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12 volts directly to 600E battery terminals?

Discussion in 'Laptops' started by vburnham, Sep 15, 2005.

  1. vburnham

    vburnham Guest

    The IBM 600E battery is at 12.6 volts fully charged and discharges to
    11 volts (according to the repair manual). This looks a lot like the
    charged vs discharged potentials of a deep cycle marine battery My
    plan is to remove the computers internal battery and feed 12 volts to
    the + and - internal terminals (where the battery plugs in). I believe
    the need for the other two terminals is to individually charge the
    LiIon cells.

    Am I overlooking something obvious that will cook the computer???

    Thanks,
    Vance
     
    vburnham, Sep 15, 2005
    #1
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  2. vburnham

    mike Guest

    YOur computer may or may not let you put volts in the terminals
    without connecting the others to the proper place. Try it.

    Remember that your battery can approach 15V fully charged. That may
    or may not be a problem.

    The problem comes when you try to hook up a battery charger when
    the laptop is connected. That depends on your charger.

    And if you REALLY want to blow things up, hook it directly to your
    car battery and start the engine.

    The negative battery terminal is probably not connected directly to
    ground, even though your multimeter will try to convice you that it is.
    IF you connect a modem, you can get a ground path thru there that can
    mess up the battery sense system.

    How are you gonna connect it all up. Remember that anything that
    CAN be hooked up backwards, eventually WILL get hooked up backwards.
    Goodbye laptop.

    So, the problem is not so much what you have thought about doing.
    The problem is with the "little" incremental things that you are likely
    to do later.

    Why can't you stuff the volts in the external DC power connector?
    Might not work, but worth a try. Still doesn't solve your overvoltage
    transient problems.
    mike


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    mike, Sep 16, 2005
    #2
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  3. The 600X (uses the same pack) will run down to 10.5V off the PS
    jack so I would be inclined to try that since the PS is also 16V,
    well within the marine's range if there is no external charger on
    the marine or spikes well filtered out..

    As you surmise, the other two terminals are for pack detection:
    one is a thermistor, the other a data line. Both must give
    correct readings or charging will not occur although power can be
    drawn from the pack (no fuel gauge in that case too and LEDs blink
    annoyingly), I'd be leery of connecting anything other than a
    pack because there are probably no overvoltage or overcurrent
    protection circuits on those terminals since only a small fused
    and protected pack is expected there.

    One thing I'd worry about is someone plugging into the jack while
    the marine is directly connected, again, due to design was for a
    standard IBM pack and its current range.

    ..
     
    H. Dziardziel, Sep 16, 2005
    #3
  4. Possibly.

    First, lithium batteries have a microprocessor in the battery that
    communicates with the laptop. Without this communication, the laptop
    may not work.

    Second, the lead-acid hi-capacity battery may damage the charging
    circuits of the laptop by looking too much like a short-circuit.

    Finally, even ignoring both of the above issues, connection to a battery
    may be ok, but do not attempt to connect the laptop directly to the
    power bus of a vehicle (car, boat or airplane) even if it's nominally
    the same voltage. Vehicle power systems have incredible spikes on them
    that can destroy a laptop.
     
    Barry Watzman, Sep 17, 2005
    #4
  5. 12.6 volts corresponds to a fully charged Li-Ion battery that has 3 series
    cells (or (more usually in Laptops) several paralleled 3 cell blocks).
    However the fully discharged voltage of such a battery is 9 volts. There is
    quite a bit more to the interface with the battery. Most contain battery
    monitoring and charging circuitry which communicates with the Laptop via
    those extra terminals that failed to escape your notice. With nothing
    connected, the Laptop may assume that the (missing) battery is either
    faulty, discharged or both. It may even attempt to charge your external
    battery.

    Personally, I wouldn't recommend your intended course of action.

    If you really want to run the laptop from a 12 volt external submarine
    battery (it's marine isn't it?), you would be better off obtaining a
    universal type laptop power supply which includes the ability to operate
    from car and aeroplane electrical systems. The added bonus is that it would
    also charge the official battery if required.
     
    The Electric Fan Club, Sep 21, 2005
    #5
  6. vburnham

    zwsdotcom Guest

    The downside is efficiency. If you come in through the DC input, you're
    almost certainly going through one more regulation stage than if you
    come in the battery terminals.
     
    zwsdotcom, Sep 21, 2005
    #6
  7. vburnham

    John Doue Guest

    Does it really matter? Laptops have been designed, like it or not, in
    such a way that trying to bypass the corresponding constraints will
    almost certainly harm them. So, yes, theoratically you may be right, but
    ....
     
    John Doue, Sep 21, 2005
    #7
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