What Can Happen if a Car Battery Explodes?

Written by jody l. campbell
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Car batteries use a chemical reaction to produce electricity. Lead plates are lined up in a series and sectioned by conductive metal separators. There is one positive and one negative plate per chamber. Each chamber is then immersed in a distilled water and sulphuric acid mixture to cover the plates. Lead oxide is also added to the chemical mix to create a electrical reaction. When an input or output charge is placed on a battery, the internal combination of lead plates and chemicals creates a small amount of hydrogen gasses. Hydrogen combined with oxygen in the air is flammable. Add to this a spark created by the electrical demand on the battery and you have all the ingredients for an explosion. While exploding car batteries are not everyday occurrences, they do happen more often than people realise, and most often occur due to human error. Crossing jump-start cables or battery chargers incorrectly are a leading cause of battery explosions. Another cause can be connecting the cables directly to each battery and creating a spark from the negative terminal. The spark ignites the concentrated gasses lingering around the outside of the battery casing, which in turn vaporise instantly and find their way inside the battery. The pressure is too much for the plastic housing of the battery, which then bursts, sending plastic and lead shrapnel outward with a lethal spray of sulphuric acid.
A battery doesn't always explode just when being jump-started or charged. There are cases where they suddenly explode from their installed position. The spark created is the ignition switch being turned on to start the car, but the battery has built up internal pressure. The pressure has created an external emission of gasses trapped inside the compartment, under the hood or wherever the battery is installed. The battery, in this case, is defective, but there could be other underlying reasons. For example, a faulty alternator not functioning properly could be putting out too many input volts back into the battery, creating an overcharging of the battery. The battery casing may swell and perhaps leak small amounts of the acid/water mix. But most drivers don't think to inspect their batteries until it's not working anymore (or until it explodes!).

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Explosion Effects

Battery explosions can cause severe injury and can even be fatal, depending on where you are during the explosion. Because most explosions occur during a jump start or battery charging procedure, most people find themselves directly in the line of fire. Maiming from the polypropylene plastic housing, lead and metal plates, and lead external terminals can occur as these become dangerous projectiles from the explosion. The sulphuric acid spray is another nasty effect from an exploding battery. Sulphuric acid burns almost anything it touches. Eyes are susceptible to injury without proper safety glasses.


While you can never guarantee that a car battery will not explode, you can take precautions to minimise any potential injuries. Inspecting the car battery and electrical system is the best place to start. Make sure that the battery terminals are clean and free from corrosion and that the battery housing is not swollen. Know how to jump start a car battery correctly (see Resources). While you may not be able to control the gasses emitted from a battery, you can connect the cables correctly and minimise sparks. Purchase safety gear to wear when handling car batteries. Safety glasses that wrap around your eyes are better than safety glasses that just shield your eyes. Full face shield masks may seem a little extreme in the unlikely event of a car battery explosion, but considering the consequences, you can never be too careful--and some of these shields cover your face and neck. Safety gloves and long sleeves will protect your skin from the sulphuric acid spray.

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