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Old 03-03-2014, 17:23   #1
Guy
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cabin fans on low voltage

I want to leave the boat for the next year with the cabin fans turned on and powered just by the solar panels, when the sun shines. Batteries will be turned off. As the sun goes down the volts drop and I'm wondering if this will harm the fans. In a brief test, 3 of the fans ran on 6 volts just fine with the panels turned away from the sun.
I am most worried about some sort of fire damage not so much about the fans . Everything is fused.
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Old 03-03-2014, 17:32   #2
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Re: cabin fans on low voltage

There is also the problem of higher voltage. The voltage will go up to about 22v.
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Old 03-03-2014, 18:03   #3
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Re: cabin fans on low voltage

Hello,

Install a proper solar ventilation van and system. No worries !

http://www.marinco.com/en/n20704w/4-...ight-plus-vent

Alan
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Old 03-03-2014, 18:18   #4
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Re: cabin fans on low voltage

I decided to pick up a pair of solar vents myself, to see if it helps when I'm away from mine, saves having to worry about the batteries or direct connection. Might be an option.
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Old 04-03-2014, 07:23   #5
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Re: cabin fans on low voltage

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Originally Posted by noelex 77 View Post
There is also the problem of higher voltage. The voltage will go up to about 22v.
There is a controller that takes care of high voltage.
We are not in a place or time (the jungle and leaving in a few days) to buy anything else.
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Old 04-03-2014, 07:27   #6
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Re: cabin fans on low voltage

I have a NicroVent in the head and I leave the head door open. The vent in the dropboard completes the ventilation circuit.

The solar panels need to be regulated to run the fans. While you can get away with these sort of big swings in voltage with LEDs (8-30 VDC tolerant, if I remember correctly), something with a motor in it will be damaged or will melt if you ramp up the voltage to nearly twice what it's rated.

The way to do this is to regulate the power going into a fully charged battery to "float" range, and to run fans from a fused circuit.

If you don't want the fans running at night (which would be the case with solar, even regulated solar), run a 12 V timer inline for 8 PM-8 AM shutoff.

Really, it's easier to just keep your batteries charged via solar to a voltage set point, and to install a self-contained solar powered vent.
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Old 04-03-2014, 07:50   #7
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Re: cabin fans on low voltage

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Originally Posted by Guy View Post
There is a controller that takes care of high voltage.
A controller helps, but be aware that controllers self power from the battery side. If the 12v supply is disconnected from the battery side they may not power up even if over 12v is available from the solar inputs. Some controllers will continue to function when the battery is disconnected, but fail to start up again, without a battery supply, during the next solar day.

I think the risks of problems are small. The DC motors in the fans are generally tolerant of voltage fluctuations, but it is difficult to know for sure.

Another potential concern is that with the batteries disconnected if the regulator does not function the OC solar panel voltage of 22v could be applied to general electronics (depending on how they are wired). This will damage some electronics even if switched off.

I don't think the risks of problems are high, but I do think these risks out-way the benefits (presumably reducing mould) of the fans running, at least without some careful checking before leaving the boat unattended.
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Old 04-03-2014, 10:17   #8
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Re: cabin fans on low voltage

My experience with DC motors is as the voltage drops the RPM drops and low voltage doesn't really do any harm in the short term. The opposite is true with high voltage but I suspect damage could occur faster at higher RPM because the shaft bushings or bearings may not take the higher RPM. I would also go with the solar vents to avoid possible problems with the system your contemplating. Good luck
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Old 04-03-2014, 10:40   #9
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Re: cabin fans on low voltage

Cooling fans fail on startup. If you have enough solar to keep them running overnight without killing the batteries that would be the way to go. Of course we are only talking about a few hundred cycles on and off so you will probably ok. In my job we have fans running 24/7 all year and come December when it drops into the 50s they shut off and fail to restart. Job security since winter is slow for moisture and lightening failures. Oh wait, I am rambling.........
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