How do batteries go dead if you are only sending current through them?
As current flows through a battery, from its negative terminal to its positive terminal, the battery does work on that current. It must pull positive charges away from the negatively charged negative terminal and push them toward the positively charged positive terminal. An alkaline battery needs 1.5 joules of energy to transfer each coulomb of positive charge in this manner. This transfer operation consumes the stored chemical potential energy inside the battery and eventually causes the battery to go dead. Just because you don’t see anything moving in the wires or in the battery doesn’t mean that something substantial isn’t occurring inside the battery—it undergoes electrochemical reactions whenever current is flowing through it.