Guys, I actually wanted to do a video to solve this but I just can't find the time. To solve this you will need to recalibrate the battery. Follow the instructions below :

1. Let the phone run until it shuts itself off.
2. Without turning the phone on, plug it in and let it fully charge up. (It will show full green battery image)
3. Unplug, turn the phone on and let it run flat again. (Without connecting to charger the whole time)
4. Battery and battery stats are now recalibrated.

**NOTE**
After recalibration, with Smart Endurance on, my phone can last until 3-4% and shutdown itself with the Lenovo boot up animation, only in reverse.

Do not worry as Lenovo's software will force shutdown when you reached around 3-4% by displaying the shutdown animation (if your battery is calibrated properly). Those who self shutdown at around 20% (like what happened to me previously) will not show the Lenovo shutdown animation. It will just turn black prematurely.

This is mostly due to eager owners (myself included) who straight away charge the phone and turn it on to play with it  after they buy a gadget. Proper way is to let the device charge fully without turning it on during the first charge. That way the battery will be properly calibrated.

Depend on what u do with it..normal use 1day
yesh..the knock feauture gt issue with too..sometime can work sometime need to knock harder or multipletime to work...so i end up nt use it

i thought k900 is li-po as lenovo website stated  

that link you mentioned is broken, like i said before.
the one i posted is the latest, rooted and tweaked.

EDIT : i suppose Ronald has the same link with mine?

that's weird. even other people also get 2000ma in the box, while i get 1000ma.
gonna get an iPad charger to save the hassle.