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Old 08-02-2012, 09:52 PM   #1
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converter DC voltage varies

I found the battery completely dead in my Safari. I plugged in the trailer to shore power and tried to charge the battery, but it would not take a charge. The battery was not dry this time, but I have had to add distilled water occasionally. I checked the converter's output voltage across the battery cables with the positive cable disconnected from the battery, to see if the converter was gone. When I checked it with the multi-meter it starts at just below 13.6 v and varies up to 13.9 and in between. The only load on the converter at the time I was checking it was the CO detector. All other 12v loads were turned off. I have been told my converter is probably the original Parallax 7455, though I have not removed the gaucho and plywood cover to enable me to see the converter.

I bought a new battery, but am concerned that the converter may be the problem, that the 18 month old battery might have been damaged by the converter.
  1. Is this voltage range on my converter high than normal? Shouldn't the voltage stay steady when there is only this small load on the converter? Is my coverter the problem?
  2. I'm thinking about a new Progressive Dynamics 9260 or a PowerMax Boondocker PM3B-60 Converter. I like the de-sulfation featrue on the PD, but I like the 3 year warranty on the PM. What are your thoughts on which unit is better?
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Old 08-02-2012, 10:02 PM   #2
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Most converters don't produce especially stable output with a really light load. I wouldn't be too worried about the Parallax having gone bad. The 7455s despite their many shortcomings do tend to last forever and if they fail they usually don't work at all.

The 7455 is actually pretty easy on batteries. Its main shortcoming is that it takes forever (well, 24 hours or so, maybe a little less in hot weather) to charge batteries to a more or less fully charged state. People who try to charge batteries from a generator find this problematic.

My main complaint with the 7455 is that the fan runs all the time.

People here have had reasonably good luck with the 9260. Don't know much about PowerMax.
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Old 08-02-2012, 10:06 PM   #3
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The PD 9245 is a very common unit to put in, and I have it in all three of my rigs. Some will put the 9260 in, but probably unnecessary. The PD unit is pretty bulletproof in my experience. I have no knowledge on the Power Max.
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Old 08-03-2012, 08:15 AM   #4
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I don't know the internal working of the CO detector.
The multi stage converters vary the output voltage to the battery(s) based on the state of the charge to said battery.
If you would run the same check on the alternator circuit in the TV, you would find a similar phenomenon. The voltage regulator in the alternator varies the voltage depending on the state if charge of the battery.
The multi stage converters work in a similar manner. Some have a maximum output voltage of 14.6 volts, which will trim down as the battery charges.
I would not be concerned about the converter output voltage varying by .3 volts in the 13 volt range.
If you are concerned about overcharging the battery while in storage and connected to shore power. Put plug the converter into a timer. Set the timer for a couple hours a day.
I use this method on my farm tractors while they are in winter storage. Just plug the battery charger into a timer.
I have 10 year old batteries that still start equipment.
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Old 08-04-2012, 03:53 PM   #5
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It is not the Parallax. It is a Magnatek 7455

Thanks for all the responses!

I had time today to remove everything covering up the converter. I found it is not the Parallax as I was told. It is a Magnatek 7455. I assume it is basically the same as the Parallax, since the Magnatek brand was spun off into the Parallax brand.

I found some literature that says the output range between 13.5 and 13.9 vdc is normal, so I guess my converter has not failed.

I also found the PowerMax I was considering as a replacement is made in China, so I think I'll go with the Progressive Dynamics.
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Old 08-06-2012, 04:44 PM   #6
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I have a PD9260 and a Powermax and find both work pretty much the same. The Powermax is 14.6 surge 13.6 normal and 13.2 float. On my 78 Argosy the Powermax runs at 13.15 most of the time. Only the frig controls are on the batteries. The PD9260 has a monitor that I like that blinks at various speeds depending on the stage and the Powermax is mute except for a fan periodically. I actually like the PD, but the word I got was for AGMs the Powermax is best. We will see.
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