Two weeks after Apple launched iOS 16, users continue to complain the mobile OS is sucking their battery power far too quickly.

Battery life tends to take an initial hit when new OSes are rolled out because updates to software and apps, as well as the reindexing files, photos, and other functions, taxes the processor, and thus, the battery. But over time, those background updates cease, and battery usage levels typically return to normal levels.

According to the business analytics service Mixpanel, about 13.3% of iPhone users have upgraded to iOS 16 since it was rolled out on Sept. 12. That's when reports of battery issues started popping up.

"Running on a 13 Pro and I'm getting noticeable battery drain compared to iOS 15.6.1," said one user commenting on MacRumors' iOS 16 Battery Drain Thread. "I had to recharge mid-way through the day (I don't allow my phone to dip below 30% to keep battery health in tip top shape). FYI my battery health is at 99%. And yes, this is iOS 16 production (non beta)."

Another poster wrote yesterday, "This is ridiculous. It's been how long since 16? My phone still gets hot...and the battery drains a lot faster than before 16. Just got this pop up. And I'm not even doing anything!"

Apple news site 9to5Mac polled its readers last week and found 63% of iPhone users indicated their battery life is worse after installing iOS 16.

"This seems to broadly line up with public sentiment regarding iOS 16's battery life impact," the site reported.

Gordon Kelly, a senior contributing writer for "Forbes," said the problem is so pervasive that Apple iPhone owners should consider remaining on iOS 15 until the issue is fixed by Apple.

"The problem has been hiding in plain sight. In my iOS 16 Upgrade Guide, I flagged multiple reports of battery drain, but the process of reindexing after updates makes this challenging to verify," Kelly wrote. "One week later, however, complaints are still flooding in, and evidence is mounting that Apple has a big problem on its hands."

Apple did not respond to a request for comment.

Since being introduced, iOS 16 has had its share of problems. The mobile OS got two rushed updates to fix bugs and security issues as well as problems with loading iMessage and FaceTime, among other things. And users are being more cautious about updating to iOS 16.

"It's not uncommon for new versions of iOS (and apps) to have glitches, but usually they are found in pre-release testing. If the battery life issue is real, then Apple did not do adequate testing before releasing the update. And that's an issue with their quality control," said Jack Gold, principal analyst at research firm J. Gold Associates

Generically speaking, Gold said, there are many things that can cause such issues from one generation of OS to another. New features and functions added to an OS can cause power drain if not properly optimized. New capabilities in the OS running in the background could also be a battery drain.  Also, things like not putting OS components to sleep when not used, or not optimizing specific coded functions to the processor and low-level architecture, can affect battery life.

"There are lots of reasons why updates of OS or apps can cause excessive battery drain, but the basic issue is, it should not have made it through to the user base if adequate testing and optimizations were done in the pre-release code," Gold said.

Users of iPhone 13 devices or earlier that have already upgraded to iOS 16 can downgrade to iOS 15.7. But owners of Apple's newest iPhone 14 line can't backtrack to any version of iOS before 16, which is what came with the newer phones.

"It might just be some sort of errant setting in the OS, but the majority of users would not have the knowledge to fix that if that were the case," Gold said. "They essentially have to wait for Apple to fix the problem. But it does show Apple in a bad light when these things happen, particularly since Apple makes a strong message around their security and simplicity of operations."