Why do car batteries explode?


Batteries are the most valuable part of cars. But why do car batteries explode? If you own a car, you should know that it’s pretty much useless without your car battery. Usually, your battery will serve you a long time if you take proper care of it. 


But in some cases, you would face a battery explosion. A car battery explosion can be fatal for both you and your car. Don’t panic about this. Your car battery won’t explode for no reason. 


Batteries, especially lead acid batteries, explode for various reasons. With proper attention and care, you can save your battery from exploding.  Stay with us as we’re going to explain why do car batteries explode.

What would cause a car battery to explode?

Battery explosions are not regular events that a car owner would likely face. The car battery explodes for various reasons and manufacturing defects. Sometimes, the explosion can happen without any previous glimpse. 


However, you should keep a clear idea of why do batteries explode. Here are some factors:

Chemical reaction

Lead-acid batteries are made of two major components. Lead plates and distilled sulfuric acid. A lead plate reacts with the acid. This chemical reaction produces electric power for your car.  A by-product, hydrogen gas vents out of the battery case during the charging process. 


Hydrogen gas is highly flammable. Direct contact with hydrogen can make a small fire, leading to an explosion. Explosion in one battery cell will create a chain reaction to other cells, and your whole battery is going to explode.

High temperature

Thermal runaway is one of the leading causes of a battery explosion. The battery can not bear high temperatures. When your battery overheats, it will break open the battery’s cells. 


A short circuit in your car’s electrical system can overload the battery’s pressure. This pressure will lead your battery to overheat. Besides, manufacturing defects can also create load to the battery cell. 


Connecting a battery charger too much longer will overheat your car battery in case of a lithium battery. This type of sealed battery also doesn’t have a safety vent, leading it to explode.

Leaking battery

Leaking batteries is another reason for car explosions. Lead batteries use sulfuric acid for charging and discharging. Both sulfuric acid and hydrogen are flammable. Sulfuric acid can leak through the battery case. 


Likewise, hydrogen or other gases can spread through the battery terminal. A short circuit near these gases or acids can cause a car battery explosion.

What can possibly go wrong?

Either way, your car can get damaged by a battery explosion. The essential part of your engine can get damaged by a blast.  It is harmful to you as well. The battery explosion sounds like a gunshot which can cause you hearing damage. Particles from an exploded battery can also harm you.

Why do car batteries leak?

You may have asked yourself can a leaking car battery explode? Well, it indeed can explode if it receives direct contact with fire. Let’s see how your car battery can leak:


  • Overcharging is one of the leading causes of battery leakage. A malfunctioning alternator does this overcharging during the charging process. Through overcharging, the gases from battery acid get out through the vents. A smart battery charger can prevent overcharging.
  • An old battery tends to leak the most. The older the battery gets, the parts of it become more vulnerable. 
  • Overfilled batteries can leak. Adding more than enough distilled water to battery cells can overflow the battery, and the sulfuric acid can leak through the terminals.
  • A crack in your battery pack leaks the acidic solution of your battery. Besides, cracked batteries can also leak gas through the battery terminal.
  • Extreme cold temperatures can freeze the liquid of the battery. This freezing solution needs more space. So, they keep pressurizing the battery cells, which leads to a crack.
  • High temperatures and overcharging can expand the lead plates of your battery pack. These expanded plates need more space to fit in, pushing the battery acid since they are liquid. 


Cars depend on a battery to function properly. Whether it’s an acid or lithium-ion battery, every battery can explode. But before exploding, they need to meet some requirements. 


In most cases, the explosion can be well prevented. Thermal runaway is the most common reason for a battery explosion. Besides, extreme temperatures can make your battery explode. A leakage on your car battery is also very concerning. 


Leakage means both gas and liquid leaking from your car. Your car battery contains hazardous gas, which is highly flammable. Likewise, the battery acid is also flammable. 


So, if these objects get a fire source, they would cause fire to the battery. Thus, the battery will explode, conducting damage beyond repair. However, manufacturing defects can also create explosions.


  • Can batteries explode when not in use?

This is a concerning question. Yes, your lead acid battery can explode when not in use. But don’t panic. Car batteries would leave some sign before they explode. If you maintain the battery too well, it may not ever explode in its service life. Sometimes, it doesn’t show any sign, though.


  • Can dead batteries explode?

A dead battery can indeed explode. An unused old battery may seem harmless and dead. Though, it can release harmful gases or leak sulfuric acid. So, if a dead battery can leak, it sure can explode by catching fire. Don’t throw a dead battery towards the fire.

  • Do batteries explode in the fire?

Yes, they do. It is obvious that car batteries have materials inside which are highly flammable. Statistically speaking, fire is one of the main reasons behind battery explosions. A lead-acid or lithium-ion battery will indeed explode in direct contact with fire.


  • What happens if you touch an exploded battery?

A battery contains acid and other flammable objects. If you touch an exploded battery without wearing gloves, it could give you several burns. You can face skin irritation, redness, and dead skin. Be careful about disposing of an exploded battery.

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