CMOS Battery Test in XP

[Jack Gillis]

Is there a way in XP to test the state of the CMOS battery? Or, how about a
utility that will do it.

I am trying to help my daughter in another town fix her machine that
exhibits the symptoms of lost CMOS data. Would like not to have to ask her
to remove and replace the battery or reset the BIOS to factory defaults if
possible.

Thank you.

 

[Lil' Dave]

Should be a hair over 3 volts with an accurate voltmeter, nothing else
touching the battery including fingers.

A way to verify if the cmos is retaining user entry data, is to modify it.
For example, disable com port 1. Save this change in the bios setup.
Unplug the PC for about 10 minutes or more from the AC outlet on the wall.
Plug it back in, turn on the PC, and immediately enter the bios setup and
verify if the change was retained.

Don't know of any PCs with an onboard voltage sensor for the CMOS battery,
even though it makes sense to have this for the long term. Which is why, I
guess. They're not thinking about long term use.

 

[Ron Sommer]

You don't mention what the symptoms are.
Loose power or data cables have some of the same symptoms.

Is the time correct?
Is the time off after the computer has been off for awhile?
Does the time stay correct if the computer is running?

 

[Malke]

Is there a way in XP to test the state of the CMOS battery? Or, how
about a utility that will do it.

I am trying to help my daughter in another town fix her machine that
exhibits the symptoms of lost CMOS data. Would like not to have to
ask her
to remove and replace the battery or reset the BIOS to factory
defaults if possible.

Thank you.

No. A motherboard battery is easy to replace and costs around $3-4 usd.
If your daughter can't do this herself, then have her take the machine
to a local professional. This will not cost much and it is a really bad
idea to have a novice messing around in their BIOS being directed by
someone over the telephone.

Malke

 

[Jack Gillis]

Thank you.

I don't think I want my daughter poking around the inside with a voltmeter
.

I have had her modify some BIOS settings and the didn't take at the next
boot from a long power down so that pretty well points to the battery I
think. The machine is about 5 to 7 years old.

It seems I remember, back in my DOS and OS2 days that I was able to check
the battery with the machine running but that was long ago and I don't
really trust my memory at this point.

Thanks again.

Should be a hair over 3 volts with an accurate voltmeter, nothing else
touching the battery including fingers.

A way to verify if the cmos is retaining user entry data, is to modify it.
For example, disable com port 1. Save this change in the bios setup.
Unplug the PC for about 10 minutes or more from the AC outlet on the wall.
Plug it back in, turn on the PC, and immediately enter the bios setup and
verify if the change was retained.

Don't know of any PCs with an onboard voltage sensor for the CMOS battery,
even though it makes sense to have this for the long term. Which is why,
I
guess. They're not thinking about long term use.

Years ago, I went into a local retail computer store to by a replacement
battery and the young man said he had never heard of such a thing and the
desktop computers they sold there didn't use batteries. I thanked him, left
and then ordered one on line.

 

[Jack Gillis]

No. A motherboard battery is easy to replace and costs around $3-4 usd.
If your daughter can't do this herself, then have her take the machine
to a local professional. This will not cost much and it is a really bad
idea to have a novice messing around in their BIOS being directed by
someone over the telephone.

Malke

You got that right!

Thanks.

 

[Yves Leclerc]

I always find that if the data/time settings do not retain, or correctly
advance, the info correctly this "usually" means that the battery is slowly
failing.

 

[Plato]

Is there a way in XP to test the state of the CMOS battery? Or, how about a
utility that will do it.

Use a voltmeter. But, a voltmeter will cost around $20 so its best, if
you thing the battery is gone, to just spend $4 to replace it.

 

[Ken Blake]

In

I always find that if the data/time settings do not retain, or
correctly advance, the info correctly this "usually" means that
the
battery is slowly failing.

Not quite.



Before anyone whose clock doesn't keep correct time assumes it's
a failing battery and rushes out to buy a new one, he should
first take note of whether he is losing time while the computer
is running or while it's powered off. If it's while powered off,
the problem *is* very likely the battery. But if it's while
running, it can *not* be the battery, because the battery isn't
used while the computer is running.

 

[Spikey]

the problem *is* very likely the battery.

I think that confirms mine needs changing - it is 6+ yrs old!!

As a matter of interest, how long would you reasonable expect them to last??

If you always switch off an unused computer ( on/off once in 24hr) does it
have a bigger drain on the battery than if you leave it in hibernate or
standby??

 

[Ken Blake]

In

while
powered off,


I think that confirms mine needs changing - it is 6+ yrs old!!

That is a long time for a battery to last.

