Oh I'm sorry to hear that they don't have CWM and in the Other hand ... as I know Rooting is a bit risky in this Device So I recommend to use one of the battery calibration ways I give you here ( tell me if they work ) :
------------------------------- first way : ( works for galaxy S2 )
1. Turn off your phone.
2. Fully Charge.
3. When getting 100% signal, unplug quickly.
4. Pull off the battery and put it anywhere.
5. Wait for 180 seconds exactly (be careful )
6. Meanwhile, take this opportunity to dust off the internal compartment.
7. Put back the battery on the right side.
8. Turn on the phone.
9. Pray the Battery god
10. ... and voilà !
11. After that, you can make some cycle of fully charge/discharge to ~15/20% TO complete the method
------------------------------ way 2 : ( works for galaxy S3 )
- Drain battery till it turns off.
- Get your USB jig and insert it on your s3
- Remove the USB jig and leave it till it turns off.
- Leave it for 5 minutes until the heats wears off
- Charge your phone for 10 minutes
- Turn it on
- Drain til 5%
- Insert USB charger and let it full charge
- Once full charge ( Green light appears )
- Remove charger and Enjoy.
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If non Of them worked you can try
this app and it may solve your problem ... Good luck
With Best Wishes
Hitman1376