Replacing CMOS Battery

  • Thread starter Thread starter Jack Gillis
  • Start date Start date
J

Jack Gillis

My machine is roughly 6 years old and I expect to have to replace the CMOS
battery one of these days. Can someone tell me approximately how long I have
after I remove the old battery until I put the new one in without losing the
CMOS settings? On an old, old machine with the box type battery, I had a
few minutes to change it out. Is the same true with the current type?

Thank you very much.
 
Jack said:
My machine is roughly 6 years old and I expect to have to replace the CMOS
battery one of these days. Can someone tell me approximately how long I
have after I remove the old battery until I put the new one in without
losing the
CMOS settings? On an old, old machine with the box type battery, I had a
few minutes to change it out. Is the same true with the current type?

Thank you very much.
Click to expand...

Somewhere between seconds and days. Really. I recall a 486 board that
remained knowledgeable for a couple of days (!!) after the (coin-style)
battery was removed. And a P166 that lost its settings before my fumbling
fingers could swap in a replacement battery.

A capacitor stores the charge that's supposed to ride through a battery
change. Since the old battery is (probably) near its end-of-life, the
voltage on the capacitor at the beginning of the discharge period is
lower than fresh-battery level, so ride-through time is reduced a little.
A larger contributor to discharge time is the health of the electronics
in the BIOS and real-time clock. Old components may have higher than
normal leakage currents that bleed off the capacitor's charge too soon.
The capacitor itself may be the culprit.

So: no guarantees. You know what to do.
 
Jack said:
My machine is roughly 6 years old and I expect to have to replace the
CMOS battery one of these days. Can someone tell me approximately how
long I have after I remove the old battery until I put the new one in
without losing the CMOS settings? On an old, old machine with the
box type battery, I had a few minutes to change it out. Is the same
true with the current type?
Thank you very much.
Click to expand...

There are freeware programs available that will save the bios settings to
reloadable file on a hard drive or floppy disk.

You might want to post a similar message over in the alt.comp.freeware
newsgroup asking for directions to a program that does this for you.
Include the motherboard/Bios type your computer has.

Others have been known to use digital cameras to snap a picture of the
computer screen while displaying the various BIOS screens.
 
Jack said:
My machine is roughly 6 years old and I expect to have to replace the CMOS
battery one of these days. Can someone tell me approximately how long I have
after I remove the old battery until I put the new one in without losing the
CMOS settings? On an old, old machine with the box type battery, I had a
few minutes to change it out. Is the same true with the current type?

Thank you very much.
Click to expand...

in most cases it doesnt matter anyway, bios will detect a bad checksum
and load defaults.


NT
 
GlowingBlueMist said:
There are freeware programs available that will save the bios settings to
reloadable file on a hard drive or floppy disk.
Click to expand...

Some of the motherboard manufacturers have such utilities and you might
find one for your specific BIOS.


Richard.
 
Jack said:
Interesting. That would make sense and I will do it.

Thanks.
Click to expand...

No problem! It would make sense you'd think but then.... ;-)

One nice board manufacturer actually had screen shots of what it should
look like and I do hope you're one of the lucky ones.

Good luck.

Richard.
 
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