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Old 10-08-2002, 08:08 AM   #1
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Post Univolt FACTS

I am studying the UNIVOLT and I see many opinions on the Function of the Univolt.

May we please dispell all guesses and arrive at the facts only please.

Will the Univolt overcharge a battery?

Can a Univolt Provide 12 volts to the AS without a Battery?

Will the Univolt become damaged if ran without a battery in the mix?

Is there a way to provide limitation between the Univolt and the battery, (a timer or state of charge limiter)?

Is there a Univolt manufacturer available for info?

Does the Tow vehicle provide 12 volts to the trailer or the trailer battery via the Univolt?

And of course the ever persistant question of why does the 120 volt, shore power, indicator, (at the control panel), either stays on or off when connected or disconnected from shore power.


Looking for the facts only,

Smily
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Old 10-08-2002, 08:43 AM   #2
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Here are some links for more info...


http://www.timberman.com/Default2.htm

http://www.phrannie.org/phredex.html

Those are two of the more informative resources that goes into detail how the univolt / electrical systems on RV's work
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Old 10-08-2002, 09:06 AM   #3
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Wink Looking for Univolt Specific

Thanks for the links. The second is very informative especially in battery maintenance but, neither are specific to Univolt. Since a lot of the Vintage AS have Univolts, including mine.........

I am looking for information specific to Univolt.

Thanks anyway.

Smily
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Old 10-08-2002, 10:20 AM   #4
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I started a thread on the Power-on indicator light that comes on when connected to 110/120 volt shore power. Andy from Inland RV thoroughly explained how the light worked in conjunction with the Univolt. That should take care of one of your questions if you do a forum search for the power-on indicator and read the responses.
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Old 10-08-2002, 11:20 AM   #5
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I didn't even know I had a power-on light. never seen it. anyone know where its supposed to be on a 73 safari?

while we're on the subject, just what exactly is the "ammeter" measuring? amps, I know but is it the amount of power that is being used, or the amount of power that is available? Mine always says the same thing when I push the button to activate it, regardless of the state of charge on the battery......needle wants to float between "fair" and "poor". I've seen mention in other threads that it can be calibrated with a screw/shunt on the univolt. (I still have the univolt in the trailer).
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Old 10-08-2002, 11:48 AM   #6
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Red face Univolt

Smily. I am interested in the same answers because after reading all the info on these threads, conclusion:
1. Don't charge the battery via the Univolt because it will overcharge the battery??? Use a Battery minder. [ If the CB to the Univolt is flipped off while connected to shore power, as in boondocking, is not the Univolt 'off'??] Use 12v lighting supplied by the battery, and let the battery minder maintain the battery.
2. Disconnect the charge line to the battery when towing to prevent overcharging??
3. Use solar power to charge batteries when boondocking.
4. If the Univolt is NG to charge the battery, what did the previous owners do for 30 years??

Tom
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Old 10-08-2002, 12:23 PM   #7
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Exclamation Indicators and Univolts

Davidz,
I participated heavily in your thread on indicators and I never did really understand the Power on indicator so I gave up.

But please understand, this thread is specific to the Univolt and not the control panel.

I am hoping that the Gurus will chime in sometime soon and maybe have some feed back.

I have seen conflicting statements on the Univolt and i am trying to get to the bottom of it.

My Univolt definitely charges my battery to the point of dry cells. I have cooked my battery and I am trying to figure out how one can install or implement a device that would cut off the Charger effect of the Univolt. (similar to an Automatic Battery Charger).

Since my Univolt provides 12 volts well to the branch circuits, and the fuses all provide over current protection, and it hooks to the trailer connector, I do not want to go out and buy an up to date converter so I am hoping that I can jerry rig my Univolt so that it will not overcharge my battery.

I have installed a "disconnect" switch between the Univolt and the trailer battery so that I can maintain 120 volts to the reefer and the outlets while parked in my driveway. This allows me to disconnect the battery from the Univolt but that leads to the question of " can you power the Univolt with out the Battery in place"?

Very respectfully,
Smily
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Old 10-09-2002, 08:12 AM   #8
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Univolt follow up

Still have not got the answers I was looking for so I thought that I would refresh the thread.

Any electrical engineers listening?

