A battery-backed cache system with a pluggable battery module. The system includes a RAID controller and a cache. A back up power board is provided upon which a second power connector is provided and the two power connectors are connected. A socket assembly is mounted on the board and is connected to the second power connector. The socket assembly is a standard socket for use with PC Cards and includes a bulkhead adapter for mounting to a case wall with a slot of the socket assembly accessible through the case wall. A battery module is included having a body with dimensions corresponding to the slot. A battery is positioned within the body and a connection interface is provided in the battery module for mating with the socket assembly. The body and connection interface of the battery module comply with PCMCIA specifications for card bodies and interfaces.