Solar panel

valhalla360 wrote:
If the controller does require a battery, you also will need a timer.

If you put a battery in and the fan runs when there is voltage from the battery, the battery will tend to run down at night. Might last a few weeks but constantly running the battery to 0% charge will kill the battery very quickly.

This 12V timer would work for your application.

I agree with Boondock Docker. With the minimal cost difference between PWM and MPPTs why not go with the more efficient MPPT?

ewarnerusa wrote:
Sounds like a nice controller, but now you'll need a battery. In fact, many controllers will be damaged if you hook solar input to them without having it hooked to a battery.
I'm not sure why someone said it needed to be an MPPT, we're talking a single 100 W 12V panel here. I'm not saying MPPT can't provide more than PWM, but on a small scale like this it is not something worth paying for.
Some controllers do have a "load" output which would do what you're trying with the fan. But I think would still need a battery.

The difference between PWM and MPPT would be at least 1.5 amps more using an MPPT controller with that panel.

If the controller does require a battery, you also will need a timer.

If you put a battery in and the fan runs when there is voltage from the battery, the battery will tend to run down at night. Might last a few weeks but constantly running the battery to 0% charge will kill the battery very quickly.

Sounds like a nice controller, but now you'll need a battery. In fact, many controllers will be damaged if you hook solar input to them without having it hooked to a battery.
I'm not sure why someone said it needed to be an MPPT, we're talking a single 100 W 12V panel here. I'm not saying MPPT can't provide more than PWM, but on a small scale like this it is not something worth paying for.
Some controllers do have a "load" output which would do what you're trying with the fan. But I think would still need a battery.

Least expensive MPPT from Renogy I see is $85. Good for up to three 100 watt panels.

Op here. Ok, ordered a renogy mppt controller. As much $ as the panel. Had asked the question to renogy yesterday afternoon, got an email from them at 2:20 AM! Somebody works late, or another country.

I have a 5 0r 10W panel connected to an on/off switch and then to a fan mounted in the ceiling vent of my fiver in reverse to suck the hot air out in summer. Its been working for the last few years without an issue so it can be done. Naturally the fan speed will be variable depending on how much sun is hitting the panel

red31 wrote:
the fan will not operate at full speed but should at least spin!

20W Solar Panel / 21W Bulb - A Perfect Match? (part 1)
https://www.youtube.com/watch?v=JZQEJ33xblE

Very informative video series.

OP - This is worth watching. Part 3 drives it home.

Maybe something like This Buck Converter would help.

The panel may not be able to provide enough in-rush current to start the fan on its own. Maybe it will, maybe it won't.
You may need to connect a capacitor on the converter input with the converter turned off. Let the cap charge up then turn the converter on to kick start the fan.

I vote for hook it up and try it. You won't harm the panel. If it's an automotive radiator fan they are rugged. You may not get to full speed but see what you do get.

The fan is a big inductive load so placing a diode on the positive output of the panel may not be a bad idea. Plus the diode will lower the voltage a bit.

Come back and let us know how it worked out