Univolt FACTS

[overlander63]

Originally Posted by smily

I am studying the UNIVOLT and I see many opinions on the Function of the Univolt.
Does the Tow vehicle provide 12 volts to the trailer or the trailer battery via the Univolt?


Looking for the facts only,

Smily

The tow vehicle does not provide DC voltage to the battery through the Univolt, It is provided through a separate feed wire to the battery.
Terry

[Lumatic]

I am having a problem with my 12v system on my 73 Sovereign. I do not believe there are any shorts or draws although it is possible. The problem seems to be occassional. At times 12v power is very weak or dead, even when I have had the coach plugged in to shore current for a while. On occassion I have unplugged shore current and reconnected to shore current and voila the 12v system is working again. Also, I don't know if this has anything to do with the problem or just old control panel guages but my ammeter does not work at all and my battery level never reads above fair even with a new, charged battery.

[bryanl]

The Univolt in the Airstreams I have seen is a constant voltage, current limited device usually with little filtering (one reason why they are noisy). As Andy noted, they have a 'regulated' output that is sometimes set to a safe float voltage depending upon battery temperature.

Overcharging occurs when the Univolt voltage is set a bit too high. This could happen with a bad cell causing the battery voltage to be too low but usually happens because the Univolt output is set to near 14v. Over time, this will boil off the battery water. This means you need to pay careful attention to battery water levels if you leave the Univolt on. It also means that the Univolt doesn't take care of a battery with equalization type activity like the intelli-power with charge-wizard or a good battery maintainer does.

The Univolt is not a good battery charger because its voltage is fixed at float level. This means that the current it will provide to a battery will quickly decrease as the battery voltage comes up. Charge current depends upon the difference between source and battery. It takes a long time to get a battery recharged when using a float voltage source. 3 Stage chargers do their rapid charging by starting at 14.5 volts or more and reducing that voltage only after the battery has indicated a good charge (by its voltage and current acceptance).

[Anon]

Originally Posted by smily

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

You left out one other question.
How quickly can I change out my Uni-Volt with a new, less noisy, more efficient converter?

[overlander63]

Originally Posted by pattersontoo

You left out one other question.
How quickly can I change out my Uni-Volt with a new, less noisy, more efficient converter?

If your Univolt is as accessible as mine is, about 30 minutes to remove the old one, about an hour or so to change over the outputs (fuse panel), and about 45 minutes to replace the assembly.

[FrenchBern]

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

Will the Univolt overcharge a battery?
A properly operating univolt will not overcharge a battery because the output is set at less than 14 volts through the series voltage regulator. I have seen 3 univolts with shorted regulator and the output voltage is then over 17 volts which will boil a battery and ruin it in just a few days.
Can a Univolt Provide 12 volts to the AS without a Battery?
Yes it will but I do not recommend it because I believe they have a design problem with the rating of the regulator which is probably the cause for all the shorted regulators.
Is there a way to provide limitation between the Univolt and the battery, (a timer or state of charge limiter)?
Diodes can be added between the output and the battery. For each diode the voltage will be lowered by .7 volts so u can select the amount of charge you want on the battery. However if you do this you will decrease the amperage and increase the charging time.
Is there a Univolt manufacturer available for info?
I called Airstream and they could not provide me a schematic and said the manufacturer is not available anymore??? I would appreciate anyone who could help me find the information on the regulator board.
Does the Tow vehicle provide 12 volts to the trailer or the trailer battery via the Univolt?
Yes it does contrary to the reply you had before. The car battery is wired through fuse "m" which is directly in series with fuse "d" going straight to the battery on the camper. These fuses are located in the univolt fuse board. check page 45 of the owner manual.
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.
I hope you are referring to the "power ON" light. That light is ON when the univolt has 120v input and therefore output also. The 12 volt output of the univolt is directly connected thru fuse "o" to wire j powering the power light on the panel.
Smily, you wanted facts only and now you got them and I am sticking to them. lol

[joatmon]

Facts appear to be somewhat subjective on the subject of the Univolt. I do not agree with a lot of what FrenchBern has posted. But he/she is entitled to the ability to post an opinion.

Take what is posted above, as well as my response, as "just another opinion from the Internet". I have neither the time nor the inclination to debate points of, what I feel are inaccuracies that have been discussed repeatedly in this forum.

Parallax.com (sp?) has a schematic of the Univolt for interested parties.

Jack

[Inland RV Center, In]

FrenchBern

Airstream has had some seven different Univolts.

Which Univolt models have the problems you posted?

Being "specific by model numbers", will give a clearer understanding, to those concerned.

What you have posted for most part has nothing to do with the Univolts that have been in use for the last 10 years, or so.

Andy

[Janets Husband]

I guess that the name "Univolt" is being used as a name for many different models of chargers used in trailers over the years . Sort of like "Kleenex" is a name used for most tissue.

