laptop AC power vs. battery power

Discussion in 'Computer Support' started by mb_, Oct 6, 2005.

  1. mb_

    mb_ Guest

    There are situations where I am using my laptop on my desk using just
    battery power. However, I could also easily plug in the power adapter
    and
    run off of AC Power. In such situations, is one preferable over the
    other??
    Does it make more sense to use AC power whenever possible since that
    would
    save battery power??

    Or am I missing something?

    Mel
    mb_, Oct 6, 2005
    #1
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  2. mb_

    Plato Guest

    mb_ wrote:
    >
    > There are situations where I am using my laptop on my desk using just
    > battery power. However, I could also easily plug in the power adapter
    > and run off of AC Power. In such situations, is one preferable over the
    > other?? Does it make more sense to use AC power whenever possible since that
    > would save battery power??


    If you dont need the battery recharged all the time then it wont matter.





    --
    http://www.bootdisk.com/
    Plato, Oct 6, 2005
    #2
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  3. mb_

    Fred Guest

    "Plato" <|@|.|> wrote in message
    news:4344d114$0$237$...
    > mb_ wrote:
    >>
    >> There are situations where I am using my laptop on my desk using just
    >> battery power. However, I could also easily plug in the power adapter
    >> and run off of AC Power. In such situations, is one preferable over the
    >> other?? Does it make more sense to use AC power whenever possible since
    >> that
    >> would save battery power??

    >
    > If you dont need the battery recharged all the time then it wont matter.
    >
    > --
    > http://www.bootdisk.com/


    It's probably good to use the battery, run it almost right out, then fully
    rcharge it. Sometimes if they are just left fully charged they give up. Best
    left run down if storing, although someone's bound to tell you the
    opposite.
    >
    Fred, Oct 6, 2005
    #3
  4. mb_

    Mitch Guest

    In article <>, mb_
    <> wrote:

    > There are situations where I am using my laptop on my desk using just
    > battery power. However, I could also easily plug in the power adapter
    > and
    > run off of AC Power. In such situations, is one preferable over the
    > other??
    > Does it make more sense to use AC power whenever possible since that
    > would
    > save battery power??
    >
    > Or am I missing something?


    Rechargeable batteries have a limited number of recharge times; it's a
    higher number these days, but you'll get a better lifetime if it cycles
    less frequently.

    On the gripping hand, a laptop typically makes concessions to running
    on battery power -- check your OS, and you may find it cuts processor
    ability in half, spins down the hard drive more, turns off idle
    features you might like, maybe logs off earlier than you'd like.
    Mitch, Oct 6, 2005
    #4
  5. mb_

    Keme Guest

    mb_ wrote:
    > There are situations where I am using my laptop on my desk using just
    > battery power. However, I could also easily plug in the power adapter
    > and
    > run off of AC Power. In such situations, is one preferable over the
    > other?? [...]


    Yes!

    Considerations:
    - Performance: When you unplug your computer, it will probably switch to
    a power saving mode, reducing the performance of processor, screen and
    disk drives. If you run demanding applications (large mathemathical
    models, photo editing, etc.) or many apps simultaneously it's best to
    stay plugged in. Most applications use 10% or less of the processing
    power, so you probably don't need the performance most of the time. Try
    it and see if you notice degraded performance. If not, performance is
    not an issue.

    - Safety: When you run on batteries, they eventually run out. Normally
    the computer will save the state when low power is detected. With old
    batteries the power characteristics are unreliable, so the save state is
    not reliable. Some software will disable the power monitoring (turn off
    or render it useless, XP SP2 will refuse to run on battery power,
    probably because of this). You risk losing data. Save your work regularly.

    - Battery life: For most batteries it's best to use them to their full
    capability. I.e. charge them completely, then use them 'till they're
    empty. Otherwise the "memory effect" comes into effect. The battery
    "forgets" its full capacity. Apple's iBook/powerBook batteries are said
    to keep their capacity even when constantly on external power, but those
    must not be fully discharged! (I work on a school where 100 pupils got
    iBooks, and after the first summer vacation, half of their batteries
    were defective.)
    Keme, Oct 9, 2005
    #5
  6. mb_

    Toolman Tim Guest

    Keme wrote:
    > mb_ wrote:
    >> There are situations where I am using my laptop on my desk using just
    >> battery power. However, I could also easily plug in the power adapter
    >> and
    >> run off of AC Power. In such situations, is one preferable over the
    >> other?? [...]

