This is a small command line utility to measure and record battery statistics in Microsoft Windows. It should report the battery capacity in milliwatt hours, the voltage in millivolts, charge or discharge rate in milliwatts, and for each measurement, the number of seconds since recording began.
It was written to profile the power consumption of mpv media player using various hardware video decoding scenarios, but may be useful for development of other applications for which battery conservation is important.
With no arguments, win_battery_log simply prints these statistics to the console every two seconds until interrupted. So the command
win_battery_log
Will return output like
time(s) capacity(mWh) voltage(mV) rate(mW)
0 79700 12674 -12521
2 79690 12640 -12437
4 79690 12659 -12418
6 79670 12673 -12394
win_battery_log can also be used to measure the battery statistics for the running duration of any command. Simply add that command, and its arguments as arguments to win_battery_log itself. In this case, the statistics are written to a log file named by sanitizing the commandline into a file-friendly name suffixed by the Unix time in seconds and the ".log" extension. win_battery_log will automatically stop logging as soon as the command exits.
For example:
win_battery_log c:\windows\notepad.exe c:\windows\win.ini
will create a file called with the ugly, but functional name
c--windows-notepad.exe_c--windows-win.ini_0000000001458235621.log with
contents similar to the output shown above.
win_battery_log can be compiled using mingw-w64 in the MSYS2 environment, or as a Cygwin program. In the latter case, the path to the executable used as its second argument must still be in Windows (as opposed to Unix) format.
Other than standard Windows libraries, win_battery_log should only depend on make and a functioning c compiler (although it has only been tested with gcc). To build it, from inside the project root simply type
make
To remove the resulting executable and object files, as usual, it is sufficient to type
make clean
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It simply reports statistics on the first battery it finds. If you have multiple batteries and you want to know other batteries, some modifications to the source code may be necessary.
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It is possible that your battery does not actually provide voltage or discharge rate in comprehensible units. In MSDN terminology, the battery reports only "relative" units. This will be reflected by the absense of units in the output header. There's probably not more much that can be done about this.
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After the child process has ended, win_battery_log may take up to two seconds to return to the command line. This is because it only checks if the program is terminated every two seconds. It's no doubt possible to handle this better, but the added complexity is probably not worth it.