Time and Date
The only purpose of the on-board battery is to keep the clock going.
A sure sign of a dead battery is when you see "PRESS POWER AGAIN TO CLEAN" when you turn on the printer.
Essentially, the printer doesn't know when it was last cleaned, and thus it will initiate a normal cleaning before regular operations.
On most Roland mainboards you will find an easily replaceable 2032 watch battery in a standard holder.
The latest revision service record for the SJ-1045 shows the the 2032 battery "scratched off" the parts list.
I've never seen a SJ-1045 mainboard... is your battery non-replaceable?
~E
Does anyone know what the backup battery is for, and what happens if it doesn't work anymore?