Harvey walker, if you are certain that your cables are good and that the chargers are working, it could most likely be your charging port. Use something like this [guide|139802] to get to teh PCB. Check the charging ports soldering connection and the wiring. If that looks alright you want to use a multimeter and see if you get power etrc. on the broadside of the connector. If not then consider replacing it or resolder. Post some good pictures of your work with your QUESTION so that we can see what you see. BTW tell us how you know that the battery is okay.