Corroded battery terminals eventually lead to all sorts of trouble including hard starts and worn parts. You should check your terminals for corrosion every three or four months. If they are dirty, remove the negative cable first, then the positive cable. Cover the terminals with baking soda. Sprinkle enough water on it to moisten the baking soda. Use a battery terminal cleaner to get the corrosion off the terminals. Dry them with a shop rag and reinstall the cables. To help prevent corrosion, glue a penny about 1/16-inch away from the terminal. The copper in the penny discourages corrosion. Do not let the penny touch the terminal or the cable.