Hot swapping CMOS batteries

[Peabody]

The standard instructions for changing out a desktop CMOS battery say you
should turn everything off and unplug the power cord. But I wonder if guys
who do this kind of stuff for a living don't hot swap the batteries with the
power on, or at least leave the power cord plugged in so the always-on 5V
supply provide power to the CMOS. That should prevent losing the contents of
the CMOS memory, including the TOD and the BIOS settings.

On a related question, I also have an old Toshiba Satellite L35 laptop that
I'd like to replace the CMOS battery on. It looks like I would have to take
the entire laptop apart so I can remove the motherboard, turn it over, and
replace the battery. Or, it turns out I can see the battery through the side
of the wireless compartment, and I should be able the cut a window in the
bottom of the case through which I could switch out the battery, then hot-
glue the window back in place. Is there any reason not to do it that way?
It's a lot more likely the laptop would survive the latter procedure.

[N_Cook]

Yes, I added a tag to the battery line, so I could easily swap the
battery , while jumpering in an external battery supply with a bit of a
dropper resistor

[mike]

Problem with doing anything with the power on is the unexpected.
Suggest you at least put some tape on the battery so you have
something to hold onto while you try to pry it out.

The other issue is the reset. Assuming you have a reason/symptom
to change the battery, it may be that the state of the memory is
compromised. I've had laptops with rechargeable CMOS batteries
that wouldn't run after I manually recharged them.
Removing/waiting/replacing the charged battery fixed it.

[Benderthe.evilrobot]

"Peabody" <waybackNO...@yahoo.com> wrote in message
news:20170111-0...@Peabody.ssl.astraweb.com...

> The standard instructions for changing out a desktop CMOS battery say you
> should turn everything off and unplug the power cord. But I wonder if
> guys
> who do this kind of stuff for a living don't hot swap the batteries with
> the
> power on, or at least leave the power cord plugged in so the always-on 5V
> supply provide power to the CMOS. That should prevent losing the contents
> of
> the CMOS memory, including the TOD and the BIOS settings.

There doesn't seem to be any logic to hot swapping a CMOS battery - many
motherboards have a jumper header to discharge the smoothing caps on the RTC
rail - it holds for at least a few minutes with the battery out.

Usually you don't even know it needs replacing till boot up reports a CMOS
checksum error - then I just fit a new battery and load optimum defaults.
There's only a couple of values I need to set manually.

[N_Cook]

The clue for me , is progressively worsening internal clock timekeeping.
Incidently , hot soldering a tag, remove the power from the soldering
iron before soldering , while still hot

[John Robertson]

Propane soldering irons work very well for this sort of thing -
ungrounded...

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
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(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
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"Old pinballers never die, they just flip out."

[Michael Black]

Wasn't that one reason for promoting the cordless soldering iron sold in
the seventies? I forget who made it, Radio Shack sold it under their
name also, but there was something about an "iso-tip". Since it didn't
plug in, you could use it where other irons might not be safe.

Michael

[Ralph Mowery]

In article <alpine.LNX.2.02.1...@darkstar.example.org>,
et...@ncf.ca says...

>
>
> > Propane soldering irons work very well for this sort of thing -
> > ungrounded...
> >
> Wasn't that one reason for promoting the cordless soldering iron sold in
> the seventies? I forget who made it, Radio Shack sold it under their
> name also, but there was something about an "iso-tip". Since it didn't
> plug in, you could use it where other irons might not be safe.
>
> Michael

Wal made them, maybe still do. They started out making battery powered
shavers. Maybe that was just another product to that line. The main
usage was for places that you did not or could not get a cord to. I had
one and used it because it was quick heating when I only wanted to make
one or two quick connections. Did not have to wait for the wall powered
unit to heat up. Now I have an iron that heats up in just a few
seconds.

[Benderthe.evilrobot]

"N_Cook" <div...@tcp.co.uk> wrote in message
news:o56624$li0$1...@dont-email.me...

IME: The time and date data usually survives - but it surprises me every
once in a while.

[Benderthe.evilrobot]

"John Robertson" <sp...@flippers.com> wrote in message
news:wPGdnb7WJrWnserF...@giganews.com...

Even so - I wouldn't bother hot swapping a soldered in CMOS battery.

[Michael A. Terrell]

Michael Black wrote:

>
> Wasn't that one reason for promoting the cordless soldering iron sold > in the seventies? I forget who made it, Radio Shack sold it under their name also, but there was something about an "iso-tip". Since it
> didn't plug in, you could use it where other irons might not be safe.

Wahl made, and still makes them.


--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

[Michael Black]

On Sat, 14 Jan 2017, Michael A. Terrell wrote:

> Michael Black wrote:
>
>>
>> Wasn't that one reason for promoting the cordless soldering iron sold > in
>> the seventies? I forget who made it, Radio Shack sold it under their name
>> also, but there was something about an "iso-tip". Since it
> > didn't plug in, you could use it where other irons might not be safe.
>
>
> Wahl made, and still makes them.
>

Thanks. I suddenly couldn't remember who made it.

Michael

[Michael A. Terrell]

You're welcome. :)