3G Iphone, OS version 2.2, Dev-Team SIM unlock software installed.

The phone works perfect until the green battery status icon displays 3/4 full. At this point when I push the power button to wake up the screen, the big red battery charge screen is displayed and I can not farther unless I plug the USB cable which result a normal green battery charge icon displayed and then I can slide it to get access to springboard.
This issue comes back again when the battery status is 3/4 full. I tried to restore my phone as a "new Iphone" in order to get a "clean" OS,I jailbreaked it but no change… 3/4 battery brings the big red battery charge screen again.
Any ideas? Thanks!