Car batteries can and do explode. The causes are mainly a build up of gas produced by an over heating or overcharged battery. If the gases cannot escape and a spark is introduced into the mix, the battery will explode.
We mostly see this phenomenon with lead acid batteries when the battery is are being manually charged, or when the battery’s vent valves are blocked and the gas cannot escape. However, another reason for battery failure and explosions is when your alternator is faulty. The alternator should not charge your battery above 14.5 (optimal is between 13.9 to 14.2) this can excite the chemicals, causing the battery to overheat and swell. These condition can lead to your battery exploding in your car.
Always make sure that your alternator is charging at the correct rate. You can ensure this by visiting any battery shop that replaces car batteries. They should have a diagnostic tool on hand that can tell you whether your alternator needs attention.
The alternator does not necessarily need to be replaced if it is diagnosed as faulty. They can be serviced, regulators and diodes can be replaced to get them working properly. if the armature is damaged, then it cannot be repaired cost effectively. To service the alternator, find a local auto-electrician.