Look at the in the usb ports and in the controller and charging cord to ensure no "gunk" has built up. If that checks out try a new charging cord. If that doesnt work but you know the contollers are good, open the PS3 and look at the circuit board for "burnt" spots. If you could even see that, it would probably be on the backside of the circuit board. Also check the ribbon that connects the usb circuit board to the motherboard.