9 Mar
2011
9 Mar
'11
7:37 p.m.
One of my computers is a 486SX. The soldered-in battery is apparently
failing; after a period of power-off, the time is badly off at re-start. The
date and BIOS are so far unaffected.
The motherboard has provision for an off-board battery. I am thinking of
using a socketed CR2032 battery which I believe is rated at 3 volts. The
manual for the computer describes the off-board battery as 3.6 volts.
Is it asking for trouble to use a 3v rather than a 3.6v battery? If so,
where are the 3.6v batteries available?
Thanks,
Kurt
9 Mar
9 Mar
7:47 p.m.
The CR2032's are 3v, but its of no huge difference, generally the drop
off voltage for the memory retaining will be around 1.8-2.0v's so you
should be totally fine, what is on the board or was on the board
previously? Volts are important but the millamps to allow it to
last longer are actually more important, you may want to consider
putting them in parallel if what was there is a higher ma amount
Also, check and see if what was there is no a rechargeable cell because
if so, you'll have to put a diode into the circuit to keep the power
from backwashing into the battery and damaging it, LiON
button batteries
like the CR series are not rechargeable and youll damage it if the
current battery is setup to be a rechargeable....
Hollandia at ccountry.net wrote:
One of my computers is a 486SX. The soldered-in
battery is apparently
failing; after a period of power-off, the time is badly off at re-start. The
date and BIOS are so far unaffected.
The motherboard has provision for an off-board battery. I am thinking of
using a socketed CR2032 battery which I believe is rated at 3 volts. The
manual for the computer describes the off-board battery as 3.6 volts.
Is it asking for trouble to use a 3v rather than a 3.6v battery? If so,
where are the 3.6v batteries available?
Thanks,
Kurt
10 Mar
10 Mar
5:47 a.m.
--- On Wed, 3/9/11, Hollandia at ccountry.net <Hollandia at ccountry.net> wrote:
The motherboard has provision for an off-board
battery. I
am thinking of
using a socketed CR2032 battery which I believe is rated at
3 volts. The
manual for the computer describes the off-board battery as
3.6 volts.
Is it asking for trouble to use a 3v rather than a 3.6v
battery? If so,
where are the 3.6v batteries available?
I've used CR2032's as replacements before on similar machines, it's worked
fine.
Just remember - whatever you do, REMOVE the old soldered in battery from the board.
It'll leak and corrode through traces. I've desoldered them and installed CR2032
sockets in their place with good success. But if you don't want to go to the trouble,
you can just clip off the old battery.
-Ian
7:19 a.m.
On 10/03/11 13:47, Mr Ian Primus wrote:
I've used CR2032's as replacements before on
similar machines, it's
worked fine.
Just remember - whatever you do, REMOVE the old soldered in battery
from the board. It'll leak and corrode through traces.
I'll second this with one addition -- the electrolyte in NiCd batteries
also eats some types of glass-fibre PCB substrate. What this means is
that you not only lose the tracks, but the board itself basically turns
to dust as well...
Get a pair of wire cutters (the "flush cutting" kind ideally) and cut
the thing off the board, then desolder the stubs and clean the PCB with
vinegar, then water (ideally deionised or distilled), then isopropyl or
a standard PCB cleaner / flux remover.
This works thusly:
1. The vinegar neutralises the alkaline electrolyte (usually
potassium hydroxide)
2. The water gets rid of the vinegar and any water-soluble dirt
3. The IPA removes any alcohol-soluble dirt (e.g. solder flux) and
helps the water evaporate more quickly.
I've
desoldered them and installed CR2032 sockets in their place with good
success. But if you don't want to go to the trouble, you can just
clip off the old battery.
Usually there's a 4-pin header which allows you to install an external
battery once you've removed the board-mounted one. These are usually
designed to take 4.5V alkaline batteries and generally have a diode and
series limiting resistor on the PCB.
The Acorn BBC Micro (actually the Master series) used three AAs in a
shrink-wrapped package shoved in the gap between the keyboard and the
case... IIRC there was a 120-ohm resistor and a 1N4001 diode inside the
package -- the resistor limits current if the diode fails.
Earlier machines had a battery holder by the side of the motherboard.
You could remove the old batteries and replace them with off-the-shelf
AAs. Unfortunately the battery holder sits in the Tube co-processor bay,
so you can't install an internal co-processor without replacing the
battery pack with the shrink-wrap version. There's nothing stopping you
installing an external cheese-wedge co-processor though...
(And with that tangent over and done with...!)
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
7:26 a.m.
This was a major design flaw in the Pole Position arcade PCB's, someone
positioned the backup battery at the top center of the board when it was
mounted sideways on the inside side wall of the cabinets and when the
batteries died, they died a horrific messy death, usually taking out a 3
square inch of the PCB traces with them.
