S60 Battery life

Hi

I've been using my S60 for over a year with no issues, however came to put it on to play yesterday and battery was at critical level which was very unusual because i charged it in the week. So i charged it fully during yesterday afternoon and then unplugged it. Went to put the watch on today and again the battery was at critical level...

I haven't - as far as I'm aware - downloaded anything or in fact even touched it between it working fine and then the battery having issues.

Im currently using v6.10, and apparently it is up to date.

Any one have any thoughts on what might be the issue?

Paul