MBP 15 owner question: Does your MBP battery discharge under load while plugged in?

Discussion in 'MacBook Pro' started by Penn Jennings, Dec 9, 2011.

  1. Penn Jennings macrumors 6502

    Joined:
    Apr 22, 2010
    Location:
    Michigan
    #1
    Hello All,

    I got a late 2011 MacBook Pro 15 (quad core 2.4 Ghz i7, 8 GB & 6770m) in October. I've noticed since the day I got it that if I encode video with handbrake or play Civ 5 that the battery will actually discharge while plugged in. Using iStats I can see that the power supplied to the system is negative. I assume that this simply means that the system is using more than the 85w adatper can supply. If this is true, this is a HORRIBLY designed system. I've had 8 laptops over the years, including other MBPs, Dells, IBMs, Toshibas and Acers and this would be the first time that I've ever seen this.

    The other thing that is bothersome is that the while the system and plugged in and the battery is discharging, the little LED on the mega-safe is green, not orange. If I didn't know what was going on, I would have no clue this was happening. At this point though I've learned that "If I hear the fan, the battery is discharging".


    I keep wondering what happens when the battery dies, will the system throttle down or crash?

    Does anyone know if is common to all MBP 15s or is my system defiective?
     
  2. GGJstudios, Dec 9, 2011
    Last edited: Dec 9, 2011

    GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #2
    This is normal. Read the AC POWER section of the following link. This should answer most, if not all, of your battery questions:
    Actually, the fans have nothing to do with the battery. They spin faster as required to maintain temperatures in a safe range.
    It would simply shut off.
     
  3. Eidorian macrumors Penryn

    Eidorian

    Joined:
    Mar 23, 2005
    Location:
    Indianapolis
    #3
    This has been noted in many other threads. It probably involves a design decision to limit the size of the power adapter.
     
  4. Penn Jennings thread starter macrumors 6502

    Joined:
    Apr 22, 2010
    Location:
    Michigan
    #4
    Thank You for the quick reply :)

    I just wonder what happens when the battery dies. I have at times encoded over night and noticed the battery under 50%. If I try this a year from now, when the battery isn't new I'm still wondering if the system will throttle or crash?

    Although, there will also be the problem that I won't be able to just pickup and in the morning after encoding over night either. I'm a little surprised about this from a $2,500 system but it is what is I guess.
     
  5. GGJstudios macrumors Westmere

    GGJstudios

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    May 16, 2008
    #5
    See the edit to my earlier post. I was interrupted by a few phone calls while composing it.
     
  6. Penn Jennings thread starter macrumors 6502

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    Michigan
    #6
    The fans don't directly have anything to do with the battery but when the system is under load it gets hot. The fans get loud are just an indicator.
     
  7. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #7
    Fans spinning faster is an indication of heat, whether running on battery or AC power. Fans can spin faster to maintain heat with no battery drain at all, if running on AC power. Increased battery drain can also occur from other factors, such as screen brightness, WiFi, Bluetooth, etc. which may not contribute to heat. Therefore, fans are an indicator of heat, not necessarily of battery drain.
     
  8. thundersteele macrumors 68030

    Joined:
    Oct 19, 2011
    Location:
    Switzerland
    #8
    This has been observed in both the early and late 2011 MBPs. The system draws a maximum of 93W, while the adapter only provides 85W. I'm too lazy to do exact math right now, but it should be 12-24 hours from a full battery. The MBP battery is supposed to stay above 80% capacity for 1000 cycles, or at least 2-3years. So you won't run into trouble anytime soon.

    It is a bit strange that Apple does not provide an adapter that is strong enough to power the laptop. I'm not sure if a 95W or 100W would be sufficient, or whether one also would have to modify the receiving part on the logic board. I prefer this to not having a quad core i7 and a dedicated GPU, but it's not really well designed. Apparently there's also a class action lawsuit now:
    http://appleguru.org/2011_Macbook_Pro_Battery_Lawsuit.pdf

    I don't know how often you encode videos over night, but an option would be to tell the laptop to shut down/sleep an hour before you get up in the morning, or to tell the program to end.
     
  9. Quinoky macrumors regular

    Quinoky

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    Sep 18, 2011
    Location:
    Groningen, Netherlands
    #9
    The same happened to my Late 2011 MBP. Normally I wouldn't mind since the battery drains only very slowly anyway. But this one time I had to do some resource intensive work on the go at the university, and eventually the battery died. So when I got home I plugged it in, tried to continue the work, but it obviously kept shutting down. I therefore had to wait for an hour or two before I could continue, which was a very much less than optimal experience. I wish Apple would at least have given us the option to get a larger power brick to avoid these kind of issues. :(
     
  10. Penn Jennings, Dec 9, 2011
    Last edited: Dec 9, 2011

    Penn Jennings thread starter macrumors 6502

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    Michigan
    #10
    My point was, when the fans are on high, I usually experience battery drain. Why? Because the system generates more heat when it use more power. It's just a typical chain of events.... More power use, more heat, more fan noise. Thus, fan noise is a good sign of battery drain. There is no other way to have the slightest clue by casually walking.

    If you have a late model 2011 MBP, how often do your fans stay on high and you NOT have battery drain?


    EDIT:
    I my case, I have never seen the battery drain while plugged in without the fans being on high at the same time.... Not once.
     
  11. ivoruest macrumors 6502

    ivoruest

    Joined:
    Jul 12, 2010
    Location:
    Guatemala
    #11
    You can actually have your fans at high speed and NOT have your battery draining. For example in a hot environment and under a medium load.

    I understand you like the idea of fans as an indicator but that is not accurate. You can have a Battery Indicator App or Widget such as these:
    http://www.coconut-flavour.com/
    http://www.makeuseof.com/tag/two-tools-to-monitor-your-macbooks-battery-mac/

    This will help you with your doubts.
     
  12. Penn Jennings thread starter macrumors 6502

    Joined:
    Apr 22, 2010
    Location:
    Michigan
    #12
    Yes, I am aware of that. I suppose if I had a good layer of dust inside, worked where it warm or maybe if worked with it on me lap things could be different. My MBP sits on a raise metal pad designed to allow air flow in room with low dust and 72 degrees at all times. However, I've had this system since October, if the fans are high, the battery is discharging whenever I happen to look at the battery meter. The fans are just a symptom, a correlation to high system utilization that causes the battery to drain and not the cause. In MY CASE its pretty rare for the fans to stay on high and the battery not drain, so it's pretty damn accurate for me.

    A good example, If I start play Civilization V for a few hours, the fan stays on. When I stop, I've had my battery as low as 40%, even though I started at 100% and was plug in the entire time.

    PS. The fan does get high for a short period of time and then return to normal after a few minutes. That is not what I'm talking about. I'm talking about the fan on high for hours.
     
  13. ivoruest macrumors 6502

    ivoruest

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    #13
    Ok, I get it. You have a good point and I understand. Just remember, correlation doesn't always imply causality.
     
  14. doh123 macrumors 65816

    Joined:
    Dec 28, 2009
    #15
    sounds like it may be draining pretty fast.

    on my 17" 2011 pushing it ot the max, i only lost about 5% in 5 to 6 hours.
     

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