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Old 03-31-2015, 11:44 AM   #1
Junior Member
Brand: Thor Motor Coach
Model: Miramar
State: Vermont
Posts: 8
THOR #1772
Dead batteries

I need help. We purchased a 2014 miramar in Nov 14. had it in storage for the winter and when I went to get it out of storage, the batteries were dead. I was able to get the generator started and use that to start to coach.

However when I got it home and plugged it in, the batteries didn't recharge and went completely dead. The generator wouldn't even start. When I look at the battery compartment, I saw acid on top of the batteries. I thought that when I plug the coach in, it was supposed to recharge the batteries? That is what camping world told me when I bought it.

This is our first motor home.

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Old 03-31-2015, 01:48 PM   #2
Senior Member
Bruce's Avatar
Brand: Thor Motor Coach
Model: Axis 25.1
State: Pennsylvania
Posts: 299
THOR #1503
All of your batteries couldn't have been dead if you were able to start the generator.

You should not have acid on the top of the batteries. Is it acid or just moisture?

I assume that the engine battery did not take a charge during the drive home?

Was the battery switch in the storage position? If not, then there would be small current drains on your house battery(s) that can in a relatively short time drain the power.

The converter/charger in your coach will charge your house batteries when connected to shore power. Have you verified with a volt meter that the batteries are getting voltage from the converter?

Batteries self discharge over time. If the acid concentration gets low enough the battery can freeze and be damaged. Ideally your batteries should be trickled charged while in storage to avoid this happening.

Some types of batteries have lower self discharge rates and will still have a usable charge after several months in storage. An AGM (absorbed gas mat) type is one and also has the advantage of being a sealed battery so no maintenance is required.

You may want to pull your batteries and have them tested.


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Old 03-31-2015, 05:58 PM   #3
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FW28z's Avatar
Brand: Thor Motor Coach
Model: 2011 Four Winds 28Z
State: Michigan
Posts: 1,273
THOR #531
Its not uncommon for the batteries to fully discharge during winter storage, especially if there is some parasitic loads on them. Turning the contactor OFF does not necessarily mean you have removed all loads, especially if you had the dealer install any aftermarket goodies.

Typically, when in storage, you should keep the RV plugged in over the winter if you can. I plug my coach in 2 weeks then unplug 2 weeks, just to keep the batteries charged.

If you have no source of shorepower over the winter, you should start the generator once a month and let it run to charge the batteries. Depending on the coach, you may also be able to charge the coach batteries with the engine alternator.

You should be running the engine and generator once a month or so anyway during storage.

I have really never heard of acid coming out the top of a battery. If it is cracked, it will run out the sides, but not the top.

If a battery is fully charged, the concentration of sulfuric acid suspended in the electrolyte will be the greatest. The concentration of sulfuric acid prevents the battery from freezing.

However, as the battery disharges, that acid migrates to the battery's plates, and the electrolyte almost becomes water. At that concentration, the electolyte can freeze and become ice, and burst the battery.

So if you store a battery in the winter and if temps get to freezing, and you allow the battery to become fully discharged, it can potentially burst.
The only thing that works on a RV is the owner...
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