Best and fastest way to drain a battery

Discussion in 'General Electronics Chat' started by electronewb, Nov 15, 2012.

  1. electronewb

    Thread Starter Member

    Apr 24, 2012
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    What's the best and fastest way to drain lithium ion batteries? I have about 10 14V lithium ion batteries to fully discharged right now I'm using an halogen lamp but it takes about 2-3 hours to fully discharge. What could I use to discharge it very fast?
     
  2. BillO

    Well-Known Member

    Nov 24, 2008
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    Well, it would depend on the batteries. However, before we get into that, why do you want to do this?
     
  3. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
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    I knew that question was coming!!!! ;) It's where I work we have to dispose of those batteries and apparently there's a "protocol" that we have to fully discharge the batteries before disposing of them. I know it doesn't make any sense if you dispose of a battery fully charged or discharged. BTW Those batteries don't hold their charge anymore
     
  4. Six_Shooter

    Member

    Nov 10, 2012
    33
    1
    The fastest way is shorting the battery, the best way is to not short the battery, but have a controlled discharge, like you are doing with the lamp.

    While I will suggest this, with the preface of exercising caution, you could connect a couple lamps together in parallel to reduce the resistance of the circuit.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If you short the terminals of a battery or cell, you risk having a fire, explosion and/or red hot conductors. Using incandescent lamps is very good due to the resistance decreasing with a decrease of temperature; the more discharged the battery becomes, the more rapidly it gets discharged.

    One oddity you'll run into is the weak cells can get charged in reverse polarity, while the remaining good cells still will have a positive charge on them. That's why a battery seems to recover after its been discharged heavily, then allowed to rest for a period of time.

    If you need to guarantee that every cell within the battery has been fully discharged, you will need to open the battery pack and discharge each cell. Remember. you're getting rid of these batteries because they won't hold a charge - it's actually just one or more cells that have gone bad.
     
  6. takao21203

    Distinguished Member

    Apr 28, 2012
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    Don't short a lithium battery. It will burn the internal wires, and/or it will shut down.

    Some battery chargers actually can do a controlled discharge (for instance my NiMH charger can do it).
     
  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    You should NEVER fully discharge a lithium battery. It ruins it.

    You should also NEVER discharge them fast as that will create internal heating which could cause them to explode or catch fire.
     
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    If these lithium cells are sealed in a pack made by any reputable manufacturer, they won't allow fully discharging. The packs contain internal protection circuitry that opens the lead when either excessive current is detected or the battery voltage gets too low.
     
  9. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    That's my goal to ruin it they have to be disposed fully discharge which boggles my mind why wasting time discharging batteries that will end up in a recycling bin I tried to get an answer on the reason but I couldn't get a straight answer
     
  10. takao21203

    Distinguished Member

    Apr 28, 2012
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    I wish you good luck with that.
    Consumers are not normally expected to discharge these kind of batteries before tossing them into recycling.
     
  11. tpny

    Member

    May 6, 2012
    216
    0
    what's the voltage on these batteries? I've let my 12V lead acid discharge thru a 50 ohm 10 watt resistor, it dropped pretty fast, but i only needed it to discharge it down to 10V. You can use a resistor size suitable to your battery voltage and current size.
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    Lithium batteries are not "recycled" because they are hazzardous waste and might blow up or catch on fire. I think they are sealed in concrete then buried.

    I have some LiPo cells that are swollen and might blow up. I cut one in half with a shovel (woopee!) and it smoked but did not blow up nor catch on fire.
    I store them in a tin can that also might blow up before I take them to the hazzardous waste dump.
     
  13. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    By recycling I meant those orange bins. I was thinking about a 5W resistor but wouldn't higher the resistance the faster it would discharge? For real those batteries are burried in concrete? If that's the case I don't see why we have to drain them!!!
     
  14. davebee

    Well-Known Member

    Oct 22, 2008
    539
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    If you don't drain them, and they are holding a good amount of charge, they could catch fire or explode in the face of someone who accidentally shorted them in the recycling center.
     
  15. Six_Shooter

    Member

    Nov 10, 2012
    33
    1
    No, lower resistance = higher current.

    I=V/R
     
  16. crutschow

    Expert

    Mar 14, 2008
    12,974
    3,220
    As SgtWookie noted, an incandescent bulb is a good way to discharge a battery since their resistance reduces as the voltage drops, tending to maintain the discharge current. Just use more lamps or a larger lamp to obtain a faster discharge. But don"t exceed the batteries maximum current rating (not necessarily determined by the AH rating).
     
  17. BillO

    Well-Known Member

    Nov 24, 2008
    985
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    As has already been said, most modern LiPo battery packs have internal circuitry to prevent them from discharging to a point where the cell would be damaged. However, this achieves your goal. Just discharge them at about C/10 until they do not pass anymore current. So if they are a 5Ahr battery, discharge them at 500 mA until they go dead. C/10 should be a same rate for most battery packs

    The concern is that if you try to dispose of them while they have power, they may short an overheat causing the release of undesirable chemicals or even fire. Although this is only a real danger with older or poorly designed packs.
     
  18. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    FYI: in the first generation of Lithium Ion batteries, allowing them to discharge too far caused formation of internal shorts and extreme heating...... as in law suits where some guy's family jewels got fried by his laptop computer.

    In the case of first gen Li-Poly batteries, similar problem: discharge too far and they short internally and cook and melt whatever they are in. Was not good because Valence Technology's first contract for their Li Poly cells was to the ARMY for their night vision goggles. They were not happy when they were cooking on their face.:eek:

    Don't screw around trying to "fully discharge" Li cells.

    It's the same reason I don't give razor blades to children: while I can't predict exactly what will happen, I know for sure that it is almost certainly going to be bad.:p
     
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