The update for Apple’s iOS5, aimed at solving the excessive battery use problem experienced by iPhone users running the OS, has failed to work in many cases, reports Bloomberg. Apple’s website message boards have seen user complaints saying the iOS5.0.1 update, released last Thursday, hasn’t fixed the flaw.

Apple said it will investigate further in a bid to solve the remaining issues. “The recent iOS software update addressed many of the battery issues that some customers experienced on their iOS 5 devices. We continue to investigate a few remaining issues,” Apple spokeswoman Trudy Muller told Bloomberg.

The latest Apple mobile OS was launched in October alongside the latest version of the iPhone 4S but it soon became clear that iOS5 was causing both 4S devices and older versions of the iPhone running it to use their battery up much more quickly.

Apple confirmed at the beginning of November that a glitch in the iOS5 platform update was causing a “lower than expected” battery life on devices running the OS and promised the update to fix the issue. The Guardian reported that Apple engineers contacted individual users to try to pin down the causes of the problem.