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Inverter blew a fuse!!

Discussion in 'Electronic Repair' started by Jon Davis, Aug 18, 2004.

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  1. Jon Davis

    Jon Davis Guest

    I was using my new emachines M6811 laptop, which has an A/C adapter with a
    "90W" blue sticker on the end of it, with a 150W cigarette lighter DC/AC
    inverter, Tripp Lite brand, in a 2002 Toyota Echo. The car has a new battery
    and
    the cig lighter had never before been used. The first day, with about
    7 or 8 hours on the road, there were no problems. Eventually, however, one
    day I plugged it in the inverter again and within about ten minutes the
    inverter alarm started sounding. I kept resetting it and in another five
    minutes the inverter's fuse blew, and the car's fuse blew, too, but it was
    somehow delayed by a few hours I think for some reason because we didn't
    notice the stereo wasn't working until hours later).

    A few dumb questions:

    - Is it possible that the laptop adapter is already going bad, drawing more
    power than should be? (Every time I plug it into the wall while the laptop
    is running I get a VERY visible and loud spark.)

    - If I bought an inverter that supported more wattage--say, 250 watts--would
    that decrease the chances of the *car* fuse from blowing out, or does the
    car fuse not "care about" the power handling of the inverter? (I don't know
    much about electricity.)

    - Would a direct DC-to-DC step-up converter be better? Any recommendations
    on a model of such an adapter for a laptop marked on the bottom with "18.5
    watts"?

    Thanks,
    Jon
     
  2. Jerry G.

    Jerry G. Guest

    I am very sure that you have a short somewhere. This inverter can draw a
    bit more than 20 amps at its peak load. These inverters are very efficient,
    and draw very little power when there is no load. They normally do not have
    more than about a 5% to 10% internal loss.

    I suspect that something in the power supply section for the laptop is
    defective, and it is drawing too much current. These low cost inverters are
    not pure sinewave, and this is what is keeping their cost down. It is
    expensive to make a true sinewave inverter. They are what is called a
    "modified sinewave". The waveform from these low cost inverters is a crude
    stepped sinewave, that is almost a square wave, and it is very high in its
    distortion because of this.

    Many types of power supplies for appliances and devices can be damaged by
    one of these inverters. These inverters are good for lights, devices with
    brush type motors such as an electric drill, or similar devices. There are
    many types of switching supplies that can also work with these, but not all
    of them. I have seen some equipment damaged by these inverters. Before using
    one on any device, it would be a good thing to enquire to the manufacture of
    the product you plan to use with it.

    You should take your laptop with its power supply (if it is an external
    supply), to the manufacture service rep to have it checked. This way you
    will know if there is a problem with it. I have seen a few computer power
    supplies damaged by some models of these inverters.

    --

    Jerry G.
    ==========================


    I was using my new emachines M6811 laptop, which has an A/C adapter with a
    "90W" blue sticker on the end of it, with a 150W cigarette lighter DC/AC
    inverter, Tripp Lite brand, in a 2002 Toyota Echo. The car has a new battery
    and
    the cig lighter had never before been used. The first day, with about
    7 or 8 hours on the road, there were no problems. Eventually, however, one
    day I plugged it in the inverter again and within about ten minutes the
    inverter alarm started sounding. I kept resetting it and in another five
    minutes the inverter's fuse blew, and the car's fuse blew, too, but it was
    somehow delayed by a few hours I think for some reason because we didn't
    notice the stereo wasn't working until hours later).

    A few dumb questions:

    - Is it possible that the laptop adapter is already going bad, drawing more
    power than should be? (Every time I plug it into the wall while the laptop
    is running I get a VERY visible and loud spark.)

    - If I bought an inverter that supported more wattage--say, 250 watts--would
    that decrease the chances of the *car* fuse from blowing out, or does the
    car fuse not "care about" the power handling of the inverter? (I don't know
    much about electricity.)

    - Would a direct DC-to-DC step-up converter be better? Any recommendations
    on a model of such an adapter for a laptop marked on the bottom with "18.5
    watts"?

    Thanks,
    Jon
     
  3. Jon Davis

    Jon Davis Guest

    Emachines has little to no cust. support, certainly no "service rep" as I
    bought it through mail order. I'll get a third party adapter replacement for
    the laptop. Is there a good inexpensive inverter that you might recommend?

