Optimum Solar Panels for Apex 300 in cold climates (Canada)

Product Discussion Solar Panel
1

I recently purchased an Apex 300 and am working on the optimum Solar Panels for this model. If i understand correctly, there are 2 solar inputs and each input is rated 60v max @ 10 A. Since i am in a cold climate, i needed to calculate the Voc for -40 C which is likely colder than i might need but there may be a remote chance it could drop to -40 C.
I used an Excel Spreadsheet to calculate the Voc for various panels and found that the JA Solar model JAM60D41-510/LB seemed to provide the best results. Other panels had a Voc that seemed close to 60v but i would like a safety margin on the voltage of maybe 7 or 8v.

The specs for the JA Solar panel are:

Pmax=510w
Voc=44.25v
Vmp=37.31v
Imp=13.67A
Voc temperature Coefficient=-0.25% / Deg C

I calculated a worst case Voc @-40 C as follows:

25 C - -40 C = 65 C temperature change
-0.25% * 65 C = 16.25% per 65 C change
16.25% of 44.25 = 7.19v change in Voc
So worst case Voc (@ -40 C) would be 44.25v + 7.19v = 51.44v

Max power generation would be 37.31v x 10A (ma clamped at 10A) = 373.1w * 2 Panels * 2 inputs = 1492 Watts.

Do these calculations seem correct ?
Will there be any issue with the Apex 300 being able to clamp the 13.67A to 10A without causing overheating ?
Is my safety margin of 7 or 8v too excessive ? Some panels generate a worst case Voc of 58.4 but have the ability of producing about 1678 Watts.

Thanks
Andy

1 Like
3
  • The calculation is generally correct, but the maximum current of 20A per channel for the Apex 300 is an input current limit, not “clamped to 20A.” The AP300 automatically adjusts the operating point by lowering the voltage to limit the current to no more than 20A.
  • In practical use, the output current from the solar panels will decrease as the light intensity weakens, so having a slightly higher rated value allows for buffer space in low-light scenarios.
  • A safety margin of 7V or 8V is not very high. In cold regions, the actual operating temperature of solar panels may be further reduced due to wind speed and light conditions, so it is safer to leave an additional margin of 2-3V.
  • Additionally, there is a mismatch in the calculation formula described by the customer: “The maximum power generation is 37.31V x 10A (clamped at 10A) = 373.1W * 2 panels * 2 inputs = 1492W.” The matching should not use the maximum power generation efficiency but rather the open-circuit voltage: ensuring that at low temperatures, the Voc does not exceed the device’s maximum input voltage.
  • The best way of connection:
  • Pmax = 510W
  • Voc = 44.25V
  • Vmp = 37.31V
  • Imp = 13.67A
  • Voc temperature coefficient = -0.25% / °C
  • You can purchase four solar panels and connect them in parallel on both sides, which is an effective way to optimize your setup.