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Battery removal and CMOS battery

Discussion in 'Hardware Components and Aftermarket Upgrades' started by JOSEA, May 23, 2010.

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  1. moral hazard

    moral hazard Notebook Nobel Laureate

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    My Toshiba tecra A9 did charge its CMOS battery (so did my M9).
    This info was written in Toshibas documentation.

    I believe all notebooks should recharge their CMOS batteries. Otherwise how could 1 small battery keep its charge for 3+ years (I have a 10 year old notebook that never had a problem with its CMOS battery).
     
  2. Trottel

    Trottel Notebook Virtuoso

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    If you take out the battery, look at it, and read it, you will see that it is a non-rechargeable, 3v lithium button cell battery. Think about how often you need to replace the battery in a watch. Just because the battery is small doesn't mean it won't last a very long time under such minute loads.
     
  3. moral hazard

    moral hazard Notebook Nobel Laureate

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    When I was a kid I used those batteries for small moters and other things, I recharged them myself many times. Ripped them out of old desktops.

    Anyway, if you don't believe me, maybe you will believe the toshiba tecra a7 service manual:

    Toshiba Satellite Pro A100 / A105 - Tecra A7 Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics

    It's a multi part download, if you have trouble downloading it, I will upload it for you on rapidshare or something (it's a 10Mb file). Just let me know.
     
  4. Trottel

    Trottel Notebook Virtuoso

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    Neat. I never knew NiMH CMOS batteries existed. They don't appear to be very common.
     
  5. BruBoo

    BruBoo Notebook Evangelist

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    Agree. Every CMOS battery I have seen in ages has been a disposable lithium coin cell type, but moral hazard illustrates the need to read the service guide for your particular machine. good old Tosh ! :) My experience of rechargeable backup batteries in domestic time switches has been that they last less time than the lithium disposable ones.

    It is true that keeping the battery in the laptop will avoid the CMOS battery having to supply the CMOS. But generally it is big enough to last c 5 years doing that. The shelf life of a Lithium back up battery is 8 - 10 years but less at high temperature . .ah that would be in a a laptop then . ..

    Best assume you will replace your cmos battery in year 5. Even if soldered in it is not too hard a job - your local TV repair shop can do it quicker and cheaper than a laptop specialist if you have opened it up for them.

    The main battery will also die in 5 - 6 years even stored at 40% outside the laptop. Stored at 100% inside the laptop 3 years is more like it before significant capacity loss. Main batteries also have a cycle life so if you use it as a 'laptop' a few days a week it will last less time.

    Better approach is to assume a 3 - 4 year old laptop is about to start needing expensive replacement HDD's, Batteries, adapters, Fans, CMOS batteries etc and that if you bought all of those one day you could probably spend half the cost of a new, guaranteed 2013 model netbook with the same (now totally obsolete) spec. So be glad it lasted that long and save up for the new one :)
     
  6. woofer00

    woofer00 Wanderer

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    I was under the impression that CMOS batteries didn't discharge unless no other power source was plugged in - so for desktops, if the power is disconnected; for laptops, if both AC plug and main battery are out. I've got had computers that survived well over 8 years without ever changing the CMOS battery, as well as CMOS batteries that came to me dead from the manufacturer. Oddly enough, 2 of the 8 or 9 desktop motherboards I've purchased over the years arrived with the CMOS battery flipped over.
     
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