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Author Topic: Operating trailer on 110VAC with dead battery  (Read 5068 times)

Dczerwon

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Operating trailer on 110VAC with dead battery
« on: April 14, 2015, 11:18:26 PM »
I've read on some posts that people can operate their 12VDC and 110V while connected to a 110V supply with the battery disconnected.  On two occasions, I've had no power while connected to house power and both times I had a dead battery. How can people operate their system with no battery connected when I can't operate with a dead battery?
« Last Edit: April 14, 2015, 11:32:12 PM by Dczerwon »

John From Detroit

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Re: Operating trailer on 110VAC with dead battery
« Reply #1 on: April 15, 2015, 03:39:27 AM »
Some can, some can not,  Depends on your converter and selected other systems in the RV.

For example.. Many older RVs have a Magnetek 6300 converter, this unit needs a battery to work properly.

Some RV's have special Energy Management Systems.. Now that term applies to two different devices..ONE uses only mains power (120vac) to power itself,,the other however can use 12 VDC to run its computer.. And this one is the one that decides if things like the air conditioners and water heater work when you are on 30 amps. (Load shedding).

A handy device many RVers should carry is a Jump-Start pack,, This is a small AGM battery in a carying case with jumper cables attached.  Useful if your car is not interesting in starting it can also Sub for the missing battery in the RV when needed... I prefer the ones WITHOUT the built in extra stuff (Radio, Air Compressor, Inverters, Lights,though lights are optional) but if you want one that WILL start your car go for ones with MORE than750 peak amps.

NOTE The battery is only in the 20 amp hour range (Roughly 1/10 of a pair of GC-2) so it will not run your RV long.. But it will make the Magnetek happy.
« Last Edit: April 15, 2015, 03:44:02 AM by John From Detroit »
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Great Horned Owl

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Re: Operating on house power with no battery?
« Reply #2 on: April 15, 2015, 08:54:15 AM »
A dead battery sucks up lots of current while your charger tries to charge it. A missing battery doesn't suck up any current.

Joel
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Gary RV_Wizard

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Re: Operating on house power with no battery?
« Reply #3 on: April 15, 2015, 09:32:20 AM »
Hard to say from the limited info provided, but nearly all RV electrical systems are designed to work without a battery connected if shore power is present. Note however, that a dead battery is somewhat different than "no battery", as Joel already stated. And a Santa Fe probably has a pretty simplistic converter/charger, so it might in fact require a battery to be present and usable. Not likely, but possible.

Without some more technical detail about how and why your battery was "dead", it's difficult to guess. An easy test would be to disconnect the negative post on your functional battery and then plug to shore power to see if things still work. If not, you know that your system requires a battery. We also might be able to help if you could give the make and model of the converter/charger in the Santa Fe.
Gary
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Dczerwon

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Re: Operating trailer on 110VAC with dead battery
« Reply #4 on: April 15, 2015, 10:21:32 PM »
I'm new to this forum and have to say you guys are great. I tried the electrical system while connected to shore battery without a battery and no power. So it appears as John suggested that my converter requires a functioning battery otherwise it's an open circuit.

Another question: I installed a charged (at least 75% charged) battery and within 3 hours connected shore power. It was the next morning that I noticed that I had no power and my battery was dead. I looked for possible reasons and found that my fridge was switched to 12VDC. I wouldn't have expected my battery to drain while connected to shore power even if the fridge was operating on 12V. Does this seem reasonable or do you believe that I have another issue as well?

Dczerwon

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Re: Operating trailer on 110VAC with dead battery
« Reply #5 on: April 16, 2015, 08:33:18 AM »
After thinking about I more I realized that the trailer and fridge was running on the battery for about 8 hours. So it's most likely that 8 hours with the fridge on caused the battery to drain. I feel more confident that I don't have some other electrical problem that is draining my batteries. Thanks for your help.

Dave

Gary RV_Wizard

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Re: Operating trailer on 110VAC with dead battery
« Reply #6 on: April 16, 2015, 09:24:08 AM »
Are you sure your converter/charger is working at all?  That would be the other explanation for the symptoms. If your battery is going dead while plugged to shore power, it seems likely that the charger isn't charging. A simple test is to measure the voltage at the battery with the charger active (RV plugged to shore power). It should be well above 13 volts. You can get a basic voltmeter for under $10, often under $5 at places like Harbor Freight.

