German website finds Facebook app is the reason why the performance of the iPhone’s battery is so poor. Solution: either quit the app from multitasking bar when done or delete the app. Disabling chat etc doesn't fix it.
I don't use the actual fb app often but do use the messenger app and that drains battery like a bitch. Having a convo for 3-5mins can drain like 10% battery sometimes
I find that quitting the app is the best bet for battery life. Any location based apps are going to be battery hogs, like weather or maps. It's just the nature of the beast.
I only recently (less than a year) started using Facebook. I haven't noticed a difference in my battery life between devices or since I've been using Facebook.
I wish there was a way to deactivate "multitasking" for specific apps, i.e when I close the Facebook app it closes completely like they did before multitasking came around.