How to Replace an RV Battery That Doesn’t Hold a Charge

Like the rest of our equipment, we take very good care of our batteries. But there comes a time when even well-maintained batteries start to lose their juice. That’s why knowing how to replace an RV battery is important.

In this post, we’ll show you exactly how to do that, even if your battery bank has several batteries that appear to have a complex configuration.

What Is an RV House Battery?

As you may recall from our RV Battery Guide: House, Chassis, Lithium & More, the “chassis” battery (starting battery) starts your RV’s engine, and the “house” batteries power the interior lights, vent fans, water pump, and other 12-volt equipment.

Through the use of an inverter, which converts 12-volts DC into 120-volts AC, they can also power your coffee maker, hair dryer, TV, microwave, and other household appliances.

One of the greatest things about RVing is the ability to travel widely with all or most home amenities handy.

However, you need a working house battery bank for all of these amenities to work (especially when you love boondocking the way we do). There are different types of 12-volt batteries, but again, our Battery Guide post can sort all of that out for you in detail.

It’s easy to be intimidated by the prospect of replacing batteries, especially if you’ve got a complex setup such as a bank of four or more 6-volt batteries wired in series-parallel. Just the sight of all that wiring is enough to tempt many people to walk away.

But as long as you follow a few simple guidelines and precautions, getting new RV house batteries installed can be a pretty easy DIY job.

Let’s show you how replacing RV house batteries is a manageable task that can ensure your power needs are met.

How to Replace Your RV Batteries

We’ve been on the road full-time for 20 years, so we’ve had to replace our RV batteries more than once.

Our rig came from the factory with four 6-volt flooded lead-acid house batteries, wired in series-parallel, which is like having two large 12-volt batteries.

When the time came to replace them, we installed four Lifeline AGM (absorbed glass mat) batteries. They’re also 6 volts, vs 12 volts, so wired in the same series-parallel configuration.

The AGM batteries were more expensive but superior to traditional “wet” lead-acid batteries. They’re completely sealed, accept a charge faster, and perform better in every way. They’re also maintenance-free, so well worth the added cost.

We’ve since switched to the ultimate: lithium batteries, which, while even more expensive than AGM, work incredibly well with our new, larger array of solar panels.

Regardless of what kind of batteries you choose, here’s how to replace them:

Take a Photo of Your Current Battery Bank

As with most projects, planning is a crucial part of the job. And among the most important steps in the planning process is taking a photo of what you’re about to replace so that you’ll have a reference to look back on, should you need it.

Take a clear photo of the top of your current battery bank so you’ll have a record of the wiring layout, allowing you to safely route the cables for the new batteries in the exact same way.

But a simple photo isn’t enough…

Draw a Diagram of Your House Batteries

Despite having a photo to refer back to, it’s best to draw a diagram of the layout of your house batteries as well.

If your RV battery replacement project also includes your chassis batteries, be sure to include those in the diagram. Note: We were only replacing our house battery bank at that time, so our diagram included only those four batteries.

Number the batteries on your diagram, and be sure to include the battery posts and mark them positive and negative.

Be sure not to skip this step. We know it’s tempting, but the diagram really is crucial, so take the time to sketch one out before you begin the battery replacement process.

Create a Tab on Both Ends of Every Cable

Use masking tape to create a tab on both ends of every cable on every post.

We used a Sharpie to mark the tab for the negative post on battery #1 with a 1- (to indicate battery 1’s negative post).

Next, we marked the other end of the same cable with a 3-, to indicate battery #3’s negative post.

Note that each end of every single cable connected to a post gets labeled.

So, for example, every cable end that’s connected to battery #1’s negative post gets the label “1-“.

 

Continue in the same manner, making sure to tag every end of every cable on every post. Did we already mention that? You’re darn right we did! If you fail to tag all the cables, you’ll know why we’re making a big deal about this when it comes time to re-install everything.

If you plan to remove/replace your chassis batteries, be sure to tag and mark them as well.

Turn Off All Power Coming to Batteries

Before going any further in this project and removing a single cable, be sure to turn off all power coming into the batteries.

