How To Fix An Overcharged Car Battery

If you’ve overcharged your car battery, you may think that there’s nothing more you can do for it. And in fact, you are best off just purchasing a new one. However, this doesn’t have to be the case. In the age of recycling and being less wasteful, now is the perfect time to learn how to fix an overcharged battery! And the best part is, it will also save you money.

So here’s exactly how to fix an overcharged battery, as well as what causes it, who to check if the battery is overcharging, and how you can be certain that the problem is, in fact, an overcharged battery! So keep reading to find out everything you want to know!

What Are The Signs Of An Overcharged Battery

Before you learn how to fix an overcharged battery, you should be making sure it is inf act overcharged. Otherwise, you’re just wasting your time, and the problem that actually caused all the issues will go unnoticed.

Here are the most common signs that your battery is overcharged.

The Lifespan Decreases

The first thing you’ll notice is that over time the lifespan of your battery becomes shorter and shorter. You may notice these same problems not just in your car but on your other devices, such as phones and laptops.

The more often you leave your batteries to overcharge, the shorter and shorter their lifespans will become.

The Battery Dies Completely

When your battery is overcharged too often, it will simply die completely. You might think this is annoying, but it’s actually a safety function to make sure nothing more severe happens when the battery isn’t being charged properly.

If this didn’t happen, there’d be an increased possibility of the battery simply exploding.

The Battery Will Start To Swell

Fortunately, if you have a newer battery, this isn’t likely to happen. However, in older batteries, it’s possible that the battery can begin to swell and sometimes even melt. Because overcharging will cause more chemical reactions, more gas is going to build up, which can alter the shape of the battery over time.

The Battery Could Start To Melt

As well as swelling, the battery may begin to melt as the electricity being passed through the battery generates more and more heat. At a certain point, the battery will no longer be able to handle the heat, and some areas of it will melt.

It Will Start Leaking

As the battery continues to be overcharged, you’ll also notice that the battery is starting to leak as well. This is generally the result of the swelling and certain components of the battery melting. You should always be cautious around a leaking battery as the acid is going to be corrosive.

As well as the fumes the acid gives off can also be noxious as well.

It Exploded

Luckily, this is rare. However, it’s not unheard of. If your battery becomes too overcharged, then it could end up completely exploding. If you’ve noticed that your battery is bulging, then that’s an indicator an explosion could be imminent, so caution should be taken.

An open bonnet and engine, storage battery of a modern car

What Other Signs Could Show Your Battery Is Being Overcharged?

As well as the signs listed above, there are other things that could currently be happening that indicate your battery is being overcharged. However, if you catch them at this point, It is possible to fix them before your battery is ruined for good.

Your Battery Is Hot Too The Touch

When batteries are charging well, they shouldn’t be getting hot. However, if you notice that the battery is warm or hot to the touch, then that’s definitely a sign that overcharging is occurring or there’s something else wrong with the battery.

Of course, this is a lot more likely to happen when you’ve been driving.

The Electrolyte Levels Keep Dropping

If you notice that the fluid level in your battery is dropping over and over again, then that’s another sign that the battery is being overcharged. Every time your battery gets overcharged, the electrolytes are going to evaporate, causing the fluid to drop.

There’s A High Voltage Reading

When you’re reading the voltage of your battery, it should always fall between 12.6v – 14v. Anything more than that and it means the battery is being overcharged. At the same time, this could be a simple fix if you’re charging the battery yourself. It can show a sign of a faulty alternator when it’s due to the car charging itself.

You Can Smell Acid

And lastly, if you can smell acid when your car is on, or you’re near the battery, then that’s another sign that overcharging is occurring. Unfortunately, actually being able to smell acid is rare, so you shouldn’t use this as the main symptom to look out for.

What Causes An Overcharged Battery

There are a whole bunch of things that can cause an overcharged battery, and knowing what they are can help you prevent it from happening in the future.

