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Dangers of using power inverter to run laptop?


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Dangers of using power inverter to run laptop?

  • I want to be able to power my laptop (Inspiron 600m) in the car, and I have read some suggestions, both in this forum and elswhere, that say that a power inverter is a better deal than an auto/air adapter: inverters are cheaper (under $50), will definitely allow the laptop to charge (which  some auto/air adapters won't, for some laptops), and more versatile since they can be used with any appliance within the inverter's power limits.

    But I have also read a couple of things that make me wonder if the inverter is a good idea for a laptop:

    1) The cheaper inverters put out a modified sine wave, rather than a pure sine wave. (Pure sine wave inverters are much more expensive, over $100.) A couple vendor websites I have seen say that some laptops won't work properly with modified sine wave input, and to check with  the laptop manufacturer. Does Dell say whether or not Inspirons--specifically the 600m--will work with a modified sine wave?

    2) At least one inverter was described by the manufacturer as "much less likely" than a generator to damage sensitive electronics. Does that mean there is still a reasonable danger of damage to a laptop with an inverter (compared to when plugged into a wall outlet)? And can this danger be reduced by using a surge protector?

    Finally, if any 600m users have used an inverter and can tell me whether it seemed to work fine or not, I'd like to hear it.


  • 1) You definitly want a pure sine wave inverter - Dell will probably only sell your their air/auto dapater.

    2) As long as you get an intervert properly rated, theres no significant danger - worst you can do is kill the power brick. However, the rating you'll need is about 3x the draw on the power brick. So,, for example, if you have a 65W adapter on your 600m, you'll want a (3x65=)195 = 200W inverter to be safe. Otherwise, the spikes of power that are pulled by the brick will overload the inverter.
  • mattcowger,

    Could you say why you recommend the pure sine wave inverter? They're expensive, so it would be cheaper for me to get the auto/air adapter if the modified sine wave inverter won't work or might damage the computer.


  • The problem with a non pure converter (either square wave or stepped square wave) is that switching power supplies like thpose in a laptop tend to be very sensitive to square edges. less deamnding devices like, say, an electic motor can deal with a stepped wave (though its still nto good for them).

    Its the characteristic of a switching power supply that makes it not deal with a stepped inverter well, btu again, it all depends on use. If you buy a nice stepped inverter rated for well above your needs, and aren't running your laptop off of it for 8 hours a day, ti will be fine. However, if you are buying something, for, say a RV and plan to contantly use the laptop on the inverter, get the nicer pure sine wave.
  • Thanks; that's very helpful.

    Others who are interested in an inverter for running a laptop might be interested to hear what Dell tech support finally told me:

    "The AC adapter for the Inspiron 600M needs a DC inverter that outputs Modified Sine Wave. But I would suggest that you get the Dell recommended auto adapter which is available from our sales department."

    That's a little more straightforward than the answers some other people report getting from Dell (such as "I don't think it will hurt your computer...").

  • That's a nonsense comment from a tech at Dell that knows nothing about power. Does he actually beleive the AC adapter was designed for modified sine wave AC? Give me a break! I suppose Dell should tell all the power companies to start chopping their output into more inefficient, dirty signals. And the Dell DC DC adapter, of which 38000 were recalled (65 watts at that!), is a poor solution at best. Ideally, a DC to DC converter would be the best solution. Unfortunately, Dell has incorporated proprietary comm chips in their units so third party adapters will either not work at all, or in the case of the D series (an a couple others) will work but not charge. Dell is a marketing company. You must remember they do not develop technology, and in many cases, know very little about it.
  • I thought I would post this message regarding the use of surge suppressors.  Below is the response I received from a technical support rep from Tripp-Lite regarding the use of surge suppressors.  I had purchased a 350w inverter from them and I noticed when I plugged in my Tripp-Lite notebook surge suppressor into it the ground lite did not light up, but it did when I plugged the suppressor into my Coleman 800 watt inverter that I have hard wired to my vehicles battery. 

    I no longer use surge suppressors on my modified sine wave inverters after reading the reply I received.  Once I can afford one I am sure I will just get a pure sine wave inverter.

    "Thank you for your inquiry.  Our inverters have a floating ground & the
    unit will have no reference to ground.  You cannot plug a surge suppresser
    into a inverter, this can possibly cause a catastrophic failure of either
    the surge suppresser or the inverter.  Inverters output a modified sine
    wave & surge suppressers only recognize a pure sine wave.  The surge
    suppresser will act against the modified sine wave because it is not
    recognized & possibly cause the surge suppression components in the surge
    suppresser to explode or the inverter to become damaged because it is
    receiving a feed back of its own power."

  • Powering laptop in car. Bought a 75W power inverter for Dell Inspiron 4150. A 75W inverter will not charge battery or allow laptop to turn on......but, remove battery from laptop, connect power inverter as normal and laptop runs forever (my son ran his on a 5.5 hour drive, no problems) 
  • Dell sells TrippLite 200W and 400W power inverters on their web site. Considering they're half the price of the small Dell car adapter, they're probably not pure sine wave.