Mazak QuickTurn 10N, battery location

Hello all,

I am getting the "23 NMI Battery Alarm". In the past (and only in the last year or so) I would only see this if the machine had been down for quite a long while, like when the spindle was away getting rebuilt. But it always charged back up and never lost the programs or parameters. But now it does not seem to want to charge no matter how long the machine is powered up. Before it completely dies and dumps the parameters, it would be prudent to replace it. As far as I know it is the original 1988 battery! Trouble is, I cannot find the darn thing. I cannot find any mention of the battery in the maintenance book, either location or replacement procedure. Nor in the electric schematics book. I had a look through the electrical cabinet and have yet to find anything that looks like a battery or battery pack. Most recently I pulled the cover off the CPU and have been looking behind that, but unless it is buried towards the back edge of a board (and I do not want to be hasty pulling those out unless I am sure) I cannot see it.

Can anyone tell me where it is located?

Specs:
1988
Mazak QuickTurn 10N
T3 Mazatrol controller (live milling)
16 station tool belt.

Thanks,
Doug