1 Reply Latest reply: Feb 4, 2012 10:45 PM by capt huffnpuff
capt huffnpuff Level 1 Level 1 (0 points)

The Lion OS X 10.7.2 battery management software appears to be very erratic.


I just brought a new MacBook Pro direct from Apple last week (late 2011, 15", 2.4 GHz, 8 GB 1333 Mhz DDR3, 7500 rpm disc) with Lion OS X 10.7.2 preinstalled, i.e., the latest and greatest. I was only getting 3 hours on a battery charge until it ran out. After searching the forums nothing quite matched (older models, different graphic cards, more constrained systems, Lion software upgrades, etc).


I have the screen brightness set to about 50%, the power option "put disks to sleep whenever possible", and the keyboard set to turn off the light after 30 seconds of non-use. On battery, I have "display sleep" at 6 minutes and "computer sleep" set to 10 minutes. So I am not pushing the power consumption very hard.


I ran a "repair" from the recovery partition and my hard disk had no problems.


So I tried the Reset Power Manager metioned in another thread:

  • Shutdown
  • Depress Ctrl+Option+Shift
  • Power on
  • Hold for at least 10 seconds
  • Power on


and that extended my battery charge to 6 hours, not quite the 7 hours advertised. (I even tried it on my mid 2009 Mac Book Pro 13", Snow Leopard OS X 10.6.8 and its battery life was extended by about .67%).


But I started seeing odd reporting in the "time remaining" in the battery icon. The "time remaining" would fluctuate by as much as 20% in a just a few seconds, going either up or down! For example, it would jump from 4 hours to 3 hours, then up to 3.5 hours then up to 4.5 hours, down to 1.3 hours, and back up to 4.0, and so forth whenever I changed the state.



So I watched the "battery charge remaining" over several hours with different states:  (WIFI on/off, start/stop applications, turn Thunderbird/Firefox to offline and back to online; Thunderbird is not an issue because I have it set to check for incoming messages every 2 hours not every few minutes) and I monitored using the Activity Monitor and the widget iStat Pro. The cpu was reported to never exceed 2% busy, user+system, and free memory never fell below 5.9 GB with minimwl swapping and paging, i.e. the machine was basically idle even when I had WIFI on with Firefox watching Adobe Flash video from the net, which is purportedly a CPU hog (it is not).


Has anyone else seen this erratic battery software managemt behavior? Does any have an explanation?

MacBook Pro, Mac OS X (10.7.2), late 2011,15",5.4Ghz,8GB,7500 rpm
  • capt huffnpuff Level 1 Level 1 (0 points)

    I noticed in some archived threads that someone suggested changing "time" to "percentage" because "time" remaining is calculated every few seconds and is very sensitive to changes of state as I noted in my post. I don't see that "solution" as much use because it doesn't tell me "percentage" of what? The amount of charge left? What I really what to know is "how long will my charge last?". 70% of 3 hours is something quite different than 70% of 7 hours. It seems to me that the time remaining ought to be calculated less often. The value is reported in hh:mm. I don't see much point in calculating it every few seconds. Once a minute would actually be more accurate.