Stop dischargie of laptop battery by disconnecting?


M

micky

I pretty much only use my laptop when I go out of town, so that means
I don't use it for months at a time sometimes, and even if it was 100%
charged last time I used it, it's as little as 1% (or 0%?) charged
after 4 months. That's bad for me and the battery too, I think.

Can I stop the discharge of laptop battery by disconnecting it? It's
easy to do since the battery is not under a cover, its at the edge,
above the keyboard, and two plastic sliders release it, and it plugs
back in even more quickly.

It's an ACER Aspire.

Thanks.
 
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C

Computer Nerd Kev

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.

At the end of the day, batteries always loose charge over long
periods of time (whether used or not), and it gets worse as they
get older. Perhaps get a new battery, or leave the laptop
plugged into a power point timer set to turn on the power
supply and give the battery a little charge for half an hour a
day (or week etc.).
 
M

mike

I pretty much only use my laptop when I go out of town, so that means
I don't use it for months at a time sometimes, and even if it was 100%
charged last time I used it, it's as little as 1% (or 0%?) charged
after 4 months. That's bad for me and the battery too, I think.

Can I stop the discharge of laptop battery by disconnecting it? It's
easy to do since the battery is not under a cover, its at the edge,
above the keyboard, and two plastic sliders release it, and it plugs
back in even more quickly.

It's an ACER Aspire.

Thanks.
Executive summary:
If you expect to get on a plane and write a memo after 4 months of disuse,
you're likely to be disappointed. I'd charge it, run it down and
charge it again before the trip, no matter what the battery gauge says.
YMMV.

You'd have to give the exact model number to get much relevant help.
Battery management is a crap shoot. I've got a Toshiba that cautions
do not leave the charger connected when you're not using the laptop.
That's a BAD design.
One school of thought says charge it every week whether you use it or
not. Some laptops put way more load on the battery than others
when off.


In general, if it's lithium, the battery power management IC won't drain
it fast, but it will discharge over long periods. You can improve the
self discharge of the cells by storing it in the fridge...NOT THE
FREEZER". But that won't help the tiny drain of the battery management
computer.

But that's not the only issue.
There's a battery or capacitor or something in the laptop that
maintains the clock when you remove the battery. Leave the battery
out too long, (too long varies from minutes to months) the clock
and cmos configuration info get lost. A minor annoyance if that
internal battery is rechargeable. Major annoyance if it's a coin cell
that requires laptop disassembly to replace.
 
C

Computer Nerd Kev

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/article/safety_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
 
M

mike

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.
 
V

VanguardLH

micky said:
I pretty much only use my laptop when I go out of town, so that means
I don't use it for months at a time sometimes, and even if it was 100%
charged last time I used it, it's as little as 1% (or 0%?) charged
after 4 months. That's bad for me and the battery too, I think.

Can I stop the discharge of laptop battery by disconnecting it? It's
easy to do since the battery is not under a cover, its at the edge,
above the keyboard, and two plastic sliders release it, and it plugs
back in even more quickly.

It's an ACER Aspire.

My guess is your battery is old, like 3 years, or more. It isn't
retaining a charge plus being old means it can't store as much a charge.
The older the rechargeable battery then the less it will hold. Also,
there is reduction/degradation with an increased number of charge
cycles, so the more often you recharge the weaker (less total charge)
the battery becomes. Laptop batteries have a lifetime of around 400
charge cycles. Over time, capacity wanes. With recharging, capacity
wanes. Consider the battery a physical component that encounters wear
(chemical instead of abrasive). Expect to replace the battery after 3
years (sometimes only 2 for less quality units).

The battery won't last forever. Don't believe me? Then go read what
others state, like:
http://www.dell.com/content/topics/...sitelet/en/batteries_faq?c=us&l=en&cs=04#faq1
http://www.ehow.com/decision_7231941_long-laptop-computer-batteries-last_.html
http://www.maximumpc.com/article/features/white_paper_rechargeable_batteries
(sorry, don't remember the white paper that delved deeply into how these
batteries operate, that lithiums do have a memory but not like nicads,
why recharging reduces capacity, why age reduces capacity, and why 3% is
considered the bottommost charge level at which a lithium should be
stored).

