Li-On Cells from Laptop Battery Packs

Discussion in 'General Electronics Chat' started by PCBoy, Dec 26, 2011.

  1. PCBoy

    Thread Starter New Member

    Dec 14, 2011
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    I was wondering, could I use the cells inside battery packs as normal AA batteries?

    I got an old battery pack here that doesn't hold much charge anymore and was thinking of opening it up and check if some of the cells still work and use them for my digital camera.
     
  2. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Please do not open up an old battery. Lithium batteries can be dangerous if used other than intended by their maker, and even trying to take the battery apart can be dangerous.

    If the battery blew up in your face, you could lose your sight, or worse. The risk is not worth it to salvage a few cells which are probably nearly useless anyhow.
     
  3. PCBoy

    Thread Starter New Member

    Dec 14, 2011
    26
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    Oh, thanks for the heads up.

    I was actually trying to open up the pack now and got cut, haha.
     
  4. JMac3108

    Active Member

    Aug 16, 2010
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    I can't overstate how dangerous it is to try to open up a LiIon battery pack. Lithium is volatile when exposed to air. If you were to nick or cut into a cell in some way when opening the pack, it will go up in flames.
     
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Does lithium really explodes ?

    Cause I am making thingamabob to break open a lappy battery really soon.
     
    Last edited: Dec 26, 2011
  6. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    Lithium is not to play with.

    This is from this wiki article:
    http://en.wikipedia.org/wiki/Lithium

    Bertus
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    oh boy..this is gonna be fun.....
     
  8. tom66

    Senior Member

    May 9, 2009
    2,613
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    Yes, lithium ion and polymer types are -extremely- dangerous.

    I have accidentally punctured a Li-Po. The reaction rapidly put the battery in flames, spewing molten lithium all around it. Luckily I was outside, and I had a bucket of water nearby. The water smothered the battery and stopped the reaction but it was still rapidly bubbling for several minutes afterwards. These batteries store a -huge- amount of energy and are NOT to be messed with.
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    lesseee..I will get welding gloves and helmet and a body suit to go with it.
    then I check 'em Lithium
     
  10. tom66

    Senior Member

    May 9, 2009
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    Be extremely careful, I would advise against playing with them outright. They are also quite expensive.
     
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Expensive ??? :confused:

    I got plenty :D
     
  12. CraigHB

    Member

    Aug 12, 2011
    127
    15
    Barring all the hazards of Li-Ion cells already mentioned, you can NOT use them as replacements for AA batteries.

    Laptop packs commonly use 18650 round cells which are 18mm x 65mm compared to the 14mm x 50mm of an AA battery.

    Alkaline cells are nominal 1.5V where the Li-Ion cells used in a laptop battery are nominally 3.7V.

    Li-Ion cells require a charging profile that's totally different from something like an AA NiMH or NiCad rechargeable cell. You need a Li-Ion charger to charge a Li-Ion cell.

    If you can safely remove the cells (don't cut or puncture them), you can use them if you add the necessary protection. They need to be protected from over-current, over-discharge, and over-charge. Charging or over-current faults can result in thermal runaway which causes the cell to go up in flames spewing super-heated electrolyte. Over-discharge (draining a cell below a threshold voltage) is not dangerous, but can damage a cell irreparably.

    Keep in mind that Li-Ions have shelf life as well as cycle life so even if the batteries are well within their cycle life, they may be worn out from sitting around too long. Li-Ions can drop down to less than half their original charge capacity after 300 cycles and/or 3 years, but some hold up better depending on the exact chemistry and quality.

    You'd do much better to buy new round cells instead of harvesting old ones from laptop packs (you can also get flat cells). They are readily available at places like http://lighthound.com You can buy them with the necessary protection electronics built in. The laptop cells don't have any since protection is built into the laptop pack. They are not safe to use without it.
     
  13. Audioguru

    New Member

    Dec 20, 2007
    9,411
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    To the Original Poster:
    An alkaline battery cell is 1.6V when brand new and it quickly drops to 1.5V then to 1.1V. It slowly gets less and less.
    A rechargeable Ni-Cad or Ni-MH cell is 1.4V to 1.5V when fresh out of the charger then it quickly drops to 1.2V for most of a discharge.
    A rechargeable Lithium cell is 4.2V when fresh out of the charger then it slowly drops to 3V when its protection circuit disconnects its load.

    See how the Lithium cells have a much higher voltage than the others?

    I used the battery cells from a laptop that malfuctioned but its battery was still pretty good. I built a charger that charged each cell slowly up to 4.20V.

    I powered my electric RC airplane with them. Some cells were better than others. They got pretty warm but the motor in the airplane got hotter.

    I still have the cells and have not used them for 3 years. Each cell still measures 4.1V.
     
  14. CraigHB

    Member

    Aug 12, 2011
    127
    15
    That would be the exception, hobby applications. They use high drain LiPo (Lithium Polymer) flat cells without protection. This is the same type of cell you find in many consumer devices such as cell phones and cameras, but low drain for those applications.

    You can buy LiPo cells designed to drain as much as 60C or 60 times their charge capacity. They're available within a range of maximum allowable drain rates, anywhere from 2C to 60C. You trade off charge capacity for higher drain with higher cost.

    The motor controllers used in RC applications offer some protection, mainly over-discharge, but it's not practical to incorporate over-current protection. Drain rates as high as 100 Amps are not uncommon, especially for performance aircraft. It's not unusual for them to explode into flames on a severe crash if the batteries get crushed. A wiring fault can meet the same end.

    Hobbyists use expensive multi-channel balancing chargers to recharge the cells. I've read stories of charging mishaps that result in flaming batteries as well. They put the batteries in a fireproof containter when charging because of that.

    People who use these cells for hobby applications know the risk and take appropriate safety precautions. It's not the kind of thing you could ever expect someone to do with a consumer device. Consumer devices rely on electronic protection mechanisms.
     
  15. tom66

    Senior Member

    May 9, 2009
    2,613
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    All of the above is completely true. I fly model aircraft and use 20C and 25C LiPolys. This is why I am highly advising Rifaa doesn't try and blow up one of these cells.
     
  16. clavemartin

    New Member

    Jan 18, 2012
    5
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    Did you lately notice poor performance of your notebook Li-Ion battery?. do not be balled over, this is often happening even to the most effective battery! currently days Li-Ion batteries are widely utilized in moveable devices owing to there glorious energy to weight ratio and for the rationale they're not tormented by "memory effect".
     
  17. clavemartin

    New Member

    Jan 18, 2012
    5
    0
    For the diagrammatic function of Li-Ion battery [​IMG]
     
  18. JMac3108

    Active Member

    Aug 16, 2010
    349
    66
    Seriously .... LiIon cells are just not something a hobbyist should be playing with. Even many large companies with experienced design groups (including ones I've worked for) outsource battery pack design because they are afraid of the consequences of making a mistake with the safety and protection circuits that are required to be used with LiIon cells.

    Never open a LiIon battery pack.

    Never use raw LiIon cells. Only use battery packs with proper safety circuits inside.

    Don't try to design a LiIon battery charger unless you are experienced and fully understand the charge profile and safety considerations.

    These things will go up in flames and hurt you or someone else if not handled properly.
     
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