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Old 07-11-2009, 07:24 AM   #1
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1976 31' Sovereign
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Univolt for Idiots

Is there such a book? If not.... Seriously though. I have a 31' International Sovereign that was absolutely wonderful until 2 weeks ago. It is permanently parked on site and plugged into 110/30amp service. The interior lights kept getting dimmer and dimmer last weekend. I did not realize the battery still played an important role in lights/fans. I am sure the battery is toast (it was included in the Ebay sale) but I DO NOT understand the univolt. Mine is located (I think) behind the range in the galley. If i unplug and replug it, the fan will blow for about 2 minutes tops and then stop. I have read many of the strings of emails on this site and hear people complain all the time about a "humming" sound. Mine does not make such a sound. Should it run/hum all the time? Should the fan blow all the time? When I replace the battery, how can I best test the Univolt's functionality. I had some electrical work done on it at the Airstream factory back in January due to some "reverse polarity" problem but I don't believe the Univolt was serviced. HELP!
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Old 07-11-2009, 07:48 AM   #2
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You don't need to understand the Univolt, you need to replace it.

Battery failures are often caused by the Univolt overcharging the battery and sometimes boiling the water out of it. A new battery is doomed to the same fate if the trailer is left connected to shore power for long periods. There are several very good 3 stage converter replacements available that will not damage your battery. I installed a InteliPower 9245 in my trailer, there are others to choose from.

The noise is a common issue with most, but not all of the Univolts.
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Old 07-11-2009, 07:58 AM   #3
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How old is the battery? It may just need watering (use distilled water for this). If there's plenty of water in the cells then, yes, your battery is toast and needs replacing. If your battery is dry as a bone, then your battery may be ruined (fill the individual cells with water just above the plates, then charge it. If it holds a charge, you're good. If not, then it's time to get a new battery).

Truth be told, the univolt is old technology. The modern charger/converters are more efficient and won't overcharge your batteries. If you find you have an issue with your univolt after fixing/replacing your battery, you will want to replace it, too.
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Old 07-11-2009, 08:11 AM   #4
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Doesn't the univolt provide 12v power to the trailer when hooked to shore power, and only "maintain" the battery for use when shore power is not available?

I ask this because I have no house battery, and near as I can tell everything works as far as lights and fans, I am hooked up to shore power.
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Old 07-11-2009, 08:17 AM   #5
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Quote:
Originally Posted by Dakota's Dad View Post
Doesn't the univolt provide 12v power to the trailer when hooked to shore power, and only "maintain" the battery for use when shore power is not available?

I ask this because I have no house battery, and near as I can tell everything works as far as lights and fans, I am hooked up to shore power.
It all depends on how you're wired. Some trailers are wired with the battery in between the fuse panel and the charger (like mine).

In your case it sounds like your converter/charger is wired directly to your fuse panel.
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Old 07-11-2009, 08:34 AM   #6
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Quote:
Originally Posted by Dakota's Dad View Post
Doesn't the univolt provide 12v power to the trailer when hooked to shore power, and only "maintain" the battery for use when shore power is not available?

I ask this because I have no house battery, and near as I can tell everything works as far as lights and fans, I am hooked up to shore power.
Like it or not, a Univolt will not and does not function properly unless you have a battery in the system, period.

No if, and's or but's.

Andy
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Old 07-11-2009, 10:15 AM   #7
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The univolt does not put out pure DC voltage. It is a square chop because of the diode bridge configuration. This means that it has a quantity of AC voltage present. This will cause problems with some electronic devices such as DC radios or 12 volt TV's. The inclusion of the battery in the circuit damps out some of these ac voltages and makes the appliances run better (lower noise). Later model converters/battery chargers have better ac filters so are lower noise.
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Old 07-11-2009, 11:47 AM   #8
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Your trailer was designed as a "travel trailer" and , as such, has it's own independent electrical system powered by a battery(s) just like the tow vehicle. Airstream thoughtfully provided a way to also use regular domestic (mains) power when it is available such as it often is in campgrounds. Since the two types of electrical energy used in these systems is incompatible, you need some way to convert the household high voltage alternating current to low voltage direct current-that is what the Univolt does. The Univolt lowers the voltage from over 100 volts to less than 15 and rectifies the current from AC to DC so that it can replenish the battery and run the 12V appliances and lights. The idea here is to use the plug-in (shore power) to obviate the need to run the tow vehicle to recharge the battery and so is not really meant or designed for prolonged use as a substitute for the 12 volt system and during long term use may damage the batteries by boiling the electrolyte out. For prolonged or permanent use, a different type of "smart" converter is required. These will adjust their output to keep the battery charged or recharge it, but not overcharge it and damage it. These newer type converters will usually replace the Univolt with room to spare. Many of us who park the trailer some months out of the year have upgraded to this system.
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Old 07-11-2009, 03:21 PM   #9
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I need More Univolt

