Car Troubleshooting

Can You Overcharge Your Car Battery?

All batteries have the possibility of being overcharged. Overcharging a battery means you charge it past the intended capability of the battery.

Most chargers do not monitor the battery level as you charge it. Therefore, it is possible to overcharge. Overcharging a battery can permanently damage the battery, resulting in the need to replace it. 

Overcharged batteries will degrade to the point of consistently losing charge regardless of how long you run your car or how often you charge it. Once a battery is overcharged, it cannot be repaired. 

Symptoms of an Overcharged Battery

An overcharged wet battery will boil the sulfuric acid mixture and will become hot to the touch. It can also emit a burning sulfur smell, and the sealed cells can swell or melt. 

An overcharged gel or AGM battery will become porous and lose its ability to hold a charge. 

Why Charging a Battery is Important 

Batteries have two cycles. Charge and discharge. These are very important to the battery. Suppose a battery sits in either of these two states for too long.

In that case, the sulfates inside the battery will begin to crystallize and harden. These crystals will degrade the life of the battery. These crystals can be broken up using a restorer, which will convert these particles into useful charged material. 

Typically, your vehicle’s alternator will charge your battery as you drive, continuing the process between the two cycles of the battery, from charged to discharged. But some things can prevent your battery from charging to its optimal state.

One way is if your vehicle sits unused for too long. Another way your battery can sit in a state of discharge is if your alternator uses the incorrect voltage while your car is running.

Either way, while your car’s battery sits in a state of discharge, it will build up those crystals that degrade your battery. And cause your battery to lose the capability to hold a charge altogether. 

Even if you are storing batteries, you will need to charge them. But before you hook your battery up, there are some things you need to know to prevent overcharging your battery. 

What happens When You Charge a Battery? 

When you charge a battery, you are conducting a chemical process that reverses the discharge of your battery.

This chemical process differs depending on the material of your battery (liquid, gel, or glass). But the main thing to understand is the core of the battery must return to an original “charged” state.

Chargers create heat to accomplish this. However, too much heat or amperage can create an adverse effect, damaging your battery or even catching fire. Always charge your batteries in a well-ventilated location, away from flammable items. 

How You Overcharge a Car Battery

Your battery can become overcharged through your alternator or the use of an external charger. Either way can permanently damage your vehicle’s battery, costing you a lot of money to replace the battery.

However, if the problem is your alternator, it can go unfixed for a long time. Suppose your car batteries seem to continue to degrade quickly. In that case, you should check your alternator and make sure it is not overcharging your battery while you drive. 

A multimeter is a tool that can check the volts of your battery while your vehicle is running. A fully charged battery can read anywhere between 12 volts to 14 volts depending on the load placed on your battery.

If your lights, radio, or ac is running when you check your battery level, you should expect it to read closer to 14 volts. If your battery reads higher than this, your alternator may be overcharging your battery. To fix this problem, you can simply replace the voltage regulator on your alternator. 

The other way that often causes overcharge to your battery is to leave it on an external charger too long. The amperage level of your charger dictates how long you can leave a battery on a charger.

Unfortunately, many times people fail to monitor their batteries appropriately and end up overcharging them. To prevent this, you should always use the lowest amp level and keep a timer set to check your batteries or use a maintenance level charger. 

Things That Affect Charging Your Battery

When charging your battery, there are a few things you need to keep in mind. The ampere level of your charger, the size of your battery, and the type of battery you have all affect how long you should charge your battery. 


One of the most critical things that affect the batty when you charge it is the ampere of the charger. The ampere released by your charger will affect how quickly or slowly your charger reaches full charge.

Ampere is a unit of measurement of electric current. When choosing which charger to use to charge your car battery, this number will tell you how fast it can charge your battery. The higher the number of the ampere, the quicker it can charge your battery. 

While many people may wish to have their batteries up to full charge as quickly as possible, using such high ampere chargers can damage the battery. 

Sometimes you may need to charge your battery quickly; however, it should not often be done. Charging a battery too fast can damage the battery, reducing its capabilities and shortening the life cycle of the batter. Batteries have even been known to catch fire if charged too quickly. 

