What Happens If You Overcharge An Auto Battery?

what happens if you overcharge a car battery?

Can you overcharge a car battery? Was the question I asked myself back in the day that I bought my first car. Unfortunately for me, I learned the answer to this question the hard way; when I had to deal with a dead car battery after several years and the mechanic told me that overcharging it caused its demise. My car battery didn’t reach its expected lifespan due to my lack of knowledge, but it also allowed me to learn from my mistake.

So now, I am equipped with the proper knowledge and writing this blog to help the newbie car owners out there about this issue. In this post, I will be answering that particular question and provide readers with some essential and significant information about automotive batteries that every car owner should know. Information that will allow them to keep their car batteries healthy and at the same time extend their service life.

​I hope that you ready to learn this information because I am about to start. So, sit back, relax and enjoy the ride while reading through this entire post.

The Effects Of Overcharging A Car Battery

Based on my own experience, I’ve learned that overcharging your car battery will significantly reduce its service life. So, to answer the question above. No! You can’t overcharge a car battery unless you want to waste a good amount of money as I accidentally did.

To give you an idea of the effects of overcharging on a car battery. They are explained below.

Overcharging a car battery will take a significant toll on it and eventually kill it. If the car battery is overcharged, the sulfuric acid and distilled water mixture within it will boil and cause its casing to be hot. When this happens, the battery housing will either melt or swell creating small vents that will allow the introduction of hydrogen to oxygen. This will make your car battery a sitting time bomb that can explode once it is introduced to a small electrical spark.

The scenario of an exploding car battery can be scary, but it is not likely to happen. However, it is still possible if the battery gets too hot. In most cases, if a car battery is always left overcharged, the boiling of the liquid components within it weakens its housing. This will significantly shorten the lifespan of the car battery preventing you from getting the most of it.

​What Causes

Several causes result in an overcharged car battery. Keeping these causes in mind will allow you to avoid them and help you protect your automotive battery from being overcharged. To learn about these causes, you can refer to the list below.

● Failing Alternator Voltage Regulator - All modern vehicles today are equipped with an alternator that has a voltage regulator. This is to regulate the supplied electrical charge on the battery when the engine of the vehicle is running. If the voltage regulator of the vehicle’s alternator fails, the car battery will receive an unlimited amount of electrical charge, overcharging the automotive power cell.

● Human Error - In most cases, overcharged batteries are caused by human error. In a case like this, car owners use battery chargers to charge their car batteries, but they don’t have any idea of how to do it correctly. An incorrect voltage setting or amperage setting may result in an overcharged battery, and it is one of the leading causes why batteries are overcharged.

No knowing how to can causes the issue.

Sometimes, car owners also often leave the battery charger unattended which may result in an overcharged battery. In a case like this, the battery charger is an older model since most of the newer ones are equipped with smart features that prevent overcharging.

● Faulty Battery Chargers - Using a defective battery charger to recharge a car battery can also cause an overcharged car battery. If a battery charger has its settings wired incorrectly, it can overcharge the car battery even if it is carefully monitored.

​Trickle Charger​

If you are wondering if you can overcharge a car battery with a trickle charger, the answer is YES. Although trickle chargers are considered to be highly advanced devices used to recharge automotive batteries. There’s always a chance that you might overcharge your car battery with it which will lead to severe damage to the battery; significantly reducing its service life.

With this said, you have to keep in mind that even though you are using a trickle charger to recharge your automotive battery. There’s always a chance that your car battery may be overcharged.

Can A Flooded Lead-Acid Battery Be Overcharged?

For those car owners out there that uses a flooded lead-acid battery for their cars, this section of the article will provide explain what happens to the battery when it is frequently overcharged. If you have a new car and it is equipped with a flooded lead-acid battery, you may want to take note of what is explained below.

When a flooded lead-acid car battery is overcharged, the battery acid within will boil. It will cause the battery housing to be weak and vulnerable to physical damages like cracks and swells. The power cell will also generate too much heat that may cause the electrolyte to evaporate risking the battery to overheat when it is used without refilling the battery electrolyte.

These factors will put the battery at risk of severe damage that may significantly reduce its service life. Preventing you from getting the most out of the battery. A car power cell that suffers from overheating will also take a massive toll on the battery since its battery plates will get thinner at a higher rate. It reduces the battery cycle which will shorten the lifespan of the battery.

​What About Sealed Lead-Acid Batteries?

When a sealed lead-acid battery is overcharged, the same effect will happen. However, the due to the sealed battery casing of this type of battery, it can be dangerous to use, and it can risk a battery explosion. As the acids within the battery boil, the volatile gasses in a sealed lead-acid battery will badly react with an electrical spark that may cause it to explode.

