Mark Wilson writes: A study conducted by security research firm Wandera shows that iOS 11 is causing iPhone and iPad batteries to drain faster than ever -- much faster. The difference between iOS 10 and iOS 11 is anything but minor; batteries can drain in half the amount of time following the upgrade. Wandera's report shows how, on average, an iPhone or iPad running iOS 10 takes 240 minutes of usage to drain the battery from 100 percent to zero. With iOS 11 installed, this number plummets to just 96 minutes -- over twice as fast. Users have also complained about the issue.