Here are the causes of an overcharged battery:

A Problem With The Alternator

One of the most common causes of an overcharged battery is a problem with the alternator. When the alternator doesn’t work correctly, it can end up creating too much of a charge. If you think that it’s a problem with the alternator, some of the signs you will notice are:

  • The check engine light or ALT light on your dash comes on.
  • There’s a screeching, squealing, or grinding sound coming from the engine (a potential sign there’s a problem with the serpentine belt).
  • The lights have become dimmer or tend to flicker when they’re left on.

Of course, if you notice any of these problems, the best thing to do is take your car to a mechanic to be fixed.

Your Car Has Been In Extreme Heat

Unfortunately, while it can be hard to avoid, keeping your car battery in extreme heat can cause complications. When possible, you should try to park your car in the shade and in areas where the battery and engine remain properly ventilated.

A Problem With The Voltage Regulators

Another reason that your car battery may be overcharging is when there’s a problem with the voltage regulators. The regulators are there to ensure the right amount of electricity is entering the battery. However, when there’s a problem with them, too much or too little could enter, which of course could result in overcharging.

You’re Using A Faulty Battery Charger

When there’s a problem with a faulty battery charger, once again, it’s either going to result in overcharging or undercharging. And if it’s transferring too much electricity, then, of course, your battery is going to become overcharged.

If you plan on using a battery charger, it’s a good idea to test it beforehand. To test your battery charger, plug it in without the battery, and then use a multimeter to check the voltage. If it comes in around 13V, then your charger is working correctly.

It’s Being Charged For Too Long

And, of course, the most simple explanation is that your battery is simply being charged for too long. If this happens, then the cells are going to become damaged, and the more damage that occurs to the battery cells, the less and less charge your battery is going to be able to hold.

How To Check Whether Your Battery Is Overcharging Or Not

There are a couple of different ways you can check whether the battery is overcharging or not. And fortunately, they’re quite simple! Here are the different ways to check!

Use A Multimeter

The first thing you can do to check the charge of your battery is to use a multimeter. When your battery is fully charged, it should read 12.6v. If you turn the car on, the battery will tend to rise to around 14v. However, you can tell there’s a problem if the voltage ever goes higher than 14.8v. At this point, you can assume that the battery has become overcharged.

Check The Alternator

While this isn’t checking the battery directly, by checking the alternator, you’ll know whether or not there is a problem with the battery. The whole time the car is on, the alternator will be providing the battery with power, so if there’s a problem with it, too much power may be entering the battery.

Reconditioning Your Car Battery

When your battery has been overcharged, you may think that the best thing to do is replace it with a new one. However, this isn’t always the case. Sometimes it’s entirely possible to recondition your battery and get it working almost as good as new!

So here’s how to recondition an overcharged battery!

What You’ll Need

Before you recondition your battery, you’ll need to make sure you have the following:

  • Battery terminal cleaner
  • Apron
  • Mask
  • Disposable rubber gloves
  • Toothbrush
  • Flathead screwdriver
  • Charger
  • Funnel
  • Baking Soda
  • Bucket & Distilled Water
  • Voltmeter

What To Do

Now you’ve collected everything you need, here’s what to do to recondition your battery!

Step 1 – Prep The Battery

The first step is to prep the battery. To do this, put on all your safety equipment, and make sure you’re working in a well-ventilated area. It’s also a good idea to be close to a tap so you can wash off any battery acid that may end up on you.

Before anything else, you should then remove the battery from the car, ensuring it has been completely detached.

Next, clean the battery terminals making sure that they’re free from any corrosion or salt that has built up over time.

(You can clean the corrosion by creating a solution of baking soda and water. Keeping the ratio between 1:1 and 2:1 of baking soda to water. Keep mixing them together until a paste has formed, which you can then rub onto the battery terminal. Then use a toothbrush to wipe clean the terminals, or in more severe cases, use a steel brush or steel wool.)

Step 2 – Checking The Voltage

Now use your voltmeter to check the voltage.

To use the voltmeter, connect the red wire to the positive terminal and the black wire to the negative terminal (unless the instructions say otherwise).

