battery drains but converter reads 13.5

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kmdiddy

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Jul 16, 2018
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I am very confused...I purchased a brand new 31 class Platinum deep cycle battery a few weeks ago.  I have a 3 stage converter.  We went on a trip and we're plugged into shore power the entire time but my battery dropped to the point it almost wouldn't pull my slide-out back in.  I plugged in once home and made sure everything was off but after 24 hours I still only measure 11.7 on the battery.  My confusion is that I thought my converter went bad...I pulled the battery to put on a battery charger and plugged my rig in.  I measured the output from the converter...to my surprise 13.5 at the battery leads! 

I have a 2007 29' gulfstream TT.  There is a wiring block on the underside of the frame towards the front of the rig.  Could I be losing power there?  I am fairly handy but this is very confusing to me.  It seems that something is pulling juice but what?  The only thing running off my 12V system would be lights and water pump...right?
 
The fridge was switched to electric while on shore power.  Understood in regards to hot water heater but we were only camping for 2 days...Friday morning thru Sunday morning...those shouldn't have had such a profound negative impact on the condition of the battery...right?
 
This is confusing!  If you measure 13.5 V from the converter at the battery, it is working as expected.  Since you were on shore power, the battery should have been fully charged.  Problems pulling the slide in is a classic low battery symptom.  The converter usually does not put out enough power to close a slide without help from the battery.

I suggest getting the battery tested.  It may have a dead cell.  Even new batteries can have problems on occasion.
 
I would agree except for the fact that I pulled the battery out of the rig and have it on a dedicated charger.  After 3 hours on the slow charge setting (12.4v pushing from the charger) I am reading over 12 volts on the battery.  I can't help but think something is draining the battery faster than it can charge on the camper. 
 
kmdiddy said:
I would agree except for the fact that I pulled the battery out of the rig and have it on a dedicated charger.  After 3 hours on the slow charge setting (12.4v pushing from the charger) I am reading over 12 volts on the battery.  I can't help but think something is draining the battery faster than it can charge on the camper.
Click to expand...
How much over 12 volts?
 
Dragginourbedaround said:
How much over 12 volts?
Click to expand...

And, to get a good reading you need to turn off the charger and let the battery rest for about 30 minutes before you take a voltage reading
 
Battery operatres some systems directly and some via the disconnect switch.

Steps. Slides and Safety gear (Propane detector) are often direct.

ARE YOU CONNECTED

page 2: Is there a fuse between the converter and the battery???

Page 3
Take a AUtomotive TEST light (looks a bit like an ice pick with a wire)

At the battery it should be dim compared to what it looks like at the converter.

Now follow the wores till it gets bright. problem betwen dim and bright.

Or you can use a volt meter same way.. Problem between 11 and 13 volts
 
Somw points to be made...

1) Full charge on a 12v battery is 12.6v (at rest) and typically reads 13.3-13.6 immediately after charging.

2) 12.4v from a 12v charger is insufficient to charge anything

3) Even operating in 120v (shore power) mode, the fridge and water heater circuit boards us a small amount of 12v power. So does the LP gas detector and CO detector (unless it has its own battery)

Plus a question:
Where did you read 13.5v from the converter?  At the battery, or somewhere else? Your statement implies the battery had already been disconnected when you measured this.

The symptoms all suggest a bad battery, even though new. A shorted cell or possibly a bad internal connection.
 
You should consider checking the individual cells with a hydrometer to be sure each cell is charging properly. As grashley stated even new batteries can have an issue.

https://www.napaonline.com/en/p/BK_7001146
 
Read 13.5v at the battery leads with battery removed.  I followed the diagnostic procedure for converter problems, pulled the battery and then plugged into shore power to measure output from converter. 

My converter has LED lights that indicate a blown fuse but I still checked all of them.

The battery was at 12.1 last night.  It is now at 13.45v after 15 hours of charging. 

I am going to do an amp draw check tonight with everything off to see if I have parasitic drain.  I am thinking the new power tongue lift I put on last fall might be the culprit.  I had an issue with my old battery after installing it.  I am wondering if because I went cheap...its drawing juice even when I am not using it. 
 
13.5v without a battery tells you the converter is functioning. It's conceivable it fails when a load (battery) is online, but that's not very common.  A bad battery will cause the charger to ramp up output to try to keep up the charge, but if the high load is sustained it very likely either shuts down completely or reduces output (voltage, amps or both). Because battery testing is relatively easy, the smart thing is to rule out the battery as the problem before tackling the more obscure possibilities.  The fact that your other charger can't get the volts above 12.4 makes the battery very suspicious [in my mind].
 
Now that you have the battery removed and charged to 13.45 volts why not take it to Auto Zone or similar and have it load tested to eliminate the battery as the cause of problem.
 
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