Have you checked for a bad battery connection? It is possible that the battery cables are not making contact at all.Try taking off the cables and cleaning the contact area with sandpaper then replacing them. While the battery is disconnected you could take a wrench and check that the other end of the cables are tight, where they go on the starter and the ground. Do not do this with the battery connected, and do not overtighten as these are copper bolts and will not stand too much torque.