@ maacruz, I implemented your formula and it doesn't work.

Device idle, active time of 1 hour and 25.2% battery, your drain rate is 25.2%. A rate based on one data point doesn't work well.

While playing a video with wifi active ASUI reported a 3%/hr drain while my battery was dropping from 25.2 to 23.9 and 1 active hour, dropping to 0 for two of the 10 capacity changes. Not sure how that zero active hours should be handled but the drain rate was decreasing under load.

The formula appears to be okay at higher capacities because active hours is able to fluctuate between a larger range but due to the lack of precision in active hours it breaks down at lower capacities. I'm going to comment out the code for now and play around with a drain rate for last 5,10,15 minutes but if you want to tweak the formula I'll turn it back on.