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:
- 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?