I'm having problems with my 3G 2.2 iphone (jailbroken). The battery icon on the status bar show significantly less battery than that big icon that shows on lock screen when the iphone is plugged into a wall/pc. How do I solve that? which icon is accurate and wich is not?
There is an application called "BatteryLog" on the iTunes. It's a good app that you can see your battery percentage or look at your batteries situation thorugh a graph. This will probably give you the exact status.
However to solve problem you're having now you will have to do restore to your iPhone.