Keyless locks like the C-series, M-Series, and 2900 series are entirely mechanical. That means the locks do not operate off of electricity, but rather use mechanical combination tumblers to lock and unlock doors. This makes for a secure, reliable lock that is completely unaffected by blackouts of large-scale power outages. However, E-series keyless locks, like the E930, do require a battery to operate. The reason for this is E-series locks can be accessed using an E-remote (sold separate from the lock).