Why Your RV Battery Overcharges & What To Do About It?

 Although you may not always think too much about them when you are out enjoying yourself on your latest RVing adventure there is a lot riding on your rig’s battery, literally.

That’s why it’s crucial that you understand at least a little about how you RV’s battery works and how to take care of it, especially when it comes to preventing it from overcharging, something that can cause all kinds of problems.

RV Battery Basics

RV owners demand a lot from their batteries, especially these days when there are probably more electronic devices and gadgets in the average RV than ever before.

To cope with this demand the RV battery you make use of should be a deep cycle battery. 

Only deep cycle batteries can truly cope with the demand placed on them. Some people try to make use of a standard engine starting battery instead, but that’s a poor solution, as they are likely to go flat or burn out almost immediately. 

There are three types of deep cycle batteries currently found in most RVs:

  • Conventional flooded cell batteries
  • Gel batteries
  • AGM or dry batteries

Most RVs come with conventional flooded cell batteries installed as standard. And that is fine. Flooded cell RV batteries are efficient and can offer good performance at a reasonable price.

However, they need more maintenance than other battery types.

The flooded cell part of the name refers to the fact that these batteries have to be filled with water to function.

If the water runs low to the point that the batteries plates are exposed the chances are good that they will be ruined for good.

That’s why overcharging these batteries is something to be avoided whenever possible, as doing so will literally boil them dry.

Gel batteries, as the name suggests, are gel filled and do not need to be topped off with water. This means they usually last longer, but as they are more expensive, fewer people make use of them.

Dry batteries are also more expensive. Their plates are wrapped in fiberglass and these batteries are almost maintenance free.

However, neither type is perfect and they can be overcharged as well.

What Causes RV Batteries to Overcharge?

There are several reasons why an RV battery will overcharge, but the most common reason it happens is because the converter in use while the battery is being charged is either not suited to the job or it is malfunctioning.

The converter that should be used to charge RV batteries is called a smart converter or three stage converter.

These have three charge modes: bulk, absorption and float. Bulk takes the battery to 90% quickly, absorption brings it up to 100% a little slower and then float keeps things topped off so that the battery does not run flat.

What some new RV owners don’t realize is that even when their RV is parked up in the garage it contains ‘energy vampires’; unseen things that continuously draw a small amount of energy. Over time this could lead to a flat battery.

The overcharging problem occurs when smart chargers malfunction and get stuck in bulk or absorption mode. Or if an RV owner does not have a three stage converter and leaves a standard converter in place for too long.

Preventing Your RV Battery From Overcharging

To prevent these problems if you don’t have a ‘smart’ charger you should consider getting one. If you do, you need to ensure that it is working properly. Some RV experts feel that while most new RVs do come with a smart converter that the quality of those included as standard is not always as high as it should be.

There are other reasons why a battery may overcharge, including a problem with the battery itself. Like car batteries RV batteries don’t last forever, and usually need to be replaced after 3-4 years. However, when it comes to an RV battery overcharging, converter problems are by far the most common reason.

The Importance of Keeping Your RV Battery Charged

Although you don’t want to overcharge your RV battery leaving it undercharged is something that should never be done either. Allowing any type of RV battery to discharge more than 50% significantly shortens its useful life. This is because when a battery is undercharged its cells become ‘sulfated‘ and it will begin to lose its ability to hold a charge.

Some people wonder how they can determine if their battery is fully charged. Most RVs do have a battery level indicator, but if yours does not then you can make use of a standard handheld voltmeter to find out for yourself.

When a standard fully charged RV battery is at rest (with no active power draw at all, aside from those tiny energy vampires) it should read at 12.6 volts or higher. If it is charged to 75% you should get a 12.4 volt reading. If the reading drops to 12.0 or lower then your battery has dropped to below 50% charged and should be charged as soon as possible.

The Future of RV Batteries

Technology is always evolving, and that is as true in the RV space as anywhere else. And the ‘next generation’ of RV batteries is already starting to arrive. Lithium-ion batteries – the kind becoming more and more common in higher end cars – are also now available for RVs as well.

Li-ion batteries as they are commonly known offer a lot of advantages. They are very light, they can hold a lot more power while still being correctly sized for RV use and are almost impossible to overcharge. The downside is that they are, at the moment, far too expensive for the average RV owner to consider.

Hopefully this will change over time, but until that happens, making sure that you take great care of the RV batteries you have – especially when it comes to charging them and preventing your RV batteries from overcharging – is the best way to ensure they perform as well as they should and your RV adventures are not slowed down by battery issues.


2 thoughts on “Why Your RV Battery Overcharges & What To Do About It?”

  1. What can I do without having to buy a whole new charging system? converter was replaced last year with the service panel. is there something i can get that will stop it from charging the battery when it doesn’t need it?

    1. This is a common problem with converters. My solution was to install isolator switches and a built in battery tender. An RV service guy could help you with this.
      I often check electrolyte levels before trip and while camping to ensure battery doesn’t overcharge.

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