There you have it, in the title. Google engineer Dianne Hackborn, who has previously explained Android’s hardware acceleration, took to Google+ again to clarify some myths about the Android operating system. This time, it’s a point of common advice that you’ll see in virtually every FAQ thread about custom ROMs and flashing: wiping battery stats in order to improve battery life.
The reasoning behind that piece of advice was something like this: If you, at some point, did not charge your Android device fully (for example, only to 80%), it would supposedly remember that battery level as “fully charged” – in this case, you’d only ever get to use 80% of your battery, which is of course less than optimal. So, if you wipe the battery stats, usually done in ClockWord Mod Recovery, the device would “forget” the previous level, here 80%, and instead charge to the full 100% once again, thereby re-calibrating the battery. Or, as Hackborn puts it in more technical terms:
The battery indicator in the status/notification bar is a reflection of the batterystats.bin file in the data/system/ directory.
However, as she explains, that’s not the case. Because those battery stats, stored in the batterystats.bin file, are only used to maintain information about what is using the battery when not recharging. That is, it essentially holds the information displayed in the Settings > Battery screen. Nothing more, nothing less. Thus:
It has no impact on the current battery level shown to you.
It has no impact on your battery life.
What’s more, you’ve probably noticed that the battery usage data is reset once you recharge your device anyway. From this you can correctly deduce that the battery stats are wiped as well – every time your device is recharged. More or less every day. If there was any effect, you would’ve noticed it without going into recovery and doing that stuff. Typical placebo, eh?