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Laptop power supply mod - too many volts & watts?

Discussion in 'Power Electronics' started by totalsurf, Mar 23, 2013.

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  1. totalsurf


    Mar 23, 2013
    Hello everyone.

    This is my first post and I am a complete monkey when it comes to electronics compared to 99.9% of people on this forum!

    If anyone with knoweldge could advise on my query, I would be very grateful.

    I have 3 laptop power supplies which are extremely close to my new laptop and I want to know if it is safe to use them once I change the tip on them so they fit.

    They are all 20 volt DC, 2 amps (using an online calculator gives me 40w) - I seem to remember a triangle relationship between AVW from school!

    My new laptop adapter is 19 volt DC, 1.75amps (using an online calculator gives me 33.25w)

    Now my limited knowledge tells me that the increase in AMPS is completely fine as the unit will only draw the number of amps it needs

    I am hoping that the difference in 6.75w AND the 1v will be absolutely fine and won't blow my lovely new laptop - but could someone please advise?

    The tips don't fit, but I should be able to get some new tips and save myself about $150 in new power supplies!

    Thanks in advance.
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    It is most likely that a 20V 2A power supply can be used for a 19V 1.75A load.

    The main thing to check is the polarity of the power supply (connecting it around the wrong way can damage either/both of them)

    Power is just Volts x Amps for DC.

    You are correct that the device will draw the current it requires.
  3. totalsurf


    Mar 23, 2013
    Fantastic - I am not as thick as I thought ;-)

    Really appreciate your quick reply :)
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