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    Laptop idle power useage with and without battery.

    Discussion in 'Hardware Components and Aftermarket Upgrades' started by HTWingNut, Sep 12, 2010.

  1. HTWingNut

    HTWingNut Potato

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    I was just messing around with my Kill-A-Watt meter and measuring idle watt consumption on my Sager laptop. Interesting thing is even with a fully charged battery, it idles consuming ~ 7W more than with the battery removed.

    38W without battery
    45W with battery

    Wonder the reason for this?
     
    HTWingNut, Sep 12, 2010
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  2. slickie88

    slickie88 Master of Puppets

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    Is there a BIOS level switch for disabling charging?
     
    slickie88, Sep 12, 2010
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  3. newsposter

    newsposter Notebook Virtuoso

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    Are you measuring the ac drain of the adapter or the dc drain of the laptop as it is connected to the adapter? Makes a difference. You could be measuring the inefficiency of the ac adapter instead of the efficiency of the laptop itself.

    What also makes a difference is the running temp of the adapter. If the adapter noticeably heats up while running, the ac current draw can change. Hot power conversion components are inefficient components. Same thing applies to the internal power MOSFETS of the laptop although those usually have decent heat sinks on them.

    I suspect that if the battery is installed, the internal charging circuit in the laptop is running, supplying current to the battery where the battery internal control circuit decides to use or dump the available current.

    But unless you're measuring the actual dc power draw of the laptop, it will be hard to tell for sure.
     
    newsposter, Sep 12, 2010
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  4. Trottel

    Trottel Notebook Virtuoso

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    Are you sure all settings are identical for on battery and off battery?
     
    Trottel, Sep 12, 2010
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  5. othonda

    othonda Notebook Deity

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    Interesting, how long did you monitor your meter? Does windows show the battery as fully charged and not charging? 7W is a lot of current, that just does not seem right.

    Edit: Well actually that is not a lot of current, after realizing that is the on the AC side.

    e * i = p or in this case p/e = i or 7w/120vac = .058 amps.

    That sounds like a reasonable amount of current to run the internal safety circuits of the battery.
     
    othonda, Sep 12, 2010
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  6. HTWingNut

    HTWingNut Potato

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    No, no option for that.

    Measuring AC from the wall.

    Those wouldn't matter because they're both plugged in.

    Yes windows shows it as fully charged, as does BatteryBar. I monitored it for a good ten minutes each after windows loaded and idled for about two minutes. Hard drive was pretty much inactive as well.
     
    HTWingNut, Sep 12, 2010
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