245w module to 12v 80w exhaust fan

DirtDart

I have several unused 245w panels and would to apply at least one to a 12v 80w exhaust fan in my attic. The panels are metering at 35vdc. The fan is a 12v 80w, listed as ASIN B07H8KJCLM on amazon. I doubt this would be direct connect without something in the middle to control the output of the module. How do I avoid killing the fan? Would I use a dedicated dc speed controller or charge controller? Any advice would be appreciated.

BB.

You are correct... You would toast the 12 volt fan.

On Amazon, Ebay and such, there are lots of DC to DC converters out there that are pretty close to dirt cheap. Find one rated for >= to 8 amps and over 50-60 volts input (roughy):

https://www.amazon.com/Converter-DROK-Regulator-Constant-Adjustable/dp/B01MSJQAKY

That is one that would probably work... But do your own research (the reviews have some mixed issues for this link--And the issues are typical for these devices--electrical interference, a bit optimistic output specifications, etc.).

-Bill

DirtDart

Thanks Bill

garynappi

I wrote a DC attic ventilator vendor on EBAY about this, and he also sold PV panels in a fan package that were 18.5 volts VMP and he said those fans were 20+ volt tolerant. 

I'm thinking that the sellers of those DC fan / PV packages know that the VMP of an 80 watt panel will be ~18+ volts and if I had to bet, I would that the fans are actually 24 volt rated. 

You "could" use something like a series ginormous cement resistor or like Bill said a DC-DC converter but it's cheaper and safer in the long run to get a small PV to run it. 

mike95490

Or get a 14V 300w zener diode .  That will clamp the panel voltage to 14V, but also generate a fair amount of excess heat that has to get disposed of