At this point, the voltmeter should be able to read the voltage. A battery in good condition will have a voltage reading of 12.6v or above. or 13.7v – 14.7v when the battery is connected to your car and turned on. If the voltmeter is reading anything below 12.4v, then the battery can be reconditioned.

Step 3 – Remove The Electrolyte Solution

If you notice that the voltage is below 12.4v, then it’s time to start reconditioning your battery. To begin, you’ll need to remove the electrolyte solution. So take a screwdriver and remove the battery caps. Once they’re off, slowly pour the old electrolytes into a bucket. If at any point there’s a spillage, cover it with baking soda to make sure it’s been neutralized.

Now that you’ve done this, fill each battery cell using the baking soda/water combination you created earlier, add the caps and then shake the battery for about a minute to make sure everything inside is getting coated. Once done, allow the battery to sit for another minute before emptying the baking soda as well.

And to neutralize the battery acid inside the bucket itself, pour half a pound of baking soda into it or a 3:1 mix of baking soda and water solution.

Step 4 – Refill The Electrolytes

Now it’s time to begin reconditioning the battery. The first step is to refill the battery with an electrolyte solution, and the simplest way to do this is by dissolving 120 grams of Epsom salt in 1 liter of distilled water. To make sure the salt dissolves properly, you can make the distilled water lukewarm.

Once the solution has been made, you just need to top the battery cells back up with the electrolyte solution and replace the battery cap.

Step 5 – Charging The Battery

Now it’s time to recharge the battery, and this is going to be the longest step. To recharge the battery, you just need to connect the red wire from your battery charger to the positive terminal on your battery and the black wire to the negative terminal, then allow the battery to charge at 2amps for 12 volts for 24 to 36 hours.

After 36 hours, test the voltage of the battery again. If it measures between 12.4v – 12.6v, then the reconditioning has been a success; however, if not, then you charge it for another 36 hours.

If the battery still isn’t within the required voltage, then it’s time to replace the battery in your car with a new one!


Here are some commonly asked questions people have about their overcharged batteries and what to do with them!

Can You Leave A Battery On Charge Throughout The Night?

Unless you’re reconditioning your battery, you should never let it charge for more than 24 hours at a time. While charging a low battery overnight could help it get a full charge, it can also completely damage the battery as well, so it’s not recommended for this reason.

Does Having A Bad Battery Cause Overcharging?

If you have a bad battery, then it can give a false voltage reading to the car’s charging system. When this happens, the alternator will continue to increase the voltage output in an attempt to charge the battery, which in turn will overcharge it.

Is It Possible To Overcharge A Battery At 2 Amps?

It’s entirely possible to overcharge a battery, even at 2 amps! At 2 amps, it’s still possible for the battery to suffer from excessive gassing caused by the electrolyte getting too hot and generating too much hydrogen and oxygen gas.

What’s The Lifespan Of A Reconditioned Battery?

Generally speaking, your reconditioned battery should last for up to 1 year after it’s been reconditioned. However, if it’s an older battery or one that’s been reconditioned multiple times, then the lifespan may be even shorter than that.

Can You Add Vinegar To A Reconditioned Battery?

You should never under any circumstances add vinegar to your battery. Vinegar will react with the electrolyte solution inside the battery resulting in sulfuric and acetic acid reactions together, which will then coat the battery terminals in lead acetate.

How Long Can You Leave Your Battery Without Being Used?

If you’re keeping your battery in good weather and climate conditions, it’s possible for it to last up to four years without being used. However, the moment the elements start to come into contact with it, you can expect the lifespan to go down.

When Should You Avoid Reconditioning Your Battery?

You should avoid reconditioning your battery if you’ve already reconditioned it three times before, if the battery has sustained too much damage, or if you simply don’t have the right materials and equipment to recondition them.


As you can see, there are so many different reasons that your battery might become overcharged. However, fortunately, if you’re taking care of your battery, you can drastically reduce the chances of it happening in the first place!

However, in times when the battery has become overcharged, then you can still try to recondition it in order to fix it! If you liked this article, make sure you check out the rest of the website! Otherwise, have a great day!

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