96 ford explorer no electrical power

went to start vehicle, starter clicked like battery was low, put charger on battery, now there is no power at all to vehicle no instruments brake lights or anything, slowly over the day the power prob got worse as I tried to start the vehicle. no power windows locks or anything. over the course of the day the battery seemed to get worse , battery charger reads battery is charged, my friend thinks a relay, could this be and if so which one?





http://freeautomechanic.com/mechanic/forum/2010/06/96-ford-explorer