iPhone 4S users are running through its battery at a prodigious rate, according to reports on the Apple support forum.

A long thread dedicated to the problem had more than 2,300 messages, ran for 160 pages and had been accessed more than 160,000 times as of 5pm yesterday, all huge numbers for an Apple support discussion.

"I've had the 4S since the launch day, and I've been pretty pleased with battery life," said someone identified as "andyfromsomerville" on the thread early yesterday. "Until this weekend. My phone just went from a full charge to empty within <14h standby time and about 95 minutes of light usage."

Others, however, said that the fast-battery-drain issue had been there from the start.

"Seems to lose 1% every 3-4 minutes, even when locked/asleep," noted John Goldman on October 15, the day the thread debuted .

Possible iOS 5 link

The iPhone 4S went on sale in the UK, US and five other countries on October 14. Three days later, Apple boasted that it had sold four million of the devices, more than double the number of iPhone 4 smartphones sold in the same span last year.

Although the bulk of the battery complaints pertain to the iPhone 4S, some users have also reported faster exhaustion for older devices - including the iPhone 4 and iPad - after updating to iOS 5, the operating system upgrade Apple issued October 12.

As is usual on Apple's support forum - which Apple representatives monitor but rarely contribute to - users posed numerous hypotheses about the problem's root, as well as multiple solutions.

Among the possible explanations, users put forward the iPhone 4S' location-monitoring service, the Siri voice control system, the on-by-default diagnostics option - which sends data to Apple - and iCloud, Apple's new sync and backup service.

But many unaffected

Some customers said that a variety of settings had mitigated, but not solved, the problem, while many more said that changes had had no effect on their phone's battery life.

While users themselves seem unable to pin down the cause, there is no shortage of claims by bloggers that they have found the source: Last week, for instance, the iDownloadBlog claimed that a bug in iOS 5's location service was at fault.

According to Apple, the iPhone 4S' battery should be good for eight hours of talk time, six hours of internet usage and 200 hours in standby mode. As a comparison, the iPhone 4 was rated at seven hours of talk time, six hours on the internet and 300 hours in standby.

Apple did not reply to a request for comment about the iPhone 4S battery complaints.