Voltage rise vs. temp drop help me understand

[richard cabesa]

I know you should not over volt a charge controller. The panels I am looking at have voltage ratings of 30.7 Vmp and a voc of 37.8. . I’m thinking I should not run three of these on a 100v charge controller. Absolute low temp could be 20* F. Input?

 

[Subdood]

Your panel Voc is measured at 25C (77F), so even at 77F, you're looking at 113V Voc. So, right off the bat you're over the limit of the charge controller. If you get down towards freezing, the Voc goes up, and you're probably going to be around 120V. So three panels with that Voc at either temp is not good, and will probably damage your charge controller.

 

[ryankshaw]

that's right. i would not run 3 of them in series on that 100v charge controller. you'd be fine with 2 in series though

 

[dp09]

Someone posted this LINK in another thread a while back. You can input your panel info into it and it’ll calculate the voltage increase at a specific temperature.

 

[MaikaiLifeDIY]

The VOC is critical, if the mppt unloaded the panels and your voltage surged beyond the max for the mppt it’s very likely the mppt would fry.

If these are they panels you need, you could run them in parallel instead which would increase the amps but not the voltage, but you also have to make sure you don’t exceed the maximum amperage also.

 

[richard cabesa]

Thanks guys. So I guess i jump to a 150/? SCC?

 

[ryankshaw]

what voltage of battery are you charging? what charge controller is it? another possibility is putting the 3 in parallel if the voltage is higher than the battery charging voltage. or if you have 4 panels you could put them 2s2p (2 parallel strings of 2 in series)