Android phone discharges when it has 20% [duplicate]

Question

Possible Duplicate:
Why does my Nexus One power off with 15% power remaining?

I've noticed that when my Google Nexus One phone is showing ~20% of the battery, after using it for a minute or two it completely discharges to 0%. Everything started before two weeks or so. Before that phone was fine, but now if it's showing ~20% of battery, after a few minutes it turns off and when you turn it on, it shows that there are 0% left in a battery and turns off... Where's the problem?

Answer 1

There are rumours on bad battery stats being able to cause this, and recommend "battery calibration". If your device is rooted, you could try that (it certainly cannot hurt or cause damage) -- though other sources doubt that theory, there are several apps on the market to help you with the calibration process (e.g. Battery Calibration).

Background: The system learns about the battery state, to understand it better with the time. So if it learned wrong, it might think "hm, battery should still be good, 20%" -- while it's already empty. Then the battery suddenly does not provide enough juice -- and the phone turns off.

It also works the other way around, according to reports, where the device kept running for 2 hours on 1% charge...

Edit: You might also want to check battery - Why does my Nexus One power off with 15% power remaining? - Android Enthusiasts

Answer 2

Battery calibration is a myth and was busted by the Google Engineer Dianne Hackborn. See this :)

This is the quote:

"The battery indicator in the status/notification bar is a reflection of the batterystats.bin file in the data/system/ directory."

No, it does not.

This file is used to maintain, across reboots, low-level data about the kinds of operations the device and your apps are doing between battery changes. That is, it is solely used to compute the blame for battery usage shown in the "Battery Use" UI in settings.

That is, it has deeply significant things like "app X held a wake lock for 2 minutes" and "the screen was on at 60% brightness for 10 minutes."

It has no impact on the current battery level shown to you.

It has no impact on your battery life.

Deleting it is not going to do anything to make your more device more fantastic and wonderful... well, unless you have some deep hatred for seeing anything shown in the battery usage UI. And anyway, it is reset every time you unplug from power with a relatively full charge (thus why the battery usage UI data resets at that point), so this would be a much easier way to make it go away.