The charger I replaced was a 'Ferro Resonant type charger', I called it a "Univolt".
The 'Ferro Resonant charger is a very old technology, it is not used much since the Switched Mode Charger came on the scene. They were were heavy, loud, poor in voltage regulation compaired to modern standards, if left chargeing the battery for extended periods they would boil the battrey dry.
The 'Ferro Resonant charger was built around a large transformer which was noisy, Hence the HUM everyone talks about.

The Switched Mode Charger technology lends itself to better regulation, lower ripple output, low noise, and the ability to institute many battery preservation techniques.

In my opinion, the benifits of the newer style chargers far outweigh any cost difference between repair of a "Univolt" or replacement with a newer style charger.

[garry]

On my Univolt (1969) there is no regulator board and it will boil a "good" battery in just a few days.

It will run the 12VDC lights & stuff without a battery as long as you have the 120VAC connected.

While camping and on shore power for extended time (more than one night) I use a cut off switch to prevent over charging.

In storage with 120AC connected you could disconnect the battery (cut off switch) and use a small 3 stage charger run off 120VAC to maintain battery. This would save you taking the battery out to store for winter or whatever.

I use a marine cut off switch with removable key as pictured.

Garry

[bdlwet]

New to Airstream forum, I am just started working on my 65 tradewind but some of smily's questions are pretty easy.....I in fact have never found 'univolt' on my wiring, but haven't torn up much and will only this weekend put different battery in trailer. I intend to find out wiring schematic of airstream somehow/someway....this forum gives lots of good answers and leaves lots of questions..............mine mainly have to do with why all the wires in line to hitch....mine are worn and showing aluminum..I intend to replace. But someone in forum mentioned sytem charges battery when hooked up. Thus on newer vehicles you need relay like described and I might put in electronic amperage limiter, (Radio Shack), limiting charging voltage to 14 volts @ 2.5 amps thus not heating up system....ie trickle charging. But I am going to change plug system to newer style. I have no paper on trailer, Secretarial Svcs is sending me a owners manual, does anyone have wiring schematic from 64-66 models they might photocopy and send to me??

[FrenchBern]

Inland Rv
My Univolt is in a 1970 overlander. The model is 35 and the serial number is 5132. the nominal output on the tag is 13.5 volts. I also took a picture of the regulator board in it but can't copy it in this text? What is the best way to include pics in this text? Maybe my posting does not apply to the last 10 years for the Univolts but I am willing to bet nobody can give me facts proving any of my statements are wrong for my 1970 Overlander.

[tinman7]

My "univolt" which is a "Parallax" converter series 7400 started to act up this last weekend. The 12 volt lighting got dull then bright and it finaly quit alltogether. Its less than 2yrs old, I checked the breakers and I still have 110 from shore power and the battery was fully charged (its not now) I looked at my warrenty and it says I have to bring to the dealer and they will send it to them ....this will take a month....its camping time now! GRRRRRR

[FrenchBern]

joatmon, sorry but that parallax.com is wrong. Can you help me get the proper address to get that schematic. I really would like to restore my Univolt.

[68 Overlander]

Frenchbern,
Sounded like you had that UNIVOLT all figured out for a minute there. Here is the site www.parallaxpower.com but I don't think you will find the schematic for a 1970 Univolt there. I think Litton was making them then but I'm not sure. I would not throw good money after bad trying to restore that thing but rather get a new 3-stage. We carry the Inteli-Power, WFCO, and several others too but shop around. Airstream recommends the Parallax 7400 series. We have those too but not huge fans as they are not 3-stage, but they do work.

[Inland RV Center, In]

Frenchbern.

The early 70's Univolts were made by Newmark.

Andy

[FrenchBern]

Andy, Right you are by saying Newmark is the manufacturer of the 1970 Univolt. It is marked on the front plate.
The facts I stated in prior message are still valid since all of the 12 volts fuses are located in the Univolt. Therefore the tow vehicle system and the shore power 12 volts are all interconnected through the Univolt and that is why I listed the appropriate fuse and path for the current flow.

[sander17]

Originally Posted by pattersontoo

You left out one other question.
How quickly can I change out my Uni-Volt with a new, less noisy, more efficient converter?

If your converter is mounted in a deep hole like mine is, you need to add two weeks for recovery from the hernia surgery. What a beast!

[FrenchBern]

By Cleaning up the wiring where my univolt was, I gained a big storage area. Really worthwhile to do it. It took me a day because I soldered all wires instead of just crimping the lugs.

[Gigawatt]

Are there any words of wisdom in replacing my Univolt in my 70's Overlander... I found the unit deep inside a work hole next to the battery box... I would also like to replace the battery box with a larger box, big enough to hold two Golf Cart Batteries... I plan to attach two, 90 watt PV cells to the battery...

I have been off grid at my home for years, and would now like to add solar charging to the Overlander... I am experienced at working with my PV setup, and think it will work good on the trailer...

The Univolt seems to be located somewhat under the bath tub... and from all the screws in the top of the tub, it looks like at one time, the tub was cut loose and taken out to get to the Univolt... the Univolt hums loud, and does not keep the two Golf CArt batteries charged....

Are there any words of wisdom from anyone on this subject?

Gig