engine wont start

son had radio blasting while cleaning up my 97 discovery. Told him he was running down battery so he hooked up charger while still listening to radio. Went to use truck and will not turn over. I cleaned and replaced all cables from battery and also put on new starter. Still wont start. Turn key on to position 2 and instrument cluster does not light up radio and dome work but as you put key in position 3 lights all black out. Any help will be appreciated:confused