iPhone 3GS turning off randomly while being used While using the phone it randomly shuts down. And when I turn it back on battery drains by about 3 or 4 percent. Could this be a battery problem or a sign to another major problem? So the only way I use my phone nowadays is while its plugged in. Battery also drains like hell. While using 3G battery goes from 100 to 50 in an hour. Are the random shut downs related to the excessive battery drain? Just last month I changed my battery IC beacause it displayed the " charging is not supported with this accesory" warning.
It sounds like you need to backup your iPhone with iTunes and change your battery... but I'm a little confused by your post. You have tried to put a new battery in it already? If so your issue is probably related to other internal components of your phone and not the battery. The 3GS is quite old now. It may be time for an upgrade.