Backup power architecture for rack system

A computing device (130-132) is associated with a circuit for sharing and distributing backup power. During normal operating conditions, a main bus bar (134) provides power to each computing device in a rack (110) via a main power bus (455) of the corresponding circuit (400). In the event of an AC power outage, the main power bus is deactivated and a backup power path (460) of the circuit is activated. Backup power is provided to the device from a battery (405) of the circuit via the backup power path. A shared power path (465) is also activated in the circuit such that backup power may be provided from the battery to the main bus bar. By providing backup power to the main bus bar, the other computing devices in the rack that do not have sufficient backup power may receive backup power from the main bus bar until AC power is restored.