Can You Overcharge A Deep Cycle Battery: What To Know

Can you overcharge a deep cycle battery? The short is “yes”, it is possible to overcharge. However, things must go wrong for your battery to get more charge than desired.

This post will review how deep cycle batteries can get overcharged and how you can to avoid it. We will take a look at the following:

  • How a deep cycle battery can be overcharged
  • How to avoid your battery from being overcharged

As a side note, this post relates to all types of 12V batteries that you can use for your boat, RV, or trailer. The information below applies to all kinds of cell batteries, including a marine battery, AGM battery, or even lithium-ion.

Table of Contents

How a Deep Cycle Battery Can Be Overcharged

When we refer to overcharging, we are talking about going above the battery’s capacity to safely and effectively hold a charge. After all, a battery is a method to store power. But can that power be overcharged to where it will damage the battery or reduce battery life? As you read above, “yes” it can be overcharged. However, knowing how battery voltage works, you can watch for issues and signs of your battery being overcharged.

12 volt Battery

We are referring to the batteries we all use for boats, cars and RVs. These are flooded batteries that have been around for decades. They are lead-plates set in an acid solution and produce 12V of power. As we review the potential for overcharging, the same principles apply to the following battery type:

  • Deep Cycle Battery
  • Marine Battery
  • AGM Battery
  • Lithium Battery

All of these batteries are 12V and can be charged and re-charged with the potential of being overcharged.

Charge Voltage

The charge voltage is the amount of electricity that must be present in an electrical system to be considered “fully charged.” In a 12V battery, you will likely get more than that amount of voltage. Most of these batteries are considered fully charged when around 14.4V at rest. Is anything over 12V considered overcharged? The answer to that is “no.” A battery can safely hold around 14V and is not considered overcharged.

What is Overcharge

An overcharge on a 12V system is a voltage on your battery greater than 14.4V.

When a battery becomes overcharged, its cells become exposed to too much energy and heat. This can cause the cells to start breaking down – leading to various issues, including corrosion of the terminals and damage to internal parts. Additionally, extreme heat may boil off the electrolyte stored inside the battery. The resulting gas created from this process is highly flammable and could lead to dangerous situations if not addressed quickly.


So how does a battery get overcharged? Good question, but let’s first look at how a battery charges, and then we can see how it can be overcharged.

A battery is a simple transfer of power from one source to another. And that transfer of power, in simple terms, is higher voltage going into a battery with lower voltage. So if you have a fully charged battery at 14V and connect it to a weak battery with 10V, power will be transferred from the full charge battery to the weak battery. Eventually, the batteries will become equally in voltage once the difference in power is transferred from one battery to the next.

Chargers and Alternators give over 14V to charge the battery

When you charge your battery, you are connected to a truck engine (car battery) or plugged into shore power (your RV battery). A charger gives your battery power while driving your truck or having your RV plugged in. The voltage supplied by your charger is around 14V, giving added voltage to your 12V battery. Usually, a good charge battery charge rate is when there are 2 more volts from the battery to the charger. Other principles come into play, like amps, but in terms of volts, that is a good difference to note.

How Does a Battery Get Overcharged

Let’s get back to the question of overcharging the battery. Since we know that a battery can be overcharged, let’s now see how that can happen.

We reviewed that a charging system will provide 14V to a 12V battery to keep it fully charged. What happens if we have a charger that is not working correctly and is giving out higher voltage?

Since a battery is not smart and just a bunch of battery plates and lead acid, it will keep taking that charge as it tries to get to equilibrium with the power source. That means if your charger or is giving out say 17V, then your battery will keep charging past the 14V that it was designed to hold.

For more info on battery, capacity and cells, visit my post on the difference between 6v and 12v RV Batteries.

How to avoid your battery from being overcharged

Since we know that a battery can be overcharged, what are the best practices to avoid this issue? The first step is to ensure your charging source (whether an alternator from your truck or your trickle charger) is in good working order and only gives out around 14V. How do you check your charger:

  1. Get a multimeter and set it to DC Voltage
  2. Put the probes on the battery terminals as the system is charging or your truck is running
  3. You should be getting around 14V
  4. Make sure the battery terminals are clean – voltage needs to get to the battery

If your charger has a defect, it could mean it is not regulating the output voltage and giving you more voltage than desired.

Smart Charger

Get a smart charger. The smart charger works by monitoring the battery when it’s being charged and detecting any changes in voltage or temperature.

A smart charger regulates voltage and temperature during the charge

This allows it to adjust its power output accordingly, eliminating the risk of overcharging or damaging the battery.

Final Thoughts

Yes, a deep cycle battery can be overcharged. The good news is that it is not likely to overcharge if the charging system functions correctly and provides the needed 14V to keep the battery topped off. Whether you have a deep cycle marine battery or any other acid battery, the above post applies to them. By keeping your charger in good working order or using a smart charger, your battery should be in good shape and provide a decent battery life.