As a matter of interest, how long would you reasonable expect
them to
last??

I find great variability, and wouldn't try to quote anything like
an average. For one thing, you usually have no idea how old the
battery is when you get the computer.

If you always switch off an unused computer ( on/off once in
24hr)
does it have a bigger drain on the battery than if you leave it
in
hibernate or standby??

I'm not an electrical engineer and I don't know for sure, but I
would *think* that being powered off saves the battery rather
than draining it faster. I'll defer to someone else who knows
more about this than I do, however.

 

[Spikey]

That is a long time for a battery to last.

I do seems to have got good service from it. I had thought ( until
enlightened by eldest) that it was a rechargeable of some sort.

I'm not an electrical engineer and I don't know for sure, but I would
*think* that being powered off saves the battery rather than draining it
faster. I'll defer to someone else who knows more about this than I do,
however.

I'll watch this space then. Many thanks for your reply.

)

 

[Code-Curious Mom]

I'm certainly not an electrical engineer either, lol, but from what I've
read on usenet, my understanding is that the CMOS battery is only used when
the machine is completely disconnected from power, as in unplugged or
switched off at a power strip. Thus unplugging it will cause the CMOS
battery to drain quicker. Keep in mind that they generally last a long time
and often the computer is obsolete before they go bad.

 

[Malke]

I do seems to have got good service from it. I had thought ( until
enlightened by eldest) that it was a rechargeable of some sort.



I'll watch this space then. Many thanks for your reply.

)

Actually, it is when the computer is powered off that the motherboard
battery is active. That is the reason for its existence - to save the
CMOS settings when there is no electrical power going to the
motherboard.

I've had amazing batteries that lasted forever and some that died
quickly. I've never bothered replacing a motherboard battery as part of
the "computer health regimen". If you want to do it ahead of time,
fine. Otherwise wait until you get an error message in the POST about
settings not being saved or the time is off after the computer has been
off. It never hurts to have a few extra batteries on the shelf. As was
said earlier, they are only around $4 usd.

Malke

 

[Ron Sommer]

In


That is a long time for a battery to last.




I find great variability, and wouldn't try to quote anything like an
average. For one thing, you usually have no idea how old the battery is
when you get the computer.




I'm not an electrical engineer and I don't know for sure, but I would
*think* that being powered off saves the battery rather than draining it
faster. I'll defer to someone else who knows more about this than I do,
however.

The CMOS battery is used when the computer is off.
The amount of battery power consumed is small.
The life of the battery will be several years even if the computer is never
started.

 

[Lil' Dave]

I think that confirms mine needs changing - it is 6+ yrs old!!

As a matter of interest, how long would you reasonable expect them to last??

If you always switch off an unused computer ( on/off once in 24hr) does it
have a bigger drain on the battery than if you leave it in hibernate or
standby??

Lithium battery life varies widely. May last a year, may last 10 years.
Rechargable batteries were designed to be depleted to a certain extent, then
recharged. A rough example is the type in digital camcorders or similar.
Once a certain degree of discharge has been repeatably attained, they cannot
fully charge. A complete discharge, followed by a full recharge may fix it,
but not always. Maintaining a full charge, leaving it on the charger all
the time, is not recommended either, it internally degrades the battery.
So, if you throw all this information into a related cmos battery; it would
make sense to turn off the PC on a regular basis to allow some discharge to
occur. Standby or hibernate in XP does not constitute turning off the PC
even though MS implies that in their turn off options, as the onboard power
supply is still running charging the cmos battery. Follow me?

 

[Ron Sommer]

When the computer is turned off, the CMOS battery is used.
When in hibernate or standby, the battery is not used.

 

[Plato]

I'm certainly not an electrical engineer either, lol, but from what I've
read on usenet, my understanding is that the CMOS battery is only used when
the machine is completely disconnected from power, as in unplugged or
switched off at a power strip. Thus unplugging it will cause the CMOS
battery to drain quicker. Keep in mind that they generally last a long time
and often the computer is obsolete before they go bad.

Yes cmos batteries seem to last longer these days. Perhaps its because
windows takes so long to boot people are leaving their pcs on. Unlike
the dos days when it only took a few seconds to boot.

 

[Spikey]

It never hurts to have a few extra batteries on the shelf. As was

said earlier, they are only around $4 usd.

Its so frustrating that everything costs double over here in the UK!!!

 

[Plato]

It never hurts to have a few extra batteries on the shelf. As was
Its so frustrating that everything costs double over here in the UK!!!

Except for breakfast. I like breakfast so much in the London area, in
those small places on the sidestreets, that I want to go back.