By Liam Gilliver It’s mad how just three simple words can make your heart sink: “Warning, low battery.” If you’re constantly haunted by this modern-day dilemma, you will have inevitably tried to find a hack to boost your phone’s longevity on a night out. Perhaps you walk around with your device in airplane mode, accepting that any incoming texts will just have to wait. Or maybe you make sure the brightness is so dim you can’t actually see anything on the screen. However, there is one popular method that people think will save them a little bit of juice that is in fact draining your device. Bot…