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I bought a new second hand computer with probably the wrong adapter. It's a 30 euro laptop with Windows Vista on it. The girl who sold it to me told me you have to wiggle the plug a little and then it charges. It does. But I have an old adapter from my old crashed laptop which plug fits perfectly into the slot. Also if I look at the back side of the laptop, the current there is exactly the current on my old charger. So I am 99% I can try that old charger on that newly bought second hand laptop without the risk of blowing things up, right?

To rephrase the devices are:

  • Newly bought second-hand laptop: 19V 3.42A
  • The non-fitting adapter I got with it:23V 2.50 A
  • My old adapter I still got from another laptop: 19V 3.42 A

Question 1: Should I try to use my old adapter rather then the non-fitting thing I got with it?

Question 2: How come the non-fitting adapter does charge that?

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  • 2
    Use the old adapter with the same voltage. Do not use the adapter with different voltage - even if it works. Apr 2, 2016 at 12:37
  • Verify that the polarity of the connector matches (which contacts are + and -). Some laptop brands only work with OEM adapters. Assuming the polarity matches, and the mismatched adapter worked, your adapter would be better.
    – fixer1234
    Apr 2, 2016 at 20:23
  • "How come that the not fitting adapter does charge that" - Ask the person who sold it to you why they provided the wrong adapter to the device they sold you.
    – Ramhound
    Apr 3, 2016 at 2:20

3 Answers 3

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Yes, you should try your old adapter, it sounds like it is more correct than the one supplied with the laptop. Verify the polarity is correct first though, if that is incorrect it could damage things.

As far as why does it charge, it makes electrical connection and supplies enough voltage and current within tolerance to charge the battery, dies mean it's optimal.

I doubt the PS supplied with with laptop is correct for it, my guess is someone misplaced the original or it failed and they happened to find something that worked to get by. It's more common than you would think.

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  • Thanks, I did not know what you meant with polarity, but found it in wikipedia. I could not find that symbol on the backside of the laptop, and just tried it. I could find it on the charger. But it works like a charm. I am going to put Bodhi Linux on it. I have some experience with that OS. I am happy today, 30$ for a working laptop!
    – Marc W
    Apr 2, 2016 at 13:57
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    Most (not all) laptops use the center as positive and the barrel as negative. Look at the markings on the charger supplied with the laptop. Those are obviously correct.
    – acejavelin
    Apr 2, 2016 at 13:59
  • Yes, I see it. My charger is like the most. And I can see the battery charging up. Thanks a lot!
    – Marc W
    Apr 2, 2016 at 14:02
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Do not use an adapter that exceeds the rated voltage in your laptop. And also check the polarity of the adapter and compare it against the data on your laptop. (Optional) It's best to buy an adapter with higher current rating than you laptop to prevent overloading and so as your laptop can have enough current in case you're doing a hard gaming. The laptop will just pull the current it needs.

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As long as the adapter fits the socket, has the same amperage, the same voltage, and polarity, it should work. Do not use the 23V adapter, it's going to irreparably damage the laptop.

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    The amperage may differ. If the adapter's electric current in ampere is equal or higher than that of the computer it is find. If it is lower, it may overheat. However, the latter depends on the manufacturer (see comments in superuser.com/a/247315/504096). Apr 2, 2016 at 13:15
  • While this answer is not wrong - and thus should not be downvoted (I upvoted to try and mitigate that), it is not a good answer - as @daniel.neumann said, having an adaptor with greater current is fine. Having an adaptor within 5% voltage is also normally OK - and above this does not guarantee irreparable damage to the laptop, although that is definately a possibility.
    – davidgo
    Apr 3, 2016 at 6:09

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