This post may contain affiliate links or mention our own products, please check out our disclosure policy.

RV Battery Maintenance: Tips for Evaporation, Corrosion and Capacity

This post was updated on March 15th, 2024

rv-battery-maintenance-fLike most anything else, your RV needs some occasional RV battery maintenance (TLC -Tender Loving Care) to stay in good health and continue to serve you well. So what does that mean?

First of all, even the best quality RV battery will suffer from corrosion on the terminals. Even a bit of corrosion can cause a voltage drop, especially under load, and also reduce the amperage that can flow. Battery corrosion generally looks like a white or greenish-blue powder that forms around the wire connections.

RV Battery Maintenance – Corrosion Example

Photo Credit:
Photo Credit:

Flooded cell batteries (those with water in the cells) will out-gas when charged, and the gasses contain sulfuric acid that corrodes anything it touches. Out-gassing simple means that bubbles rise through the water-acid solution in the RV battery cells and burst, scattering a film of acid through the cell vents. If you see a wet film on the top of the battery, this is a result of out-gassing. Out-gassing isn’t a major concern with sealed batteries, e.g AGM, Gel or most “maintenance free” types. However, there may still be some corrosion from other sources and these battery types also need at least a periodic inspection for corrosion.

Sign up for the newsletter today!

Please enter a valid email address.

An error occurred. Please try again later.

× logo

Thank you for subscribing to the Do It Yourself RV newsletter, keep your eye on your inbox for updates.


RV Battery Maintenance – Battery Brush


What to do about corrosion on the terminals? Prevention is a key part of RV battery maintenance, so cleaning the terminal and applying an anti-corrosion agent is your first line of defense.

Cleaning is best done with a wire brush and there are specialized circular battery brushesavailable online and in auto parts stores made for brushing top post batteries and cleaning the cables that attach to them. Baking soda makes an excellent cleaning paste for corroded terminals, so get some at the grocery store if you have visible corrosion. An old toothbrush is a handy application tool for working the paste into corners and crevices. After cleaning and reassembling, apply a dielectric grease to the post and cable ends to help prevent new corrosion. Auto parts stores will also sell a convenient anti-corrosion spray, usually red in color. But plain old Vaseline works too.

RV Battery Maintenance on Flooded Cell Batteries

Flooded cell RV batteries also need to have the water in the cells replenished occasionally. The liquid in the cells is a mix of water and acid, but just the water evaporates and needs to be replaced. Check the water in the cells by removing the caps. The liquid should be 1/8” to 1/4”above the top of the lead plates inside. If it is not, add distilled or de-ionized water to bring it up to that level. The water produced by reverse osmosis purifiers is also ideal for this purpose. Check your batteries monthly until you have an idea how quickly the water evaporates, then adjust your schedule so that you always refill before the water reaches the top of the plates.

RV Battery Maintenance  on “Maintenance Free”

So-called maintenance free flooded cell batteries are sealed, so you cannot replace the lost water. However, the sealed tops also reduce the rate of loss, so replacement is not as critical. AGM and Gel batteries trap the liquid in a sponge or a gel-like material, so they also do not lose fluid and require no periodic inspection and refilling.

Keeping Your RV Battery Area Clean

When it comes to RV battery maintenance, you should also periodically clean any metal parts near your RV batteries, because these too may suffer corrosion. Even just spraying with a hose will help, but the best option is to wash the RV battery area with a mild solution of baking soda and water. If the frame that supports the batteries shows signs of rust & corrosion, clean with the baking soda solution and remove any flakes with a wire brush. Some people use a chemical treatment such as Ospho with good results. Once the area is clean and dry, you can apply pick-up truck bed liner coating, e.g. Dupli-color Truck Bed Coating / Herculiner or paint with an anti-rust primer and paint such as Rust-Oleum

Another important aspect of battery maintenance is to make sure the connections are tight.  Periodically try to wiggle the cables and re-tighten any that are loose.