OK. I'm following this thread, thanks to Aage as I am having power issues. I was testing voltage to my lights and was seeing a constant 9 volts, and slowly dropping. My indicator panel was showing the battery as WEAK, and as I turned off lights it went to FAIR, then GOOD. I then decided to unplug my Univolt and see what happened. I tested some circuits, and boom, voltage jumped up to 11. So, does this mean, that I can run without the univolt if I so decide and everything will just run off of AC power, but I won't be charging my batteries? Or, when I test those lights am I running off of the battery and it will soon run out of charge? My Air Conditioner is running just fine too which obviously isn't on the 12V system. This all started because some lights in my rear bathroom went out, and I can't get them to work at all now, and have no idea what the problem is.
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Old 07-11-2009, 04:15 PM   #10
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Without the Univolt, you are running your lights and other 12 volt stuff off of the battery only. At 11 volts, you are running on fumes and your battery is very low. If plugging in the Univolt causes the voltage to go to 6 volts, I would say that your Univolt is failing. You need to charge your battery as soon as possible.

The Air Conditioner will run fine since it is not connected to the 12 volt system.
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Old 07-11-2009, 06:07 PM   #11
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Battery Low on Water

As I understand it, the univolt will boil the water out of batteris when plugged into shore power for a long time, which I have been. I checked my batteries. One, curbside, was not low in any of the cells. The other, roadside, was low in every cell, so I filled it up. Is it normal for one to be that much different than the other? Also, what is the purpose of 2 batteries vs. the 1? After i filled it, I checked my voltage on a light switch, which was 9 volts yesterday. Now, it is 11.5 volts. Vast improvement.

Would a low voltage cause lighting issues in the back bathroom? I wouldn't think so, but am just learning about electrical problems. I have no lights or voltage in the overhead, nor in the mirrors over the sink. Underneath night light still works though. Lights in closet still work. Last I checked, I took off the light fixture overhead and checked the blue and white wires coming out of the roof and had no voltage. With this being said I don't know if this is also the cause of the light over the sink not working, but I assume they are related as they both stopped working at the same time. Question here is trying to understand how one affects the other, and which one is first in the series if they both have to work for either to work?

I hope to hear back and thanks any and all input is appreciated.
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Old 07-11-2009, 06:21 PM   #12
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So what years did AS use Univolts? Do I need to change out my converter to protect my batteries?

Dennis
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Old 07-11-2009, 06:32 PM   #13
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Quote:
Originally Posted by dstalzer View Post
So what years did AS use Univolts? Do I need to change out my converter to protect my batteries?

Dennis
I cant tell you the years Dennis, but it was back in the day. Your rig was made well after the reign of the univolt.
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Old 07-11-2009, 07:10 PM   #14
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Quote:
Originally Posted by dstalzer View Post
So what years did AS use Univolts? Do I need to change out my converter to protect my batteries?

Dennis
Dennis:

The Interstate batteries in our Classic were ruined on the dealers lot, too long plugged into shore power without checking, replaced under warranty in 05.
It has the 50amp 7400 series Parallax two stage converter, it will also overcharge, and damaged the batteries in three seasons. (I do remove during the off season and keep them on float chg.)

Just got Lifeline AGM batteries, and am in the process of installing this,XADC 60A Converter/Charger (Corded), simple 4 wire installation.

If you like to boon-dock and want to save the batteries you should consider a three stage converter up-grade.
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