Something like this works fine:
http://www.amazon.com/DIGITAL-MULTIMETER-MULTITESTER-VOLTMETER-OHMMETER/dp/B00UYK8EYK/ref=sr_1_5?ie=UTF8&qid=1429194089&sr=8-5&keywords=vom

Walmart voltmeter
Gary
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Lou Schneider

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Re: Operating trailer on 110VAC with dead battery
« Reply #7 on: April 16, 2015, 09:48:17 AM »
What kind of fridge and converter do you have?  If it's a 3 way fridge (gas/120v/12v), the two electric positions use electric heating elements to replace the heat of the gas flame, and the DC mode uses 20-30 amps of 12 volt power.

This may be more than your converter can supply to charge the battery, if so the excess will indeed discharge the battery even if the converter is working properly.

If you have a two way fridge (120v,12v) without the gas option, ignore the above.  These use a compressor and are much more efficient than the gas/electric absorption refrigerators.

Dczerwon

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Re: Operating trailer on 110VAC with dead battery
« Reply #8 on: April 16, 2015, 10:49:42 PM »
I have a 3 way fridge so as you say and I suspect the fridge may draw more than the converter can supply to charge battery. I'll also check the voltage across the battery while connected to shore power and keep an eye on the voltage.  Thanks again, much appreciated.

Gary RV_Wizard

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Re: Operating trailer on 110VAC with dead battery
« Reply #9 on: April 17, 2015, 08:14:54 AM »
You haven't mentioned the RV year/make/model or the converter/charger brand/model, but most can easily produce 30A. A typical rating for even a smaller rig is 45A or 55A.

Refrigerator make & model would also help get better advice.
Gary
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Tinmania

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Re: Operating trailer on 110VAC with dead battery
« Reply #10 on: April 17, 2015, 11:05:17 AM »
I have a 3 way fridge so as you say and I suspect the fridge may draw more than the converter can supply to charge battery. I'll also check the voltage across the battery while connected to shore power and keep an eye on the voltage.  Thanks again, much appreciated.
Presumably you had 120V A/C, at least before the battery was completely dead, yes? If so why not just let the fridge run on A/C? That would take much less power from the converter than running on D/C.

Regardless, it still seems odd that the converter could not only not keep up with simultaneously charging the batteries and running fridge on D/C, but actually had to use battery power as well. Still, I see no reason to use the fridge on D/C when connected to shore power anyway (or for that matter, when on battery power).




Michael

Dczerwon

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Re: Operating trailer on 110VAC with dead battery
« Reply #11 on: April 17, 2015, 11:31:56 PM »
I have a centurion CS 3000 with an output of 30 amps and a dometic fridge RM 2193 with a draw of 10.5 amps. Assuming my battery has a life of 60-80 amp hrs, the battery would be dead after 8 hours. So it looks like the fridge is the culprit. Thanks again for helping me reason this through.

To michaels question:  the fridge wasn't meant to be on 12v while connected to shore power. It may have been left switched to 12V from a previous road trip.

Gary RV_Wizard

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Re: Operating trailer on 110VAC with dead battery
« Reply #12 on: April 18, 2015, 08:58:27 AM »
While the fridge power is more efficient in 120v mode when shore power is available, it is still acceptable to use 12v in that case. The converter/charger is continually producing up to 30A of 12v power from  shore power, so the battery should never run down.  There is a slight loss from the converter making 12v from 120v, but the fridge works the same.  But if the converter is not working, or not working properly, then the battery would drain even with shore power active.
Gary
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Tinmania

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Re: Operating trailer on 110VAC with dead battery
« Reply #13 on: April 18, 2015, 10:56:34 AM »
The only 3-way I had didn't seem to cool as well on 12v. I only used it when driving, figuring I could save little propane. I don't know if that is the norm.




Mike

Lou Schneider

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Re: Operating trailer on 110VAC with dead battery
« Reply #14 on: April 18, 2015, 11:01:11 AM »
Yes, that's normal.  The 12 volt system can't deliver enough power to make the same amount of heat provided by either the small propane flame or the 120 volt heating element, so cooling capacity is reduced in the 12 volt mode.

12 volt mode is only meant to slow the rise in interior temperatures compared to turning the refrigerator completely off, not keep things cold indefinitely.

 

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