rMBP Battery - Is it supposed to "drain" to 95%?

Discussion in 'MacBook Pro' started by Reimer, Jan 16, 2014.

  1. Reimer macrumors regular

    Reimer

    Joined:
    Sep 15, 2006
    #1
    I've had my late 2013 15" rMBP for about a week now and I've had it mostly plugged into the AC adapter. I've noticed the battery charge level has stayed at 100% constantly, whereas with my 2010 15" MBP, the battery would drain to 95% and then recharge back to 100% every so often.

    Just wondering if this is now normal charging behavior. Thanks
     
  2. disasterdrone macrumors 6502

    Joined:
    Aug 31, 2013
    #2
    This is normal.
     
  3. raptor402 macrumors 6502

    Joined:
    Jun 30, 2011
    #3
    On AC Power, the MBP drains the battery down to around 95% to keep the battery healthy.

    I have a mid-2010 15" MBP but I haven't noticed that happening. Weird...

    Raptor
     
  4. disasterdrone macrumors 6502

    Joined:
    Aug 31, 2013
    #4
    The battery management technology has got more sophisticated over time - I'm not sure when this was introduced, but I seem to recall it doesn't happen on older machines.
     
  5. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #5
    No, it is not normal charging behavior. If you leave your MBP plugged in, the battery should not drain at all, unless you are putting extremely high power demands on your system, in which case your MBP may draw power from both the AC adapter and from the battery. These are very rare circumstances, however. Of course, if you leave your Mac plug in for weeks at a time, the battery will lose some power, but not from your MBP draining it.
    That is not true. In fact, Apple's battery charging technology is designed to prevent this from happening, since such short discharges in recharges are not good for the battery. When your battery is plugged in and fully charged, it stops charging and runs on AC power. Except in very rare circumstances, your Mac will not draw power from the battery while it is plugged in.

    The link below should answer most, if not all, of your battery/charging questions. If you haven't already done so, I highly recommend you take the time to read it.
     
  6. disasterdrone macrumors 6502

    Joined:
    Aug 31, 2013
    #6
    "My battery will not charge to 100%

    Occasionally, the battery may not show a full charge (100%) in OS X, even after the power adapter has been connected for an extended period of time. The battery may appear to stop charging between 93 percent and 99 percent. This behavior is normal and will help to prolong the overall life of the battery."

    http://support.apple.com/kb/HT1446?viewlocale=en_US&locale=en_US
     
  7. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #7
    That quote refers to not being able to charge the battery until it has dropped below 93 to 99%. It has nothing to do with the OP's concern about the battery actually draining while plugged in.
     
  8. disasterdrone macrumors 6502

    Joined:
    Aug 31, 2013
    #8
    Modern macs use the battery even when the power is plugged in. Some power flow is necessary to keep the battery healthy. Letting the battery discharge a little then recharge is part of the maintenance that the system automatically does.

    http://www.tomshardware.com/news/apple-macbook-pro-battery-benchmarks,6643.html
     
  9. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #9
    That is absolutely false. Read the FAQ I posted, which quotes directly from Apple's own documentation. Short discharges and recharges are bad for the battery, and Apple's technology is designed to prevent this. Apple notebooks only draw power from the battery while plugged in under periods of extreme power demands, which are not common to the average user. The article you linked does not indicate otherwise. That article refers to the fact that if you remove the battery from a Mac notebook, the CPU will be throttled, as there are situations where the Mac can draw power from both the battery and AC adapter, as I indicated earlier.
     
  10. raptor402 macrumors 6502

    Joined:
    Jun 30, 2011
    #10
    I seem to misinformed in that case. I never really went into the depth of the matter since my battery life has sucked for almost 2 years now.

    Nevertheless, maybe the OP was overusing his mid-2010 MBP when he noticed the discharging behaviour.

    Raptor
     
  11. Reimer thread starter macrumors regular

    Reimer

    Joined:
    Sep 15, 2006
    #11
    Hmm, that's odd. All I know is that my 2010 15" MBP has always done this. It has practically been a desktop replacement laptop so it has been plugged in the majority of the time I've owned it.

    It always trickles down to 95% and then recharges back to 100%. Rinse and repeat. It hasn't shown any other ill effects otherwise.
     
  12. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #12
    Over what period of time does it do that?
     
  13. Reimer thread starter macrumors regular

    Reimer

    Joined:
    Sep 15, 2006
    #13
    I'd say.... over a week or so.

    There has been a time where the "Service battery" message has come up before but I haven't seen it for months now. So, it could very well be that the battery is defective.
     
  14. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #14
    The "Service Battery" message could indicate a defective battery, but it also appears when the battery health has dropped below 80%. In the latter case, the battery is still usable as long as it holds sufficient charge to meet your needs.

    If you're not already doing so, use iStat Pro (free) or iStat Menus ($16) to get accurate readings of battery health and cycles and computer uptime, among many other things. A forum member has posted a copy of iStat Pro that has been "tweaked" to enhance compatibility with Mountain Lion. You can download it here.
     

Share This Page