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  • If you overcharge your car battery you risk putting your vehicle out of commission.
  • Overcharging a battery can cause excessive gassing that ruins the device, and it can also accumulate flammable hydrogen.
  • Common causes of an overcharged car battery include a bad alternator, a faulty voltage regulator, and human error.
  • You may need to recharge your battery when your vehicle refuses to start.
  • Warning signs include a battery that’s hot, curving battery sides, low battery fluid level, and an acid smell.
  • You can check a battery’s state of charge with a multimeter and other tools.
  • In most cases, you’ll have to replace an overcharged car battery, and you might also have to replace other parts.
  • A battery replacement may cost around $100 to $500 for parts alone.

Your car’s battery is the heart of your vehicle’s electrical system. It provides the jolt of electricity needed to start the engine and powers other electrical components in your vehicle. A battery can last around three to five years. However, certain conditions like overcharging may contribute to its premature failure.

So, can you overcharge your car battery? The short answer is yes. This may leave your vehicle out of commission until the faulty battery is replaced.

What Happens When You Overcharge a Battery?

In most cases, an overcharged battery will eventually become ruined due to excessive gassing. With an older vented battery, the electrolyte boils away, ruining the battery’s plates. If your car has a newer, sealed-style battery, the battery may burst due to the internal buildup of gases.

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Flammable hydrogen can also accumulate inside the battery’s sealed cells and make its casing swell, and the hydrogen may seep through the vents and mix with oxygen. This can spell disaster because one spark can ignite the gas and make the battery explode. This may also damage other parts surrounding the battery.

car battery charging
In most cases, an overcharged battery will eventually become ruined due to excessive gassing.

What Can Cause an Overcharged Car Battery?

Overcharging a battery can result in costly repairs and part replacements. Here are some of the most common causes of overcharging you should watch out for:

Bad Voltage Regulator or Alternator

Most vehicles today come with alternators that have internal voltage regulators, which supply a controlled electrical charge to the battery while the engine is running. If a voltage regulator malfunctions, it may send an uncontrolled voltage to the battery, resulting in an overcharged condition.

In some cases, an incompatible alternator replacement may also cause car battery overcharging. So if you need to replace your alternator, make sure to buy one that’s compatible with your ride.

Human Error

Charging your battery with incorrect volts or high amp charger settings can overheat your car battery or charge it faster than usual. Overcharging can also happen if you leave your battery charged for too long.

Read up on how to properly charge your car battery or have your mechanic talk you through the process. Make sure to always use the correct charger and settings for your vehicle to avoid overcharging.

When Should You Charge a Car Battery?

You may need to recharge your battery when your vehicle refuses to start. Take note, however, that this usually means that your battery is nearing the end of its service life. Have your vehicle checked right away to determine its battery’s status and identify the faulty parts (if there are any) that are draining the charge.

See also  Underhood Checks

Signs of an Overcharged Car Battery

The damage caused by frequent overcharging won’t be noticeable from behind the wheel. You’ll have to open the hood, visually inspect your battery, and keep an eye out for these telltale signs:

Hot Battery

A car battery that’s too hot to touch even after resting your vehicle for more than thirty minutes may be overcharged. Have your ride inspected by your mechanic right away, and replace any faulty charging system components that may be causing the issue.

man replacing car battery
A car battery that’s too hot to touch even after resting your vehicle for more than thirty minutes may be overcharged.

Curved Battery Sides

Pressure build-up and the overproduction of gasses inside your battery can cause swelling. As a result, you may notice the sides of your car battery are curved.

Constant Drop in Battery Fluid Level

If your battery is not sealed and you notice the fluid level dropping more often than it should, then you may have an overcharged battery.

Acid-like Smell

As the heat of an overcharged battery boils off acid, you may smell an unusual acid-like odor from under the hood. If the smell isn’t coming from your car battery, there’s a high chance something else is wrong with your engine, so take your vehicle to your mechanic for an accurate diagnosis.

How To Test a Car Battery

You can check a  battery’s state of charge with a multimeter, a device used to measure voltage, amperage, continuity, and resistance in electrical components.

You won’t be able to conclude your battery’s condition based on multimeter readings alone, but it’s a good place to start. Check out this step-by-step guide on how to test your car battery using a multimeter.

Fully charged car batteries usually give out approximately 12.6 volts when the engine is off. If the voltage is significantly higher, you may be dealing with an overcharged battery.

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If you’re not used to doing DIY car repairs and tests, it’s best to leave the job to a trusted professional.

How to Repair an Overcharged Battery

In most cases, you’ll have to replace an overcharged car battery, especially if the damage is extensive. You may also have to replace other components, depending on what’s causing the issue. For instance, if a faulty alternator caused the problem, you’ll need to replace it along with your damaged battery to keep the same issue from happening again.

Get a Replacement Battery That Fits Your Vehicle

If you’re thinking of driving around with an overcharged battery, think again. Not only can an overcharged battery accumulate gas and start swelling, it can also explode. For your own safety, it’s best to replace your overcharged battery as soon as possible. Luckily, getting a brand-new battery is fast and easy with offers a wide selection of car batteries, all sourced from the most trusted manufacturers in the industry. Plus, you can easily browse through them by using our vehicle selector and search filters. Just be sure to input your vehicle’s correct details. Thanks to our strategically located warehouses around the US, also guarantees fast shipping. Order by 12 p.m. ET, and you can expect your new battery to arrive in as fast as two business days.

Don’t wait until your battery completely dies before getting a new one. Check out our catalog of high-quality batteries at today!

About The Author
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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