problem with my samsung galaxy s2 – plese help me.

Hi,
I need help from you, experts.
My Samsung Galaxy S2 phone’s battery always 0%. But when I connected to the charger, I can switch on and do anything from my phone. But when I charge disconnected, phone get shutdown showing batter is 0%. When I plugged in, charging is display, but not any changes, only 0% appears. But battery is 100% charged. I put my battery to another same phone of one of my friend. It shows battery is full. 100%, 90% and so on. Then from that I can come to the decision, that there’s no error with the battery.
So, as I think there’s a problem with detecting the current of the battery. Because when I switched on with battery (without plugged in), phone get vibrate, but no any color to the display come. So, I think, when I switch on, it get the value from IC connected to detect the battery current. So, if that IC is damaged, then the value is 0%. So power on failure. When plugged in, as it not directly get from battery, phone get switch on and can work as earlier.
THIS IS ONLY MY VIEW. AND IT MAY NOT THE ACTUAL ANSWER

I want your suggesstions. If any IC is gone, how can I identify exactly what IC is gone. Please help me to solve this problem.