Battery Drawdown

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January 9, 2013
Filed under Resources, Trailer Q&A

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Q: I have a 2009 Skyline Malibu 24-foot travel trailer and have been careful not to leave the shorepower connected for more than four days at a time for fear of “cooking” the battery. I disconnect the battery at the end of the season, take the battery in the house and put it on the battery charger once a month while in storage. Still, after these precautions, I usually go through a new battery every season.

I have also noticed when parked in my driveway, not being used, and not connected to shorepower, the battery will drain in about six days. This is without anything on in the trailer. I can kill all the breakers in the panel and the battery will still not make it a week before fully discharging. What can possibly be the drain? I have noticed that after shutting off everything in the panel, the lights on the stereo display, the CO2 detector, and the smoke detector are still functioning. The only way to completely shut these down is to disconnect the battery, but surely these would have such a minimal draw that they would not pull down a deep cycle in a week. What could be going on? I’m getting tired of buying batteries.
Vince, Knoxville, Tenn.

A: A couple of items jump out at us from your letter, Vince. First, when you “kill all the breakers” in the circuit panel box, meaning you throw the large black circuit breaker switches from ON to OFF, you aren’t disconnecting anything from the battery. Those breakers are for devices powered by the 120-volt AC shorepower supply. Any potential battery-draining 12-volt DC powered devices happily remain connected to your battery. To effect such a disconnect at the breaker box, you would need to pull all of the small fuses that protect the 12-volt DC circuits, but it’s a lot easier to disconnect one of the battery terminals to accomplish the same job.

Next, those various parasitic-draw devices could likely drain the battery if it wasn’t fully charged in the first place, or if the battery was damaged.

If your RV has a low-cost converter without a multi-stage charging capability it could cook the battery if left connected too long, so you’re on the right track by limiting its plug-in time. Better yet, you could replace the original converter/charger with a higher-quality smart charger by Xantrex or a similar company. These smart chargers take the battery up to a full charge; then switch to a maintenance or trickle charge to keep it powered up without damaging it. At the end of the season when you remove the battery connect it to a small battery maintainer such as a Battery Tender or a similar product. These inexpensive trickle chargers are specifically designed to keep a battery charged when in storage without damaging the battery.
– Jeff Johnston


To send your questions to RV Clinic, write to 2575 Vista Del Mar, Ventura, Calif., 93001; or email Tech@trailerlife.com. Also, check out TrailerLife.TV for our expert RV how-to videos.

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