Switch off the circuit breakers and unplug your power cord from the pedestal. Make sure your generator is off, and any solar panels are disconnected.

If you have solar panels but don’t have an on/off switch or breaker to disconnect the power, use towels to cover the panels to prevent them from sending power to the batteries, especially if it’s a sunny day.

Also, turn off all power coming from the batteries inside the RV and at your battery disconnect switch(es).

Begin Removing the Cables

Using a socket wrench, begin removing the cables, starting with the main negative wire leading out to the RV. Be sure not to accidentally allow the ends of your socket wrench to touch a positive and negative post at the same time.

Touching hot and cold terminals at the same time is dangerous and will cause sparks to fly. This could cause a fire or even an explosion.

Using a socket extension is a good idea to keep the end of the wrench further away from the terminals. Better yet, wrap the entire handle of the socket wrench with electrical tape.

Disconnect the Main Negative Cable Leading to the RV

Always disconnect the main negative cable leading to the RV first. It’s likely one of the thickest black cables in the bunch, and will lead from the battery bank into the RV.

The main negative cable is not only the first one to disconnect but also the last one to reconnect at the end of the job.

Disconnect the Remaining Cables and Remove the Batteries

Once you’ve disconnected the main negative cable, you can continue disconnecting the cables one by one until they’ve all been removed from every battery.

Then you can remove the batteries from the RV and set them aside.

Clean Your Battery Box and the Cable Ends

This is the perfect time to clean your battery tray. A paste of baking soda and water neutralizes battery acid. We also used a wire brush to remove loose paint and any rust, then painted ours with black Rustoleum paint. Then we used the wire brush to clean the ends of all the cable ends until everything shines like brand new!

Install Your New Batteries

Place your new batteries into the RV, and connect all the cables in accordance with your diagram and the tags you created with the masking tape.

Remember to connect the main negative cable that goes into the RV last.

Note: If you’re installing regular lead acid batteries, slide a felt battery washer down over each post before reattaching the cable will reduce corrosion.

Finally, remove all the masking tape tags and turn the power switches back on.

We hope these steps and the accompanying photographs have been helpful. But if you’d prefer a more visual tutorial, check out our video:

How Can You Tell If Your RV Battery Is Bad?

It may be very easy to tell that your RV batteries are failing. Signs such as lights being dim or vent fans running more slowly than they typically do can be nagging indications that your batteries need replacing.

To check the condition of your RV batteries, you can test the voltage of each battery using a multimeter. Using a hydrometer, you can also check the specific gravity of the electrolyte in flooded lead-acid batteries.

Conduct either or both of these tests when the battery is fully charged and “at rest.” That means no power coming into the battery and no loads coming out.

How Long Should an RV Battery Last?

The answer to this question depends on the type of RV batteries you have, how they’re used, and how well you maintain them. But we can give you some generalizations.

Typically, a well-maintained flooded lead acid battery should last anywhere from 4-5 years.

AGM and Gel batteries tend to last a bit longer, often in the neighborhood of 6 years or more. The Lifeline AGM batteries we had before we upgraded to lithium lasted us 7 years… and still had some life left in them.

Lithium batteries have the longest lifespan, and often have a 10-year manufacturer’s warranty.

Can I Replace My RV Battery with a Lithium Battery?

Although many lithium battery manufacturers advertise their batteries as “drop-in replacements,” that primarily refers to the battery’s physical size.

They may be designed to fit into a standard flooded lead acid battery’s space. Still, there are other components of your rig’s electrical system that are likely to require upgrading, such as the converter/charger, solar charge controller, and possibly other charging components.

Even the charger that takes power from your chassis battery and alternator to charge your house batteries while you drive may need to be upgraded. So, you may be able to fit a lithium battery into the space where your lead acid battery sits, but other factors also need to be evaluated.

Have You Replaced Your RV Batteries as a DIY Project?

Did you replace RV batteries yourself? If so, we’d love to hear about your experience and the type of batteries you chose. Leave a comment below with the deets!

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