A connector apparatus for a battery includes: a connector block assembly mounted in a battery case of a battery assembly, and including first and second electrodes facing the interior of the battery case; and a header assembly releasably mounted to the connector block assembly, and including first and second terminals connected to the first and second electrodes, respectively. The header assembly is exposed to the exterior of the battery case and the first and second terminals are electrically connected to terminals of a mating connector, respectively.