Philip Pemberton wrote:
On 10/03/11 13:47, Mr Ian Primus wrote:
I've used CR2032's as replacements before
on similar machines, it's
worked fine.
Just remember - whatever you do, REMOVE the old soldered in battery
from the board. It'll leak and corrode through traces.
I'll second this with one addition -- the electrolyte in NiCd
batteries also eats some types of glass-fibre PCB substrate. What this
means is that you not only lose the tracks, but the board itself
basically turns to dust as well...
Get a pair of wire cutters (the "flush cutting" kind ideally) and cut
the thing off the board, then desolder the stubs and clean the PCB
with vinegar, then water (ideally deionised or distilled), then
isopropyl or a standard PCB cleaner / flux remover.
This works thusly:
1. The vinegar neutralises the alkaline electrolyte (usually
potassium hydroxide)
2. The water gets rid of the vinegar and any water-soluble dirt
3. The IPA removes any alcohol-soluble dirt (e.g. solder flux) and
helps the water evaporate more quickly.
I've
desoldered them and installed CR2032 sockets in their place with good
success. But if you don't want to go to the trouble, you can just
clip off the old battery.
Usually there's a 4-pin header which allows you to install an external
battery once you've removed the board-mounted one. These are usually
designed to take 4.5V alkaline batteries and generally have a diode
and series limiting resistor on the PCB.
The Acorn BBC Micro (actually the Master series) used three AAs in a
shrink-wrapped package shoved in the gap between the keyboard and the
case... IIRC there was a 120-ohm resistor and a 1N4001 diode inside
the package -- the resistor limits current if the diode fails.
Earlier machines had a battery holder by the side of the motherboard.
You could remove the old batteries and replace them with off-the-shelf
AAs. Unfortunately the battery holder sits in the Tube co-processor
bay, so you can't install an internal co-processor without replacing
the battery pack with the shrink-wrap version. There's nothing
stopping you installing an external cheese-wedge co-processor though...
(And with that tangent over and done with...!)
7:34 a.m.
--- On Thu, 3/10/11, Curt @ Atari Museum <curt at atarimuseum.com> wrote:
This was a major design flaw in the
Pole Position arcade PCB's, someone positioned the backup
battery at the top center of the board when it was mounted
sideways on the inside side wall of the cabinets and when
the batteries died, they died a horrific messy death,
usually taking out a 3 square inch of the PCB traces with
them.
Don't remind me...
And it was many more than just Pole Position. There were *lots* of 80's video games,
as well as pinball machines that suffer from the same fate. I've spent more hours
repairing battery damaged boards than I care to think about.
-Ian
7:55 a.m.
On Thu, Mar 10, 2011 at 10:34 AM, Mr Ian Primus <ian_primus at yahoo.com> wrote:
Don't remind me...
And it was many more than just Pole Position. There were *lots* of 80's video games,
as well as pinball machines that suffer from the same fate. I've spent more hours
repairing battery damaged boards than I care to think about.
I've got a dead Commodore Colt (PC-III) that was working when it came
to me (and was used to burn many GG2 Bus+ GALs) then the battery
leaked and took out the traces nearby. I moved the burner to a Compaq
286/SLT laptop (its timing is such that it does not work with anything
as "new" as fast as a 25MHz 386), but the Colt is still on the repair
pile.
-ethan
11:59 a.m.
One of my computers is a 486SX. The soldered-in battery is apparently
failing; after a period of power-off, the time is badly off at re-start. The
date and BIOS are so far unaffected.
Yes, I think you're right. The battery still has enough voltage to keep
the CMOS RAM contents preserved, but not enough to run the oscillator
properly. So the time runs slow (if at all) when the machine is turned off.
The motherboard has provision for an off-board battery. I am thinking of
using a socketed CR2032 battery which I believe is rated at 3 volts. The
manual for the computer describes the off-board battery as 3.6 volts.
I assume the manual says toy can connect an external battery even with
the soldered-in battery in place. It doesn't parallel them or anything
daft does it (if so, the external battery will try to charge the on-board
one with very unpleasant results).
Actually, I'd remove the on-board battery anyway. If it's failing, it may
strt to leak, and then you'll ahve bigger problems. is there any reason
you can't jsut replace this battery with a similar (electricallly) one?
If you do use the extranl battery connector, I would check that the
motherboard doesn't try to charge the battery (attempting to charage a
lithium coin cell is spectacualr, and you don't want to be near it. I
think there's a youtube video of it...). Connect a voltmeter across the
external bettery conenctor pins with the machine tunred on and check you
get no voltage there.
