It wouldn't be a problem for the motor because as the voltage rises, current flows through the motor and the panel can't rise to open-circuit voltage. A solar regulator is different because there are times where the controller could open the charge circuit and let the panel rise close to Voc.
Application for 100W panel
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I agree that's an easy way to check for compatibility. Another way to ensure compatibility is to add auto buck/boost converter the will allow you control the voltage and current to the DC fan. I actually use one to ensure compatibility but also to maintain stable fan speed and noise.Comment
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It wouldn't be a problem for the motor because as the voltage rises, current flows through the motor and the panel can't rise to open-circuit voltage. A solar regulator is different because there are times where the controller could open the charge circuit and let the panel rise close to Voc.
over more weather. Bruce RoeComment
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It wouldn't be a problem for the motor because as the voltage rises, current flows through the motor and the panel can't rise to open-circuit voltage. A solar regulator is different because there are times where the controller could open the charge circuit and let the panel rise close to Voc.Comment
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I sometimes wonder what happens internally when DC motors are placed in series. Putting a couple small brush motors
in series for reduced speed has worked for me. But a brushless DC motor has electronics that draw big pulses, and those
are not going to line up time wise for 2 motors in series. Bruce RoeComment
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A friend of mine ended up with a 100W panel like that and I told him to get rid of it, that it wasn't worth much at home. Well, against my advice he bought two automotive 12V radiator fans and connected them in series, I think. Lo and behold, when the sun is around mid day, the fans go like hell. He made an attic fan out of it. It was weird how the current draw worked out just about right. If it was me, I'd put in on Craigslist.2.2kw Suntech mono, Classic 200, NEW Trace SW4024Comment
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I've done exactly that with a pair of 12 volt radiator fans and a 65 watt 12 volt panel. This moves hot air out of my flat roofed garage in Baja. It has worked flawlessly for 2 1/2 years now. A single fan was screaming at a really high RPM but when I added the second fan it slowed down the fan motors to a reliable speed the more direct the sun's angle the faster they run so they kind of self regulate, depending on the time of day.
Well built high quality motors would have more than enough headroom to handle this i would think since current would be low at that point, i just have always wanted to know if every motor/fan are able to handle that "stall" situation, that may go on for an hour, or if that shortens their life, etc.?
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The panel's max voltage is its open circuit voltage, but the voltage on the motor can never be that if the motor is connected and drawing current, it will be something less than that, and you don't know what it is until you try it. If you really want to be safe you could size the panels so that the Isc is about what the motor current draw at 13-14V is. Bruce, there is probably DC input filtering that is required for RFI suppression that takes care of that situation you described.Comment
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This is the inconvenient part as it's dependent on the specific fan and weather condition to verify. I did this and it was tedious. So, Voc would be more convenient albeit conservative spec to verify even though the panel voltage under load will never actually get that high.Last edited by solardreamer; 06-24-2017, 08:48 PM.Comment
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Originally posted by sdoldBruce, there is probably DC input filtering that is required for RFI suppression that takes care of that situation you described.
themselves together so the pulses line up. These are pretty low audio frequencies, so an RFI filter won't help. Bruce RoeComment
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I guess I just got lucky in my situation after listening to all this debate. As I said it has worked flawlessly for 2 1/2 years now. When The sun is bright and especially directly overhead it runs the fastest and moves the most hot air.2.2kw Suntech mono, Classic 200, NEW Trace SW4024Comment
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Moving the fastest when the sun it overhead make sense. The problem comes if the fan speed exceeds it's mechanical design. That is all I want to convey to anyone that try's this out.Comment
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