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Old 08-06-2013, 09:36 PM   #1
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Help - mystery battery draw in the middle of a 10 day dry camp!

Dry Camping this week and our fully charged batteries died completely in 2 days. Had to buy two new batteries and now they are draining quickly (hours) with nothing on except the refrigerator.

We've done the following tests:
1. Disconnected the ground from the battery and measured The voltage across the battery negative terminal and ground - Nearly a 12 V draw!

2. When battery disconnect is disconnected, there is no draw.

3. With battery CONNECTED, pulled Every fuse one at a time, and the 12 V draw remains.

I'm very confused and concerned since we still have five days left on our trip. The only thing I can think of is that the Trailer brakes or somehow engaged, but that would mean with the battery disconnect in on there would still be a voltage And we are measuring only millivolts.

Suggestions?

Many Thanks.

mb
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Old 08-06-2013, 09:52 PM   #2
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Oh.....maybe the 12V measured is not really a big deal? I measured only 1.5 mA which would make sense given that the CO/LP detector should draw about that much. Measured only 2ish amps when I turned the fridge back on - we have rigged up a small fan (less than an amp?) in there to reduce ice build up.
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Old 08-06-2013, 09:52 PM   #3
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Are you looking and Volts or Amps? Checking Volts will not tell you where the draw is from. It will only show you what voltage you have. Now in a case with an extreme draw the voltage will rise if you remove the source of the draw. However, on a small draw "battery dead after 2 days" you wont see much if any voltage rise.
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Old 08-06-2013, 09:56 PM   #4
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Also 4 amps of continuous draw over two days (48hours) would be 192 amp hours. Depending on how many amp hours your batteries are rated for there is your dead batteries.
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Old 08-06-2013, 09:58 PM   #5
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Cable guy,


Thanks for the quick response. In my update post, I mentioned that I measured 1.5 mA.

Question: should I be measuring the amps between the pole and disconnected ground or just across positive and negative poles with ground connected?

Q2: should I repeat the "Remove one fuse at a time" Test while measuring amps?

Thanks!

MaryBeth

Corrected: 1.5mA not amps!
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Old 08-06-2013, 10:01 PM   #6
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Quote:
Originally Posted by Acableguy06 View Post
Also 4 amps of continuous draw over two days (48hours) would be 192 amp hours. Depending on how many amp hours your batteries are rated for there is your dead batteries.
I am measuring only 1.5mA, not amps. (I got it right in my first post).

I'm running two group 24 12v batteries in parallel

mb
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Old 08-06-2013, 10:09 PM   #7
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Quote:
Originally Posted by mbvell View Post
Oh.....maybe the 12V measured is not really a big deal? I measured only 1.5 mA which would make sense given that the CO/LP detector should draw about that much. Measured only 2ish amps when I turned the fridge back on - we have rigged up a small fan (less than an amp?) in there to reduce ice build up.
you stated 2 ish plus about 1 amp? then any other parasite loads. I just used 4 amps to give you a rough idea where your batteries are going. This does not include any lights you are using in the coach. Everything adds up.

I do not know what volt meter you have to tell you how to use it. However, you will probably have to move the red lead to another port on the meter and switch your setting to the dc amp setting then you would measure across the + side of what you ar working on. remove the cable from the battery and put one lead on the batt. and the other on the terminal you just took off. Most meters only have a 10-20 amp rating for amp draw in this configuration. From the sounds of it you are not very familiar with using a VOM and should seek some help from someone that is.
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Old 08-06-2013, 10:18 PM   #8
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If you have pulled each fuse one at a time and checked for a voltage drain, and have not found the bad line, then it would seem that you have a 'grounding' between the battery and the fuse box. This should shorten your search for the grounding/ chaffed wires.

Also if you dry camp very often, invest in some solar panels (generator) to help keep your batts up.
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Old 08-06-2013, 10:32 PM   #9
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Sorry for the confusion cable guy. I mis-stated amps in my original posting. The built in CO monitor shouldn't draw Very much at all and the refrigerator fan is .12 A according to the advertisement for it on eBay, where we bought it.

The voltmeter I am using switches automatically from milliamps to amps and is in DC mode so that's not a problem. And I do know how to measure with it, but apparently I don't know how to properly record what I measure! LOL.

So. I measure ~1.5mA and 12.5 V across the poles when ground is connected (when the fridge is on and the fan is running). I measure slightly less between the disconnected ground wire and the negative pole under the same conditions (fridge, CO), ~1.4mA and 12v. I am positive of the readings, just trying to make sense of it.

Thanks,

mb
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Old 08-06-2013, 10:41 PM   #10
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Originally Posted by Brother Les View Post
If you have pulled each fuse one at a time and checked for a voltage drain, and have not found the bad line, then it would seem that you have a 'grounding' between the battery and the fuse box. This should shorten your search for the grounding/ chaffed wires.

Also if you dry camp very often, invest in some solar panels (generator) to help keep your batts up.
Thanks, Brother

I'm wondering why, if there was a short between the batteries and the fuse box, the voltage measured between ground and the neg poke would go to zero. Sure you are right, just trying to recall my 30 years-ago circuits class!

And yes, I have solar. I went with goal zero for the plug and play ease, but have regretted it ever since. I have had 3 charge controllers, and all three have had shorts between the negative and positive alligator clips. I'm selling it all and looking for a better system!

mb
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