The much-complained-about `battery drain' issue of the October-released iPhone 4S has been resolved for most of the users of the handset with Apple's new iOS 5.1 update, which was released along with the unveiling of the new iPad by the company last Wednesday.

The serious battery drainage of the iOS 5-equipped iPhone 4S and iPad came to the fore when several users of the handset complained on the online Apple forums that an apparent bug in the software led to battery drain, even when Siri and other prime features were not used.

Despite the fact that Apple was quick to work on a fix for the battery drain and charging issue almost immediately, with its release of an iOS 5.01 update, most of the iPhone and iPad users still remained dissatisfied with the performance of the battery of their devices.

With Apple again claiming to have improved the battery life of the two devices with its new iOS 5.1 update, a quick peek at online Apple communities has revealed that the newly-released update has apparently fixed the issue for most users.

Even though some of the users are still unsatisfied with the updated software, and claim that their device's battery continues to drain quickly, one of the satisfied users said on the Mac Forum that Apple had finally solved its battery issue with iOS 5.1; while another users said that the new update had brought about a "huge improvement" in the iPhone 4S battery performance.