Iphone 4S Battery Drain when in Stand By

hi,
have bought iphone 4s 1 of friend , have spome questions regarding battery usage when in standby.
left phone in standby 15 hours , showed 12 hours of usage (i have desactivated location services, bluetooth , in airplane mode). after 15 hours have 70 % of battery left on (doing nothing phone apparently in background).
normal ?
there problem battery (i guess more software problem) ?
still, there way see if battery working properly(some apps or playing video ....) ?

 

sounds normal me.

 

Forums iPhone, iPad, and iPod Touch iPhone iPhone Tips, Help and Troubleshooting

• iPhone
• Mac OS & System Software
• iPad
• Apple Watch
• Notebooks
• iTunes
• Apple ID
• iCloud
• Desktop Computers
• Apple Music
• Professional Applications
• iPod
• iWork
• Apple TV
• iLife
• Wireless