Some signs of a bad car battery are more obvious than others, such as the battery is dead. Batteries typically last around three or four years. Sometimes they won't last quite as long and sometimes they will last longer. It all depends on a multitude of factors such as the climate and how hard the vehicle is typically ran. When you are getting close to that three year mark, it is always important to have the battery checked on a continual bases to ensure that is is still functioning properly and that it isn't about to just quit on you. Batteries can best be tested with electronic testers. Most auto parts shops as well as maintenance shops have these and can easily and quickly test the battery for you. This will help to make sure that you won't be surprised one day when your vehicle refuses to turn on and will save you loads of trouble!