Bought a Troy-bilt lawn mower abt 2 yrs ago from Lowes. Used to cut a lawn of approx. 1/2 acre or less about once a week. Just used it last week with no problems. Yesterday it wouldn't start. Hooked it up to charger,charger said charging. Now battery is fully charged. Mower wont start. When turning the key, Hear a click click click sound, but it isn't turning over. Not even sounding like its close. Is it the starter or something wrong with the battery?Could it be something else? Thanks.