Nexus 5 whole battery drained in a single night
We are using Exchange on serveral devices at the office (for testing) and what i noticed is that sometimes exchange services seem to drain alot of battery even when set to a low interval or push. 

This typically happens when Exchange is trying to pull some data from the server but an error occurs. The end user (you) does not always see the error. 

For me usually a reboot fixes the problem, worst case remove the Exchange profile and reinstall it afterwards.