Hi!

I've always wondered why the batteries in macs run down so quickly. I
rarely see a PC newer than 10 years old with a bad battery, but I
consistently see 3-5 year old macs with totally dead clock batteries.

Yep, I've seen the same thing here. I have a number of old Macs (6100,
6300, LC, 9600, SE/30) that still keep decent time on the
factory-installed batteries. Some of these have gotten to the point
where the machines need to be powered up somewhat often to keep the
settings intact.

By compare I have many a G3 CRT-type iMac around (the 2001 models,
350~500MHz) and almost all of them have had to have their batteries
replaced.

Looking at things I can see one difference. Most PCs new and old power
their CMOS RAM chips from the power supply when they're running. A
great many ATX systems seem to keep the CMOS RAM and clock running from
the ATX standby supply as long as it is running. Some older PCs also
have NiCad or NiMH batteries onboard along with the circuitry to charge
them when powered up.

I've investigated the Macintosh a little bit and it looks like the
clock/NVRAM battery is constantly pulled upon, even when the computer
is on. This could also shorten battery life.

William