Solar panel

[tarnold]

Just got a 100w panel and want to run a 12v 80w radiator fan, NO BATTERY. The panel is cranking out 23v do I need to put a controller in the middle. All controllers I look at have a battery hookup between the panel and output.

[ewarnerusa]

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.

[Lwiddis]

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

[tarnold]

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.

[austinjenna]

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

[2112]

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.

[2112]

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

[red31]

both the panel and motor should have the same resistance @ ~ 10v

[wanderingaimles]

For a greenhouse application, you should not need 24/7 operation.
A small battery (rv/marine group 24) and some sort of timer to turn the fan off and on several times a day could work. You may end up looking at a small 300 watt inverter and a 120 Volt timer to put it together.

[3_tons]

100w panel in ideal test conditions likely to put out just over 5.x amps, but in the vagaries of the real world subtract about 1/3 (say, for an average) and an 18v panel output is likely a bit too high for the fan…

3 tons

[Lwiddis]

Solar panels charge batteries through a controller. Batteries supply power to 12 volt fans, for instance. Or an inverter for 120 volt fans. Don’t try to reinvent the…wheel.

[CA_Traveler]

23V is open circuit voltage, ie no load. About 18V with a load no controller or battery, fan may/may not be OK.

But without controller and battery their will be a lot of power variation to the fan and it could be damaged as a result.

[wa8yxm]

Yes you need a controller .. an MMPT type (Not a PWM) and I'd recommend a battery as well.. NOTE.. 100 watt panel will not give you a full 100 watts most of the time.. closer to 50 Assuming the fan runs when needed not full time with the aid of a battery this should work

[way2roll]

I had a solar attic fan in a previous house. Pretty large fan and pretty small panel. No battery. Accomplished exactly what you want. Ran when the sun was out, passive when no sun. Even had a thermal switch you could loop in. It was rated for like 1500 CFM. Don't see why the same method would not work with your setup.

[BFL13]

Will the fan be damaged by a higher voltage? If not then panel direct might power it. Panel will do 5 to 6 amps aimed at high sun mid-day mostly under 5 rest of day

Some controllers work no battery Some say they are for running lighting

[red31]

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