    Jon
     
  4. This tells that there is something wrong... You should check things
    and not contonue to use the system unless you are sure that everything
    is right.
    You continued usign the thing even though you got warning that
    things were not right... You could have for example beign
    overheatign the inverter and then the overhatign caused
    a short-circuits..

    Delayed fuse blowing sounds strange.... You either did not
    ntice it earlier, or the incident with the inverter almost blew
    the use, and later the starting power spike on the stereo burned
    it completely...
    Sparking when pluggin in power supplies is quite normal.
    Many PC power supplies take quite high surge currents when
    they are started or plugged in.
    Higher wattage converter would not (at least theoretically)
    decrease the chances of the *car* fuse from blowing out.
    The car fuse will blow when too much power is taken from
    the outlet protected by it. This to much power intake could
    happen because of high power inverter powering very high load
    or because of inverter malfunction (short circuit etc.).
    I would quess that DC-to-DC step-up converter would be better
    suited in your applications. With this kind of device you get the
    power your laptop needs with less conversion steps in the way.
    Better efficiency and at least theoretically more reliable.

    Some inverters are not happy when feding power to devices
    like computer switched mode power supplies... They can take
    current in spikes while some inverters are designed for just
    pure resistive loads in their mind (this the load for what
    their power rating is specified).

    Check carefully on the power rating and type of adapter you need.
    You are talking on the beginning of the mssage "90W" and now
    say "18.5 watts". Which one is correct figure.
     
  5. Jon Davis

    Jon Davis Guest

    This tells that there is something wrong... You should check things
    It's a little late to say so now. At any rate, I only did this because the
    bottom of the unit said so... "If the alarm goes off or the inverter stops
    functioning, simply turn the unit off and on a few times and continue use."

    Thanks for your reply.

    Jon
     
  6. This may not be anything. It it were really drawing over 150 W, something
    would be getting very hot very quickly.
    The original inverter might just have been defective.
    No, you're probably better off with the DC to AC inverter.

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
    | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

    Note: These links are hopefully temporary until we can sort out the excessive
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    Important: Anything sent to the email address in the message header is ignored.
    To contact me, please use the feedback form on the S.E.R FAQ Web sites.
     
  7. Could be but if it were drawing more than 150 W, something in the laptop or
    its power supply would be getting very hot very quickly. I gather that
    aside from the "spark", the laptop operates normally.

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
    | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

    Note: These links are hopefully temporary until we can sort out the excessive
    traffic on Repairfaq.org.

    Important: Anything sent to the email address in the message header is ignored.
    To contact me, please use the feedback form on the S.E.R FAQ Web sites.
     
  8. Jack Edin

    Jack Edin Guest

    I don't agree at all!

    Buy an adapter specifically for you laptop, that plugs into a cigarette
    lighter.

    I have Compaq Armada series laptop(s). One I have mounted in the car.
    And YES it uses a Compaq brand DC to DC converter. It outputs 18.5 volts
    for my laptop.

    To invert up to 120V AC, then back down is NOT efficient!

    My two cents...


    Jack
    :)
     
  9. Jamie

    Jamie Guest

    replace the LapTop's AC power supply.
     
  10. That I agree with. What I don't agree with is just buying any old DC-DC
    converter to power your laptop. That would probably void the warranty.

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
    | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

    Note: These links are hopefully temporary until we can sort out the excessive
    traffic on Repairfaq.org.

    Important: Anything sent to the email address in the message header is ignored.
    To contact me, please use the feedback form on the S.E.R FAQ Web sites.
     
  11. Jon Davis

    Jon Davis Guest

    Well I don't see how plugging the AC adapter into a step-up AC/DC inverter
    is any better. You're making TWO voltage transformations (stepping up to
    120V, then stepping down again), plus your going from direct current to
    alternating current and then back to direct current which is undoubtedly
    going to be more likely to cause problems than just stepping up the voltage
    of a direct current.

    I am sure a DC-DC step-up adapter will be the best solution for me. It's
    electrically IDENTICAL to the universal external laptop batteries you can
    buy to place under a laptop and hook directly to the power input.

    Jon
     
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