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  1. #1
    Generic Member The Error Guy's Avatar
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    Default Rebuild or Replace laptop battery

    I have a DV7 6015tx laptop. The battery is over a year old now, nearly 500 days according to BCheck. It is expriancing a moderate drop in performance and is struggling to retain charge for 45 mins +

    As you can see in the pic the 4th cell appears to have died, probably resulting in this performance drop. Not sure if it's significant but the Terminal voltage is nearly 2000mv over its design... but that might be normal.

    The full charge capacity is 5100mAh and the battery is retaining approx 3000mAh of charge.

    Click image for larger version. 

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    My question is, should I locate the faulty cell/s and replace them or even rebuild the whole pack or should I find a replacement on eBay. I don't know what cells it takes yet but I found a replacement battery for about 50 NZD. I'm guessing cell replacement would be cheaper (and more satisfying) but in your experience what would be the best path to take?


    Cheers

    TEG
    The Master Of Deception


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  2. #2
    Computer "Specialist" Agent_24's Avatar
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    Default Re: Rebuild or Replace laptop battery

    Rebuilding really only makes sense if 1) you save a lot of money or 2) you can't buy that particular battery pack any more.

    Used\handled incorrectly, Lithium-based cells can be rather dangerous (Fire\explosion). If you know what you're doing then go for it if it saves you money.

    However you may also get hassles with the management circuitry in the battery not recognising the new cells properly and no capacity increase actually being gained, so you'll need to know how to work out any such issues.
    Non-system disk or disk error. Replace and strike any key when ready.

  3. #3
    Generic Member The Error Guy's Avatar
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    Default Re: Rebuild or Replace laptop battery

    Ok, the plan atm is to price out the cells. If they are Fairly priced then I'll replace the faulty cell, problem solved? Move on, if not replace all cells.

    If the replacement cells are going to be close to a replacement battery i'll just replace the whole lot. After having a LiPo explode on me I'm well aware of the dodgy things lithium cells can do, can't be too careful!
    The Master Of Deception


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  4. #4
    Senior Member 1101's Avatar
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    Default Re: Rebuild or Replace laptop battery


  5. #5
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    Default Re: Rebuild or Replace laptop battery

    It actually looks like the Terminal and Actual voltage labels are swapped.

    Good luck with the job. Let's know how it goes if you decide to do it.

  6. #6
    Generic Member The Error Guy's Avatar
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    Default Re: Rebuild or Replace laptop battery

    Just FYI for those randomly interested, current battery discharge goes along like this:

    100% - 1hr 40 reported remaining, discharges normally (a % mark every 3-5 mins) for 20 mins then drops instantly to 55% 45~ mins remaining and discharges normally thereafter.
    The Master Of Deception


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  7. #7
    VoidMaster
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    Default Re: Rebuild or Replace laptop battery

    Yes sounds like one cell has lost about half capacity, probably from leaking electrolyte.
    It's not the least charm of a theory that it is refutable. The hundred-times-refuted theory of "free will" owes its persistence to this charm alone; some one is always appearing who feels himself strong enough to refute it - Friedrich Nietzsche

  8. #8
    6146-B Billy T's Avatar
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    Default Re: Rebuild or Replace laptop battery

    Quote Originally Posted by zqwerty View Post
    Yes sounds like one cell has lost about half capacity, probably from leaking electrolyte.
    Lithium cells rarely leak, most likely the internal impedance of that cell has risen due to chemical deterioration of the internal structure. It can't be meaured directly by an ordinary meter, but an ESR (equivalent series resistance) meter will usually identify it straight away. From my Libretto: .2 / .2 / 15 ohms (old battery cells) New: .08 /.08 / .08 ohms IRMC.

    Cheers

    Billy 8-{)
    Last edited by Billy T; 06-08-2012 at 05:47 PM.
    Some days it's not even worth chewing through my restraints!

  9. #9
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    Default Re: Rebuild or Replace laptop battery

    Yes, replacement will be better, but you will face the performance problem

  10. #10
    6146-B Billy T's Avatar
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    Default Re: Rebuild or Replace laptop battery

    Quote Originally Posted by The Error Guy View Post
    As you can see in the pic the 4th cell appears to have died, probably resulting in this performance drop. Not sure if it's significant but the Terminal voltage is nearly 2000mv over its design... but that might be normal. Click image for larger version. 

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    I must be going blind! I didn't notice that Cell 4 was reading 0mV!

    That means it is a dead-short, which in turn explains why the remaining three cells are showing overvoltage. They are receiving the full charge voltage intended for 4 batteries, which is a 33% overcharge. This also explains the rapid drop off in terminal voltage/apparent charge, and subsequent levelling out.

    It is possible that the fault lies in the battery management electronics in the battery pack itself, in which case installing new cells might not be a very good idea as fully charged new lithiums can get stroppy if faced with a direct short, and might well explode/catch fire in protest.

    Cheers

    Billy 8-{)
    Some days it's not even worth chewing through my restraints!

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