How long will CMOS battery hold a charge

[Jim]

I'm sure this varies but if a PC were turned off for 3 months should it be
expected that the machine will lose it's time or not? I had 50+ systems in
storage. A few of them lost the time and others did not. I just went ahead
and replaced one of the batteries but am wondering whether they just
completely discharged and will charge back up now that they are plugged in.

Thanks.

 

[Mike Walsh]

The CMOS batteries I have seen are not rechargeable.

I'm sure this varies but if a PC were turned off for 3 months should it be
expected that the machine will lose it's time or not? I had 50+ systems in
storage. A few of them lost the time and others did not. I just went ahead
and replaced one of the batteries but am wondering whether they just
completely discharged and will charge back up now that they are plugged in.

Thanks.

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Mike Walsh
West Palm Beach, Florida, U.S.A.

 

[philo]

I'm sure this varies but if a PC were turned off for 3 months should it be
expected that the machine will lose it's time or not? I had 50+ systems in
storage. A few of them lost the time and others did not. I just went ahead
and replaced one of the batteries but am wondering whether they just
completely discharged and will charge back up now that they are plugged in.

Thanks.

a good cmos battert should hold your settings for years...
if not..just replace it..

 

[Shep©]

I'm sure this varies but if a PC were turned off for 3 months should it be
expected that the machine will lose it's time or not? I had 50+ systems in
storage. A few of them lost the time and others did not. I just went ahead
and replaced one of the batteries but am wondering whether they just
completely discharged and will charge back up now that they are plugged in.

Thanks.

Depends on the batteries.All have variables and all modern CMOS
batteries are to some extent re-chargable as they have a residual
current applied through them on ATX powered systems.
I have re-charged them successfully before(ni-cad versions and
lithium).
HTH



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[kony]

I'm sure this varies but if a PC were turned off for 3 months should it be
expected that the machine will lose it's time or not? I had 50+ systems in
storage. A few of them lost the time and others did not. I just went ahead
and replaced one of the batteries but am wondering whether they just
completely discharged and will charge back up now that they are plugged in.

Thanks.

Standard round button-cell type are not "meant" to be
rechargeable, when new (if a decent brand) they should last
several years. By the time a battery makes it's way to you in a
motherboard it may not be so new anymore, or could be cheap/poor
brand, so it might be low after sitting around.

Also if motherboard's clock is off (natural variations in
crystal) it's time will be inaccurate anyway, regardless of state
of battery. If it's important to be able to store them for
months then find a source of fresh batteries and replace them all
on a regular schedule so you'll know the age of all batteries and
can plan this replacement interval.

 

[ProfGene]

When they are too low to keep the time or hold the bios info they need to be
replaced. Usually newer MBs have a warning that the battery is low. I have
never heard of rechargeable ones but they last between 2 and 5 years.