Previously I was on Darky’s v5, with that the phone lasted 2-3 days with normal usage.
After flashing to v7 (with 100% battery) I also got the fast drainage problem. Here is what I did:
1) Turn OFF phone
2) Charge till it says it is FULL
3) Start in RECOVERY (volume UP+Home+Power), here WIPE battery stats (it is in the “advanced” menu)
4) RESTART android (yes, it might already be on 98% or so)
5) USE phone heavily. Don’t worry if it drops too fast. Use it till the Android system turns OFF automatically (it happens when your battery is below 1% – for me the phone was on 1% for about 40 mins. This is where it heavily miscalculated
6) PLUG IN your charger, TURN ON android and wait till it is FULLY charged again. (It is better if you don’t use the phone at this charging up)
Now, after you disconnect the charger, you should still have 100% for some time (I’ve been using the phone for 32 mins – writing this post – and it is still on a hundred percent) and with this, I got back the 2-3 days battery life with normal usage.
Also, you should set WiFi to: “Never when plugged in” and by default I disable Data Network. But my phone is using WiFi all the time so it doesn’t really matter
So to summerize this method, the key is to show the phone the battery’s minimal capacity too, by using it till it is on null. Because with charging to 100% than wiping or flashing only introduces the maximum capacity to the system and the minimum is only guessed. THIS gives the faulty reportes and makes us think the phone drains too fast.
Try this method, than feel free to share your results.
(from xda user: TechnicR)