Stop dischargie of laptop battery by disconnecting?

mike wrote:
On 11/15/2013 4:34 PM, Bill in Co wrote:
mike wrote:
On 11/14/2013 6:08 PM, Bill in Co wrote:
Computer Nerd Kev wrote:
Not all, but as far as I know, most laptop batteries have
protection circuitry in the battery itself that slowly drains
the charge. The effect this has depends heavily on the condition
of the battery and the the individual design and specs.

Reference???? What "battery protection circuitry" IN a battery?




Like virtually every lithium battery made?
google bq29311 for an example.
Or pop the battery out of your cellphone.
You're holding one in your hand.

I think that bq29311 is a battery protection IC, and is not inside the
battery, no?


If you're talking about being inside a CELL, not usually.
Although there are "CELLS" with electronics attached to the
end and shrink-wrapped so that they look like a bare cell.
This is one such attachment.

http://dx.com/p/charge-discharge-pro...mm-1-9mm-26112

Same site has "cells" with the attachment already installed.

Typically, a group of cells is called a battery.
You could argue that one cell does not a battery make.
If you just want to nit-pick, that's your right.
The rest of us try to discuss the issue in context.

No, I wasn't trying to be pedantic. If the battery packs nowadays have that
built in circuitry, it's good to know. I don't think that has always been
the case, however, although maybe you'd have to go back a couple of decades
or so.

Paul wrote:
Bill in Co wrote:
mike wrote:
On 11/14/2013 6:08 PM, Bill in Co wrote:
Computer Nerd Kev wrote:
Not all, but as far as I know, most laptop batteries have
protection circuitry in the battery itself that slowly drains
the charge. The effect this has depends heavily on the condition
of the battery and the the individual design and specs.
Reference???? What "battery protection circuitry" IN a battery?


Like virtually every lithium battery made?
google bq29311 for an example.
Or pop the battery out of your cellphone.
You're holding one in your hand.

I think that bq29311 is a battery protection IC, and is not inside the
battery, no?



It's inside the battery pack.

http://www.ti.com/product/bq29311

http://www.ti.com/lit/ds/slus487d/slus487d.pdf

"...the bq29311 can activate the FET drive as
a secondary protection level."

"APPLICATIONS
Notebook computer battery packs"

The schematic on page 9, hints at what it does,
but you need to look at page 6 to interpret it.
The "X" connections on the left, are to the
individual lithium cells. And the FETs at the
top of the schematic, are series pass during
charge and discharge. I'm not going to try
and figure out, which features are local and
purely hardware, and which ones require the
laptop processor in order to work.

The S-8244 is here.

http://www.sii-ic.com/en/semicon/dat...ion-ic/s-8244/

http://datasheet.sii-ic.com/en/batte...on/S8244_E.pdf

It looks like Q3 (2N7002) is there for series
disconnection of the pack. And the S-8244
provides a second opinion on opening
the circuit. Something like that. I didn't
read the whole thing. But it looks like
all that crap is hiding inside the battery pack.
No wonder it's so big and the shape is so
weird looking.

HTH,
Paul

It was all new to me, and pretty amazing!
(I guess I'm still stuck in the past with what I thought batteries were.
:-)
Apparently battery packs are what I'd call "smart batteries" (in a loose
sense).

Somewhere on teh intarwebs Bill in Co wrote:
Computer Nerd Kev wrote:
On 15 Nov 2013, Bill in Co wrote:

Computer Nerd Kev wrote:
Not all, but as far as I know, most laptop batteries have
protection circuitry in the battery itself that slowly
drains the charge. The effect this has depends heavily on
the condition of the battery and the the individual design
and specs.

Reference???? What "battery protection circuitry" IN a
battery?

Lithium Ion batteries like to get hot and catch fire if they
are charged when the voltage if too low. So there is some
small circuitry to monitor this voltage and prevent charging
when it is below a set threshold (and discharging below it,
although the circuitry itself drains a small amount of current
and thus over time self-sabotages this function (lesson of the
day: keep your Li-Ion batteries charged (actually applies to a
lot of batteries))). In addition, some also protect against
excessive current draw or heating by disabling the voltage
output when sensor readings exceed pre-set values.

References? Oh all right:
http://batteryuniversity.com/learn/a...y_circuits_for
_modern_batteries

Why I say not all laptop Li-Ion batteries have this circuitry:
http://www.fonerbooks.com/laptop_3.htm
http://www.thinkwiki.org/wiki/Batteries

The idea of a "smart battery" was new to me.

Having external circuitry to monitor it is one thing, and is
something quite different. But actually having ANY circuitry built
into tthe battery itself, per se, is something else, and was
something I wasn't aware of. Up to this point I thought all
batteries were just chemical sources of power, and that's all.

'Smart batteries' are the norm in laptops and have been for over a decade.
Most of them monitor each individual cell and protect the whole pack from
one bad cell going into thermal ranaway when charging. With ThinkPads (the
laptops I'm most familiar with) since at least 2003 the CPU and ROM in the
battery pack not only monitor the individual cells but also store
information such as designed capacity, cell manufacturer, date of
manufacture, date first used etc.

In fact I learned when replacing cells in a battery pack that it's
imperative that *some* power is maintained to the control circuitry at all
times - such as hooking it up to a bench supply while you are unsoldering
the old cells and replacing them. Failure to do so will result in a total
shut-down from the control circuitry and a non-functioning battery pack.
Removal of the control circuitry results in a laptop that won't boot from or
charge that battery as there is a 'handshake' process between battery CPU
and laptop when power is applied.

(Most) Laptops stopped using 'dumb batteries' back when they changed from
Ni-MH to Li-Ion, around the turn of the century.
--
/Shaun.

"Humans will have advanced a long, long, way when religious belief has a
cozy little classification in the DSM."
David Melville (in r.a.s.f1).
[Sent from my OrbitalT ocular implant interface]