What does "Battery Use" tell and how is it implemented?

Question

I have several questions about "Settings -> About Phone -> Battery Use", mainly because I don't understand what exactly those items mean.

(1) Does "Cell standby" indicate the energy used by the radio communication with the towers when there is no voice/data communication?

(2) What does "Phone idle" indicate?

(3) What does "Android System" indicate, energy used by the OS code execution?

(4) What does "Mediaserver" indicate?

(5) What does "Android Core Apps" indicate?

(6) It also lists energy consumed by individual apps. I'm wondering if those items only include the energy consumed by CPU+RAM+Flash, because the energy used by display+wifi+cell is already listed separately without breakdown to apps. Am I correct?

(7) How does Android measure energy used by individual hardware component? For example, to measure energy used by display, does it measure by voltage and current or just measure by the time the display and/or backlight is turned on? If the latter is the case, how does it handle different hardware?

(8) How does Android measure energy used by CPU/RAM/Flash of each individual process? I guess for CPU, it may use exampling and find how long each process occupies the CPU, just like many performance profilers do. But for RAM and Flash, it seems to be very expensive to measure it on-line.

(9) Is information in "Batter Use" accurate? :-)

Any help would be highly appreciated. Thanks!

Answer 1

If you click on each one, it will give you more info. I don't know the answer to all your questions but I'll share what I do know...

(1) Does "Cell standby" indicate the energy used by the radio communication with the towers when there is no voice/data communication?

Yes.

(2) What does "Phone idle" indicate?

It's the power your device uses to stay on when you are not using it. The CPU is still going and the memory is kept powered up...

(3) What does "Android System" indicate, energy used by the OS code execution?

There is a separate option for Android OS which refers to the execution of apps. The Android System is the energy used to run certain background services like AutoSync and the software side of communicating with cell towers...

(4) What does "Mediaserver" indicate?

I believe this is all audio and video processing. I don't think it'll reflect the total time you played music, but instead, the total processing time the CPU used to decode it.

(5) What does "Android Core Apps" indicate?

I don't have this on my phone. I wonder if this is what is labeled "Android OS" for me.

(6) It also lists energy consumed by individual apps. I'm wondering if those items only include the energy consumed by CPU+RAM+Flash, because the energy used by display+wifi+cell is already listed separately without breakdown to apps.

Great question. I don't know.