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Old 04-04-2004, 06:00 PM   #1
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Univolt Battery Boil

I have a univolt 30 which appears to be overcharging my battery. The Battery gets very hot and I have to physically disconnect it. Are there options to adjust the univolt? I do not have a manual.

Thanks,

mudd
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Old 04-04-2004, 07:21 PM   #2
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Quote:
Originally Posted by muddy_hollow
I have a univolt 30 which appears to be overcharging my battery. The Battery gets very hot and I have to physically disconnect it. Are there options to adjust the univolt? I do not have a manual.

Thanks,

mudd
The Univolt consists of a transformer, and capacitor(s), which to my knowledge are non-adjustable.
The battery getting hot could be from an internal problem with the battery, not necessarily the Univolt. Have you taken the battery out and had it tested? How old is the battery?
That said, Univolts are known throughout the land for overcharging batteries. If your battery is good, you may want to look into an updated version, with electronic voltage and charging control.
Terry
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Old 04-04-2004, 11:26 PM   #3
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Muddy Hollow,

I would have the univolt checked for charging voltage. I seem to remember that it should be about a .3volt with everything turned off. Mine, to the best of my knowledge is the original 1987 model and it works very well. I had it plugged in full time in Jan-Mar of this year and I topped off the battery water once and that was elective. I will look in my manual and confirm that .3volt.
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Old 04-05-2004, 08:48 AM   #4
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Battery

The battery is relatively new and came from the previous owner and I believe he picked it up from walmart. Are there certain type and brands of batteries that are better than others? I'm open to replacing the battery.

Is there an option to put a charge controller in between to adjust the charge rate?

Thanks,

Mudd
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Old 04-05-2004, 09:34 AM   #5
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Battery Disconnect Switch?

If one is simply taking an Airstream from shore power at home to shore power at a campground, the only purpose the battery serves is to power the trailer’s brakes should the trailer inadvertently disconnect itself from the tow vehicle while underway. During transit, the tow vehicle’s charging system will maintain the battery.

In an automobile, the battery, in addition to starting the vehicle, also serves as an electrical “accumulator” to smooth the voltage supplied by the alternator. While I have not, as yet, opened my Univolt (it still works), previous posts have indicated it contains capacitors that can/will go bad. Capacitors are also electrical accumulators which will smooth a DC waveform.

Although I have not seen a Univolt schematic, I wonder if it necessary to have the Airstream battery connected to the Univolt at all when hooked to shore power. If the capacitors in the Univolt are of sufficient size, they will do the filtering/smoothing function making the battery unnecessary.

The addition of a simple switch between the battery and the Univolt would allow the Univolt to charge the battery when the user deemed it necessary.

Anyone have details/horror stories concerning the importance of having a battery hooked up to the Univolt when the Airstream is on shore power?

Thanks,
Tom
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Old 04-05-2004, 10:12 AM   #6
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details

tom

the older univolts are ferro resonant, they need the resistance of the battery to make proper voltage.

your lights in the trailer would do the same thing. completly disconnected the univolt will show "low" voltage.

john
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Old 04-05-2004, 11:33 AM   #7
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the older univolts are ferro resonant...
Since I have a "tin ear" in electrical design , a www search provided a FAQ sheet which appears to address Univolt operation.

I wonder if the Optional SB100 "Simulated Battery" is just a big capacitor?

Tom
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Old 04-05-2004, 12:30 PM   #8
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faq

tom

good find on the pdf page.

the best thing univolt owners could get from it is the "long term storage is best handled by running the converter 10 hours a month" comment.

john
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Old 04-05-2004, 04:59 PM   #9
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A better Idea....

The last comment of running the univolt a certain # of hours a month is the way to go. I bought 2 new group 27 batterys and had them both fried by leaving it plugged in at the house for convenience.

The solution is to put a timer on the univolt that can be switched to 'full time' when wanted.

By this I mean the timer would let it run say an hour a day while on permanent plugin at home. This will keep it topped off without boiling it.

Then while traveling, turn the timer to "ON" and take it out of the equation when you need the charging at campgounds.

Whaddu think?

Steve in Sav'h GA
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Old 04-05-2004, 05:43 PM   #10
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i like the idea steve, very easy to do since the univolt just plugs into the wall.

john
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Old 04-05-2004, 06:27 PM   #11
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My univolt was boiling batteries so I replaced the capacitors and it now works like new.
-Jason
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Old 04-05-2004, 06:28 PM   #12
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timer

I like the idea and it should be very easy to set-up a timer on the wall. I was also thinking about having a manual disconnect and maybe adding a small solar panel to top it off. Thanks for the great idea!

But, as mine is an older unit what did people do in the past before they noticed the hot battery?
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Old 04-05-2004, 06:34 PM   #13
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My Father the Electronics GURU helped me fix my Univolt. It was putting out 30 volts and boiling batteries dry in a few days, im lucky they didnt explode.
Replaced Capacitors with 2-20UF@480 VAC wired in series which gives 10UF@960VAC. Works great now!

a properly working univolt will not overcharge batteries.
mine puts out 13.5 now and i leave it plugged in all the time, just keep water in the battery and it will be fine.
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Old 04-05-2004, 06:43 PM   #14
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Quote:
Originally Posted by jjonesnc
a properly working univolt will not overcharge batteries.
mine puts out 13.5 now and i leave it plugged in all the time, just keep water in the battery and it will be fine.
Your Univolt is overcharging if you have to make a concerned effort to keep water in the battery.

A battery will bubble (i.e. lose water) if left charging at 13.5 volts AFTER it has reached fully charged.

Sorry,
Tom
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