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Old 01-03-2007, 08:21 AM   #1
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1979 31' Excella 500
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Running trailer directly off Univolt (no battery)

Hi, I'm wondering if a trailer can safely be powered by the Univolt to run the furnace and such with no battery in the trailer. I'm in the process of buying an AGM, but don't have it yet and may use my trailer this weekend.
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Old 01-03-2007, 08:42 AM   #2
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the battery is not necessary. But you need to do something with the battery cables so they do not short out if they are still connected to the Univolt.
I have no battery in my trailer at present, and the only thing that does not work of course is the breakway switch which would be wired to the battery directly. Also you might have a refrigerator that needs steady 12v oiwer for its board, but mine does not.
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Old 01-03-2007, 10:17 AM   #3
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None of my 12 volt stuff works without the battery does that mean my univolt is not working?
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Old 01-03-2007, 10:19 AM   #4
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There have been some warnings in the past about always having a battery in place since going from the Univolt directly without a battery load may cause higher voltages and thus shorten 12 volt appliance life.

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Old 01-03-2007, 10:25 AM   #5
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Your propane detector may not work if no battery is present - but I am not sure. Check the light - if it flashes every now and again you are ok.

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Old 01-03-2007, 10:38 AM   #6
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Originally Posted by jcanavera
There have been some warnings in the past about always having a battery in place since going from the Univolt directly without a battery load may cause higher voltages and thus shorten 12 volt appliance life.

True for old converters. They need a minimum load in order to regulate (I use the word loosely--the old coverters weren't very precise in their voltage control even under the best conditions) their output voltage. You won't have a problem with things like water pump or fridge (if yours uses 12V) because their load is sufficient. However, small things like a single light, or maybe a radio, provide such a small load that they might see 16-18 volts if they are the only thing turned on at the time. Not great for a light bulb.

The other problem is that without a load there will probably be significant ripple imposed on the dc voltage. You'll hear this as hum when you have the radio on and the peak voltage could be bad for electronic items and the min voltage is bad for motors.

Bottom line is that everything should work, but cross your fingers regarding silent damage and early light bulb burnout. I'd do it in a pinch, but avoid it for the long run.

Modern converters, like the Intellipower, are well regulated and put out a max of 13.9 volts, which is perfectly OK for 12V items.

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Old 01-03-2007, 12:03 PM   #7
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The best thing to do, is go to someplace like Batteries Plus, and get a blem battery for about $20. Put it in, and use it until you get your AGM. Then you won't have to worry about any of the above, and your breakaway switch will work also (required by law if you are going to be towing anyway).
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Old 01-03-2007, 02:41 PM   #8
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I have a converter that's probably 20 years old and am currently running without a battery, no problem. Like they say, just make sure the battery-charging cables are protected from shorts, for example by wrapping the positive connector in electrical tape.
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Old 11-08-2008, 12:35 PM   #9
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After winterizing this year and removing the batteries, I have noticed intermittent fluctuations in vDC while plugged into shore power.

The 12v bedroom outlet sometimes reads a steady 13.5v, and other times it bounces around by more then .5v causing the lights to flicker. I have also seen the 12v outlet very slowly drop from 13.5vDC to 12.5vDC while nothing was running.

I have seen the lights stop flickering and actually get brighter when other lights or the furnace fan is turned on. Almost like the voltage increases and steadies itself when more amps are drawn.

I measured the 120v outlets while the lights flickered and saw a steady 120vAC. I also checked around the converter for any loose wires, but found none.

Stupid question of the day........Is it safe to assume I have a converter problem?
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