Univolt Testing

Craig · 08-21-2002, 08:41 PM

The repair manual for 1978 describes how to test the Univolt with a Newmark or Triad tester. What are these testers? Are these brand names or a type of tester available today? Thanks.

83Excella · 08-21-2002, 08:59 PM

You can test your univolt using a voltmeter at the battery, with the univolt off you should read battery volts, with the univolt charging you should be reading 1.5V higher than battery volts, I will double check the figures to be sure.

John

Craig · 08-22-2002, 08:19 PM

Thanks, John. I'm going to pick up a voltmeter. Stupid question, but does that mean if everything is in order the battery would read around 12V unplugged and then about 13.5V with the Univolt on?

davidz71 · 08-22-2002, 08:31 PM

With univolt turned on, the voltage must be within 13.8 to 14.2 volts according to my service manual. If not, it says replace it.

davidz71 · 08-22-2002, 08:36 PM

I just went out and measured my battery voltage. Both Delco Voyager batteries are hooked up to a 5 watt Solargizer Solar charger/maintainer so the maintenance charge stopped at sundown. The batteries measured 12.75 volts each.

Craig · 08-22-2002, 08:38 PM

Thanks, David. If the battery is bad, would you still expect that reading when the Univolt is on and connected to city power?

My battery isn't holding a charge, but I'm trying to figure out if both need replacing or if the problem is just with one before I replace.

Thanks again!

thenewkid64 · 08-22-2002, 09:03 PM

Craig,

You are about to enter into a sticky wicket!!!

If one batery is bad it will kill both batteries. The only way to know for sure is to disconnect one and charge the other. Then see what 1 does. If the first one is good then do it with the other. Word to the wise, they may both work fine independently, but together they drag each other down. You should replace batteries in pairs, or you will just spend the $$ and have the same problem.

If you have a battery that will hold 12.0 VDC and you connect one that is at 11.5 VDC the 12.0 volt battery will try to charge up the lower one, draining itself to a possible lower voltage than the weaker of the two batteries. Then when you apply a charge, buy plugging in the univolt, it just cranks up the voltage and expects the batteries to take as much as they can. Once you power down the charger the weak battery starts to suck down the good one. This causes the "good" battery to work hard and the "weak" one to get weaker, so in the end they are both bad.

If you are going to run on one battery be sure to tape over the + end of the cable as it will be powered from the other battery.

davidz71 · 08-22-2002, 09:14 PM

I have been told that you should not run the Univolt for long periods of time without the battery. According to my service manual you should test the Univolt:

1. Confirm that 120 volts are going into the univolt.
2. Remove all fuses from the remote fuse panel.
3. Connect black lead of tester (-) to terminal marked "ammeter red only". (Any of the four terminals on the negative side of the univolt may be used.)
4. Connect red lead of tester to any fuse clip on the center aluminum bar of the fuse panel. (This is the Univolt positive wire and it energizes the entire bar.)
5. Voltage must be within the limits noted earlier.

The manual does not say anything about the battery being connected.

What kind of battery do you have, how old is it and have you been charging it just with the Univolt? It could be that your battery is at the end of its service life or the plates on the inside are covered with sulphur plating. Some deep cycle batteries can be brought back around with proper charging and a desulphation. Be aware that some battery chargers in trailers will boil out the water in no time because they do not have a multistep charging system. Many individuals wire in a switch to turn the Univolt off at night because the humming bothers them and it is not charging the batteries all night long.

Craig · 08-23-2002, 07:10 AM

Thanks to both of you for the help. I only have one battery now, which came in the AS when I bought it a few weeks ago. From what I understand the trailer sat for a couple of years, so I'm going to assume the battery is bad at this point.

I think I'll start by replacing the battery (and adding the second) and then test the Univolt based on your instructions above. Thanks again.

This forum is great!

Craig

davidz71 · 08-23-2002, 10:13 AM

Craig,
If you have the same battery boxes I have on my '77 Excella 500, one on each side of the propane tanks, be aware that some group 27 batteries (105 amp hr) will not fit. I found that Duralast grp 27 were 1/4" too long. Some Trojan grp. 27's are fine and the Delco Voyager 27M just fit in the box with no room to spare as far as length is concerned. Two batteries are the way to go but buy both of them new as mentioned earlier.