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Ask Dave: Why do my RV’s batteries drain during storage?

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses possible causes for an RV’s batteries to drain during storage.

Dear Dave,
I have a ’21 Forest River Geo Pro. When parked, the batteries go dead unless hooked up to my vehicle or dedicated power source. Both batteries are good. It has roof solar panels, which I assume would charge the batteries. Anything drawing power is off. The mobile RV mechanic has found nothing either, including fuses, etc. Any thoughts on this? —David

Dear David,
First, any house battery will drain even without something being on in the coach. However, it will take a few weeks for that to happen.

Look for parasitic drain

The first thing I would do is look for a parasitic drain on the batteries. You most likely have an LP leak detector which will draw about 1 amp. You might have something else like a smoke detector or CO detector that is powered by the house batteries. Another culprit is a radio that has preset stations, as it also needs power to store those.

Get a multimeter and place it on the DC setting and pull the negative cable off the house battery post. Place the red probe on the positive post and with the negative off the post, touch the black probe to the negative cable as pictured. If there is a reading, you have a drain somewhere in the system as indicated on the multimeter. This one was the LP leak detector. You can start pulling 12-volt fuses to identify what is drawing power.

Batteries might be sulfated

Also, you might have batteries that are sulfated and seem to be good when fully charged to 12.6 volts, but freefall immediately after the charger shuts of. The only way to tell the condition of your batteries is to conduct a proper charge, then hook them to a 25-amp draw machine and count the hours! Most service centers just hook up a digital meter and if it reads 12.6 volts they claim they are “good”.

I would suggest charging your batteries properly, test to make sure they are at 12.6 volts, then periodically check the voltage and record it with the time and voltage. Do this every other day for a week or so and see what reading you are getting. If you don’t have a parasitic drain and the battery voltage is dropping fast, you have sulfated batteries.

Read more from Dave here

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Ray
27 days ago

Stereo lights, detectors, thermostat switch not in off position…who knows. Half of these are assembled at the factory and then some at the dealer. It’s like the stereo in the ’70 Buick Skylark you had in high-school…too many people have worked on it.

Fred
27 days ago

You ignored his solar system. That should be keeping the batteries charged.

Drew
27 days ago

I would advise him to use a disconnect or buy one if it’s not there. A solar panel that charges the battery can be a double-edged sword. If there’s no regulator it can over charge your batteries and ruin them in a short time. My disconnect switches shut off all loads and my batteries stay charged enough to run my appliances and start the generator even after 2 months in storage. Personally, unless there’s a specific need I’d never keep my batteries under charge at all between outings. When I see people using panels and chargers it makes me think they are compensating for problems elsewhere- JMHO.

Crowman
27 days ago

When you say the LP detector draws 1 amp is that an hour, day, week or month? That would be a key bit of information.