Enter Privacy Guard through Settings/Security or Settings/Privacy, then click Advanced or Show Built-In Apps (depending on which ROM you're running). From here you can select Google Play Services and deny the Wake Up, Keep Awake, and Auto-Start options. This should drastically reduce the amount of battery that Google Play Services and Android OS consume.
Please note: If you rely on your location being updated frequently then this method might not be right for you. This method disallows Google Play Services from waking your device every minute to obtain your location and Google Now cards are affected as a result. All other Google services should function normally.
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