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How to Maintain RV Batteries for a Longer Life


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Photo by Race Across America / CC BY 2.0); ?>

Photo by Race Across America / CC BY 2.0

How to Maintain RV Batteries for a Longer Life

If you have a deep cycle battery for RV living then you will want to know how to get the most out of your RV charging system. Read on to find out how to preserve and maintain your battery’s performance with our guide on RV battery maintenance.

RV Battery Maintenance 101

Your RV battery is the heart of your RV camping experience. All of the comforts and conveniences that you take on your camping trip require the power that your batteries provide.

But if you don’t know how to maintain RV batteries, then you’ll likely find yourself shelling out for new ones every few years. If well maintained, deep cycle battery life expectancy can be over six years. If not maintained, you may have to replace it every two years or sooner.

Battery technology has improved our lifestyles in many ways and continues to improve each year. However, we only need to follow a few simple guidelines to take care of our batteries, so that our batteries can take care of us.

This short article will explain the ins and outs of how to keep your lead-acid RV deep cycle batteries in good condition. Look after them, and they’ll keep you powered up wherever you park your rig.

Want to Know How to Maintain an RV Battery Bank?

  • Types of RV batteries
  • How to conduct proper maintenance
  • Inspection and tests
  • Proper storage protocols
  • Use of proper safety precautions

Common Types of RV Batteries

Traditional lead-acid deep cycle batteries for RV use are typically one of three types: Flooded Wet Cell, Absorbed Glass Mat (AGM), and Gel-cell batteries. Newer lithium-ion batteries (Li-ion) are starting to infiltrate the market, but these types are still expensive and impractical.

Flooded Wet Cell Batteries


Flooded lead-acid batteries are built with sheet lead plates fully submerged in a conductive electrolyte solution. This type sometimes needs to have the suspension liquid topped up. This liquid can also freeze at low temperatures, or evaporate in a process called electrolysis. This separates the water into hydrogen and oxygen gas, which can then escape the flooded battery case. 

Absorbed Glass Mat Batteries

Absorbed-Glass-Mat Battery

Absorbed Glass Mat (AGM) batteries use glass fiber mats soaked in the same kind of conductive fluid. These mats fill the space between the electrode plates instead of fully immersing the battery plates in the fluid. This prevents many of the problems that flooded wet cell batteries have, such as fluid leaking, freezing, or evaporating.

Gel-Cell Batteries

Gel-cell batteries have a gel material that’s a more stable electrolyte fluid. This prevents any leaking, freezing, and evaporation problems. A gel-cell or AGM battery are described as “maintenance-free batteries” since they do not need regular refilling of the suspension liquid.

How to Maintain RV Batteries for a Longer Life

How to Prevent and Remove Sulfation

An important part of your routine maintenance is to keep your batteries free of corrosion, or more accurately, sulfation. Sulfation is the growth of sulfur crystals on the lead plates or battery terminals and occurs when storing batteries that are not fully charged. Sulfation is a leading cause of lead-acid battery failure.

lead acid battery showing signs of sulfination around the terminals

The best way to prevent sulfation is by keeping your batteries fully charged during the off-season when they are in storage. When sitting in storage for long periods, they will self-discharge. You might leave your batteries disconnected for several months and find the battery plates or terminals covered with sulfur corrosion and a fully discharged battery. 

To make sure they stay charged and healthy, you should check the charge once every month with a multimeter. If the voltage drops significantly, then use a battery charger to charge.

If you only have minor sulfation inside the battery cells, slowly reconditioning them may clear the sulfation up. Follow these steps to safely recharge and reverse sulfation:

  1. Remove the plastic cover with a flat-head screwdriver.
  2. Check the fluid level inside. The fluid should rest between the high and low fill markers.
  3. Carefully refill each battery cell with distilled water until the fluid level is restored.
  4. Connect the alligator clamps from your external battery charger to the terminals. Connect the red terminal first, then the black terminal.
  5. Set the charger to its lowest setting, and then plug it into an outlet.
  6. Leave your lead acid battery charging for 36 hours. Check after the first 12 hours to make sure the fluid is forming small bubbles. This indicates de-sulfation.
  7. After 36 hours, check again. If there are no bubbles at this point, the battery may be dead.

Corrosion on the positive and negative terminals is a different matter. This kind of sulfation can be removed with a wire brush and a solution of baking soda in distilled water. Mix a quarter cup of baking soda with one and a half cups of distilled water, and apply this to the terminals. Let it soak for about five minutes, then use a stiff wire brush to scrub both terminals.

Maintaining Flooded Cell Batteries

The two most important things to maintain flooded batteries are (1) Maintaining the fluid level and (2) preventing freezing. 

Both are easily achieved and worth the minimal effort. Firstly, if your fluid leaks or evaporates, refill the unit with distilled water. Secondly, keep your battery stored in a warm, dry location to prevent the fluid from freezing. Simple.

Another important maintenance procedure is called equalizing. Flooded deep cell RV batteries can develop acid stratification, where the acid becomes more concentrated at the bottom than at the top. Equalizing your battery means overcharging it with a high voltage charger which should restore the chemical balance inside the fluid.

Maintaining Battery Housing

Unfortunately, if the housing becomes cracked, or otherwise compromised, you will have to replace the lead-acid battery. There’s no recommended way to repair the housing of house batteries.

Keeping your batteries clean can protect the housing. You can clean the housing with the same baking soda solution that you used on the terminals. Don’t allow other chemicals or heated items to come in contact with the battery case. Also, keep them out of direct sunlight and UV rays, which can degrade the plastic of the housing.

