Making your Android's battery last longer is a fairly simple task, disable push notifications, manage your 3G usage, turn off GPS, the list goes on. However what you may not realise is that your battery life may be being hampered by incorrect calibration. Basically your battery stores no information, it's juice is measure by a stats file on the device itself; if that stats file is wrong your battery life will read wrong. Your battery stats file can be incorrect for reasons such as flashing a new ROM, therefore after each ROM flash you should calibrate your battery.
Note: To properly complete battery calibration you need 'root' access.
The method is in two process, steps 1-4 are 'conditioning', this allows the battery to make sure it's absorbing as much juice as it can. The remaining steps are 'calibration' steps which work by re-writing the battery stats file on the device.
- Run down your device's battery until it turns itself off
- Turn it back on and wait for it to turn off again; this may be straight away of after a few minutes
- Remove the battery for at least 20 seconds
- Replace the battery and charge until full and then for at least another hour - while the device is off
- Delete you batterystats.bin file using one of 3 methods (requires root): Terminal Emulator - type su then press enter, next type 'rm /data/system/batterystats.bin' (without quotes). Using a Battery Calibration App (from market) - there are many choices available, they just delete your batterystats.bin file. In market, search for battery calibration. Make sure to read review and provided info in case of device incompatibilities. Manually - if for any reason the previous two methods didn't work you may want to try deleting the file manually. Using a file manager with root access (such as Root Explorer) navigate to 'data/system/batterystats.bin'. Delete 'batterystats.bin'
- Your device will now creates itself a new batterystats.bin file with a correct 100% battery reading.
- Run down the battery until it turns itself off
- Turn on the device and charge for at least 8 hours
- Unplug the device, turn off and charge for another hour
- Unplug the device, turn on and wait for 2 minutes
- Turn off and charge for another hour
- Use the device as normal!
You really only need to do this very few months or when you change ROM. Providing you don'd change any major settings the battery stats file will remain accurate.
This may not always produce results because your battery stats file may not be affected at all.