Dead RV battery issue leaves owner in the dark


By Chris Dougherty
Chris Dougherty is a certified RV technician. Here is a letter he received from a reader while he was serving as’s technical editor.

Dear Chris,
Dead RV battery issue leaves owner in the darkI have a perplexing issue on my 2012 Holiday Rambler Vacationer. When I put the coach away in storage I carefully make sure the power switch is off for the house batteries. When I return in a week or 10 days, the batteries are depleted. I cannot find or think of any device or thing that is left on that could do this when the switch is off. The batteries are topped up and only about a year-and-a-half old (two Interstate deep cycles). Any tips on how to troubleshoot this, or ideas???  —Bill G

Dear Bill,
Thanks for writing in. It is not uncommon for the batteries to be depleted over a longer period of time, but not that short a time.

RVs will often have components wired directly to the batteries, bypassing the master switch, like propane gas and carbon monoxide detectors, the memory circuit for a stereo, etc. Most of the time these parasitic loads are less than a couple of amps. Evidently, something else is going on.

The first thing to do is check DC voltage at the batteries when the coach is plugged in and when it’s unplugged. This will determine if the converter/charger is operating properly. A reading of 12.3 VDC or so is right for a coach that’s been unplugged for, say, an hour. When the coach is plugged in, an average of mid to upper 13’s is about right depending on the charger system, and if it’s a multi-stage charger, what stage it’s in. If the batteries are not being fully charged while the coach has an outside power source, than this could contribute to the problem

The next thing to do is, after charging, disconnect the coach from the power source and turn off the battery switch. Then, with a DC amp clamp-type meter, you can check the positive leads from the batteries to see what the amp draw on the battery bank is when everything is supposed to be off. Be sure to include not only the large cables, but any smaller conductors that are attached to the batteries directly. If an amp draw is found, then track it to its source.

Lastly, I would check to make sure the batteries are clean, full of distilled water and the terminals are tight. Loose and corroded terminals can cause similar symptoms.

If all this fails, then its time to have the batteries tested by your Interstate Battery dealer.

Oh, one last thing. I don’t think your coach has an inverter/charger, but many of those coaches did … usually a larger battery bank came with it. Please make sure the inverter is OFF because the inverter/charger common in many of those coaches is connected directly to the battery and could still drain them.

Hope this helps! —Chris


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Judy and Mark Wiemer

I have a similar problem with my 2016 Holiday Rambler Vacationer as Bill G. but it’s not the house batteries, it’s the chassis. I store my coach and do all the right things. Within TWO days my chassis battery is depleted and I have to use the battery booster to start the motor, what am I doing wrong?

Mel Goddard

Last Oct. I replaced my Parallax converter with a Progressive PD-4655 to maintain and charge my two relatively new Interstate 12V Batteries over Winter.
When I checked the SG last week both were in the Red at 1.200 and below. VDC WAS 12.5 on bat. Pwr. and 13.5 on charge.
The dealers question was:” Is the Hydrometer calibrated for Deep Cycle batteries”?
Never heard of such a thing.
I understand that ALL batteries used the same acid; the difference being construction of the internals.
Was his question valid?