Calibrating/Correctly draining an Extended Battery I recently purchased an extended battery for my ailing Galaxy S4. It's supposedly rated at 4000 mAh over the previous 2600 mAh OEM battery.

First time I threw it in, I turned on the phone, chucked in the battery, and sat it on the charger for an hour or so.

It actually lasted a pretty long time. About 2 days and 5/6 hrs. SoT (not fantastic for 4000 mAh, but it's new so what the heck).

So, listening to the advice of others, I threw it on the charger until completely topped off while the phone was shut down. Again, I discharged it from 100%. However, this time, the battery drained much faster than usual. There weren't any particular apps draining the battery, it just drained faster.

Seeing as this was strange, I drained it to 0%, and charged it back up. Still, the same terrible battery drain. It may be I have to cycle it a couple more times.

Advice? How should I correctly calibrate an extended battery?
Firstly, battery calibration is a myth, normal or extended battery. See Bought a new battery, do I need to calibrate it?
Next, with extended batteries, there is always a possibility that the correct capacity of the battery is not being read  by the ROM and displayed ( since there are two different sources for reading the battery capacity and it may be reading from the hardcoded (ROM) rather than battery capacity files. See for more details here Where are the battery capacity files located?)


What you can do


Measure the actual capacity of your battery as explained here How to determine maximum capacity of a battery in mAh? - received fake battery using the app mentioned. 
Adjust the capacity of the battery manually in the app (from Battery Manager → Tap the 4 small square icon → Adjust Capacity or use Configuration Wizard) and create a shortcut on your home screen for the Battery Mgr widget and use that to measure


You can optionally avoid the first step above if you trust the battery provider capacity and adjust on the app