External Battery for Surface Pro?

Discussion in 'Microsoft' started by dgeffs, Feb 12, 2013.

Thread Status:
Not open for further replies.
  1. bjornb

    bjornb Pen Pal - Newbie

    Messages:
    31
    Likes Received:
    0
    Trophy Points:
    15
    You can try this: Disconnect the yellow and blue wires (leave them disconnected for now). Connect only black and red. Set output voltage to 12V on your external pack.
     
  2. chandlercv

    chandlercv Pen Pal - Newbie

    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    5
    I've just built an adapter for my xpal xp18000, and I'm noticing a faint whistling sound coming from my Surface Pro when it's connected. I'm also using the "willy" WI12: 19V in to 12V, 3A out adapter I got to use the xpal with an Asus t91.

    The question is, what does that whistling sound indicate? I'm assuming it means something bad, but I'd prefer it if somebody could explain it away as something that happens when you run your Surface off an external battery.
     
  3. bjornb

    bjornb Pen Pal - Newbie

    Messages:
    31
    Likes Received:
    0
    Trophy Points:
    15
    Strange, doesnt seem normal to me. Where does the sound come from? Speakers or somewhere else inside the Surface?

    I am thinking perhaps the 19V to 12V regulator is noisy (has poor filtering), and this noise affects the Surface in some way.

    There is no noise on mine when using my external battery.
     
  4. chandlercv

    chandlercv Pen Pal - Newbie

    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    5
    It's hard to pinpoint the source. Someplace inside the Surface. It seems equally loud on all sides. It stops when the screen is turned off. What's the worst thing noisy power can do to a Surface, would you say?
     
  5. bjornb

    bjornb Pen Pal - Newbie

    Messages:
    31
    Likes Received:
    0
    Trophy Points:
    15
    Just to be sure: Have you checked that the output voltage actually is (close to) 12V?

    Since it stops when the screen turns off perhaps noise is affecting the brightness regulation circuitry, or the battery charging circuitry (the current draw is less when you turn the screen off/entering standby).
    Is the noise constant or does it vary with brightness or load (cpu usage = current draw).
    Its hard to say what kind of effect this has, maybe nothing, but it might also reduce the life of the components affected. I would try to do something about it.

    You could try adding a filter after your 19 to 12V regulator, build a simple filter (add a ferrite bead, or more effective - an inductor and capacitor in a filter configuration), or buy one of those 12V alternator noise filters for car stereos and see if that helps. Something like these:
    12v filter car noise | eBay

    EDIT:
    If you have access to a scopemeter you could also check whether the 12V regulator actually is noisy.
     
    Last edited: Apr 8, 2013
  6. chandlercv

    chandlercv Pen Pal - Newbie

    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    5
    I did measure the output, it's a pretty steady 12.18 V. The squeal does seem to get louder proportional to the CPU load, but that's not exactly a scientific measurement.

    Is a ferrite bead filter one of those heavy clamp type thingies I see on monitor cords sometimes?

    Thanks for all your advice on this!
     
  7. Deathangel

    Deathangel Scribbler - Standard Member

    Messages:
    117
    Likes Received:
    3
    Trophy Points:
    31
    That is usually how they look when integrated into cables:
    File:Cable end.JPG - Wikipedia, the free encyclopedia
    It seems to be coil noise you have going on. But it should appear in the SP with the external battery and not the normal charger when both give you good power is weird. I have an external USB battery pack for my smartphone and that whistles when it is on, but the smartphone doesn't. Coil noise is not damaging per se, but it might indicate another problem with the power supply. :/ It would be good if you could try it out with different SP units, but I guess that is a little tough to do.
     
  8. chandlercv

    chandlercv Pen Pal - Newbie

    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    5
    When I measured my office Surface Pro charger output, I was getting 11.88V. I'm going to add a resistor in series to my homemade tip, pick up a ferrite bead, and see if that does the trick. After that, I guess I'll start hanging out at Best Buy and see what I can get away with . . .
     
  9. chandlercv

    chandlercv Pen Pal - Newbie

    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    5
    Or maybe not add a resistor - I'm calculating I need a .06 ohm resistor to get voltage drop of .18 volts with a current of 3A. Am I doing that correctly? Is a .18V over-volt not enough to worry about?
     
  10. bjornb

    bjornb Pen Pal - Newbie

    Messages:
    31
    Likes Received:
    0
    Trophy Points:
    15
    I wouldnt worry about that.
    My Pro charger also has a no load voltage of about 11.9V. The RT charger is higher though, 12.2V no load and 12.0V at 2A load. My external battery has 12.3V output when set to 12V (selectable 10V to 19V).
     
Loading...
Similar Threads - External Battery Surface
  1. desertlap
    Replies:
    3
    Views:
    966
Thread Status:
Not open for further replies.

Share This Page