Sudden standby battery drain

[Note 3 user]

Hi!
Yesterday I left my Note 3 at about 100% and when I woke up I discovered that I only had 20% left.
The battery page in settings said that during 10h and 50 min Android OS had used 34% and Google Play services 16%. Screen had used a mere 11%.
I was on HSPA+ (wifi was down and I disabled 4G to save battery) and GPS was off, as was sync. Power saving was on but does not do any difference with the screen off. I have never had such drain before. What is Android OS that uses all power and what is Google Play Services?
Please help me out!

 

[SumthinNew]

Try a hard reboot (remove the battery)
Disable power savings mode.
Have you recently downloaded a new app, as that can be the culprit.