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My Macbook Pro (Retina 13" late 2013, OSX 10.10.5) has fine battery life overall - this is not the problem.

However, when the battery drops below about 8%, and before I normally get any "your Macbook will shut down soon" messages, average CPU use (over all processors) begins to go from a background low level (<10%) to >50%. It gets laggy, fan turns on, and so forth. Estimated battery life will go from 40 min to < 10 min.

Looking at activity, the main culprits for the increase can be 'windowserver' or 'mds' or 'mds_stores', often running at 80-90% on one processor, but typically other running apps (Chrome, QGIS, Evernote, etc) seem to also have a much higher usage during this period, adding up to a total CPU load >50% (and consequent temps / fan use, lag).

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This doesn't seem to be a speed stepping issue, nor are any new processes suddenly appearing.

--EDIT 2016-04-13

Here are some more examples of the processes, taken more at less at random after the battery went below 10% and the total CPU started exceeding ~75% - the highest processes are often mds* but other apps also increase CPU by 10x:

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  • If I'm not mistaken, mds and mds_stores are Spotlight workers that index files. Seems strange that they'd pop up. Also, most of the time when my battery gets low I don't really see any performance impacts. – perhapsmaybeharry Apr 9 '16 at 7:57
  • @perhapsmaybeharry is right, these processes are part of the spotlight system. They start and stop often. It is most likely coincidence that you've seen them start up when your battery is low. – alexkent Apr 13 '16 at 6:54
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    @alexkent - definitely part of Spotlight, and are the main culprits. However, this is a consistent and repeatable problem, not coincidence - see edits above. – Simbamangu Apr 13 '16 at 7:34
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    I wonder if the CPU is reducing its frequency to save power (or switching all but one core off) and as a result the CPU usage appears greater because there is overall less CPU resources available. – André Borie Mar 18 '17 at 14:42
  • No, it's happening to all cores, total CPU is really high. – Simbamangu Mar 18 '17 at 14:43

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