I would check that the battery disconnect is properly mounted
[image|2548526]
and that when the MacBook is plugged in ( with the 5 volt cable ) that the tiny indicator light on the logic board lights up when the button near it is pressed.
[image|2548531]
Another possibility could be that the battery connections are too dirty to conduct current in which case, rubbing alcohol and a microfiber cloth could be used. Hope this helped!