RV Battery Maintenance – Discharging and Equalization

Repeated discharging and recharging may reduce the battery’s capacity.  If your flooded cell RV battery “won’t hold a charge”, you may be able to restore it by a process called equalization. This requires a charger that has an equalization mode, which charges at 15.5-16.2 volts while limiting the current to about 1 amp. An equalization charge will often break up the chemicals (sulfation) that were robbing the battery’s capacity. The battery should be disconnected from the RV when equalizing because the high voltage can damage other electronics and burn out light bulbs. Do not attempt to equalize sealed batteries unless the battery manufacturer specifically approves of it.


When practicing good RV battery maintenance, a battery should not be allowed to remain discharged for extended periods, especially in sub-freezing weather. A maintenance or trickle charge, typically 13.6v at a rate of 1 amp or less, will keep the battery healthy and ready for use. Sophisticated, multi-stage chargers have a float mode that does this automatically, but you can get an inexpensive battery maintainer charger if your RV’s built-in charger lacks this mode.

See More on RV Battery Maintenance
How-to clean RV battery connections
How-to remove battery terminals

In addition to this article on RV battery maintenance, be sure to read “Choosing the Best RV Battery: Which is Right for You?” if you are replacing your current batteries.

8 thoughts on “RV Battery Maintenance: Tips for Evaporation, Corrosion and Capacity”

  1. This is always a hot topic for debate. While it’s true that “dielectric” means “non-conductive”, in practice it does not inhibit the flow of current across tightly mated metal surfaces. I’ve used it for years in my boats, cars and RVs with excellent results. I’ll speculate that the metal surfaces actually squeeze the grease away from the contact points but leave it in the pits and cracks of the surfaces, where it prevents arcing and oxidation. In my opinion, just smearing or spraying an anti-oxidant or dielectric grease over the outer surfaces doesn’t provide as complete protection as does coating the surfaces first and then making the connection. But if you are concerned about the possibility that the grease will reduce conductivity, go ahead and apply it after making the connection. It’s certainly better than no coating at all.

    Here is a relevant article on the use of dielectric and conductive greases by an experienced electrical systems engineer. He concludes that the use of grease on low voltage terminals such as battery posts is entirely acceptable.

  2. Re: Dielectric grease. This grease is NON conductive. By putting it on your battery posts, you have essentially made a worse electrical connection. The grease is designed to be used AFTER the connections are made tight, primarily to block water intrusion into small electrical connections. It is NOT designed or intended to be used for battery posts.

  3. That’s a valid technique that can sometimes be helpful. Floating a thin layer of mineral oil on top of the battery “water” (it’s actually a mild sulfuric acid solution) may reduce the tendency for it to bubble under heavy charging, and that in turn should reduce corrosion on surrounding components. However, if you have a good three stage charger in your Newmar, it should manage the charging well enough that this is not necessary. Most Newmar RVs have a high-quality charging system, so I would not do it unless you are experiencing significant corrosion nearby, or if you have to frequently top up the batteries with distilled water.

    If you decide to try the mineral oil, remove only a small amount of water from each cell and leave some water covering the lead plates. Then very carefully pour the oil in so that it does not contact the lead plates. If oil gets on the lead inside, it can ruin the battery.

  4. I just installed two new batteries in my Newmar and I’ve been told that it would be a good idea to remove some water and insert about 2 ounces of food grade mineral oil, then fill the cells up with distilled water. The mineral oil will help keep corrosion down and extend the life of the battery. Can you confirm that this information is credible

  5. I’ve been told there is a solution (like oil) that prevents water from evaporating from the battery.
    Do you know of such a product.

  6. It really depends on your charging system. Single stage chargers, especially older ones that have only crude regulation, will “boil” the batteries by overcharging them, which generates heat. Wet battery tops and corrosion on the terminals is a symptom of that, and also means that distilled water has to be added to replace the loss. For those, I recommend plugging the charger – or the entire RV – into an appliance timer so that the charger runs only an hour or two a day. That way you won’t overcharge and “cook” the battery.
    Mid-high end motorhomes and a few large trailers have three-stage chargers that won’t harm a battery no matter how long they charge. No problem leaving them plugged in 24/7.

Leave a Comment

Welcome! Please follow these guidelines:

  • Be kind and respectful.
  • Keep comments relevant to the article.
  • Avoid insults, threats, profanity, and offensive remarks.
  • Refrain from discussing gun rights, politics, or religion.
  • Do not post misleading information, personal details, or spam.

We may hide or remove comments at our discretion.