bios battery life

  • Thread starter Thread starter Linea Recta
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Linea Recta

In another newsgroup someone stated that, when leaving the computer on the
230V. mains, there would be no battery consumption, as opposed to cutting
off from the mains.
I always switch off the distributing-plug for PC and all devices when I'm
done.

Does this have any effect on the battery?



--
regards,

|\ /|
| \/ |@rk
\../
\/os
 
Linea said:
In another newsgroup someone stated that, when leaving the computer on
the 230V. mains, there would be no battery consumption, as opposed to
cutting off from the mains.
I always switch off the distributing-plug for PC and all devices when
I'm done.

Does this have any effect on the battery?
Click to expand...



The bios battery is not rechargeable so it does not matter if the
machine is connected to the mains or not. Typical life is about 5 years
 
philo said:
The bios battery is not rechargeable so it does not matter if the machine
is connected to the mains or not. Typical life is about 5 years
Click to expand...

Actually, it does matter. If the PC is left plugged into a live circuit, the
battery is not in use; CMOS settings are saved by the voltage to the board.
You can turn your PC off but parts of the board are still hot. That's why it
is recommended to unplug the PC from the wall or UPS before adding or
removing new cards or RAM.
Even with that, though, the average life is still about 3-7 years (big
average, eh?)
 
SC said:
Actually, it does matter. If the PC is left plugged into a live circuit,
the battery is not in use; CMOS settings are saved by the voltage to the
board. You can turn your PC off but parts of the board are still hot.
That's why it is recommended to unplug the PC from the wall or UPS
before adding or removing new cards or RAM.
Even with that, though, the average life is still about 3-7 years (big
average, eh?)
Click to expand...

The power supply is split in two halves. The main rails are one half of the
design (and support "soft off", where the computer can turn off the power
for itself on the main rails). The standby source is the other half. The
standby source runs all the time, until the AC is interrupted. The standby
source doesn't require the fan on the power supply to be running, as it is
intended to be a relatively low power output circuit with not a lot
of waste heat.

230VAC ---- PSU ---- +3.3,+5,+12,-12 (rails used when computer running)
Box ---- +5VSB ---+ (+5VSB is the standby voltage)
|
| -->
+------Diode---+
|
+--------- CMOS RAM and RTC
--> |
CR2032 battery ------Diode---+

The diode scheme selects the path with the highest voltage. If you've done
something to interrupt +5VSB (switch off at the back of the computer, or
flip the switch on the power strip), then the CMOS RAM and RTC will run
from battery. And that shortens the life of the battery.

The CR2032 still has a finite shelf life, even if no current is being
drawn. But if you put the computer in storage, with the CR2032 battery
left in place, then expect the battery to last about 3 years. That is how
long mine lasted, on two different computers in storage.

(The above diagram has been simplified a bit, by removing details about
a regulator just after +5VSB. The CMOS doesn't actually run from 5V,
but gets a voltage a bit higher than the 3V from the battery. The
regulator just after +5VSB might be delivering 3.3V, and that causes it
to be the preferential current flow path through the diodes. One of the
diodes ends up reverse biased, which is how the diodes manage the source
of current in this scheme.)

There is a motherboard schematic here. PDF page 85, shows the regulator
that takes 5VSB and makes 3.3V from it. The upper left corner of PDF page 82,
shows the diodes selecting the battery or +5VSB derived source of power
for the CMOS. You don't need to download this, unless you're really
really curious :-)

http://www.intel.com/design/chipsets/schematics/252812.htm

Paul
 
Paul said:
The power supply is split in two halves. The main rails are one half of
the
design (and support "soft off", where the computer can turn off the power
for itself on the main rails). The standby source is the other half. The
standby source runs all the time, until the AC is interrupted. The standby
source doesn't require the fan on the power supply to be running, as it is
intended to be a relatively low power output circuit with not a lot
of waste heat.

230VAC ---- PSU ---- +3.3,+5,+12,-12 (rails used when computer
running)
Box ---- +5VSB ---+ (+5VSB is the standby voltage)
|
| -->
+------Diode---+
|
+--------- CMOS RAM and
RTC
--> |
CR2032 battery ------Diode---+

The diode scheme selects the path with the highest voltage. If you've done
something to interrupt +5VSB (switch off at the back of the computer, or
flip the switch on the power strip), then the CMOS RAM and RTC will run
from battery. And that shortens the life of the battery.

The CR2032 still has a finite shelf life, even if no current is being
drawn. But if you put the computer in storage, with the CR2032 battery
left in place, then expect the battery to last about 3 years. That is how
long mine lasted, on two different computers in storage.

(The above diagram has been simplified a bit, by removing details about
a regulator just after +5VSB. The CMOS doesn't actually run from 5V,
but gets a voltage a bit higher than the 3V from the battery. The
regulator just after +5VSB might be delivering 3.3V, and that causes it
to be the preferential current flow path through the diodes. One of the
diodes ends up reverse biased, which is how the diodes manage the source
of current in this scheme.)

