Blackberry 9700 bold 2 won't power on

I have been trying for about a week now with some blackberry 9700 bold 2. It's the same problem with all of them, I can't get them to power on using the usb cable, the ac cord, at all. I see the red light for one of them only, the rest, just shows no sign of being able to power on, the screens are all black, using blackberry chargers and all that stuff, however for no reason whatsoever these phones won't come on even after been charged overnight and stuff, I can't seem to find any help for this at all, can someone here please help me out.

thanks