Is battery consumption linear?

Question

I am benchmarking an app using the batteryhistorian. The result is a chart where every percentile is a "tick".

After I've measured the battery consumption and let the battery drain to half, I would like to be able to save time by making a change and restarting a measurment without having charged the deviced back to full.

Is it a fair approximation to assume that a drop from 85% to 84% is the same as a drop from say 64% to 63% when benchmarking an application?

Answer 1

• Li Ion battery discharge is not strictly linear, (unlike a capacitor ). This ensures available power is utilised till the end of battery charge

• But it is fairly linear, more so at lower loads as can be seen from this figure, where C-rate or charge rate is the discharge/ charge rate

• Assuming your app is not a heavy power hog, it is reasonable to extraploate discharge. But, since the discharge isn't strictly linear, it would give better results if

  • Battery drop interval is more , say 5 to 10% and not 1% as proposed

  • Battery drop is not measured below 30% of battery ( to avoid greying into non linear portion of curve)

  • Measuring at 1% drop inherently introduces rounding off errors- if your phone has two digit accuracy, anything between 75.90 to 75.99 would show 76% . In the worst case, the error could be doubled (it won't fall to 75% till it goes below 75.90). Which means a 20% error, and that can be reduced to 2% over a 10% drop

  • Avoid measuring when the battery is fully charged to reduce errors. Measure at about 85% for the first reading and around 50% (or higher ) for second reading after tweaking your app