Avago Technologies 3ware 9650SE-12ML - Manual (Page 40)

Chapter 3. Installing the Battery Backup Unit
36 3ware 9650SE Serial ATA RAID Controller Installation Guide
3 Insert the battery power connector into the power receptacle on
the BBU.
Figure 31. Battery power connector inserted in power receptacle
The controller is now ready to install in your system.
Note: The battery will drain if it is plugged in and there is no
power to the unit. If the system will not be used right away,
wait to do this step until the system is ready for use.