Apple launched iOS 10 back in September to mostly positive reviews, but with the recent release of a 10.1.1 update, something has gone wrong. A growing number of users are reporting that their battery is no longer functioning correctly, and there's no obvious reason as to why.

As News.com.au reports, the issue stems from how quickly the battery is draining coupled with the battery percentage readout no longer being accurate. For example, a battery with 80 percent charge left unused overnight is empty the following morning. Plugging it in reports 30 percent charge after a few seconds. However, unplugging when it says 100 percent sees the figure drop below 50 percent as soon as you unlock the iPhone.

It's worse when trying to figure out when to charge your handset. An iPhone$649.99 at T-Mobile can report 30 percent charge left, but then drop to 1 percent and shut down with a completely empty battery.

A discussion on Hacker News describes multiple instances of the battery issue occurring, with reports of an iPhone 6$549.95 at Amazon running extremely hot and the battery usage list offering no clue as to what is causing the huge increase in power draw. Full factory resets have been tried, but fail to solve the problem.

There is a chance this issue may be related to the iPhone 6s repair program Apple launched earlier this month due to faulty batteries. However, that program was for a small batch of iPhones, where as this looks to be a bigger issue combined with the iOS 10.1.1 update acting as a trigger.

Apple released two different versions of iOS 10.1.1. The first appeared on October 31 as a fix for an inability to view Health data. Then on November 9 a second version appeared for anyone who hadn't previously updated to 10.1.1. However, Apple released no information as to why this new version was required.

All eyes are now on Apple to track down the problem and issue a fix. Hopefully that can be done before iPhone batteries start failing.