Facebook has a reputation as a battery hog on iOS.

http://www.scottyloveless.com/blog/2014/the-ultimate-guide-t...

I just use the website now. Somehow it manages to offer chat as well as news feed without displacing me to another domain, or whatever is analogous to opening up an entirely separate app.

I just don't buy that spinning off messenger was good for customers, especially considering they have really failed to create a good experience all around.