I bought a new Lenovo laptop, but sometimes used the power supply for my old Lenovo laptop. I just found out that the old power supply was the source of a very irritating high frequency sound (sample here). If I use the new power supply provided with my laptop, there is no sound. As it's rather convenient to have two power supplies, i would like to know the following:

Will using this old power supply damage my battery? (or some other parts of the computer? -- even though i can't see how that should happen)

(I have also tried to swap the cords going from the AC socket to the power supply -- it had no effect)

If you want to see the technical data for the two power supplies, see this image (old is left, new is right):


  • There's no reason to believe it would be damaging your battery, or your laptop. It's just an old power supply. Oct 28, 2012 at 20:41

1 Answer 1


Over time due to thermal cycling the tiny wire windings of the inductor coil that is used in the battery charge circuit will micro expand and contract and the hot glue used to keep them together can give way a little. When the battery is being charged the circuit switches at a very high frequency, however the fine control needed to keep the current constant as well as certain combinations of voltage and load can cause the coil to resonate at a frequency in the audible range, thus producing a high-pitched sound. This should not be a problem normally and should pose no danger to your battery or other parts. If the sounds gets too loud however or the adapter is getting very hot, I would recommend you stop using it.

  • Hmm, that is a good answer. It sounds like what is happening to my router: it has started making a high-pitched sound near the induction coils that is only audible when the case is off. It is several years old and gets warm occasionally and even stops working for a while, but generally it seems to work. The only difference is that the router is always plugged in, so I can’t imagine that it would/should be cycling.
    – Synetech
    Oct 28, 2012 at 23:48
  • @Synetech: I guess it could be due to a bad capacitor as well, or simply an (R)LC circuit resonating more than normal.
    – Karan
    Oct 29, 2012 at 0:27
  • @Karan very detailed answer, but could you please clarify why you would recommend I should stop using it, if the sounds gets too loud or the adapter is getting very hot? (what would be the consequences?)
    – RasmusWL
    Oct 29, 2012 at 13:41
  • That might indicate a (imminent) failure, maybe due to a break in the coil or short or a blown capacitor or something else, and may result in excess current flowing into the laptop. That's why I said that while the sound by itself does not necessarily imply that you should stop using the adapter immediately, obviously it is not behaving the same as a brand new one and so you should keep an eye on it for any further changes.
    – Karan
    Oct 29, 2012 at 16:06

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