Poulan 19.5 hp lawn tractor , wont start

I have a Poulan 19.5hp lawn tractor that wont start. When turning the key there is nothing , it wont even crank over. Tried charging battery and still nothing. Went an bought new battery and still nothing. headlights wont even come on. Son dropped a wrench on old battery last year so thinking something shorted out maybe.help please Fuse seemed to not be blown. any ideas where to start looking.