Batteries transform chemical energy into electrical energy. Electrons flow through a(n) circuit attached to the battery. A dry-cell battery is a type of primary cell. This is because it can only be used once. After they run out, dead dry-cell batteries must be removed from equipment immediately. Otherwise, a chemical could eat its way through the sealed zinc can. Secondary batteries can be recharged. This process uses an outside electricity source to force electrons to flow backward through the battery. The chemical reactions that normally make the battery produce electricity are reversed. Car batteries are secondary batteries.