Adaptec 5805 won't spin down raid5 array. Suggestions as to why.

[Asposium]

In my WHS v1 I have a RAID5 array created on an Adaptec 5805. The array is not part of the storage pool.

In Adaptec Storage Manager the array is set to power down after inactivity
The drives are five Seagate LP 2TB, these drives are on the compatible list for the 5805
The drives are held within a Supermicro CSE-M35TQ, sideband is not connected from drive module to 5805
A BBU is added to the 5805, though ASM says the BBU has failed. Doh!
Motherboard is a Supermicro X8SIL-F
I have the latest version of ASM, 5805 firmware and driver

The array will not spin down
Changing array parameters on the array config has no affect
Read cache on/off, write cache on/off; no change

Strangely the CSE-M35TQ drive access LEDs stay continuously illuminated, going off occasionally when the array is in use.
Almost inferring there is constant access to the array (drives)

Does anyone have any ideas what I might check /change?
I don't know what else to try
The whole point of getting a 5805 and setting up a RAID5 array was to allow for spin-down when not in use