Richard,
If he has an old computer, like the one I just gave away, it has no software off function, or "partial off" function, just a big mother rocker or push button switch on the front. "Off" is "Off" - no juice getting to the power supply or mobo, even if still plugged in at the wall, so when it's off it needs its CMOS battery.
I'm glad I've moved on ...
AA