Is it asking for trouble to use a 3v rather than a 3.6v battery? If so,
It won;t do any damage, but you may just see what you are seeingnow. The
CMOS RAM data will be preserved, but the clock may not run.
where are the 3.6v batteries available?
There is a type of lithium cell that's 3.6V. I seem to rememebr that some
Macs used it.
-tony
1:13 p.m.
On 2011 Mar 10, at 11:59 AM, Tony Duell wrote:
Yes, they (many Macs) did, they are half-AA size, but are rather
expensive and relatively difficult to obtain.
where are the 3.6v batteries available?
There is a type of lithium cell that's 3.6V. I seem to rememebr that
some
Macs used it. 
1:29 p.m.
On 10 Mar 2011 at 13:13, Brent Hilpert wrote:
Yes, they (many Macs) did, they are half-AA size, but
are rather
expensive and relatively difficult to obtain.
Yup, some of the PowerMacs in partitular. Why not just replace it
with a coin cell (CR2032s are almost a dime a dozen)? Is the current
draw that great?
--Chuck
1:50 p.m.
On 2011 Mar 10, at 1:29 PM, Chuck Guzis wrote:
On 10 Mar 2011 at 13:13, Brent Hilpert wrote:
And into the early iMacs. On some of the first iMacs the battery would
only last a year or 2, and the machine would not boot when it failed,
leaving one to go scrambling to source an oddball battery. Seemed to
last longer in later versions. Today I might find an alternative
solution rather than buy a new battery, but early iMacs are one machine
it could be a little awkward to fit an alternative.
Yes, they (many Macs) did, they are half-AA size,
but are rather
expensive and relatively difficult to obtain.
Yup, some of the PowerMacs in partitular. Why not just replace it
with a coin cell (CR2032s are almost a dime a dozen)? Is the current
draw that great? 
12:25 p.m.
On 3/9/11 10:37 PM, Hollandia at ccountry.net wrote:
One of my computers is a 486SX. The soldered-in
battery is apparently
failing; after a period of power-off, the time is badly off at re-start. The
date and BIOS are so far unaffected.
The motherboard has provision for an off-board battery. I am thinking of
using a socketed CR2032 battery which I believe is rated at 3 volts. The
manual for the computer describes the off-board battery as 3.6 volts.
Is it asking for trouble to use a 3v rather than a 3.6v battery? If so,
where are the 3.6v batteries available?
3.6 is 3*1.2V, and 1.2V is the intrinsic cell voltage for several
battery technologies, such as NiCd and NiMH.
3.6V is the intrinsic cell voltage for LiIon cells.
Is the motherboard expecting to charge the battery?
-Dave
--
Dave McGuire
Port Charlotte, FL
1:10 p.m.
On 2011 Mar 10, at 12:25 PM, Dave McGuire wrote:
On 3/9/11 10:37 PM, Hollandia at ccountry.net wrote:
On occasion I have dealt with this by installing a 2 or 3 cell AA or
AAA battery holder somewhere in the machine, well away from the
electronics to avoid corrosion from leaking or off-gassing (behind the
false front on some machines can be nice, or even on the back panel
exterior).
I then use junk alkaline AA or AAA cells which have been exhausted in
use for things like flashlights and remote controls, as they can still
have enough energy to run an RTC for a very long time. Alkaline cells
have a very long shelf life, making them good for very-low-current
requirements such as RTC and config-RAM maintentance.
As others have said, a blocking diode may need to be installed to
prevent 'charging' of the alkaline cells, but the 0.7V drop of the
diode can be accounted for in the number of cells used. Typically for
alkaline cells: 3 cells * 1.5V - 0.7V = 3.8V, with lots of room for
droop from an old/used cell.
One of my computers is a 486SX. The soldered-in
battery is apparently
failing; after a period of power-off, the time is badly off at
re-start. The
date and BIOS are so far unaffected.
The motherboard has provision for an off-board battery. I am thinking
of
using a socketed CR2032 battery which I believe is rated at 3 volts.
The
manual for the computer describes the off-board battery as 3.6 volts.
Is it asking for trouble to use a 3v rather than a 3.6v battery? If
so,
where are the 3.6v batteries available?
3.6 is 3*1.2V, and 1.2V is the intrinsic cell voltage for several
battery technologies, such as NiCd and NiMH.
3.6V is the intrinsic cell voltage for LiIon cells.
Is the motherboard expecting to charge the battery?
4988
days inactive
4988
days old
12 comments
9 participants
participants (9)
-
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
classiccmp＠philpem.me.uk -
curt＠atarimuseum.com -
ethan.dicks＠gmail.com -
hilpert＠cs.ubc.ca -
Hollandia＠ccountry.net -
ian_primus＠yahoo.com -
mcguire＠neurotica.com