Getting battery related information in Cocoa (OSX) development

I recently read a nice Quora answer on shallow charging and wanted to give it a try with my new Macbook Pro Retina. The core problem that I continuously faced was I would forget to plug the charger back in, or take it off and the charge would slide down below 35% or up to 100%. What I need was something that would remind me if the charge percentage would go above or below the limits. I did some research, but could not find anything in the Mac app store or in any of the open source projects. Since I was limited on time, I then setup a crude implementation using automator.

Its been three months since I implemented that crude implementation, and I finally got some time to develop an improved version.  At its core is a simple battery information API [BatteryInfo.h] which queries the system using ioreg tool via NSTask. I have even implemented a simple caching system which reduces the number of NSTask calls to the system.

The ioreg contains a lot of data, which is why I grep out only the things I need. The API can be easily extended by adding the additional keywords in the grep pattern.

The following information is available over the ioreg:

  • “TimeRemaining” = 271
  • “AvgTimeToEmpty” = 271
  • “ExternalChargeCapable” = No
  • “CellVoltage” = (3971,3976,3970,0)
  • “PermanentFailureStatus” = 0
  • “BatteryInvalidWakeSeconds” = 30
  • “MaxCapacity” = 8112
  • “Voltage” = 11917
  • “DesignCycleCount70” = 65535
  • “Manufacturer” = “SMP”
  • “CurrentCapacity” = 6917
  • “LegacyBatteryInfo” = {“Amperage”=18446744073709550084,”Flags”=4,”Capacity”=8112,”Current”=6917,”Voltage”=11917,”Cycle Count”=325}
  • “BatteryInstalled” = Yes
  • “CycleCount” = 325
  • “DesignCapacity” = 8460
  • “OperationStatus” = 58435
  • “ManufactureDate” = 16687
  • “AvgTimeToFull” = 65535
  • “PostDischargeWaitSeconds” = 120
  • “Temperature” = 3094
  • “FullyCharged” = No
  • “InstantAmperage” = 18446744073709550178
  • “Amperage” = 18446744073709550084
  • “IsCharging” = No
  • “DesignCycleCount9C” = 1000
  • “PostChargeWaitSeconds” = 120
  • “ExternalConnected” = No

A word of caution though, calls like isCharging can take a few seconds to update, I still have not been able to figure out why. Thus, should be safe to poll a few times before confirming the change.

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