For some reason, my PS3 controllers work completely fine with other PS3s. But then they don't usually sync with my PS3. For example, just the other day, I brought my 2 PS3 controllers ( both sixaxis) to my friend's house so that we would have 4 controllers including 2 of his. Then when i came back home with my 2 controllers, they failed to sync with my PS3. Instead, i get 4 blinking lights on each controller. This has happened before a couple of times, and usually, my PS3 syncs after a couple of days of just sitting idly. I know its not a battery problem since it was fully charged when i brought it home and it shouldn't be a controller problem because my controllers work fine with all of my friend's PS3s. I've also tried pressing that reset button in the back of the controller. But that doesn't work either. Any ideas? Its been almost 4 days already and everytime i try to sync my controller, I still only get 4 blinking lights.

did you update your ps3 firmware yet ? update to 3.15 , it includes a patch for some controller issues
if that doesn't help it might be because the controllers are worn out .