Electrical Problem - Fiberglass RV


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Old 10-23-2012, 05:59 PM   #1
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Electrical Problem

I am about to install a propane detector as well as a 12 V receptacle for charging my toys, but when I disconnect the battery, there is still power, something with 27 volts. It reads 12.6 when the AC power is disconnected and the battery is connected, which is normal. The propane detector works ok with DC power only, but when I connect shore power it does not work. I went back to the water pump switch and got power there even when the battery is disconnected and the shore power connected, thinking I could use that as a feed for my propane detector and 12V receptacle. Help, please. Thanks, Jim
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Old 10-23-2012, 06:09 PM   #2
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I'm not sure I'm following. Are you saying that when you disconnect the battery, but are plugged into shore power, you are getting 27 volts to the water pump switch?
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Old 10-23-2012, 06:19 PM   #3
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Yes, Tom, When I disconnect the battery froim shore power, I am still getting 27 volts at the water pump, as well as at two other 12 volt light fixtures.....Jeeezzzz.
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Old 10-23-2012, 06:23 PM   #4
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You have something wrong with the converter. It is putting out to much DC voltage.
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Old 10-23-2012, 06:24 PM   #5
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You have something wrong with the converter. It is putting out to much DC voltage.
Yea, that's what I'm thinking, too. That high a voltage may damage devices in the trailer.
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Old 10-23-2012, 06:28 PM   #6
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Are you using an auto ranging meter such as a Fluke? You may be reading 27 milli volts and not 27 volts . The fluke meter often will pick up stray voltage and display a number
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Old 10-23-2012, 07:16 PM   #7
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Tom, Yes, I believe it is the converter that is at fault, and after 31 years, it will probably be time to upgrade. The trailer is 15 amp. Would it be costly to upgrade to 30 amp converter and would I have to upgrade anything else? Thanks, Jim
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Old 10-23-2012, 09:33 PM   #8
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Originally Posted by steve dunham View Post
are you using an auto ranging meter such as a fluke? You may be reading 27 milli volts and not 27 volts . The fluke meter often will pick up stray voltage and display a number
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Old 10-23-2012, 09:45 PM   #9
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Jim, if you haven't already seen it there is a really good resource to read called The 12 Volt Side of Life with some great info in it and it might help you out with some of your decisions.
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Old 10-23-2012, 09:54 PM   #10
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Jim, The death of an old 12VDC converter is more of an opportunity then a problem. If it is like the converters I have seen, it is no good as a battery charger. Just boils the battery dry. Take a look at this thread. It probably applies to a big foot as much as a Trillium. Having a converter, that is a good multistage charger as well, would rock.


http://www.fiberglassrv.com/forums/f...ter-48962.html
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Old 10-23-2012, 10:51 PM   #11
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A 31 year old converter probably uses 31 year old battery charging technology. The charging current was controlled with a dropping resister. The idea was that when the battery got sufficiently charged the current would drop to near zero with just a trickle charge. Today's batteries have improved to the point this technology no longer works properly.
There's a couple things you can do to make it work better.
The easiest is to disconnect the converter and rely on something like a Battery Tender to keep the battery charged while plugged in. Another non-converter option is get a 50 to 80 Watt solar panel and rely on the sun to keep the battery charged.
You could remove the converter, but you might have some problems with fuse and breaker panels since they're often integrated into the converter.
If you really feel the need to have a converter, then replace it.

What would I do? Probably just simply disconnect power to the converter and use a Battery Tender. I've pretty much done that now, which works just fine.
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Old 10-24-2012, 07:18 AM   #12
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Jim, The death of an old 12VDC converter is more of an opportunity then a problem. If it is like the converters I have seen, it is no good as a battery charger. Just boils the battery dry. Take a look at this thread. It probably applies to a big foot as much as a Trillium. Having a converter, that is a good multistage charger as well, would rock.


http://www.fiberglassrv.com/forums/f...ter-48962.html
David, I agree that a 31 year old converter needs to be replaced. Thanks for the link. I tried removing the converter but could not move it out. Will try again, or take it to my RV dealer as I am not handy with electrical work. It seems like a very complicated job to re and re and of course the shore power cord has to be changed to 30 amps as well as the wiring to the battery, which seems to be only 16 gauge. I have some good prices on converter/chargers on line so will see what my dealer can do for me. Thanks, Jim
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Old 10-24-2012, 07:32 AM   #13
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Voltage

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Originally Posted by Darwin Maring View Post
You have something wrong with the converter. It is putting out to much DC voltage.
Darwin . The older converters transform 120 VAC to approx 14 VAC (secondary transformer voltage) The 14 VAC is then fed to a bridge rectifier to get DC voltage , Multiplying the 14 VAC x 1.41 to get P to P voltage you get about 19.5 VAC imput to the bridge rectifier and subtracting for the drop across the bridge diodes you get about a 17 VDC unregulated output . That is why the 27 VDC output had me puzzled its 10 VDC higher than the output voltage of 17VDC .What am I missing?
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Old 10-24-2012, 10:30 AM   #14
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Originally Posted by steve dunham

