My battery was on 77% now drained overnight to 0%

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AC Question

My phone was on 77% i did not use it at all but when i woke it would not turn on and i put it on charge and it was on 0% . i know no one else used it because it had a password on, is there anyway to fix this in the settings, or is there something wrong with my phone. P.s it charges just fine not super slow.