If it won't charge with a new battery and a different charger cord (as long as both the battery and the charging cord are OEM and not aftermarket), then it is possible that the phone is damaged internally. You don't have to drop it or get it in liquid to cause problems. A power surge could do it, a bad battery, bad charger, etc. To many variables to know for certain.
If you want to keep the device, and it is under warranty, then I would contact the manufacturer. If not under warranty, then try a local tech about a repair.