What's the worst thing about your iPhone? Most people would probably say the dreadful battery life.

Well - we've got some good news and some bad news. The good news is that there's one trick that can save you 15% of your battery power every day. The bad news is you're going to have to delete one of your most-used apps. Tests by Guardian tech journalist Samuel Gibbs found that if you deleted the iOS Facebook app your phone was left with significantly more juice. He tested it for a week with the app - and a week without and found himself with 15% more battery life at the end of the day. It's even greater for Android users who reported 20% more after deleting the app off their devices. It also saved a decent amount of space - with Gibbs claiming it consumed around 500MB in total between the 11MB app and the cache on iPhone. But if you're worried about not being able to check your Faceboook every five seconds - there's a work-around. Log into Facebook through Safari and then save a short-cut to your home screen - it's almost just as good but it won't hammer your battery.