or inverter.
There we have it! If you’ve got all that, just enter the data in below as required and the calculator will spit out the minimum voltage for you!