Why do phones still use battery when powered off?

Your battery is continually losing charge. Laura Polo/Shutterstock Even though smartphone batteries are getting bigger and more efficient, there's always that inevitable event when you get a low battery notification at the worst possible time. You might think powering down the phone entirely is a way to make your smartphone last longer. But like with any battery-powered device, a phone's battery will slowly deplete when you're not actively using it, and even when it's completely powered down. Of course, the battery drains much more slowly when turned off, so it's not a bad idea to power down the phone to conserve battery. That might be before a plane takes off, for example, and you want to ensure you have power when you arrive at your destination. If you leave an old phone in a drawer for