Thunderbolt consumes 2013 MBA Battery

Discussion in 'MacBook Air' started by jgbr, Jul 8, 2013.

  1. jgbr macrumors 6502a

    Sep 14, 2007

    An intresting one today, I was watching my Watts and mA being consumed from my battery.

    As an experiment I plugged in the thunderbolt to ethernet adapter.

    My mA increased from about 500-600 to 1130mA. Knocking my Battery lifetime in half.

    I switched to Wifi and I ended up back at the 600mA mark and 8-9 Hours of life.

    Although I am not going to get into the mA watching crowd it does seem driving thunderbold is more power consuming then the intergrated Wifi.

    I've been watching battery debate closely, such as dropbox killing battery life for instance and so on.

    Thoughts and comments?
  2. scaredpoet macrumors 604


    Apr 6, 2007
    There's a microcontroller and other circuitry in the thunderbolt to ethernet adapter that requires bus power to operate. It's basically a full fledged PCIe ethernet card, just shrunken down and using thunderbolt as its interface. It needs to provide all the hardware required to make ethernet connections possible (not being built in to the logic board, this hardware doesn't exist on the MBA itself). And that requires power.

    I'd also speculate that the designers of this adapter probably expected that if you'd be on a wired connection, you wouldn't be moving around a whole lot and so, you might also be plugged in to AC power.

    If the extra power draw is a real problem, and you're connecting via ethernet to one fixed spot, you should probably just get another AC adapter and leave it plugged in to the same area you're hooking up via ethernet. It's what I do, though I also went ahead and just got a belkin express dock, which adds ethernet, plus additional USB ports, plus audio in/out and another thunderbolt port to daisy chain (I use it for an external display).
  3. FreakinEurekan macrumors 68040


    Sep 8, 2011
    Eureka Springs, Arkansas
    It's interesting but personally doesn't bother me. If I have anything plugged into my MBA, then I'm obviously in a stationary spot so it wouldn't be a hardship to plug into power.
  4. gnasher729 macrumors P6


    Nov 25, 2005
    Sure. Why don't you plug the MBA into a power outlet when you are cabled up anyway?


    There have been posters who measured battery time while connected to two external monitors :confused:
  5. old-wiz macrumors G3

    Mar 26, 2008
    West Suburban Boston Ma
    I am picturing someone somehow managing to carry around an MBA plus two external monitors. Must be someone very strong! (and crazy)
  6. paulrbeers macrumors 68040

    Dec 17, 2009
    Sooo what you are saying is using an external device (even something as "simple" as a thunderbolt to ethernet dongle) uses power? You don't say!?!?!
  7. johnjey macrumors regular

    Jun 17, 2013
    Northern CA
    Well i think its more about the netflix silverlight battery killer that looks like is the culprit here as well or let's say a combination of the worst: Netflix HD + thunderbolt HDMI to TV = Fried battery within 3 hours :mad:
  8. andeify macrumors 6502


    Jun 10, 2012
    According to his measurements nearly double the power, for just an ethernet controller - thats a lot more than id expect.
  9. dr34mc4st3r macrumors regular


    Aug 18, 2009
    I just bought the same adapter and observed the same regarding reduced battery life. it was slightly disappointing as I did not expect the adapter to use so much power. thankfully, everything else worked well.
  10. pentool macrumors member

    Jul 20, 2013
    I just got me a Thunderbolt Ethernet adapter as well today for my rMBP. For some insane reason I bought it for the same reason, thinking (aka hoping) it would consume less power than WiFi. I had about 63% battery power when I plugged it in. I was surfing the net maybe for about 10-15 minutes. Other than that I was just reading a PDF document using Reader. No other apps were open, no other 3rd party installed plugins in the BG (my rMBP is just under 2 weeks old so not much is on it.)

    Anyhow. Just under 2 hours, my battery percentage went from 63% to 42% with basically doing nothing. The adapter was just a tad warm to the touch so it does takes some power, but I did not expect it to be this much.

    I will be returning it and go back using WiFi.
  11. Eduardo Forneck macrumors regular

    Eduardo Forneck

    Jul 23, 2014
    using it on my rMBP late 2013 and it uses way more (twices!) power than wifi, that's really awkward... i'd like to know how it compares to the regular macbook pro that has an integrated ethernet out.
  12. motrek macrumors 68020

    Sep 14, 2012
    Just listing the stuff you THINK the computer was doing during that time is fairly worthless.

    You really have no idea what it might have been doing in the background--Spotlight indexing, downloading a huge OS update, etc.

    Check Activity Monitor, that's the only reliable way to determine what's using power, and how much.
  13. tdhurst macrumors 601


    Dec 27, 2003
    Phoenix, AZ

    Why? How is battery life an issue when you're stationary, which makes plugging into power super simple?
  14. DisplacedMic macrumors 65816

    May 1, 2009
    this generation is a bunch of sissies



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