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Old April 10th 15, 07:00 PM posted to microsoft.public.windowsxp.hardware
VanguardLH[_2_]
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Posts: 10,881
Default Rechargeable CMOS/RTC Battery was a Bad Idea

wrote:

Hi,

Most PCs (laptops and desktops) have non-rechargeable CMOS/RTC
batteries, thank goodness.

I have two old laptops that used rechargeable CMOS batteries.

ISSUES WITH RECHARGEABLE CMOS BATTERY:

If you have a PC that contains a rechargeable CMOS battery, and
you do not use it often, the battery will run down to the point that CMOS
memory becomes corrupt, but not fully "wiped". When you use that
PC, the CMOS battery gets recharged. In doing so, some of the data
that changed in CMOS memory, will remain in the changed state.

I had this happen to me twice on two different PCs. The first time
on a HP laptop. The changed data prevented me from using the
laptop because it required a password during bootup. I had never
set this laptop for a bootup password. The part of CMOS memory
that contains password info became corrupted. Solution: I removed the
CMOS battery and waited a few hours. Afterwards I was able to
bootup again without a password prompt.

The second time this happened on a Gateway Solo 3350 laptop.
This time I noticed when I plugged in a USB flash drive, access
to that flash drive was very slow. Much slower than normal even though
this laptop has a 1.0 USB port. Solution: The next time I booted
up this laptop, I pressed F2 to enter settings and restored default
settings. Afterwards the USB flash drive access speed was back
to normal.


Found this on searching for the battery in the Gateway Solo 3350:

http://www.bios-battery.com/biosbatt...ttery_6951.htm

Ni-MH type. Yep, a rechargeable battery. Couldn't search on the CMOS
battery for the "HP laptop" since that obviously gives no details, like
a model number.

Of course, even an old and weak alkaline CMOS battery will case
corruption of CMOS settings. It's not the chemistry per se that is the
problem. It's letting the CMOS battery get too weak. I replace
alkaline coin cells at about 3-4 years. Since they are also chemical,
NiMH batteries are not eternal so they have to get replaced, too.

http://www.batterystuff.com/kb/artic...h-battery.html

NiMH will self-discharge. That means not using them will eventually
leave dead a once fully-charged battery. The low load on a CMOS battery
is not a good application for a NiMH battery, and equally so for any
applicable where idle storage (non-use) is a consideration.

Were these laptops bought new or used by you?
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