If you was wondering, why your Cellphone battery drains faster after installing Facebook and Messenger.
Facebook run tests on your device[1].
Back in the days I had to use Facebook, I always though that it could be drained by start watching more on your phone than you should. But since Facebook was gone from my Phone my day ends with about 70% of his capacity at last. Before it was about 50-40%.
Anyways - a former Facebook developer claimed that Facebook is doing tests on your phone.
So listen and repeat: If a Service is free - you're the product!!!
[1]
New York Post: Facebook secretly killed users batteries, worker claims in lawsuit