Why does your battery smell like rotten eggs?

If an automobile battery is in normal condition, there should be very little smell from it. The one smell that you should be aware of is the smell of rotten eggs, which indicates severe and dangerous problems with the battery. Once a battery begins to smell like rotten eggs, it cannot be saved, but must be immediately replaced. Please be aware that rotten-egg batteries can explode. Rotten-egg batteries are frequently much hotter than normal batteries would be, and the hot rotten-egg batteries are the most dangerous. The most common cause of rotten-egg batteries is an alternator which constantly overcharges, so the alternator should usually be replaced along with the battery.