iPhone 3GS Shuts off under 40% battery.

[aszynka]

Hi.
Since I have updated my iPhone 3GS iOS 5 I met lots of problems. The iPhone was shutting off and I was not able to open it (Error 28) unless battery drain completly so it could clean the BIOS memory (am I right?). Now when I got software back to iOS 4, problem did not dissapear. iPhone keeps shutting off when the battery get lower than 40% (but fortunately, on iOS 4 when it closes I'm able to open it by simply pluginng it to charger). I found a simply solution to solve it- Airplane Mode- but it makes my phone unuseful. I'm out of any ideas guys, please help.

[aszynka]

Alright guys I found the problem. It's the battery. When I open iPhone and see it's twice fatter than it supposed to be, everything was obvious to me. I bought a new one, replaced, and it works like a charm... I won't count how many nights I have spent to figure that out.

[aaddaam]

Hey where from you got the replacement battery?