How does the battery die whilst asleep?

[Sheljo82]

I factory reset my samsung s7 edge as i upgraded, i never had one problem before the reset. Gave the phone to my best mate first night after transferring data she goes to sleep it was on 70 % she wakes up its on 4% any ideas why this is happening as it was fine before?

 

[methodman89]

Open Settings, Battery usage, and see what is using it.

 

[ggrr8t]

Do you have Outlook on it? That killed my battery.

 

[Rukbat]

Also install something like GSam Battery Monitor to see what's keeping the phone awake at night. (If the mobile signal is weak where she is, that alone could be doing it.)