There is a motherboard schematic here. PDF page 85, shows the regulator
that takes 5VSB and makes 3.3V from it. The upper left corner of PDF page
82,
shows the diodes selecting the battery or +5VSB derived source of power
for the CMOS. You don't need to download this, unless you're really
really curious :-)

http://www.intel.com/design/chipsets/schematics/252812.htm

Paul
Click to expand...

LOL!!! Isn't that what I said, except in fewer sentences?
Don't take me wrong, Paul. I love your posts. Do you have these canned
somewhere, or do you type them out for each post?
Most respectfully,
 
Linea said:
In another newsgroup someone stated that, when leaving the computer on the
230V. mains, there would be no battery consumption, as opposed to cutting
off from the mains.
I always switch off the distributing-plug for PC and all devices when I'm
done.

Does this have any effect on the battery?
Click to expand...

There is less consumption, not zero consumption. Besides, even you know
when there is zero consumption that batteries still grow weak over time just
sitting on the shelf unused.
 
LOL!!! Isn't that what I said, except in fewer sentences?
Don't take me wrong, Paul. I love your posts. Do you have these canned
somewhere, or do you type them out for each post?
Most respectfully,
Click to expand...

Most people have a monolithic view of their computer, and the
above is to attempt to describe what is inside in more detail.

Paul
 
Paul said:
Most people have a monolithic view of their computer, and the
above is to attempt to describe what is inside in more detail.

Paul
Click to expand...

And I for one appreciate the time you invest on these posts. I've been
helped by your knowledge a few times.
 
VanguardLH said:
There is less consumption, not zero consumption. Besides, even you know
when there is zero consumption that batteries still grow weak over time
just
sitting on the shelf unused.
Click to expand...


I know batteries self discharge also when unused. But as I understood it
life is extended in any case by leaving the PC on the mains. I started doing
so a few days ago, and booting up is still going fine now...



--
regards,

|\ /|
| \/ |@rk
\../
\/os
 
I know batteries self discharge also when unused. But as I understood it
life is extended in any case by leaving the PC on the mains. I started doing
so a few days ago, and booting up is still going fine now...

--
regards,

|\  /|
| \/ |@rk
 \../
  \/os
Click to expand...

The only reason why the battery life is "extended" is the fact the
battery is used ONLY to retain the CMOS settings whenever there is no
current / power flowing thorough the PC from the main.
 
Linea said:
I know batteries self discharge also when unused. But as I understood it
life is extended in any case by leaving the PC on the mains. I started doing
so a few days ago, and booting up is still going fine now...
Click to expand...

There is no charging of the battery. Lithium batteries requires such a low
recharge current that it would take forever to compensate for your
consumption of energy from the battery. Recharging a lithium battery
results in severely overheating it which makes it explode. There is no
charging circuit on the motherboard for the CMOS battery.

Whether or not you leave your host always powered, you will still need to
replace the lithium coin cell battery for CMOS about every 5 years (if you
get them fresh). When you buy the battery, it has a life expectancy date.
Tape the card from the packaging or note the date on a sticky note inside
the side cover of your computer so you'll later just how soon you'll need to
replace the battery. If that date is longer than 5 years away, note a date
that is 5 years after when you purchased the battery. Personally I prefer a
4-year replacement schedule since it's a cheap replacement part. I also buy
them in a 2-battery pack since it is possible that one is defective, plus I
almost always end up with another host (friend, family, work) where I could
use the other one later.
 
There is no charging of the battery. Lithium batteries requires such a low
recharge current that it would take forever to compensate for your
consumption of energy from the battery. Recharging a lithium battery
results in severely overheating it which makes it explode. There is no
charging circuit on the motherboard for the CMOS battery.

Whether or not you leave your host always powered, you will still need to
replace the lithium coin cell battery for CMOS about every 5 years (if you
get them fresh). When you buy the battery, it has a life expectancy date.
Tape the card from the packaging or note the date on a sticky note inside
the side cover of your computer so you'll later just how soon you'll need to
replace the battery. If that date is longer than 5 years away, note a date
that is 5 years after when you purchased the battery. Personally I prefer a
4-year replacement schedule since it's a cheap replacement part. I also buy
them in a 2-battery pack since it is possible that one is defective, plus I
almost always end up with another host (friend, family, work) where I could
use the other one later.
Click to expand...

The batteries in my towers could probably stand replacements.
Unfortunately, the last time I had my less ancient system open I
couldn't figure out how to get the CR2032 out of its holder. I pokesd
and roded at it, but I couldn't get it to pop out. I wasn't able to spot
a place to get an object like a jeweler's screwdriver behind or beside it.
 
RobertVA said:
The batteries in my towers could probably stand replacements.
Unfortunately, the last time I had my less ancient system open I couldn't
figure out how to get the CR2032 out of its holder. I pokesd and roded at
it, but I couldn't get it to pop out. I wasn't able to spot a place to get
an object like a jeweler's screwdriver behind or beside it.
Click to expand...


That's curious... One would expect the holders to be standard, as the coin
cell also have standard dimentions.
In my case the cell goes under a rim on one side and a hook (which can be
bent away slightly) on the other side.



--
regards,

|\ /|
| \/ |@rk
\../
\/os
 
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