A bad alternator can lead to a number of problems with your car, battery included. If your alternator isn't working properly, it won't be able to recharge your battery as it's supposed to. This can cause your battery to work harder than usual, which in turn can make it overheat. In addition, a failing alternator can also cause your car to consume more fuel than usual, which can also lead to your battery overheating. If you notice that your car's battery is getting hot, it's important to have it checked out by a mechanic to see if your alternator is to blame.