Battery problem

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TrvlShell

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Jan 17, 2016
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98
We're getting our travel trailer ready for our first trip of the season, and we're having a strange batttery problem.  When the battery is disconnected (via the trailer's battery disconnect switch), our multi-meter shows 12.7 volts on all 4 battery terminals.  But when the battery is connected, the battery shows 12.7 volts on 3 of the terminals but only 11.7 on the fourth (which looks like the one going into the RV according to my husband), and we get a reading of "E" on our trailer's battery meter.  (The 11.7 reading on the fourth terminal is with everything in the trailer off except the things that are always "on" like the smoke and CO2 detectors).  Running off the battery, the lights in the trailer are working, but not enough power to run the water pump.  When we plug the trailer in and run off electric, everything works.

There was some corrosion on the battery terminals which my husband cleaned up, but we're still having the problem.   

Any thoughts on what might be causing this problem?

Thanks!!
 

donn

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Nov 8, 2009
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5,361
Take the batteries out take them to a shop that can do a load test.  I would suspect a bad cell.
 

Gary RV_Wizard

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West Palm Beach, FL
All 4 terminals? But battery in your post is singular?  Please tell us more about your battery(s), how many, and what & how you are measuring voltage on those terminals , and which terminal has the 11.7v?
Voltage is measured between the battery plus (positive) terminal and the negative terminal.  If you have 4 terminals, that implies two batteries (2 terminals each), but when the batteries are cabled together, they will both show the same reading.
 

TrvlShell

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Jan 17, 2016
Posts
98
Sorry for the poor description.  I was trying to describe what my husband had told me, but unfortunately I don't know all the electrical terminology.  We have a single Interstate Group 24 battery.  The "terminals" described in my last post are really the "junction fuses" between the battery and the RV.  If you look in the attached picture (the corrosion has since been cleaned up) the very top "post" conects to the positive battery terminal.  The next one down connects to the left bottom "post".  The bottom right "post" is the one that goes into the RV.  Using a multimeter the battery shows 12.7 volts across its terminals.  Checking the voltage on each of the 4 posts shows 12.7 volts except for the post that goes to the RV, which shows 11.7.  These were all measured relative to the negative battery terminal.
 

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TrvlShell

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Jan 17, 2016
Posts
98
No, unfortunately cleaning the corrosion didn't fix the problem.  My husband is wondering if maybe the bottom "junction" or "breaker"? (not really sure what to call it) that's connecting the battery to the RV could be bad (since it's reading 12.7 on one "side" and 11.7 on the other)?  Or is there something else that could be causing the problem?
 

blw2

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Aug 9, 2012
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3,338
Location
Saint Johns, FL
that looks like two auto resetting fuses
like this
https://www.ebay.com/itm/Metal-automatic-reset-fuse-bolt-circuit-breaker-car-circuit-breaker-battery-P9A2-/273585293079
a basic automotive part

If so, then you have full voltage to one post and a drop going through the fuse.
Bad connection in there.
Replace it.
Just have to hopefully find markings on the existing one to match up the fuse amp rating....15 amps, 20 amps, etc...

should be able to find one locally at an auto parts store I think....
 

TrvlShell

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Jan 17, 2016
Posts
98
Brad - Thank you!!!  My husband went to the auto-parts store this morning and was able to find a replacement.  He just replaced it, and that seemed to fix the problem.  Thanks again!  And thank you Gary and donn for your help as well.  I love this forum and how helpful everyone is!
 

grashley

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May 7, 2015
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6,591
Location
Western Kentucky
So those are fuses?!  I recently noticed several of them on the back of my battery compartment, by the "Gen Prep" bay.  Could these be fuses going to things like landing gear and slides?  Main fuse to fuse panel?
 

John From Detroit

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Apr 12, 2005
Posts
26,257
Location
Davison Michigan
Technically they are called Self Resetting Thermal Circuit Breakers.

Fuses are one and done.. Depending on the fuse you either have to replace the entire fuse or replace the element. There is not reset.  But Circuit breakers can also restore.

 

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