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I forgot my charger at home but really need to get my pc running. I have a charger from a friend of my my pc has an output of 19V / 7.1 A and the friends has 19V/ 4.3 A. I know that the charger might overheat but what if I only charge when my pc is turned of will it still draw as many electricity when it is turned off? And I have a bit of a problem finding the polarity of my pc I found the one on the charger though

Edit: Found another one 19,5 V and 6,7 A should that one work

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    If you use your friends charger you will damage his charger. Your laptop will draw more amperage then the charger can support. At least if I am reading the information you have provided correctly. In any case I personally wouldn't want to use it due to the huge difference in amperage.
    – Ramhound
    Feb 29, 2016 at 18:49
  • I found another one the new charger here has 19,5 V and 6,7 A this one is pretty close I am only worried about the higher volts cause it usually should be equal any idea? Feb 29, 2016 at 18:54

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I'm not sure on how you've worded the question. If the amperage the machine requires is higher than the power supply can provide (In this case, if the PSU provides 4.2A and your laptop requires 7.1A), this is a problem and you should not use it. Your laptop may attempt to draw more power than the power supply can provide, and cause damage to the unit. If, however, you mean the power supply can provide a greater amperage than your machine needs (EG. your machine requires 4.3 A and the PSU provides 7.1 A), this is fine to use.

Do not attempt to power up your machine with it until you are sure of the polarity and the PSU is able to provide sufficient amperage, as if it's incorrect it could damage the power supply, the machine, or both.

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  • what about 6,7 A and 19,5 V the amperage is almost the same the voltage is higher by 0,5 V could there be problems? Feb 29, 2016 at 18:56
  • There is a huge difference between 6.7 A and 7.1 A,, put it this way, 0.5 A can cause serious problems to the human body.
    – Ramhound
    Feb 29, 2016 at 18:59
  • @TenebrisNocte Amperage equal to or greater than is okay. Voltage should be equal. Any other scenario carries a high risk of damaging something. Maybe it could work for a period, but is it worth the chance of damage? I'd say not.
    – Jonno
    Feb 29, 2016 at 19:06
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The power supply on your notebook is a switched mode power supply. SMPS's powered of the power grid will always employ a transformer to archieve galvanic isolation. This has the sideeffect of limiting the amount of current that can flow (think of it like this: You can not blow out a fuse in your home by shorting the output of a PSU, because you are only shorting the secondary winding of a trafo). Therefore you won't burn anything. Unless you reverse the polarity, in which case you still won't burn anything, as the charging electronics on your nb's mobo will check for that.

The worst that can happen is that your nb won't charge.

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