Battery depletion

My iphone 5 is alrdy used for few weeks, and this problem occur once so i ignore it but then now become more oftern,

after i charged until full at night,normally i will leave it and the next day morning the phone should still in fully charged condition.

but this few days the battery keep decreasing even though not in use, all apps have been closed, data off, everything off, but the battery still being use up.

anyone has this problem?? or do you know how to solve this?