You should never let anything come between your car and a good battery connection. If you want the day to come to a grinding halt in a hurry, driving with corroded battery posts is the way to do it. It takes only a millimeter of crunchy white residue to keep your car from starting.
Your car's battery is the starting point (no pun intended) for every system it uses. This is because it's used to start the car! The conditions surrounding your battery posts create the perfect breeding ground for nasty corrosion, which will appear as white, crusty residue around the battery posts. As the corrosion builds up, it becomes harder for your car to connect strongly with the battery. That's why we need to get rid of it.
There are scores of products out there to clean your battery and help keep it that way. Here you'll find a couple of them, but the idea is pretty much the same regardless of your method - get 'em clean.