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Old 10-30-2010, 10:14 AM   #1
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Using old Univolt V charger - help needed.

I have looked at other postings several times, and not found answer to my questions. any ideas would be great.

Last year I purchased an Airstream Univolt V Automatic Battery Charger and Power Supply model TU-345A at a Hamfest.

I have cleaned the unit up, tested all the capacitors, and installed it into a van I am making into a camper. Initial use was to be a power supply when in campgrounds. I discovered:
1. With no load and no battery connected the unit only provided 11 volts DC.
2. Could not find any adjustments to correct for this low voltage issue.
3. Connected an old dead battery, raised the voltage to about 12 volts.
4. Purchased a deep cycle battery, and then voltage became 13.1` volts, yea team.
5. Looks like this unit always is charging the battery went on.
6. Found this site, and confirmed battery is always being charged, and thus boils battery (thus proved my unit is working as others do).

My questions are:
1. Is there something I can connect in place of a battery to act as a dummy battery, and have the power supply provide the 13 volts? I purchased the unit to use as a power supply not a battery charger.
2. Is there a device to add between the unit and battery to regulate the charging function without adversely affecting the power supply function?
3. Any other ideas, or did I just buy a large paperweight!

Thanks in advance for any ideas.

Robert
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Old 10-30-2010, 10:27 AM   #2
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From other info on the web I gather that that is a 1971 device. There was no such thing back then as two- or three-stage charging unit. Yours seems to be working backwards, since the old units tended to have a higher voltage if they were unloaded. I think you have a paperweight.

I've dumped several of the old Univolts, but kept one for shop power. All of them (buzzing or not) put out 13+ volts unloaded.

Your only alternative is to keep that dead battery hooked up--you'll at least have 12V.

Zep
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Old 10-30-2010, 11:48 AM   #3
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Originally Posted by Robertrr View Post
I have looked at other postings several times, and not found answer to my questions. any ideas would be great.

Last year I purchased an Airstream Univolt V Automatic Battery Charger and Power Supply model TU-345A at a Hamfest.

I have cleaned the unit up, tested all the capacitors, and installed it into a van I am making into a camper. Initial use was to be a power supply when in campgrounds. I discovered:
1. With no load and no battery connected the unit only provided 11 volts DC.
2. Could not find any adjustments to correct for this low voltage issue.
3. Connected an old dead battery, raised the voltage to about 12 volts.
4. Purchased a deep cycle battery, and then voltage became 13.1` volts, yea team.
5. Looks like this unit always is charging the battery went on.
6. Found this site, and confirmed battery is always being charged, and thus boils battery (thus proved my unit is working as others do).

My questions are:
1. Is there something I can connect in place of a battery to act as a dummy battery, and have the power supply provide the 13 volts? I purchased the unit to use as a power supply not a battery charger.
2. Is there a device to add between the unit and battery to regulate the charging function without adversely affecting the power supply function?
3. Any other ideas, or did I just buy a large paperweight!

Thanks in advance for any ideas.

Robert
The Univolt output voltage is a function of having a good battery in the system.
If not, then the voltage will be low.

The Univolt, will provide power on demand, once it fully charges the battery. From there on, it provides on demand power, and simply keeps the battery "topped off". In case the city power fails, you then have a fully charged battery to use.

There are no adjustments that you can make to the Univolt, other than on and off.

Andy
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Old 11-02-2010, 12:35 PM   #4
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Thanks for responses

Thanks for the responses. Looks like I will have to look for another power supply, since I don't want to boil my battery.

It is interesting that my voltage is low and not high. Any idea on what could cause this? I have tested the capacitors and all seem to be OK. This leaves the teransformer (does not overheat so don't think is shorted) or the diado - not tested yet. From responses, even if fix will not do the job.

So now I have a paper weight.
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Old 11-02-2010, 01:18 PM   #5
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Robertrr, I just replaced my paper weight univolt with one of these:
RV Power Converter/Chargers
My original univolt was a 70amp model that just plain quit two weeks ago. I'm thinking the same culprit with mine was the transformer after testing.
So far so good with the 80amp replacement
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Old 02-07-2011, 12:56 PM   #6
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Hi OM VE3CZN Here
The UNITVOLT is a 6 VAC transformer to a full wave rectifier with a voltage doubler circuit Thats what the AC capacitor is for.
Check the Diodes for front to back resistance and replace the AC capacitor it should give you 14VDC or there and about. The battery it feeds is the filter capacitor. so will have to add an output filter circuit if you want to use it as a power supply.

Rae
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Old 02-07-2011, 02:09 PM   #7
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If you are not going to be dry camping and you have a more modern converter you don't even need a battery. Even with the old converter, if it gets up to 11 volts and you have lights. Isn't that what you are after?
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Old 02-07-2011, 02:34 PM   #8
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You need an operating battery for travelling, otherwise the brake "failsafe" (Breakaway Switch) will not operate.

Safety first, campers!
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Old 02-07-2011, 02:41 PM   #9
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I agree

He is using it a van not towing a trailer. But you are right Aage if it is a trailer you need a battery for the brakes if it comes lose.
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