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Old 08-12-2016, 10:37 AM   #15
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1972 Argosy 24
Jamestown , North Carolina
Join Date: May 2016
Posts: 5
TG Twinkie. I'm sorry. I did state "When the 120V is disconnected". It is then that the circuitry "connects" the battery to the 12V battery. My owners manuals from '70, '71, and '72 all state the "Whenever possible, use the automatic built in charger of the Univolt System for charging. the charging circuit automatically controls the current, reducing it as the battery increases in charge." It also warns against a quick charge. This indicates to me that there is a separate charging circuit for the battery and it does not connect in parallel straight to the 12V distribution. The converter is capable of outputting 30A or more and this would be bad for the battery. It also would not be able to control the current to the battery unless it is a separate charging circuit. I don't know if designs prior to 1970 would be different. I know it shows me as a new member, but I have had an EE degree for over 20 years. I just thought I could help with a little insight. After reading the other responses, I think replacing with a new converter/charger is a would be a good option.
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Old 08-12-2016, 12:55 PM   #16
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1974 Argosy 26
Morrill , Nebraska
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Does univolt need battery to run 12 volt fixtures?

There are only 2 wires that connect the Univolt to the 12 volt system in your coach. The + and -. The Univolt is connected to the + and - buss on the fuse panel. There is NO. Switching device in the Univolt!
The battery connects to the same + and - buss. As does the charge line from the TV. The + and - buss is connected to each of the fuse holders one the "line" side. Each branch circuit is protected by it's own fuse. Some coaches have a large fuse (30 amp) in both the positive and negative leads of the battery.
The Univolt doesn't know the difference between your battery and any other 12 volt device in your coach. It does not differentiate. It is only a power source rated at about 30 amps on the output.
Since the 12 volt devices seem to work when you have battery power the aforementioned fuses are probably good.
The internal resistance of the battery is what limits the charge current. There is no kind of intelligence in a Univolt. Thus the reason these units tend to cook batteries.
Since you are a EE the use of a multi meter should be second nature to you. Trouble shooting this system only requires a basic understanding of the system.
What voltage output do you get from the Univolt when it is powered?
What voltage are you getting when the Univolt is not powered.
If you disconnect the battery from the system and the Univolt will not power the lights etc in your coach there is a problem.
You could use a battery charger to confirm this. Leave the Univolt unplugged, connect the battery charge to the + and - terminals on the fuse panel and see what happens. It won't be necessary to have the battery in the circuit. The charger should light up everything in your coach.
I think you are reading too much into what the owners manual states. In short it says the Univolt charges the battery. Don't leave it plugged in when you are not using the coach because it WILL cook the battery.

Here is a basic coach wiring schematic.

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12 volt

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