[GTALUG] war story: CMOS battery AKA Real Time Clock (RTC) battery in a notebook

[Don Tai]

486x wow. 29 year old battery, that's a battery a bunny could really cheer
for. Most of my 20+ year old desktop PCs all arrive with dead batteries.
Thankfully they are easy to change.

On Fri, 21 Oct 2022 at 22:15, Lennart Sorensen via talk <talk at gtalug.org>
wrote:

> On Wed, Oct 19, 2022 at 07:58:04PM -0400, D. Hugh Redelmeier via talk
> wrote:
> > Almost all PCs have settings that they want to keep while the computer
> is
> > off or even unplugged.  Ones that they don't want to keep on disk.
> Things
> > you set up from the firmware setup screen.
> >
> > Furthermore, they have a realtime clock that runs when the machine is
> > turned off or unplugged.
> >
> > These are all powered by a lithium coin cell.
> >
> > Eventually, that battery runs down and you have to replace it.  Five or
> > ten years of lifetime seems normal.
> >
> > When it runs down, the computer will forget the date, time, and all its
> > setting when it is turned off.  This is annoying: every time you start
> up
> > you have to fill in the time and other settings.
> >
> > Luckily, for most computers it is easy to replace: it is in a socket in
> > the motherboard.  The battery can be sourced from Dollarama or Amazon
> for
> > a buck or two.  Just get the size right.
> >
> > For (some? all?) notebooks the coin cell battery isn't used if there is
> a
> > charge in the main battery.  So you may not notice that the coin cell
> > battery is failing.
> >
> > I flattened my notebook's main battery somehow (left it sleeping for a
> > week?).  When I powered it on, it had no idea of the time nor what to
> > boot.
> >
> > Upon investigation, I find that I have to completely disassemble my
> > computer to replace the battery!  They placed it on the top of the main
> > board whereas access is to the bottom.  If you care, you can read page
> 50
> > of
> > <https://dl.dell.com/topicspdf/xps-15-9560-laptop_setup-guide_en-us.pdf>
>
> Sheesh that's dumb.  Of course I had to disassemble my wife's compaq
> laptop many times years ago to resolder the power connector that kept
> breaking off the board.  Terrible crap.
>
> > It looks as if I will need some new thermal grease since I have to
> remove
> > the heat sink from the processor.  And the coin cell assembly is not
> > generic -- no Dollarama battery.
> > <
> https://www.amazon.ca/LeFix-Replacement-Battery-Connector-Precision/dp/B082G35D4R/
> >
>
> I was recently playing around with my 486 (from 1993).  Much to my
> surprise the CR2032 is still keeping the settings just fine.  Says Sony
> and made in japan on the battery.  I guess they made good batteries.
> Good thing it uses one of those rather than those horrible varta batteries
> that leaked all over the place that were common in the 1980s.  I am
> impressed at the battery still working after 29 years.
>
> --
> Len Sorensen
> ---
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