Panels above voc?

[justinm001]

I have 18 of these renogy 100w panels in 6s3p. Voc is 24.3 each so 145.8v should be the max right? Hooked up to my 150/100 Victron mppt and today got multiple high voltage errors when driving and solar was odd since battery was full. It was during heavy rain with complete cloud coverage 45-50degrees. I've had great performance from these panels.

On top of this the panels are only using 10 gauge wire with basic mc4 combiners and the cable runs to the front of the coach, though the drivers door to a breaker, then to the middle of the basement into conduit another 25ft so a good 75ft+ so I'm assuming some decent voltage drop.

100 Watt 12 Volt Monocrystalline Solar Panel (Compact Design)

Renogy 100 watt monocrystalline solar panel, rv solar panel, off-grid solar panel for sale. Limited time sale, 10% off: Renogy10off

www.renogy.com

Am I right that panels shouldn't be able to produce above the Voc? It's possible some panels are different revisions and different specs.

 

[MisterSandals]

Voc is 24.3 each so 145.8v should be the max right?

No!
The Voc is at 25C (77F).

As the temp drops, the voltage rises at the panels temp coefficient (shown on your panel label)?

Its usually about .35% voltage rise per deg C drop.

If you want to see the math, just provide an example and your temp coefficient.

 

[justinm001]

No!
The Voc is at 25C (77F).

As the temp drops, the voltage rises at the panels temp coefficient (shown on your panel label)?

Its usually about .35% voltage rise per deg C drop.

If you want to see the math, just provide an example and your temp coefficient.

Thank you! I thought just vmp and imp changes with temp coefficient. Guess I'll be doing my solar upgrade sooner and rewiring to 5s3p then wiring the others to my little spare mppt

 

[pvgirl]

Voc is dependent on temperature, and goes up as temperature goes down. Panels are specified at 25c/77f so below those temperatures Voc will be higher then the specification. Your panels will go up 26 Voc at 32f/0c and 29 Voc at -40.

 

[MisterSandals]

Your panels will go up 26 Voc at 32f/0c and 29 Voc at -40.

Edit: fixing temp coefficient = .28 and Voc at 25C

65 deg C drop x 24.3Voc x .0028 = 4.42V increase

Fun fact: -40C = -40F

 

[pvgirl]

65 deg C drop x 26Voc x .0035 = 5.9V increase

Fun fact: -40C = -40F

Per data sheet Voc temp co is -0.28%/°C giving 28.7 or 29 volts at -40c/f. Also the 26 voc was already at 32f/0c

 

[MisterSandals]

Also the 26 voc was already at 32f/0c

Fixed post #5