In most cases, overcharged sealed lead-acid batteries always have bloated battery housings because of the re-combined gasses due to the pressure expelled by the vents of the battery. However, this is a safety feature that prevents the battery from exploding due to the extreme heat generated within the battery when it is overcharged.

Telltale Signs ​

Telltale is the indication if your car is being overcharged or not.

Another valuable lesson that I’ve learned from my mistake was to learn about the telltale signs when the car battery is being overcharged. For all the car owners out there, you can take note of these common signs that will tell you that your battery is overcharging.

● Heating - When a car battery is charging, it generates heat. But if your car battery is generating too much heat, there is a great chance that the battery is overcharging. When the battery case becomes too hot to touch, it means that it is taking too much electrical charge that indicates overcharging.

● Battery leaks - When a car battery is overcharged, it causes a build-up of hydrogen gases that creates pressure within its plastic housing. The pressure forces the electrolyte within the battery to leak out through any openings on the housing. The battery fluid or electrolyte commonly leaks out through the vents and filler caps of the battery.

● Swelling of battery housing - Another sign of an overcharged battery is a swollen casing or housing. When the battery is overcharged, an excessive amount of hydrogen is quickly produced. This gas build-up creates pressure within the battery casing that results in swelling. This causes the battery housing to bulge, and in severe cases, the pressure can cause the battery to split open or explode.

● Low electrolyte levels - Having low electrolyte levels within the battery is also a sign that it is overcharged. As mentioned earlier, overcharging the battery generates too much heat, and this heat causes the electrolyte to evaporate. The greater the heat generated by the battery, the quicker the evaporation process of the electrolyte within it.

How To Fix An Overcharged A Vehicle Battery

If you are in doubt that your car battery is overcharged or if you are starting to see the signs listed above. You can check your car battery if it is overcharged by using a voltmeter and carrying out a voltage check. By testing battery voltage, amperage, recovery time and discharge rate, it will reveal the overall condition of the car battery. It will also give you an idea if it is overcharged.

Unfortunately, repairing an overcharged car battery is not possible but rebuilding it is. This means that an overcharged automotive battery can’t be repaired, but it can be rebuilt. Once you’ve tested your car battery and the results tell you that it is overcharged, then the only way to fix it is to restore it.

When I say rebuild the car battery, this means reconditioning it to allow it to regain its ability to store charge and convert it to energy. There are battery reconditioners available in the market that you can use to rebuild your overcharged car battery, or you can also take the battery to licensed mechanics and pay them for the service.


I know you are familiar with the saying “prevention is better than cure” because it is very much applicable in the case of overcharged car batteries. To keep you from dealing with the hassle of handling an overcharged car battery, preventing it from happening is the best step that you can take. To help you with this, here are some tips that you can keep in mind.

​Make sure to take notes of these good practices to make sure that you won’t overcharge your automotive battery.

Ways To Properly Charge The Car Battery

One of the best ways to prevent overcharging your car battery is to learn the proper way of charging it. Different battery types and battery chemistry has different ways of charging them properly. So you have to make sure that you know what battery type and chemistry your battery has and learn the proper way of charging it. Or you can also study the different types of batteries, and the different battery chemistries then determine the appropriate way of charging them.

Use The Right Battery Charger And Make Sure It’s NOT Faulty

For car owners that are recharging their automotive batteries using a battery charger. You have to make sure that you are using a non-faulty battery charger since it can lead to overcharging. You also have to make sure that you are using the right battery charger to recharge your car battery. By doing this, it will eliminate the risk of having an unlimited amount of electrical charge delivered to the battery.

Make Sure That The Alternator Of The Car Is Working Properly

As mentioned earlier, one of the causes of an overcharged battery is a failing alternator. For modern vehicles, an alternator with a faulty voltage regulator can also cause overcharging. By making sure that your car’s alternator is working properly, the risk of the car battery being overcharged when the engine is running will be alleviated. So make sure that your alternator is in good condition and is working as it is expected.

Using A Battery Charger With An Overcharging Protection Feature

Most of the newer battery chargers today are equipped with microprocessors that make them smart devices that allow them to have an overcharging protection feature. Using smart battery chargers like these will let you leave the charger unattended without worrying for your battery to be overcharged. If you have an older device that doesn’t have this feature, you will have to monitor your charger during the entire charging process regularly.

Final Thoughts

To summarize everything, I shared my experience on how I learned the answer to the question, can you overcharge a car battery? In a costly manner. Where I accidentally overcharged my new car’s battery frequently and how it made me pay a huge price. To sum it up, NO, you can’t overcharge a car battery, and you must avoid doing it. The truth is, overcharging a car battery will kill it or will greatly shorten its lifespan.

Repairing an overcharged battery is also not possible but rebuilding it by carrying out the process of reconditioning is possible. I hope this post that shares my personal experience will help all the car owners out there and always remind them that overcharging a battery is very dangerous.