Chosen Solution
For some time ago my iPhone 3GS broke after using a cheap battery cover. It would loose power extremely fast and power off instantly if you used the dock connector. I have now replaced the entire back, including the cover, dock connector, mic, speaker, buttons, battery etc. The phone no longer powers off when using the dock connector, but the battery is still loosing power very fast. Is it the logic board that’s the cause? (that would make me sad) Thanks! :)
Sorry to appear like I am hijacking this question. Richdave has given you great advice and I do not mean to bump anyone :-) Before you give up, check your dock connector and your battery for any power coming in. Plug your phone in an AC charger and see what your voltage is. Also, use an ohmmeter and check for continuity on your charging fuse. Check the connections on your dock connector, make sure you do not have any overlapping contacts. Check for broken, bent contacts as well.Furthermore, make sure that you battery is for a 3GS and check on the number. There have been plenty of issues with bad batteries over the last couple of month.
More likely the battery is duff. However, before you replace it, ensure the phone does not run hotter than expected as this may indicate a short somewhere draining the battery. battery replacement battery HIH
