A3000 sometimes needs the NVRAM SCSI settings tweaked in a certain way in order for a SCSI device to play along nicely in your chain. Losing NVRAM settings after powering off every time in this scenario is a huge pain in the @$$.
If your SCSI devices work OK with the default settings, then I guess there is no need to have a battery in an A3000, however default settings mean ASYNC/SCSI1 speeds, so if you want the NVRAM settings set to SYNC/SCSI2 speeds, you need a battery installed. :-)
