Looking for a 12V DC under voltage relay - SailNet Community
 
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post #1 of 7 Old 06-24-2008 Thread Starter
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Looking for a 12V DC under voltage relay

I just installed a new Norcold refrigerator on my Gemini - powered by 195 watts of solar, a Blue Sky 200E (see other post for problems), and 200 Ah of AGM batteries.

After several unattended days of clowds, the voltage in the battery bank dropped below that required to run the Norcold. I expected the unit to turn off - but it didn't - the draw continued with no cold produced until the battery went to zero volts.

I'm looking for an undervoltage protection relay that will pull in at about 13 volts and drop out at 11.85.

Any idea where I can find one? Thanks /Stuy
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post #2 of 7 Old 06-24-2008
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I don't know about an undervoltage relay, but I think something could be made pretty easily.

If you run the frige on the load side of a relay, with the control side run in series with a zener diode, I think you can get that to work.

A zener diode blocks current flow until the voltage goes over whatever the rating on the diode is. If you can find a zener rated at 11.5 volts, and that will flow enough current to operate the relay, you should be in good shape. I don't know if you can get anything that will go off at 11.85 and back on at 13 without finding someone to design a circuit specifically for that purpose.


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post #3 of 7 Old 06-24-2008
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May be what you are looking for...Instead of mounting it directly to the battery add it inline to DC power of your fridge...You can find a cheaper version at Autozone, and other auto supply places...

-- Jody

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post #4 of 7 Old 06-24-2008
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Great minds think alike...posted a link to that same beastie in his other thread.
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May be what you are looking for...Instead of mounting it directly to the battery add it inline to DC power of your fridge...You can find a cheaper version at Autozone, and other auto supply places...

Sailingdog

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post #5 of 7 Old 06-24-2008
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Stuart, look at your previous thread. Your system is poorly designed, and this is just one piece of your problem. Go back and review your entire energy balance .... just like others say.

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post #6 of 7 Old 06-25-2008
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The battery brain is a pretty cool looking item. A couple questions though. It says that it will disconnect the battery if the voltage drops too low, but will it reconnect when voltage is restored? What the heck do you need a remote for?


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post #7 of 7 Old 06-25-2008
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US27, you might want connet/disconnect mannualy, regardless the treshold set, specially if conveniently mounted.

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