    >
    > Yes!
    >
    > Considerations:
    > - Performance: When you unplug your computer, it will probably switch
    > to a power saving mode, reducing the performance of processor, screen
    > and disk drives. If you run demanding applications (large
    > mathemathical models, photo editing, etc.) or many apps
    > simultaneously it's best to stay plugged in. Most applications use
    > 10% or less of the processing power, so you probably don't need the
    > performance most of the time. Try it and see if you notice degraded
    > performance. If not, performance is not an issue.
    >
    > - Safety: When you run on batteries, they eventually run out. Normally
    > the computer will save the state when low power is detected. With old
    > batteries the power characteristics are unreliable, so the save state
    > is not reliable. Some software will disable the power monitoring
    > (turn off or render it useless, XP SP2 will refuse to run on battery
    > power, probably because of this). You risk losing data. Save your
    > work regularly.
    > - Battery life: For most batteries it's best to use them to their full
    > capability. I.e. charge them completely, then use them 'till they're
    > empty. Otherwise the "memory effect" comes into effect. The battery
    > "forgets" its full capacity. Apple's iBook/powerBook batteries are
    > said to keep their capacity even when constantly on external power,
    > but those must not be fully discharged! (I work on a school where 100
    > pupils got iBooks, and after the first summer vacation, half of their
    > batteries were defective.)


    The memory effect is invalid for modern Lithium-Ion batteries. That was a
    NiCad problem. See the following site where it is nicely summarized:

    http://www.dansdata.com/gz011.htm

    While perhaps not scientifically quantified, the summary is similar to most
    reports I've read, and to the experience I have had with camera and laptop
    batteries.

    --
    When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
    Toolman Tim, Oct 9, 2005
    #6
  7. mb_

    Keme Guest

    [...]
    > The memory effect is invalid for modern Lithium-Ion batteries. That was a
    > NiCad problem. See the following site where it is nicely summarized:
    >
    > http://www.dansdata.com/gz011.htm
    >
    > While perhaps not scientifically quantified, the summary is similar to most
    > reports I've read, and to the experience I have had with camera and laptop
    > batteries.
    >


    OK, I wasn't quite right in the technical sense. I stand corrected. (And
    thanks for the link. Amusing as well as enlightening it was.)

    Still, for practical purposes I believe the advice stands, perhaps
    slightly modified. Most equipment manufacturers still advise against
    constant charge. (Apple is the only exception I've found, their strategy
    probably due to a more sophisticated charge level detection.)

    The voltage drop you get from constant charge gives a false (too early)
    warning about low capacity. To the common man this is not far away from
    the memory effect symptom. Using the battery occasionally is a good
    thing for what we perceive as "battery life" (time when the battery has
    sufficient capacity to be practical in use).

    While a complete battery discharge is bad (because of the risk of
    reverse charging weak cells, thus drastically reducing battery life),
    using it 'till the computer says "empty" should be safe, and will
    prolong battery life slightly for most of us, I guess (because most of
    us accept the "power low" message, and won't attempt to compensate for
    the voltage drop by playing with the warning thresholds for battery power).
    Keme, Oct 15, 2005
    #7
  8. mb_

    Toolman Tim Guest

    Keme wrote:
    > [...]
    >> The memory effect is invalid for modern Lithium-Ion batteries. That
    >> was a NiCad problem. See the following site where it is nicely
    >> summarized: http://www.dansdata.com/gz011.htm
    >>
    >> While perhaps not scientifically quantified, the summary is similar
    >> to most reports I've read, and to the experience I have had with
    >> camera and laptop batteries.
    >>

    >
    > OK, I wasn't quite right in the technical sense. I stand corrected.
    > (And thanks for the link. Amusing as well as enlightening it was.)
    >
    > Still, for practical purposes I believe the advice stands, perhaps
    > slightly modified. Most equipment manufacturers still advise against
    > constant charge. (Apple is the only exception I've found, their
    > strategy probably due to a more sophisticated charge level detection.)
    >
    > The voltage drop you get from constant charge gives a false (too
    > early) warning about low capacity. To the common man this is not far
    > away from the memory effect symptom. Using the battery occasionally
    > is a good thing for what we perceive as "battery life" (time when the
    > battery
    > has sufficient capacity to be practical in use).
    >
    > While a complete battery discharge is bad (because of the risk of
    > reverse charging weak cells, thus drastically reducing battery life),
    > using it 'till the computer says "empty" should be safe, and will
    > prolong battery life slightly for most of us, I guess (because most of
    > us accept the "power low" message, and won't attempt to compensate for
    > the voltage drop by playing with the warning thresholds for battery
    > power).


    I've run into conflicting advice even from computer/battery manufacturers
    myself. For instance, there's a utility on Dell's website that is designed
    to do a complete discharge of the battery in the Inspiron 7000/7500 series
    laptops. I don't recall right now what they called it, but it certainly goes
    against most other recommendations I've read <g>

    --
    When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.
    Toolman Tim, Oct 15, 2005
    #8
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