Users have reported a bug in the iOS 9.2 system which is forcing some iPhones to display an incorrect level of battery charge.
Apple have outlined the problem themselves in their support documents and are working on a fix for the upcoming iOS 9.2.1 update, but have offered a solution in the meantime.
When your #iPhone battery is at 47% after being at 100% 3hrs ago shows that there's something seriously wrong!! #fedup #apple
— Kt Barton 🐝 (@KtyB84) January 18, 2016
The root of the bug is said to lie in users updating the time on their phone either by changing their time zone or manually setting the time. The simple fix is to first restart your phone and then change your settings to allow your phone to update the time automatically.
If the problem continues after this, they advise you to call Apple Support.
The bug is expected to be fixed by the time the new iOS 9.3 update is released, alongside some other cool features.