Enables the transmembrane transfer of an ion by a voltage-gated channel. An ion is an atom or group of atoms carrying an electric charge by virtue of having gained or lost one or more electrons. A voltage-gated channel is a channel whose open state is dependent on the voltage across the membrane in which it is embedded. [ http://openisbn.com/search.php?q=0815340729&isbn=1/ GOC:mtg_transport http://openisbn.com/search.php?q=0198506732&isbn=1/ ]