Open circuit voltage at low temperatures or altitude

[NowhereVan]

I have 300 ah lithium batteries and 2x200w 9bb solar panels 25v max output and a 230amp alternator in a mobile application. Iam wondering if I can use the redarc 1250dcbc charger which has a max voc of 32v. I'm wondering if altitude or low (high?) temperatures may push the voc past the max voc of the module? I'm planning on traveling to high altitude and in extreme temperatures. Any assistance appreciated, thanks!

 

[NowhereVan]

Also should mention the batteries are renogy self heating

 

[mikefitz]

Approximately 0.4 %/ deg C increase in volts below 25 deg C . So around 2.5 volts Increase on Voc at 0 deg C. High temp reduces the panel volts, altitude generally increases panel current.

 

[NowhereVan]

Approximately 0.4 %/ deg C increase in volts below 25 deg C . So around 2.5 volts Increase on Voc at 0 deg C. High temp reduces the panel volts, altitude generally increases panel current.

Ok thanks so much! So by my calculations the unit should not cut out until around below -20°C? Do you have similar data for elevation you could share? What about if low temperatures AND elevation, does it compound?

 

[rhino]

temperatures may push the voc past the max voc of the module?

It is not the "module" that you need to worry about it is the solar charge controller that you need to worry about. The lower the panel temperature is at the higher the Voc can be. If you go past the Voc rating of the charge controller you have the possibility of then destroying your charge controller. You don't have to worry about the elevation in this case just the temp.

 

[NowhereVan]

It is not the "module" that you need to worry about it is the solar charge controller that you need to worry about. The lower the panel temperature is at the higher the Voc can be. If you go past the Voc rating of the charge controller you have the possibility of then destroying your charge controller. You don't have to worry about the elevation in this case just the temp.

Yes, the module I'm referring to is the redarc charger which is a dual mppt/alternator charger. It has a voltage range of 9-32v. So I think I am good down to around -20° in this scenario? And elevation will not factor in?

 

[mikefitz]

Elevation gets you nearer the sun, clear sky, more amps, perhaps 10% 15:% . Not a problem as the solar controller limits current output

 

[Renogy Solar]

In low temperature environments, the VOC of PV increases as the temperature decreases