901 Charger: 12v Home Free?

Discussion in 'Asus' started by (PeteCresswell), Dec 30, 2008.

  1. I just noted that the stated output of my 901's charger is 12v
    DC.

    Unencumbered by any knowledge of electrical stuff, it sounds to
    me like the 901 can be charged just by a direct connection to a
    12v automobile battery - as long as the polarity is correct.

    Or am I just wishing?

    If not, downside of reversed polarity? No damage? Fry the box?
     
    (PeteCresswell), Dec 30, 2008
    #1
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  2. well, chargers for 12 v automobile batteries typically measure about
    14v DC when charging the battery.

    Reversed polarity at best will fry the box, at worse will explode an
    automobile battery. (ie jump starting an automobile and setting the
    polarity wrong).

    But if you set everything up right, 12 v from a battery should mimic
    the 12 v output of your unit.
     
    Charlie Hoffpauir, Dec 30, 2008
    #2
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  3. (PeteCresswell)

    Paul Guest

    If the adapter is delivering 12VDC regulated, that may be all that
    the 901 is capable of handling.

    Most of these adapters now are regulated, and based on switching
    principles. A switching regulator uses less material (like valuable
    copper wire in a transformer), and is a preferred method. The
    switching regulator adapter can be physically smaller than a
    60Hz transformer based one, and lighter in weight.

    The automotive battery is higher than 12V, and the output drops
    as the battery drains. It is considered unregulated.

    Don't do anything you'll later regret.

    On some laptops, you can damage them by using the wrong
    "universal" adapter. The 901 may have issues in the same
    way, if you connect the car battery. If the product includes
    a car adapter plug and cable, then you know they thought about
    the implications of car usage.

    Also, if you're connecting to the lighter socket in the car,
    and the car is operating, the car electrical system, while
    it is 12V, can have up to 70V or so transients on it.
    Automotive rated equipment (like your car stereo) will
    be designed for this harsh environment. So while the
    car lighter socket may look like a benign source of
    power, it can also fry stuff given the right set of
    conditions.

    An automobile battery by itself, won't have the
    transient problem, but a battery like that is
    still a dangerous toy. (Anything connected to a car
    battery, should be protected by a series connected fuse.)

    Yes, reversed polarity can be an issue as well. Designers
    don't put in polarity protection, if they think the item is
    only going to be used with the provided A.C. adapter
    and cable.

    Paul
     
    Paul, Dec 30, 2008
    #3
  4. (PeteCresswell)

    Anssi Saari Guest

    Yes, it'll probably work. On the other hand, if you mean a battery in
    a car with the engine running, then the voltage is typically about
    13.8 V. Might be a problem or not. Also, when starting the car or
    turning electrical stuff off or on you may get high voltage spikes
    which are likely to fry the 901.
    Probably serious damage. In my part of the world, an Asus car charger
    for the EEE PC series is a good and cheap solution for charging in the
    car, if that's what you're looking for.
     
    Anssi Saari, Dec 30, 2008
    #4
  5. Per Paul:
    Bottom line that I glean from this thread: "Don't chince out. Get
    an adapter made for the PC."
     
    (PeteCresswell), Dec 30, 2008
    #5
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