How Do You Know If Your Car Battery Is Overcharged

Photo close up hand technician or auto mechanic change the car battery in auto repair car service center

Most cars have their car battery under the hood in the engine bay. Others, however, are designed with batteries in the boot or trunk. In both cases, the battery is concealed away from sight, making it difficult to know if the battery is being overcharged.

That’s why you must learn to recognise signs of battery overcharging, regardless of if you have an automotive motorsport education or if you’re just a regular car owner.

Here are the 5 ways to know if your car battery is being overcharged:

1. Excessive Voltage Readings

The first and most straightforward way to know if your car battery is overcharged is by checking for excessive voltage readings above 14.8 volts. That will instantly confirm to you whether or not the overcharging is happening.

You can check the voltage readings by using a standard multimeter and connecting it to your battery. That’s excellent for troubleshooting the battery, but it’s not practical to monitor voltage levels daily.

Some cars have a battery voltage meter built into the instrument panel, allowing you to monitor your battery’s voltage readings constantly. However, most cars only have a battery indicator that illuminates when there’s a problem, though it doesn’t tell you what that problem is precisely.

Alternatively, you could also invest in an aftermarket battery voltage meter that you can mount on your dashboard.

2. Car Battery Overheats

Many overcharged battery symptoms are subtle and only noticeable over an extended period. For example, the overcharging condition causes the battery’s electrolyte to become much hotter than usual.

As a result, the whole battery overheats. You’ll only know that when you touch the battery by hand to get a sense of its temperature.

When you study superbikes, cars, trucks, or any other motor vehicle, you’ll learn that it’s normal for automotive batteries to feel warm. That’s especially true in our hot Malaysian climate when the car has been parked under the sun.

But you’ll know the battery is overheating when it hurts your hand to touch the case. That’s a telltale sign that the electrolyte inside is overheating due to an overcharging condition.

Photo from Rac Shop (Car batteries: Why they die in hot weather)

3. Strong Smells

Another clear indicator that your battery is suffering from overcharging is when you sense strong smells coming from under the hood. Again, you should inspect the smells closely to see if they come from the battery.

Those strong smells are often described as acid-like or smelling like rotten eggs, both of which come as no surprise.

As you read earlier, overcharging causes the battery’s electrolyte to overheat. One of the side effects of that is excessive gassing, where hydrogen sulfide is produced as a byproduct.

That gas will leak from the battery and become noticeable.

Photo from La Car (Why does my car smell like burning rubber)

4. Bulging Or Curved Battery Case

When the overcharging condition of your car battery becomes too severe after going on for too long, you can also notice physical signs. The most common one is when the battery case is bulging or curved, which it should never be.

Remember: the battery case consists of hard plastic. That means its sides should always be straight, and any bulging or curving is a bad sign.

The curving happens because of the gas buildup you read about in the previous section. That gas fails to escape the battery case, so its pressure grows and pushes outward, causing the case to bulge from within.

Photo from Nocheski (Why your Lead Acid Battery is all Swollen Up)

5. Battery Fluid Levels Keep Dropping

Many vehicles on Malaysian roads still use flooded lead-acid batteries instead of sealed, maintenance-free versions. Those batteries occasionally need you to refill them with distilled or deionised water.

You’ll know that the battery is overcharged when you have to refill the water more often than usual. That’s because overcharging the battery causes its fluid levels to keep dropping at a much quicker rate.

As a result, you’ll notice yourself having to repeat the refilling process much more than usual.

What Should You Do If Your Car Battery Is Overcharged?

Suppose you discover that your car battery has been overcharged for an extended period. The battery has all of the symptoms mentioned above, including strong smells, its case is bulging on the sides, and it is constantly overheating.

In that case, the best thing you can do is to disconnect the battery immediately and remove it from your vehicle. Then, place the battery somewhere safe in the open, away from anything it might damage.

An overcharged battery is no longer safe to use, especially one that’s already suffered excess wear and internal damage. Therefore, you must dispose of the battery safely and correctly before replacing it with a new one.

Before doing that, you must troubleshoot your vehicle to find the root cause of the overcharging. That way, the problem will not repeat itself with your new battery.

Some common reasons for an overcharging car battery include:

Failed voltage regulator
Faulty alternator
Misusing an external battery charger (e.g. wrong voltage setting when using a standalone car battery charger)

A car battery doesn’t fail on its own. So, that means the root cause is somewhere in your vehicle. You must find and resolve that problem to protect your new battery.

Final Thoughts

The battery is the heart of your car’s electrical system. It’s necessary to store and distribute electrical power when required. Not only does it start your engine, but it also keeps your electrical and electronic accessories powered.

A car battery that’s undercharged can’t fulfil its purpose. However, one that’s overcharged will suffer negative consequences and potentially leave you stranded on the road.

Car batteries and automotive electrical systems are fascinating and complex. If you are passionate about these and other automotive topics, check out the courses available at TOC Automotive College, the best automotive college in Malaysia.