I found it interesting that I found on page 106 in the Toshiba Satellite M40/M45 User's Guide, they state:
"The RTC battery powers the RTC memory that stores your system configuration settings and the current time and date information. It maintains this information for up to a month while the computer is turned off.
TECHNICAL NOTE: The RTC battery does not charge while the computer is turned off, even when AC power is attached. The RTC battery charges when the computer is powered on."
So the CMOS battery is self rechargeable? I just tried to turn on an M45-S169 laptop that was powered off for over a year, and the time/date was reset. I was thinking I'd have to replace the CMOS battery. After searching what it takes to do so I had second thoughts. But reading the manual was good news.
Search Google for: TECHNICAL NOTE The RTC battery does not charge
and there's a lot of results for other models of theirs.