By Chris Dougherty
Chris Dougherty is a certified RV technician. Here is a letter about an RV’s house batteries that he received from a reader while he was serving as RVtravel.com’s technical editor.
I 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
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. Those include 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.
Check your DC voltage at the batteries
The first thing to do is to 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, then 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 else fails …
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