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Can your car battery overcharge? And How BAD is it ACTUALLY?

Your car’s battery has run dead – again!

When a car battery breaks down or refuses to work, we often suspect something wrong with the battery itself.

But wait! What if I tell you the fault could also be yours?!? Most people are unaware of this, but you can overcharge a car battery and create some unforeseen consequences.

Let’s talk about the important stuff: How could you overcharge a car battery? What happens if you do so, and how can you prevent it?

Can you overcharge a car battery?

Yes, you can overcharge a car battery without even knowing it. In fact, the subtlety of its occurrence is why many people don’t even suspect it.

A majority of commercial car batteries available on the market shelves are lead-acid batteries. Unfortunately, these batteries are anatomically susceptible to damage. Even though they can withstand a certain amount of overcharging, if you cross a particular threshold, it can cause damage.

Can a battery explode from overcharging?

Sadly, yes! If you overcharge the car to an extent where the pressure builds up extremely high, there is a chance that your battery might explode. Why? Because oxygen and hydrogen combine to make an explosive mixture. The tiniest spark can lead to ignition and cause an explosion. This explosion can be dangerous to the vehicle itself as well as the ones around it. So, as harmless as an overcharged battery might sound, it can get hazardous if you don’t address it soon enough.

Why your car battery overcharges

If you continuously overcharge a battery, it will eventually boil even if the current and voltage are low. Then, slowly, it reaches a point where it becomes scorched. The internal lead plates damage over time, and after a specific limit, they can no longer power your car enough to help it operate.

The three most common causes of car battery overcharging

Luckily, many lead-acid batteries can withstand a certain level of overcharging. If you think your battery has been charged over the optimal level, address the problem immediately. If you identify the issue before it gets out of hand, you can potentially stop the matter from worsening. However, once your battery reaches its complete charging level, any excess current breaks the electrolyte. As a result of this process, hydrogen and oxygen are released.

When you use trickle chargers, these gases are released slowly. And if you are lucky, they are vented into the air. It is also why tiny plastic tubes are typically attached to most vented batteries. They help remove the corrosive acid mixture and save the batteries from being ruined due to overcharging.

There are several underlying reasons why your battery keeps overcharging despite your efforts.

Faulty charger

If you have a lousy charger, to begin with, no matter how many precautionary steps you take and how attentive you are, it will eventually cause overcharging. Indeed, leaving your charger connected to the battery for a long time can cause overcharging. However, most modern chargers come with a smart function. This feature automatically switches off the power as soon as the car battery reaches its total limit. Therefore, if your charger is faulty or does not have this feature, there are higher chances of your battery being overcharged.

Another critical point is that if you choose an incompatible charger or select the incorrect charging setting, you can also increase the risk of overcharging.


This problem is simple: make sure that the charger you choose is compatible, not faulty, and has a smart feature. Also, follow the manufacturer’s instructions when you use the charger and choose the correct settings.

Voltage regulator and Alternator problems

If your voltage regulator or alternator is not working correctly, the battery will most likely overcharge. Voltage regulators are typically used to maintain the voltage flow towards the battery and keep it steady. If it is defective, the voltage regulator sends too much or too little charge, both of which can cause overcharging.

Similarly, alternators serve the purpose of converting mechanical power into electrical power and help the battery charge. If you use the wrong alternator or it’s not working correctly, it creates excessive energy and causes overcharging.


This problem’s solution is to replace the voltage regulator and the faulty alternative. Both of these are readily available in the market and come at affordable prices.

Bad battery

Battery problems are another common reason behind overcharged batteries. Whether you have a faulty battery or an outdated one, it can cause issues. Here’s how to check if the battery is working well:

Take a multimeter and measure the voltage across your battery. Typically, when the engine and accessories are off, the voltmeter should read 12.8 volts. So, if your reading is somewhere between 12.4 to 12.8, you’re good to go. But if the voltage is higher than 12.9, something is not right! The higher the voltage, the more voltage is running through your battery. And excessive voltage is a direct indication of overcharging.


Unfortunately, the issue of a bad battery usually has only one solution: replacement. Unfortunately, you can seldom repair faulty batteries. Most times, you need to replace them with a new, better one immediately. However, if the battery breaks down and you have a warranty, report it to the manufacturing company. You’ll probably get a replacement for lesser money if not free.

Most people try to fix the battery themselves using DIY hacks from the Internet. This, however, can be very risky. Besides, it’s not worth it, and you could potentially damage the battery even more than it already was. So, instead of doing that, report it to the company or get it replaced by a mechanic.

Signs of an overcharged battery

An essential part of this investigation is to find out whether your car battery overcharges. And for that, here are the most significant signs and symptoms to help you identify them as soon as possible:

Heated battery

Pay attention to your car engine temperature to detect battery overcharging early

Usually, when you touch your battery, it should be cool from the sides. So, if you start to notice that the walls are slowly getting warm, or maybe even hot, it is a prominent indication of overcharging. However, keep in mind that the battery will probably be warm after driving, which is pretty standard. So, you must give your vehicle about 30 minutes after turning off the engine so that it normalizes. Then, touch the battery and check the temperature.

