June 25, 2018, 01:46:41 AM

Author Topic: 12 Volt Convertor Question??  (Read 2780 times)

Offline Dave Siegel

  • Sr. Member
  • ****
  • Posts: 482
  • Stand for something, or you'll fall for anything!
    • Dave Siegel Designs
12 Volt Convertor Question??
« on: August 24, 2006, 03:36:21 AM »
In a post a few down (yesterday) I asked about a fried water pump and "Wrench" answered back by stating that a convertor "MUST" be attached to a battery.

When my convertor was  attached to a pair of batteries it would over charge the batteries and boil them out, and they would be dead. I removed the batteries and have just run the convertor to create my 12 volt power. As I had stated in the other post I only run the water pump and a few lights off the convertor, and that has worked for about a year. Do I really need to have a battery attached to the convertor?

Thanks, Dave
Dave & Jan Siegel    1948 GMC  "Silversides"
            Pinellas Park, Florida
   Dave is Host to the "Help Assist Pages"
  (Free roadside help for Bus Conversions)

Offline JackConrad

  • Orange Blossom Special II
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4448
  • 73' MC-8 8V71/HT740 Southwest Florida
Re: 12 Volt Convertor Question??
« Reply #1 on: August 24, 2006, 04:34:52 AM »
   The fact that the converter would overcharge your batteries seems to indicate that the converter was putting out too much voltage.  Too much voltage could ruin the water pump.  With only the water pump and a few lights, you might be better off with a couple house batteries and a small self regulating battery charger.  Jack
Growing Older Is Mandatory, Growing Up Is Optional
Arcadia, Florida, When we are home


  • Guest
Re: 12 Volt Convertor Question??
« Reply #2 on: August 24, 2006, 05:14:15 AM »
I don't know what kind of converter you have, but here at the campground we have a major problem with the convertors that come in camp trailers.
Many of them are so cheap they don't even have a cooling fan.
Also some of the ones with fans never get looked at unless they screw up, and they screw up because they get packed with dirt and dust which overheats them or the batteries get boiled dry which WILL cause it's own set of problems... like what you are experiencing.

Like Jack said, use a couple of house batteries and a good self regulating smart charger to keep them up.
Smart chargers are available for less than $100 all the way down to less than $50 and have 3 and 4 stage charging options.

Good luck!

Offline Brian Diehl

  • Hero Member
  • *****
  • Posts: 1147
    • www.brihil.com
Re: 12 Volt Convertor Question??
« Reply #3 on: August 24, 2006, 05:51:37 AM »
Hi Dave,
I've used a couple of good quality 24 -> 12v DC power converters for over 3 years now with no issues.  I would recommend purchasing a quality converter.  I don't run an extra "buffer" battery for my 12 volt needs because my converts are more than adequate to keep up with any power consumption I generate.  Of course, I've gone out of my way to get 24v things like water pumps, webasto, etc. so that my 12v needs are purposefully low.  You may still require a 12v buffer battery if you have larger continuous 12 needs exceeding 12amps (most reasonably priced converters seem to top out around 10 - 14 amps -- at least that I've seen).

Offline Buffalo SpaceShip

  • Hero Member
  • *****
  • Posts: 591
Re: 12 Volt Convertor Question??
« Reply #4 on: August 24, 2006, 07:56:29 AM »
Are we talkin' about a AC-to-DC converter here, or a DC-to-DC? Seems like the first few posts refer to the old AC-to-DC converters you'd find on old travel trailers and S&S MHs. Seeing how you have a Silversides, I'm going to think it's an AC-to-DC.

While there are a few nice converters out there, made by Progressive Dynamics, etc. that have 3-stage charging and decent electronics (for $250 or so), I too would vote for a quality charger. Better yet, a nice marine or RV inverter-charger can be had for less than $1000 used.

I used to think I could get by on mostly DC... but when my new coach came with a good inverter charger (and Link panel system), I found it truly changed the way we camped. If we avoid air conditioning, we can easily go a weekend dry-camping somewhere w/o firing up the genny at all. Making coffee, running the microwave, and running big AC fans to keep the air moving.

Back to your original question, though, go ahead and use a digital voltmeter on your output and see what kind of voltage it's putting out. See if it's stable and less than 14v, since even a 3-stage charger will frequently hit 14v to keep batts in prime condition. One thing it won't measure is the quality of the power and its regulation. Cheaper converters put out a lot of noise (like RF). Worse, they might simply do a 1:10 step-down... 120v = 12v, 110v = 11v, etc., so low park power might mean low voltage to your DC items... and probably worse than over-voltage in terms of heat and amperage draw. I'm no EE, so this 1:10 "theory" is just a WAG (wild a*s guess)  ;), however... so check it with a meter.

Also see how it's supposed to be wired. If your DC circuits are wired "downstream" of the battery, I'd think that the batt would be required to "filter" the loads. If the battery is on a separate line feed, the battery would only be used when the converter's not converting... I think (refer back to the "I'm no EE" phrase above  ;D).

Whatever you do, Dave, please keep your beautiful Silversides on the road. Makes me feel good to know you're out there driving such a classic creature!


Brian Brown
4108-216 w/ V730
Longmont, CO

Offline Dale MC8

  • Jr. Member
  • **
  • Posts: 81
Re: 12 Volt Convertor Question??
« Reply #5 on: August 24, 2006, 08:57:12 AM »
When I was in RV Tech school (mumble) years ago, we were told that a converter needed a battery. At the time, there were 'fake' batteries available to make the converters think a real battery was in the circuit. These were for full-time parked and lived in coaches. Times have changed and perhaps the battery requirement has also - just FYI
Dale MC8
Dale MC8

In Theory, theory and practice are the same.
In Practice, they aren't.