
"We have heard reports of some people experiencing battery issues with our iOS app. We’re looking into this and hope to have a fix in place soon", said a spokesperson for Facebook.
A number of Facebook users have reported the app is using up to 39 percent of the battery over a six day period. Some blogs have speculated that it could be due to a bug where silent audio from auto-playing videos could be playing in the background. For now it is best to turn off auto-play and possibly even background app refresh.
Source: TechCrunch