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Old 05-23-2018, 12:27 PM   #1
New Member
Findlay , OH
Join Date: Mar 2018
Posts: 2
AS draining tow vehicle battery

Hello everyone,
I am brand new to the AS forum. I have had many travel trailers over the last 10 years but this is my first AS. I have a 2015 Flying Cloud FB Bunk. So far it has been great. My question is, I pulled my AS out of storage to my driveway to clean it and get it ready to use this weekend. I did not have it plugged into shore power and left it hooked up to my tow vehicle. After 2 hours, my batteries in the tow vehicle were completely dead.

Everything was off in the AS (as far as I know). Any thoughts on why this happened? I have only had it for about 6 weeks.
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Old 05-23-2018, 01:36 PM   #2
Rivet Master

2007 22' International CCD
Corona , California
Join Date: Jul 2013
Posts: 8,590
Some tow vehicles have a continuous connection from the TV battery to the trailer umbilical receptacle. Others use an ignition-controlled relay to cut off the power when the TV is not running.

I suspect yours does not have a cutoff relay, and the trailer batteries were in a low State of Charge (SOC) and basically sucked your TV batteries flat in short order. In your case, be sure to unplug the umbilical when the TV is not running.

TO recover from this, I would first get a battery charger on your tow vehicle, after disconnecting the umbilical. For the AS, get shore power to it, and set the battery switch to 'use' to charge the batteries. If this does not work, you will need a portable battery charger to get things going...
Rich, KE4GNK/AE, Overkill Engineering Dept.
'The Silver HamShack' ('07 International 22FB CCD 75th Anniversary)
Multiple Yaesu Ham Radios inside and many antennae sprouting from roof, ProPride hitch, Prodigy P2 controller.
2012 shortbed CrewMax 4x4 Toyota Tacoma TV with more antennae on it.
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Old 05-23-2018, 02:25 PM   #3
Rivet Master
1988 25' Excella
1987 32' Excella
Knoxville , Tennessee
Join Date: Oct 2010
Posts: 3,804
Blog Entries: 1
Everything is really not off in the trailer. There are loads you do not have control over. So the batteries go very flat if it is stored for a while. The battery in the tow is not a deep discharge. So I agree that the flat trailer batteries probably pulled it down. I am also surprised that it happened.

Now it comes down to whether you have AGM batteries and how flat it went. Maybe a charger will fix it. Maybe not. Maybe just hooking the trailer to shore power for a day might do it. If flooded cell a charger should work. On an AGM it will work unless it went so low the charger won't work. I had that happen on my tow this week.

Then you will have to deal with what is causing the drain and how to store the trailer. Though it is a lot of trouble disconnecting the ground cables while in storage is effective.
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Old 05-23-2018, 02:27 PM   #4
Rivet Master
2014 20' Flying Cloud
Long Island , New York
Join Date: Jun 2015
Posts: 15,170
Welcome to the forum!

Adding to rmkrum’s good advice, if your AS batteries were not properly maintained during storage they may be compromised. I would take them to a battery store to be tested and charged. Starting the season with lousy batteries is ill-advised.

This Battery School is a good read for general background.


Good luck,

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Old 05-24-2018, 06:55 AM   #5
New Member
Findlay , OH
Join Date: Mar 2018
Posts: 2
Thanks for the good information. I have a feeling that based on the fact that this has happened twice, that my batteries are not longer viable and I will have to purchase new. I hope this ends up being the solution.

Thanks for the information, I didn't realize that batteries when in the "store" mode, do not charge. I was hoping not to have to disconnect the batteries when not in use, but I think I will, especially given the fact that on prior non-AS rigs, I always disconnected and never had battery issues.

thanks everyone!
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Old 05-24-2018, 09:12 AM   #6
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2002 30' Classic S/O
Melbourne Beach , Florida
Join Date: Nov 2013
Posts: 4,170
Two things. The connection from the tow vehicle to the trailer batteries in the trailer does not go through the disconnect switch. It appears that your tow vehicle does not have the disconnect relay so be sure to disconnect the trailer from the vehicle when camped.

Second, in your trialer the USE/STORE switch is a battery disconnect. As previously pointed out, it must be in USE to charge the batteries. For readers who have older trailers I thought I would clarify that in my 2001 and 2002 trailers the switch was a "trailer disconnect" switch. The converter was left connected to the batteries but almost everything in the trailer was disconnected from any source of power. One exception was the propane detector. There may have been others.

“You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins
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Old 05-24-2018, 09:48 AM   #7
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2017 26' Flying Cloud
Tampa , Florida
Join Date: Feb 2017
Posts: 5,352
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Is it possible the emergency breakaway switch was pulled? That kills the batteries pronto.
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Old 05-24-2018, 10:12 AM   #8
Half a Rivet Short
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 9,106

Since this is a 2015 / previously owned trailer .... who knows what the previous owner did or did not do to maintain the batteries. Given the way AS does model years and inventory, your batteries could date to 2014. Four years is a pretty typical "life" for flooded batteries in this sort of service.

One other reason to check battery condition before you pull out of the storage yard: The breakaway switch uses the trailer battery to activate the brakes. No, you never *expect* to need that function. If the batteries are flat ( or missing or disconnected ) you have no breakaway function....

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