Measure the exact amount of battery usage within a period of time
I'd use Tasker for something like this! You can make a task to do the following:


Context: run between ?? a.m. and ?? p.m. 


Check the Repeat box and set to every 1 hour

Add Task
Pick File -> Write File
Give it a title, click the "tag" button and choose Battery Level
I checked "Append" and "Add Newline" as well, but the last would be optional I guess.


This will make your phone write the current battery level to a file that you create once each hour. If you're creative with the "Text" field, you could even have it record the time and date as well (See Examples in screenshots).

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