Smily
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Old 10-09-2002, 09:47 AM   #9
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I'm not an EE, nor am I familiar with the Univolt, but most crude 12 volt power supply/chargers I've seen will have higher than normal output voltage, with more AC ripple, without the battery load on them. This may not be healthy for 12 volt lights, fans, pumps, etc., not to metion electronics like the radio.

Have you measured the output of the Univolt without a battery? Both DC and AC?
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Old 10-09-2002, 10:34 AM   #10
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Univolt=Dirty Power

I bought one of those $12 cig plug digital voltmeters. I ran the Univolt without a battery, and had the cig plug voltmeter plugged into the outlet on the tv antenna wallplate. The voltmeter got really confused, LEDs on it were blinking and the voltage reading was all over the place! Hooking the battery back up and it worked fine.

By the way, I ran into the former owner of my trailer at a campground. (He bought a new Layton). I showed him the new countertop, and explained some of the work I had done on the trailer. One of the things I mentioned was buying a new battery, because the trailer did not have one. His reply:"Oh really? What's the battery for anyway?"
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Old 10-09-2002, 10:56 AM   #11
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Converters are tough...my view

Converters are just a step down transformer with a full wave diode bridge. The bridge makes ac into pulsing ac to allow a kind of dc output.

Questions answered in order asked first post..
The univolt CAN overcharge a battery. There are methods to prevent same.

Where there is shore power to the converter, batteries are NOT required to operate all 12 volt devices. In some cases the total load is too hi a demand for converter.

Converters will NOT be damaged by use with out battery in circuit....

To control the charge rate of an old Univolt requires owner participation.. Owner must monitor batteries condition with a digital volt meter and learn about charge conditions. While connected to shore power and battery in good state of charge read 12.5--12.6 vdc, battery can be disconnected with battery selector switch. The converter will operate all the 12vdc loads including the furnace.

Univolt is no longer manufactured. Univolt is just a basic transformer with an internal fuse, and easily repaired. It is very difficult to destroy a converter.

The Univolt is not connected in any function to tow vehicle and charging system. The converter is a stand alone 12volt dc source. The tow vehicle is also a stand alone system of charging trailer batteries. The charging rate from tow vehicle is controlled by that vehicles voltage regulator.

The charge lite in Airstreams is connected to the 12volt side of the converter.

And yes.......... big is better with converters. An 80 amp will do more work than a 40 amp unit....
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Old 10-09-2002, 11:17 AM   #12
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Ok, so how does one prevent "over-charging" the battery?

I have an original univolt, and a new battery in the tt. I was under the impression that I should keep it connected to shore power to keep the battery charged, as it has been said here that any battery will discharge in 30 days or so, without any load on it at all.

for the winter, I will be parking the trailer farther away from the house, and won't be able to keep it plugged in, so I was planning on removing the battery and bringing it in the house, and keeping it on a charger. perhaps I should get one of these "battery-minder" things to prevent over-charging....but how should I handle this during the camping season?
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Old 10-09-2002, 11:39 AM   #13
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Thanks

Good detail but one issue that got my attention.

The source from the Tow vehicle is wired how?

It is pretty obvious that the blue wire which comes from the 7 way connector on the fron of the AS is definitely hooked to the Univolt.

There is a postive to the trailer battery, (red)
There is a Blue wire from the seven way connector, (Blue)

I may be wrong but If I am, how does the tow vehicle provide 12 volts, (charge), to the trailer battery? The only wires connected to the trailer battery go directly to the Univolt.

I suspect that since it is imperative that both Tow vehicle and Trailer have the same polarity (as identified in Owners manual),
The tow vehicle 12 v and the trailer 12 v are wired in parrallel to the Univolt.

Thoughts?

Smily
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Old 10-09-2002, 11:44 AM   #14
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Methods of preventing overcharge

could you please elaborate on methods of preventing Overcharge.

Of course I am only interested in the ones that will allow me to maintain 120 volts to the Univolt at all times. This is when My Univolt is Overcharging my batteries.

I leave my trailer connected to shorre power while at home to keep my reefer running.

I have installed disconnect to the battery but I have to monitor the battery at all times.

It would be nice to implement a device that will know when to not allow 12 volts +- to the battery when the battery is fully charged.

Smily
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