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    #1

    Power adapter wasting a lot of energy

    I was measuring standby power around my home with a power meter, when I noticed that my laptop's power adapter was wasting 21 watts with the laptop turned off. I tried disconnecting it from the laptop - nothing changed. Even weirder, the next day it was only using 18w without any load. I tested other power bricks that I had around - the maximum I got was 9w without a load. So 18-21w was definitely too much.

    I know that I can use a power strip and turn it off when not in use, but I'm curious what's going on. I don't think it wastes that much energy by design, so there must be a problem somewhere. I'm also worried that at some point it will die and fry my laptop (which I use as a desktop).

    The power adapter is a Delta Electronics ADP-90SB BB, made for Asus. It's 4-5 years old. If you want to look inside, I found some pictures here. I haven't taken mine apart yet, because it's glued (like most power bricks are) and I expect to have some trouble opening it.

    Any ideas?
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    #2
    Re: Power adapter wasting a lot of energy

    looks like a modern day HP and if it si then most of it is heat being generated and a small amount to the control circuits and by reading the posts the point on which his that failed was the STPS30100ST transistor(s) so if it fails like his/hers did then it won't damage your laptop.
    Last edited by goontron; 07-02-2013, 04:27 PM.
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      #3
      Re: Power adapter wasting a lot of energy

      Originally posted by cib3k View Post
      I was measuring standby power around my home with a power meter, when I noticed that my laptop's power adapter was wasting 21 watts with the laptop turned off. I tried disconnecting it from the laptop - nothing changed. Even weirder, the next day it was only using 18w without any load. I tested other power bricks that I had around - the maximum I got was 9w without a load. So 18-21w was definitely too much.

      I know that I can use a power strip and turn it off when not in use, but I'm curious what's going on. I don't think it wastes that much energy by design, so there must be a problem somewhere. I'm also worried that at some point it will die and fry my laptop (which I use as a desktop).

      The power adapter is a Delta Electronics ADP-90SB BB, made for Asus. It's 4-5 years old. If you want to look inside, I found some pictures here. I haven't taken mine apart yet, because it's glued (like most power bricks are) and I expect to have some trouble opening it.

      Any ideas?
      If it was really consuming that much, it would have got hot enough to fail.
      Almost all laptop chargers for some years now use "green" technology that greatly reduces idle power consumption such as "burst mode".
      These chargers run cool to touch while powered but unloaded.
      I would expect all of this will apply to all respected brands such as Delta.
      Sounds like you are getting a false reading somehow.

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        #4
        Re: Power adapter wasting a lot of energy

        What were you using for these measurements?

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          #5
          Re: Power adapter wasting a lot of energy

          Thanks for the answers. I was using an inexpensive digital wattmeter/energy meter for the measurements, and it's possible that I was getting false readings either due to the low power being measured or to the burst mode rievax_60 mentioned. If the burst mode is to blame, how do you measure that properly? Is a regular multimeter good enough, or do you need some special equipment?

          Comment

            #6
            Re: Power adapter wasting a lot of energy

            As it was said, 21w is too much for such a brick to dissipate through the plastic, it would be very hot.

            It's possible the power factor was too low and that confused the meter.

            A multimeter would be able to measure the current going to the brick (set it to Amps) but if there are small pulses of current the meter may fail to show them on screen or log them (if it has some logging features).

            Another idea would be to run it from an inverter with known efficiency at such low loads and measure the voltage and the current drawn from the 12v batteries. Then you can do the math and see how much energy is used within a certain period of time (let's say 10-20 minutes) and do the average.

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              #7
              Re: Power adapter wasting a lot of energy

              The meter was the culprit. It doesn't measure properly small loads. After adding a 75W incandescent light bulb to increase the load, it started giving more accurate readings. The power adapter is fine, it draws nothing when off, and around 1W when the laptop is in standby.

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