Motherboard batteries

  • Thread starter Thread starter Matt
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Matt

Just wondering if there was any particular place you would recomend getting
them from or will anyplace online pretty much work?!?
 
Matt said:
Just wondering if there was any particular place you would recomend
getting them from or will anyplace online pretty much work?!?
Click to expand...

Depending on the battery, your local drug or discount store may be the
place!
 
JR Weiss said:
Depending on the battery, your local drug or discount store may be the
place!
Click to expand...

Most are CR2032, 2/$5 at wally world or rat shack or your local drug
tore. -Dave
 
Just wondering if there was any particular place you would recomend getting
them from or will anyplace online pretty much work?!?
Click to expand...
Any local store would have them in the camera section

Its a standard CR2032

Duracells version might be named DL2032
 
Just wondering if there was any particular place you would recomend getting
them from or will anyplace online pretty much work?!?
Click to expand...

Pop it out carefully by looking at it -- a little ridge pressure clip
along the side cavity of the circular batter mount indentation -- two
circles, the larger topmost's surrounding edge being the sole and
opposite connection from the bottom face or a flat surface connect,
that just lies in there. Not much too it. It's that new Casio solar-
charged watch battery I got or when a computer's past eight years old
and still going that gets to me.
 
Just wondering if there was any particular place you would recomend getting
them from or will anyplace online pretty much work?!?
Click to expand...

CR2032 now are a standard type, used in some other devices
besides MBs. The ones I bought at a chain hardware store
last longer than those bought in chain computer stores.
 
Question about motherboard batteries (2032 type):

Is it true that the current draw from the battery will be reduced if the
computer is plugged into an AC/main power (even if the computer is not
running), but when a computer has no connection to AC power then the
current draw from the battery (to maintain the on-board system clock and
NV ram) will increase?
 
PC said:
Question about motherboard batteries (2032 type):

Is it true that the current draw from the battery will be reduced if the
computer is plugged into an AC/main power (even if the computer is not
running), but when a computer has no connection to AC power then the
current draw from the battery (to maintain the on-board system clock and
NV ram) will increase?
Click to expand...

Yes, unless you're using an AT style power supply. The newer ATX flavor
include a 5VDC output that remains on unless the power supply switch
(if there is one) is turned off or if the AC power is otherwise shut
off.

The battery should last for years regardless.
 
PC said:
Question about motherboard batteries (2032 type):

Is it true that the current draw from the battery will be reduced if the
computer is plugged into an AC/main power (even if the computer is not
running), but when a computer has no connection to AC power then the
current draw from the battery (to maintain the on-board system clock and
NV ram) will increase?
Click to expand...

+5VSB is available if

1) The power supply is plugged in. And mains power is available.
2) The switch on the back of the computer is in the ON position.
If the power supply has no switch on it, then it is ON all the time.

If +5VSB is available, there are two paths for the RTC/CMOS supply.

+5VSB --- regulator ----------- diode ---+
|
+-------- RTC/CMOS circuit
|
CR2032 battery -- resistor --- diode ---+

The sources are set up, such that if the +5VSB is present, it provides
the power needed. If +5VSB goes missing (say, you unplug or switch off
the supply at the back), the CR2032 supplies power for about 3 years.
So you can store a computer in your garage for three years, and the
next time you turn it on, the current time is correct, and the
BIOS settings are still maintained.

If you plan to store a computer for a long time, you can take pictures
of the BIOS screen with a digital camera. Then, if the battery runs
flat, you can restore any critical BIOS settings, using the pictures
you've stored on some other (running) computer.

I've had two batteries run flat while the computer was stored, and
that is where I get the 3 year number from.

Paul
 
Paul said:
I've had two batteries run flat while the computer was stored,
and that is where I get the 3 year number from.
Click to expand...

Any idea what the shelf-life is of a 2032 battery?

When such a battery is installed in a motherboard, and the board is
supplying the power for the RTC even when the PC is turned off, is there
any chance that some current is feeding back into the battery to keep
it's charge up?

In other words, if I take 2 batteries from the same production batch,
and keep one in it's package and put the other in a motherboard that is
connected to main AC power indefinately, then will both batteries age or
discharge at the same rate?
 
PC said:
Any idea what the shelf-life is of a 2032 battery?

When such a battery is installed in a motherboard, and the board is
supplying the power for the RTC even when the PC is turned off, is there
any chance that some current is feeding back into the battery to keep
it's charge up?

In other words, if I take 2 batteries from the same production batch,
and keep one in it's package and put the other in a motherboard that is
connected to main AC power indefinately, then will both batteries age or
discharge at the same rate?
Click to expand...

They should age at roughly the same rate. The idea being, that when
+5VSB is available, no current is drawn from the CR2032.

You can see in the spec here, the maximum reverse charge is one microamp,
so the battery maker, really don't want the circuit design to be charging
the battery. The Schottky dual diode scheme, will have a small amount of leakage
back into the battery, and one would hope, not exceeding that
one microamp specification.

http://data.energizer.com/PDFs/cr2032.pdf

There is an example of the actual dual diode used to prevent backward
current flow here. You can see "K45" printed on the dual diode package,
which makes it a BAS40W-05. (I have three motherboards here, that use
K45 for the dual diode near the battery.) Figure 2 shows the leakage
current. The diode would have to be raised to 125C temperature, before
the leakage would be a problem. And normally, that diode will be living
at 35C to 40C temperatures. (Leakage in this case, means backward flow
of current from the +5VSB source, into the battery, in effect attempting
to charge the battery.)

http://www.diodes.com/datasheets/ds30114.pdf

The reason those particular diodes are used, is for the low
forward voltage drop.

Paul
 
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