Darwin . The older converters transform 120 VAC to approx 14 VAC (secondary transformer voltage) The 14 VAC is then fed to a bridge rectifier to get DC voltage , Multiplying the 14 VAC x 1.41 to get P to P voltage you get about 19.5 VAC imput to the bridge rectifier and subtracting for the drop across the bridge diodes you get about a 17 VDC unregulated output . That is why the 27 VDC output had me puzzled its 10 VDC higher than the output voltage of 17VDC .What am I missing?
My best guess, no loading. The schematics I have seen of old converters were pretty simple, transformer, rectifiers, no filter or regulation. When plugged in the rectifier output supplies pulsating DC to the trailer and charges the battery. They use an SCR crow bar circuit to prevent over charging the battery. Since there is either a large current charging the battery or flowing through the crowbar, the transformer output is chosen with that current in mind. Disconnect the battery and there is no longer a large current hence no loading and a higher output. The circuit was designed to always have a battery. Raz
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Old 10-24-2012, 10:57 AM   #15
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My best guess, no loading. The schematics I have seen of old converters were pretty simple, transformers, rectifiers, no filter or regulation. When plugged in the rectifier output supplies pulsating DC to the trailer and charges the battery. They use an SCR crow bar circuit to prevent over charging the battery. Since there is either a large current charging the battery or flowing through the crowbar, the transformer output is chosen with that current in mind. Disconnect the battery and there is no longer a large current hence no loading and a higher output. The circuit was designed to always have a battery. Raz
Raz I agree , the battery acted as a regulator of sorts in the old converters
and removing the battery affects the output voltage . With that said 27 VDC open circuit output voltage still seems high . I checked my reference material and the transformer secondary output voltages vary between 13.8 VAC to 14 .4 VAC RMS on three different converters.
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Old 10-24-2012, 11:05 AM   #16
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Jim, after you get a quote locally for the rewiring etc and if you have any other big ticket items you need work done on that you dont feel comfortable doing it may turn out its worth the cost of the ferry trip to take the trailer to Escape Trailer Ind to have the work done.

I am not sure if your aware but Escape Trailer Ind. does do repairs on all makes of fiberglass trailers. Was at a trailer meet last month down south and there was a awesome little lime green Trillium that got more than a little help from Escape in its transformation & the owner was *more* than pleased with the level of help he got from Escape in the transformation of that trailer. Pretty clear they have a new #1 fan of their services. There are a number of people here who have also used their services and are more than happy with the results and cost. I personally am thankful I so far havent had an issues with my trailer yet that I havent been able to fix myself as I know that I cant trust my self to take my trailer to them for repair and not bring home a new trailer instead.
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Old 10-24-2012, 11:47 AM   #17
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Wild Voltages

I see this often with some, but not all, of my multimeters.

If the existing converter is unplugged, first turn a light ON to pull down any filters, then measure. If it is still high I would suspect that a bad ground is allowing what I call "Antenna effect" to give a false reading. Old meters required enough power just to run, so this wasn't common in the old daze.

Some of use will remember using a VTVM (Vacuum Tube Volt Meter) to read voltages in early electrinic circuits. Today, with super sensitive digital meters for less than $20, you can read "Potential" that isn't really there.

That high DC oltage isn't a voltage that wouldn't be causing other damage, such as blown out lights, if it was backed up with any current capabilities.

Best bet though... As mentioned, pull out the old converter and update to a modern converter/charger/dist & fuse panel. As mentioned xxxx times, I use and recommend the Progrssive Dynamics PD-4045 for our trailers. I have installed 7, two in my own rigs.



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Old 10-24-2012, 01:31 PM   #18
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For less than the cost of a good converter you can install a solar system to keep your battery or batteries charged and eliminate the converter.
You don't need a converter to operate you 110 system, just an inexpensive 15 Amp breaker and box to house it.
John
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Old 10-24-2012, 01:41 PM   #19
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For less than the cost of a good converter you can install a solar system to keep your battery or batteries charged and eliminate the converter.
You don't need a converter to operate you 110 system, just an inexpensive 15 Amp breaker and box to house it.
John
If the 110v is powering 12v appliances like lights, furnace fans, etc, some means of converting it to 12v must be supplied, whether by converter or by passing it through one's on-board battery by means of a charger being hooked up to it. (How's that, B.K.? )
I think an onboard converter to be the easier of those options.

I guess we still don't know for sure if the O.P.'s converter is shot or not, but if it proves to be o.K.:
I will say that I added a charging module to my forty-year-old converter and it's worked very well for over five years. On the same battery, I might add...
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Old 10-24-2012, 01:59 PM   #20
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Originally Posted by steve dunham View Post
Raz I agree , the battery acted as a regulator of sorts in the old converters
and removing the battery affects the output voltage . With that said 27 VDC open circuit output voltage still seems high .
I don't think so. Rint= (Voc-VL)/IL Assuming a charging current say 5 amps, the internal resistance calculates to Rint=(27-14)/5 = 2.6 ohms. The winding resistance and bulk resistance of the diodes could easily add to that. With out having the converter on my bench I can't say for sure but I bet it is fine, just keep the battery connected. Raz
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