Maintenance on Battery Connections

If you are frequently removing your batteries and reinstalling them in your motorhome, it’s not uncommon for the connections to become loose or worn out. Always use the proper tools when adjusting the connections to the battery (exact fitting wrenches are better than pliers). Tight terminal connections are less prone to excessive sulfation.

Discharging and Recharging RV Batteries

How Batteries Are Charged

A 12-volt deep cycle RV battery will only charge once connected to a power supply with a voltage supply greater than 12 volts. Typically 120 or 240 volts. This will generate a current that passes through the battery, causing the internal lead plates to polarize and store a charge. The greater the current, the faster RV battery charging will occur.

State of Charge

A fully charged lead-acid battery will have a voltage of 12.7 volts. Gradually over time the voltage decreases as the energy in the battery declines, either due to powering appliances or just due to the passage of time.

Many problems arise from users discharging RV batteries too far. You should never discharge your battery further than 50 percent, which will typically be reflected by a voltage of ~12.2 volts, as this will reduce battery performance more quickly.

Charging Batteries

To increase your RV battery life expectancy you should charge your batteries as often as necessary to keep the state of charge between 12.2 -12.7 volts. This can be done using a generator, solar panels, by the camper’s engine via the alternator (if you’re driving), or by connecting to shore power (either using battery chargers or a converter). Charging should be done in stages to help maintain your deep cycle battery lifespan:

  1. Bulk Charge (or bulk stage recharging): Charge to 90 percent
  2. Absorption charge: Top off the remaining 10 percent
  3. Float charge (or maintenance charge): Use a trickle charger to keep the battery at full charge

Testing and Inspecting RV Batteries

Regular Inspection

Regardless of which type of batteries you use, you should inspect your battery once a month. 

Your inspection should start with the housing – see if there is any corrosion, cracks, or noticeable leaks.

Next, open the housing to check the fluid levels inside. The inside should have markings to indicate the minimum and maximum fluid levels. If the fluid is low, refill the battery with distilled water.

Finally, check the specific gravity of the fluid using a refractometer or hydrometer. This specific gravity reading can be compared against charts to check the charge. 

Alternatively, you can close up the battery again and check the charge using a multimeter.

How to Use a Multimeter

Set your voltmeter to DC voltage, or your multimeter to 20 volts (depending on which type of meter you have).

Touch the red lead to the positive terminal on your battery. Then touch the black lead of the meter to the negative terminal.

The screen should read between 12.5 and 12.7 volts. If the reading is high, you should discharge the battery using your RV appliances. If the reading is low, then charge the battery as necessary.

How to Use a Refractometer or Hydrometer

When using a refractometer or hydrometer, you will be measuring the specific gravity of the battery suspension fluid. Because this fluid is hazardous, you should always start this procedure by wearing gloves, closed-toe shoes, and goggles for personal safety.

Using a Refractometer

  1. Carefully open the vent battery caps on the casing. 
  2. Using a pipette, draw a few drops of sulfuric acid from inside the battery.
  3. Place a few drops onto the testing plate surface of your refractometer.
  4. Close the cover of the refractometer.
  5. Keeping the refractometer fairly level, hold it up to your eye to take a reading of the specific gravity. This must be done in a well-lit area. You will see a shadow line that delineates a scale inside the refractometer.
  6. Repeat this procedure for each of the batteries cells.

Using a Hydrometer 

  1. Carefully open the vent caps on the casing.
  2. Insert the hydrometer and suck some fluid into the chamber using the squeeze bulb. Flush the chamber with this fluid a few times.
  3. Draw a full sample into the chamber.
  4. Hold the hydrometer vertically at eye level and note the specific gravity reading.
  5. Repeat this procedure for every cell in the battery.

In both procedures, the specific gravity should read between 1.255 and 1.275 for a fully charged battery. This may need to be adjusted for ambient temperature. Also, this is a good time to inspect the fluid for discoloration. Brown or gray cloudiness in the fluid indicates it is nearing the end of the battery’s life.

Storing Your RV Battery

Since you may not be using your recreational vehicle all year round, an important part of lead-acid battery maintenance is your storage procedure.

Your RV battery storage area should be:

  • Warm
  • Off the ground
  • In a cardboard tray

When putting your batteries away in storage, always start the process by ensuring that they are fully charged.

During extended storage, you should schedule check-ups on your battery once a month. For these check-ups, you should open the casing to check the water levels. You should also use your multimeter to check the RV battery voltage, and possibly top-up the battery charge if it’s dropping.

If you have a trickle charger, this is an excellent accessory for storage. A trickle-charger provides a slow continuous float charge that will keep your batteries charged without ever overcharging them.

Personal Safety

It’s important for all RV owners to understand how to conduct proper maintenance on your recreational vehicle batteries in a safe manner.


First of all, make sure you disconnect your RV from its power source and that the battery disconnect switch is turned off before working on the battery. 12-volt RV batteries cannot electrocute you, but your 120-volt outlets certainly can.

Whenever you are working on your battery, you should be wearing gloves. While there is little risk of electrocution, the battery contains acid, which can burn your skin on contact. You should also wear closed-toe shoes to protect your feet in case of splashing.

Goggles are also recommended safety items when working with lead-acid batteries. The acid is particularly dangerous if it gets in your eyes, and may lead to blindness.


Whether you’re a newbie or an old hand, we hope that this article has taught all RV owners something about the importance of maintaining your RVs 12-volt battery electrical system. If you found this RV article useful, please feel free to share it with other campers, friends, and family members. If you have any more advice or questions, please add them in the comment section!

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