Charging times with different battery chargers

  1. 2 Amp charger: 24 to 48 hours.
  2. 4 Amp charger: 12 to 24 hours.
  3. 10 Amp charger: 3 to 6 hours.
  4. 20 Amp charger: 2 to 4 hours.
  5. 40 Amp charger: about 1 hour.

Can you overcharge your battery at the lowest Amp setting? 

Even when charging a battery at the lowest Amps, you can still overcharge them. So make sure to monitor your battery’s charge so you can disconnect when the process is complete. 

Size of the battery

Another element of your battery that can affect how long it takes to charge is the size of your battery. Car batteries come in different sizes, and they are not interchangeable. Some vehicles can handle a larger battery than was originally installed.

A physically larger battery has more power and reserve time than a smaller battery. So it may be beneficial to upsize your battery if your car can handle it. 

The larger the battery, the longer it will take to reach full charge; however, they tend to hold its charge longer. 

Your battery group size can be found in your user manual. If you do not have your manual, you can usually find this information from a battery retailer. Auto Parts stores typically have this information as well. 

Types of Car Batteries

Types of batteries are interchangeable in cars/ you depend on the kind of battery you want. Just remember to get the proper size of the battery. 

There are 3 main types of car batteries: wet, gel, and AGM. Each of these types having a variety of options as technologies continue to improve. 

Wet Battery 

A wet-cell battery is the original type of rechargeable battery. This battery holds a liquid of sulfuric acid and aluminum alloy or calcium plates.

Wet Cell Batteries will need to be watered. You should add water after charging to improve the electrolysis of the battery.

Always use distilled water. YOu should also check the water level before charging/ then add water after charging. You should still use the lowest amperage setting you can when charging. 

Gel Battery

A gel battery has a gelling agent added to the electrolyte to reduce movement inside the battery case.

Gel Batteries have to be charged at a lower ampere due to how quickly they overcharge, causing them to become porous, reducing the lifespan of the battery cycle. These are best for aquatic vehicles. 

Gel batteries charge faster than your typical wet battery. 

Absorbent Glass Mat Battery 

AGM battery (Absorbent Glass Mat) battery contains a glass mat separator that wicks the electrolyte solution between the battery plates. As a result, this battery is “dry,” not wet. As a result, these batteries are best in colder locations. 

It is best to charge all batteries slowly, but the AGM battery can reach full charge fastest. 

Types of Chargers for Car Batteries 

Chargers for car batteries can be categorized into three main categories based on what they do.

  • Charger
  • Maintainer
  • Restorer


A charger will charge your car battery in a slow or fast setting. Often called a trickle charger, they can charge your battery quickly for a few hours or slowly over 24 hours.

However, these chargers do not monitor the charge level of your battery. Therefore you can overcharge using these typical chargers. Consequently, it is essential to monitor your battery while using these chargers. 


A Maintainer is a type of charger that provides continuous power to a battery without overcharging. It can monitor the level of charge in your battery and will prevent your battery from running out of charge.


Restorer Chargers can bring new life to batteries that have been left underpowered or at a low charge for a longer length of time.

When a battery is at a low charge, it can form crystals that build up called sulfation, reducing the battery’s life. The restorer will break the crystals up using a desulfator 

Can you overcharge a battery with a trickle charger?

A trickle charger is the primary type of charger. While the typical “charger” is not a maintainer or a restorer, therefore it can still overcharge your battery.

In addition, this type of charger is not monitoring the charge within your battery, so you must watch it and disconnect it when your battery reaches 80% to full charge. 

How To Dix An Overcharged Battery 

Unfortunately, once a battery has been damaged from overcharging, there is little that can be done. However, suppose you have overcharged your battery. In that case, it is essential to know what to do to prevent this from happening to the next battery, as these parts can be pretty expensive. 

Steps to prevent your next battery from overcharging: 

  1. Check your alternator. You may need to replace this part to make sure you do not overcharge your next battery while driving. 
  2. Check your charger. You may have overcharged your battery when charging at home. Replace it with a lower amp charger, and be sure to disconnect it from the charger when the battery is charged up to 80%. 
  3. Use a battery maintainer instead of a basic charger. Battery maintainers will keep your battery charged at the appropriate level and then stop charging. They also prevent your battery from losing power, preventing them from building crystals when low charged. 

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