Question:
Why does my solar panel not run the computer fan?
Brandon
2013-04-27 22:35:58 UTC
Is it because the amperage is too high? I have a 10 watt solar panel thats rated 12v. I got two computer CPU fans all 12vdc but with different amps. One is 1.2w (or 0.1A) and another is 0.6A. Weird thing is, the 0.6A one is actually about half the size of the big 1.2W one. I used a 9V battery to try to run it, and the 1.2W is trying to turn but stalling and theres this buzzing sound. The 0.6A one turns when atttached to the battery but not to a 6V battery. I attached my solar panel which I just measuered 0.89W and 12v to the fans and they don't even twitch. Why is that? I also tried my 6v, 0.5 A panel on some toy car motors that can handle 5 (1.5v) AA batteries=7,5V but no go there either. When I measured the overall voltage, it dropped to around 0V across the panel and across the fan too. Why is that?
Four answers:
scoutma53
2013-04-27 22:39:10 UTC
I don't get all the figures but, are you doing this outside in the sun? because I thought solar panels only worked in sunlight. If you are inside it won't get enough rays.
Rudydoo
2013-04-29 17:59:03 UTC
Hey Brandon, Scout has a point, the power rating on any panel is in direct sun at sea level and 59 degrees F. I personally think the real problem is that you are trying to start a motor. Any motor that is not a 3 phase AC motor has a "starter winding," that causes it to use from 2 to 3 times its normal power usage for just a second or two until it's speed reaches normal RPM. That is what the buzzing sound is you hear from one of the fans. This is also why you can't run a 750 watt motor from a 1000 watt gas driven generator, the motor needs at least 1500 watts to start up.



Try running the small fan again with the panel outside in the clear sun. I'm curious, you said you measured it at .89 W. What kind of a meter were you using? We have panels powering our entire home here, and I have lots of different digital multimeters (DMM's), but none are able to put our calculated DC watts. If it is indeed putting out .89 watts, at 12 volts would normally be .07 amps, but most 12 volt nominal panels have open circuit voltages of 18 volts. In this case .89 watts would equate to .05 amps, well below the fans requirements. Is that panel a "battery maintainer" panel? They are about the size of a shoe box cover that sit on the cars dash and plug into a cigarette lighter to keep the car battery charged. I don't think you'll ever get enough out of one that small to even run the computer fan.



Real Goods catalog has pond pump kits that use a small boat bilge pump and correctly sized panel that can be wired directly together. Generally they use Rule model 360 or similar pumps, which run at 2 amps 12 volts, but the panel is rated at 50 watts, well above the 24 watts the pump is designed to use at steady state when running. You'll probably need a panel that has at least .25 Amp short circuit current rating (I max on the panel data plate) in order to get that fan to start, and it will have to be in good sun. I did read an interesting letter to the editor in Home Power just a month or two ago about someone that wanted to ventilate their crawl space, and figured out that feediing a fan directly with a solar panel was perfect because the fan would only run on sunny, dry days, and be shut down when it rained. They had the specs for the fan and panel they were using, might be worth checking out the article if you can get it.



Good luck Brandon, Rudydoo
deloera
2017-01-17 10:58:23 UTC
Solar Computer Fan
Clara
2017-02-02 03:03:09 UTC
1


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