Ok guys. Thank you so much for your view and suggestion.
What can i conclude:
1. If i switch to wifi connection, my battery can tahan a few hours more.
2. Follow the tips form gizmodo how to save battery, and it help!
3. From my observation, as im using umobile, at my workplace the signal not so good. So my phone try hard to sustain 3g coverage and i think it drain my battery fast.
4. Last but not least, whatsapp really2 suck up my phone battery.

I try to see for few days and I will post my battery usage.

Btw im so in love with my iphone 5c! I hope it can serve me well for next 1-2 years! So i can kumpul duit byk2, and upgrade to iphone 6! Or iphone air perhaps! Haha