IBM 69Y2926 Battery Cache is a backup battery module for the cache in IBM storage systems. It is listed as a replacement part for the DS3500 storage subsystem and EXP3500 storage enclosure family.
The battery fits in a storage controller and connects at its battery connector. During controller replacement, IBM’s service guide describes removing the battery unit from the old controller and installing it in the replacement, allowing the existing cache battery module to be transferred as part of that service procedure.
This is a controller cache battery module, distinct from the separate cache backup flash memory device.