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Stop dischargie of laptop battery by disconnecting?

Discussion in 'Laptops' started by micky, Nov 15, 2013.

  1. micky

    micky Guest

    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.

    micky, Nov 15, 2013
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  2. 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.).
    Computer Nerd Kev, Nov 15, 2013
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  3. micky

    mike Guest

    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.

    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

    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.
    mike, Nov 15, 2013
  4. micky

    Bill in Co Guest

    Reference???? What "battery protection circuitry" IN a battery?
    Bill in Co, Nov 15, 2013
  5. 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:

    Why I say not all laptop Li-Ion batteries have this circuitry:
    Computer Nerd Kev, Nov 15, 2013
  6. micky

    mike Guest

    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.
    mike, Nov 15, 2013
  7. micky

    VanguardLH Guest

    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:
    (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

    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.
    VanguardLH, Nov 15, 2013
  8. micky

    Paul Guest

    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.


    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.


    "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.


    "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

    Paul, Nov 15, 2013
  9. micky

    Bert Guest

    In Computer Nerd Kev
    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

    Bert, Nov 15, 2013
  10. micky

    VanguardLH Guest

    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.
    VanguardLH, Nov 15, 2013
  11. micky

    Bill in Co Guest

    I think that bq29311 is a battery protection IC, and is not inside the
    battery, no?
    Bill in Co, Nov 16, 2013
  12. micky

    Bill in Co Guest

    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.
    Bill in Co, Nov 16, 2013
  13. micky

    Paul Guest

    It's inside the battery pack.



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

    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.



    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.

    Paul, Nov 16, 2013
  14. micky

    mike Guest

    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.


    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.
    mike, Nov 16, 2013
  15. 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.
    Paul in Houston TX, Nov 16, 2013
  16. micky

    Bill in Co Guest

    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.
    Bill in Co, Nov 17, 2013
  17. micky

    Bill in Co Guest

    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
    Bill in Co, Nov 17, 2013
  18. micky

    ~misfit~ Guest

    '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.

    "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]
    ~misfit~, Dec 26, 2013
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