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Laptop adapter 1v less

Discussion in 'General Electronics Discussion' started by BlinkingLeds, Sep 20, 2013.

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  1. BlinkingLeds


    Feb 23, 2013
    Recently a friend of mine got a new adapter for his laptop because the original adapter broke. Since he got it the laptop can't charge while it's running. If the laptop is on and i plug in the charger it has no effect (the laptop doesn't show that it's charging) other than the battery drop slower. If i turn off the laptop it charges but very slowly.
    I googled for the laptop specifications and it states that it needs 20v adapter while the one that my friend has is 19v.
    Could this be the reason that the batteries are not charging correctly because it worked fine with the original charger and the amps on the new one are slightly more than on the original one.
    I thought of checking it with a 20v switching power supply that i have but it’s not for laptops or anything it’s like the one in the photo could it harm the laptop if it try to plug it in?


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    Last edited by a moderator: Sep 20, 2013
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    This could be the reason. What is the nominal battery voltage of the laptop? The internal charger will require some voltage differential between the battery's voltage and the adapters voltage to drive charge current into the battery. I'd say if a difference of 1V between the old and new adapter provokes such a significant change in charge behaviour, the charge circuit is rather critically designed.

    Before you try the other supply you showed, make sure that the voltage is really 20V, not more (measure). You will need to jury-rig an adapter to connect this supply to the laptop. I recommend you do this for test purposes only, not as a permanent fix.
  3. BlinkingLeds


    Feb 23, 2013
    Thanks for the reply. The batery is marked 14,4v if i remember correctly also another thing i noticed is that when the battery is fully charged and i plug in the adapter id doesn't seem to slow down the discharge , but when the battery is at 10% or less and i plug the adapter it seems to discharge very slowly.

    The supply is variable from 20 to 28v at's it's lowest voltage the output reads is at 19.8v so i think it should be ok. I only want to test if the laptop's charging circuit is ok and not permanently use it (The exposed mains connectors stop me from doing that )
    Last edited: Sep 21, 2013
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