Solar Panel Maximum Voltage Calculator – Why it’s important
Snow covered solar panels – not a problem on the Gold Coast however it’s important to know that the lower the solar panel temperature, the higher the voltage the panels are producing.
With a solar power system it’s very important that the solar panels match the electrical characteristics of the solar inverter or charge controller that they’re connected to. So how do we work this out and what do you need to know? They’re good questions and this is where our solar panel maximum voltage calculator comes in handy! One of the electrical characteristics that are very important is the maximum voltage the solar inverter or controller can handle. That’s because if the voltage supplied from the solar panels is too high it won’t work and could be irreparably damaged.
Australian Standards PV array voltage requirements
Another important point is raised in the Australian Standard AS5033-2014 clause 3.1 which states the following:
“PV arrays for installation on domestic dwellings shall not have PV array maximum voltages greater than 600V. For non-domestic installations where the PV array maximum voltage exceeds 600V, the entire PV array and associated wiring and protection shall have restricted access.”
With these points to consider it’s very important that we know the maximum voltage of the solar power system. Luckily we have our solar panel maximum voltage calculator to help!
Note: This page deals specifically with the maximum 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.
Solar Panel Maximum Voltage – How to work it out
Working out the maximum voltage that your solar power system will reach is not a straightforward calculation. It’ll require information from the solar panel datasheet and some site-specific information to be entered into our solar panel maximum voltage calculator to calculate the maximum voltage the system will see. We need to take into consideration these 3 factors:
- The number of solar panels connected in a series string
- The minimum temperature found at the site
- The characteristics of the solar panels being used.
Let’s have a look at the information we require for our solar panel maximum voltage calculator, what it means and where you can get the information from.
Solar Panel Maximum Voltage Calculator – Information you need to know
REC 290W solar panel data sheet with information highlighted that’s required for voltage calculations – click for full size image.
Solar panel Voc at STC
This is the open-circuit voltage the solar panel will produce at STC, or Standard Test Conditions. STC conditions are the electrical characteristics of the solar panel at an airmass of AM1.5, irradiance of 1000W/m2, and cell temperature of 25oC. This information can be found from the solar panel manufacturers’ datasheet, please see an example here.
Solar panel temperature coefficient of Voc
The voltage that solar panels work at depends on the cell temperature. The higher the temperature the lower the voltage the solar panel will produce and vise versa. The voltage of the system will always be at its highest in the coldest conditions and the solar panel temperature coefficient of Voc is required to work this out. With mono and poly crystalline solar panels it’s always a negative %/oC figure, such as -0.30%/oC on the REC Twin Peak 2 290W solar panels. This information can be found on the solar panel manufacturers datasheet, please see an example here.
Minimum site temperature
This is very important and changes from site to site. As an example here on the Gold Coast near the beach, the lowest temperature is recorded as being 2.5oC by the Bureau of Meteorology. If you head up to Mount Tamborine in the hinterland the lowest temperature is recorded as dropping down to -1.1oC. To ensure the calculations are correct please check out the weather statistics for your local area.
No. of solar panels in a series string
When solar panels are wired in series strings (that’s the positive of one panel connected to the negative of the next panel), the voltage of each panel is added together to give the total string voltage. It’s therefore important to know exactly how many solar panels you intend to wire in series.
Got it all? Great, let’s go!
When you have all the information above you are ready to use the following solar panel maximum voltage calculator. This will quickly show if your solar panel design will suit your requirements. Just overwrite the data which is in the calculator – this data is for the REC 290W Twin Peak 2 solar panel used as an example above.
Hi Simon, one aspect of deciding on which panels to fit that confuses me still is sizing the ISC correctly. Can you tell me if this is cumulative regardless of wiring for each panel or does it follow the same rules as IM regards series and parallel connection
Hi Allan, it really depends on where you are located and what the minimum operating temperature is, saying that 3 x 47.6 Voc is 142V, that does not leave much room for higher voltages at lower temperatures on a charge controller with a maximum input of 150V so I’d recommend the 250V Victron MPPT charge controllers as a better option.
Hi Hassan, to calculate the minimum number of panels you really do need the Vmp voltage, as a rough guide the Vmp is usually 15-20% lower than the solar panel Voc. I hope that helps.
Hi Simmon;
The specifications of the solar panels I used include only the temperature coefficient of Voc, Isc and Pmax. for the minimum number of module per string, we have to calculate the minimum Vmp that needs the temperature coefficient of Vmp. is there a way to estimate it from the parameters given in the specifications.
Thank you in advance
Gday,
Ive got 6x355w panels, voc 47.6v, isc 9.56a,vmpp 39.6, impp 8.97.
This is all new to me.
Ill be using these in an off grid 12v lithium set up.
Whats the best charge controller/s to use for this input?
2x strings in parallel?
would i need two victron 150-35 charge controllers?
Thankyou in advance.