My Samsung Galaxy S3 battery died. A green robot with download message appeared when I plug it into a wall outlet to be charged. Seeing this for the first time, I thought it might have been some virus, so I removed and replaced the battery. The same thing happened again. After removing and replacing the battery a second time, the robot disappeared and my phone has been dead since, despite being left to charge for 5+ hours and several attempts removing/replacing battery and using the 2/3keys turning methods and plugging it directly to a laptop. How do i get it working. If fast boot is a possible solution, how is that done?
you can Follow this Guide to Flash your Galaxy S3's Firmware again.
Things you have to do for this are as follows
- Download the latest firmware for your device at sammobile
- Copy the firmware to your device either by Recovery mode or Samsung Kies or Samsung ODIN
- Flash the firmware on to your device using ODIN
The Complete process with pictures is provided in that link. Hope it helps