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Why are My RV's House Batteries Shorting Out

by Bill Jamison
(Franklin, NC USA)

Why are My RV's House Batteries Shorting Out

Why are My RV's House Batteries Shorting Out

I am on my fourth house battery in two years. I have replaced step motor twice. Awning and slide don's want to work properly at times. RV is used very little. Dealer says that my electrical system is ok, I only need to replace another shorted battery. What's up?????????

ANSWER Greetings Bill thanks for submitting your question on our free Ask An RV Question Page.

First let me say that I am sorry that you are going through this problem with your RV. RVing is supposed to be fun, but when little gremlins like these pop up, it can take the fun out of RVing.

Based on the information you have provided me, I can tell you that there is a problem with your electrical system. It is not normal to have to replace four batteries and two step motors in two years. I cannot tell you what the exact problem is, but I can give you some suggestions on where to start looking for the problem. Here are some of my suggestions.


Get a second opinion from a qualified RV Mechanic. It is apparent that the dealer's technician is not able to find the problem. If you have friends that are RVers ask them if they can recommend a good RV Mechanic.

You are saying that your house batteries are shorting out. I have to assume that when you say "shorted our" you mean that they will not accept a charge or will not hold a charge. The first thing we need to determine is if the battery that you are using to power your 12 volt system is the right type of battery.

There are basically three types of batteries available.

1. Starting Battery is normally used to start the engine of a vehicle. This type of battery should not be used as a house battery.

2. RV/Marine Battery is a hybrid battery that is a cross between a starter battery and a true deep cycle battery. I also do not recommend using this as a house battery. The RV Dealer may tell you that the RV/Marine battery is just fine, but in reality it is not.

3. Deep Cycle Battery is designed to provide a small amount of power for a longer period of time. They are definitely not designed to crank over an engine. They can be charged and discharged more often and last longer than either the Cranking or RV/Marine Batteries when it comes to powering the 12 volt accessories in an RV. So make sure this is the type of battery you are using, regardless of what the RV Dealer tells you.

I would also suggest that you read the answer to this question Are 2 Six Volt Batteries Better Than 1 Twelve Volt Battery To Provide Power To Inside Of RV? This will give you a lot of other need to know information on RV batteries.

The battery problems could be caused by:

1. The house battery being overcharged or undercharged.

2. A short somewhere in the RV's 12 volt system.

Any of the above can also be causing the problems with your step motor, as well as your awnings or slides not working properly.

Let's address the charging issue first. Most RVs come with a power converter. When you plug your RV into a 120 volt AC electric source the converter converts the 120 volt AC current to 12 volt DC current. The converter in most cases also doubles as a charger for the house battery.

If the converter is undercharging the battery it can cause problems with the battery and the 12 volt accessories on an RV. If the motors for the step, awnings and slides are not getting sufficient voltage it can cause them to go bad.

If the converter is overcharging the battery it will boil it out, in other words the electrolyte in the battery will boil and evaporate. When there is not sufficient electrolyte in the battery to cover the battery plates the battery will go bad.

If the excessive voltage or amps are passed to the motors on your steps, slides, etc. it can burn them out.

I have a sneaking suspicion that the charging system is the problem with your RV.

Maintenance Tip If you are going to keep your RV plugged in for long periods of time when not in use. You need to check the electrolyte level at least once a month. If it is low, you need to top it off with Distilled Water. Do not use tap water as it will cause corrosion to the plates in the battery and drastically shorten its life span.

I am not going to go into the technical specs of what voltage and amps the converter is suppose to supply to the battery. A good RV Technician (mechanic) will spot this problem very easily when they test the charging system.

If the charging system checks out OK, then the next area I would look at is the wiring of the 12 volt system in your RV. You may have a grounded or shorted wire somewhere in the system. Normally if you have a short in the system the fuse or fuses for the shorted wiring will burn out and have to be replaced. You do not mention having to replace blown fuses.

Wiring problems are not always easy to find. Sometimes these problems were caused by the factory when a worker has put a staple or metal fastener through one the wires in your RV. The RV Technician may have to run continuity tests on each of the circuits in your 12 volt system, until they find the short.

I hope that the information that I have provided will be helpful to you. The main point in all of this is that you need a good RV Technician to get to the root of the problem.

If any of our visitors would like to add any information, they can click on the Click Here To Post Comments link at the bottom of this page.

Happy RVing
RVing Al

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Excessive Charging Current on 1980 Winnebago Brave
by: Anonymous

I have I guess a similar problem....I just installed the house battery after the winter. Upon tightening the terminals, I hear a consistant clicking and then checked the breaker panel. The breaker panel is showing a flash sequence for "Excessive Charging Current". Is this something to worry about? When I unplugged the main cord from the 15 amp plug, the panel continues to flash excessive charging current. I am baffled.

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STARTING
by: Anonymous

MY MOTOR HOME WILL NOT START. THE BATTERIES ARE GOOD BUT I DON'T GET ANY POWER TO THE STARTER. CAN SOME ONE HELP ME.

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Aux battery boilout
by: Anonymous

I have a 1983 Winnebago Brave that I have hooked up to house power. The hook-up required a converter plug to step down 220 house power to 110 in my MH. Since then the auxillary battery has boiled out. I know that the converter recharges the aux battery, but I am confused about the boil out. Is it a matter of needing a new battery or removing a fuse from the converter? Can I unhook the aux battery as long as I am hooked up to house power? Thanks

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