Do not allow lithium batteries to go under 3% charge. Add a reminder to
your calendar to check the charge of your rechargeable batteries. If
the charge remaining is above 3% then change the reminder's recurrence
to every 2 months. Keep increasing the recurrence interval for the
reminder until the battery approaches 3%. I'd probably not go under
10%. Then shorten the recurrence by a month and thereafter recharge the
battery to full charge. Unlike nicads, there is no point in discharging
(to 3%, not a full discharge) and then recharging (i.e., don't cycle the
battery) since lithiums don't have a memory like nicads, plus you want
to minimize how many times you recharge. That's why, for example, you
don't discharge your cell phone to charge it up. You just charge it up
from whatever state it is currently. The only reason to do a cycle
charge (discharge to 3% and then recharge) to recalibrate the power
level monitor, if and when needed. The cycle charge is for the logic,
not the battery itself.

If it's an old battery (over 2 years and especially over 3 years) then
start hunting around for a replacement.
 
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P

Paul

Bill said:
Reference???? What "battery protection circuitry" IN a battery?

How many contacts are on the battery interface ?

Only two would be needed, if it was "just a battery".
There are multiple pins on the connector, implying it
is "smart".

Only an older battery technology, one that doesn't
catch fire, could be more careless. Like NiCD batteries
that swell or leak, nothing bad could happen there :)
Lithium on the other hand, is nothing to be toyed with.

In this example, there are connections for the
current carrying part of the battery, plus digital
connections for SMBus. The laptop can talk to the
battery, and get status information. And the status
information could say "too low for safety". It's not
like the chip in the battery necessarily breaks
a connection with a series pass transistor or
anything. But the pinout here suggests the laptop
can query information from the battery monitor chip.

http://www.allpinouts.org/index.php/DELL_D500_D600_battery

The battery monitor chip really doesn't need to do
anything when it is not running. But as soon
as a clock signal appears, then the logic inside
can be used to do stuff. Such as measure the
overall battery voltage or temperature or whatever.

The battery does have "dumb" physical features,
to protect the battery. But once activated, the
battery is toast.

http://batteryuniversity.com/learn/article/safety_circuits_for_modern_batteries

"a circuit interrupt device (CID) that opens the
electrical path if an over-charge raises the
internal cell pressure to 1000 kPa (145psi)"

The CID inside the battery, is shown here.

http://www.ntsb.gov/investigations/fulltext/HZB0501_6.JPG

"Figure 6. Lithium-ion cell with safety devices.

A: The disc is a temperature-sensitive polymer that resists
electron flow as the temperature increases. [PTC ???]
B: The CID opens with internal pressure breaking
the cell circuit.
C: Increased pressure causes the CID to vent to the cap.
D: A polymer sheet between the anodic and cathodic foils
melts at a given temperature, stopping the electron flow
"

HTH,
Paul
 
B

Bert

In Computer Nerd Kev
Not all, but as far as I know, most laptop batteries have
protection circuitry in the battery itself that slowly drains
the charge.

All chemical batteries, LiIon or otherwise, self-discharge without the
help of any external circuitry.

If you choose to believe Wikipedia, it says

"Li+ batteries have a self-discharge rate of approximately 5–10% per
month"

https://en.wikipedia.org/wiki/Lithium-ion_battery
 
V

VanguardLH

Paul said:
Only an older battery technology, one that doesn't
catch fire, could be more careless. Like NiCD batteries
that swell or leak, nothing bad could happen there :)
Lithium on the other hand, is nothing to be toyed with.

Yep, lithiums can cause a fire.

The first was a recorded fire at LAX. I can't tell for sure if the cord
from the laptop was for charging. The other fires shown were induced
but show that Li packs will not only catch fire when overheated but
sustain a fire and are explosive.

Anything that overheats the Li battery causes it to go aflame. That
includes trying to charge a bad Li battery assuming the protection
circuitry doesn't prevent the problem of overheating.

More than just physical damage can result if your laptop gets ran over.

Fire from overcharging a Li battery pack.

And you thought buying fireworks in your state was illegal.
 
P

Paul

Bill said:
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/da...-ic/lithium-ion-battery-protection-ic/s-8244/

http://datasheet.sii-ic.com/en/battery_protection/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
 
M

mike

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-pr...hargeable-li-ion-batteries-17-4mm-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.
 
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P

Paul in Houston TX

Bill said:
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.

Many cameras not only have regulator circuitry built into the battery
pack but also have ID chips built in as well. If the camera does not
confirm the battery ID as factory oem, it will not work.
May be the same for most other devices as well.
 
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M

~misfit~

Somewhere said:
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]
 

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