Swollen battery

A terrible sight to see. But should you happen to see it, replace your battery immediately

Another very significant and common finding of an overcharged battery is its changing shape. If your battery has been overcharging for a long time, the sides will start to curve and swell up. These curvatures are a result of the over-produced gases that begin to accumulate inside the battery. They cause bulging and compromise the battery’s integrity. After a certain point, this change in shape will become very prominent and noticeable.

Smelly battery

When a battery overcharges, the acid starts to boil. And sometimes, this boiling gives off a very noticeable smell. So if you notice something smelling off inside or around your car, check the battery immediately.

Fluid level consistently dropping

If the fluid level consistently drops and you have to top it up very frequently, it is a sign of an overcharged battery. So, monitor the fluid levels very closely.

The Five-C tips to avoid overcharging

Luckily, overcharging can be avoided if you take appropriate preventive measures. The following are five ways to prevent overcharging, and you can remember them as the Five-C Tips.

The simple, easy to remember methods to keep your car battery from overcharging

Be Correct

Use a suitable charger for your battery and select the correct charging setting.

Be Cool

Make sure you regulate the room temperature of your garage. As mentioned earlier, temperatures too high can affect your battery. Suppose the heat accumulates around it; the chances of overcharging become significantly higher. Also, make sure the charging area is ventilated so that gases can escape.

Be Clever

Get a smart battery charger. Yes, it is slightly more expensive than typical chargers, but it will save your battery from overcharging. As a result, this investment will prolong the life of your battery and make sure you don’t have to spend frequent money on replacing it too often.

NOCO GENIUS1 1-Amp Fully-Automatic Smart Charger
NOCO GENIUS1 Fully-Automatic Smart Charger
NOCO Genius1 is ideal for general battery charging and battery maintenance tasks for the average car owner.

An excellent modern charger is the NOCO Genius 1 Smart Charger. It’s fully automatic, easy to use, and comes at a very reasonable price.

Be Calm

Choose low currents when charging your battery. It takes longer, but it significantly improves battery life.

Foval ‎BC01B-1 Automatic Trickle Charger
Foval Automatic Trickle Charger
A good trickle battery charger. Foval BC01B-1 is automatic, spark-proof, and comes with an 8-foot output cord.

A good trickle battery charger is one by Foval. It’s automatic, spark-proof, and comes with an 8-foot output cord. Other features, like a four-step charging program and a small size, also make it a crowd-favorite.

Be Clean

Lastly, keeping the battery clean can also protect it from overcharging. Battery maintainers can be lifesavers in this regard. These devices are specifically designed to supply limited electricity to the battery over inactive periods. This way, it protects the battery from being overcharged and extends its lifespan.

Battery Tender Junior 12V
Battery Tender Junior 12V
It is great for ATVs, motorcycles, and other vehicles. As a charger that specifies maintenance charging, this is perfect for those who want to keep their car battery healthy in the garage.

The Battery Tender Junior 12V is an incredible battery maintainer if you decide to get one. It is great for ATVs, motorcycles, and other vehicles.

Can you fix an overcharged battery?

In a majority of cases, you cannot repair overcharged batteries; you can only replace them. Even if you decide to pull the battery apart, take out the lead plates, and replace them, it might work temporarily. However, it is not a cost-effective solution. So, how do you “fix” an overcharged battery? You can recondition it. A popular method to restore overcharged car batteries is using distilled water and Epsom salt. Cleaning the car battery and using electrolytes to replenish it can potentially bring a dead battery back. Several re-conditioners are also available commercially. However, their success rates vary, and this method only works sometimes, not always!

Moreover, these re-conditioners can sometimes cost more than buying a brand new battery, so most people opt for the latter. On the other hand, investing in an expensive re-conditioner might not be a bad idea for those who have multiple car batteries and wish to recondition them.

How long should you charge your car battery?

Charging times can vary depending on the battery, charger, and other aspects. The most effective method to identify the accurate charging time for your car is to figure out the battery amp-hours and the charger amps. For example, let’s say your battery runs at 100 amp-hour, and your charger successfully supplies 2 Amperes. The resultant charging time would be 50 hours. You can also use battery charging time calculators online or refer to the manufacturing company for help.

Final Thought

In summary, choosing a good battery and a suitable battery charger can prolong the life of your battery and keep it safe from overcharging hazards. But if you don’t want to choose between a trickle charger, a smart charger, and a battery maintainer, you should go for the Schumacher SC1281. It is a versatile charger and maintainer with a wide compatibility range and exceptional features. And despite that, it is still effortless to use!

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