iPhone 17 Pro getting warm and losing 20%+ battery even when completely powered off after updating to iOS 27

iPhone 17 Pro getting warm and losing 20%+ battery even when completely powered off after updating to iOS 27

Hi everyone,

I’m experiencing a very unusual battery and temperature issue with my iPhone 17 Pro after updating to iOS 27.

I updated my iPhone about a week ago. For the first two days, everything was completely normal — the phone was smooth, cool, and battery life seemed normal.

However, starting around the third day, the phone began staying noticeably warm during normal/light use, and the battery started draining much faster than before.

What concerns me most is that the battery continues to drain significantly even when the iPhone is completely shut down.

What I have already tried:

• Force restarting the iPhone using the button combination
• Turning off Siri Beta
• Fully backing up the iPhone
• Performing a complete factory reset
• Setting the phone up again after the reset

Unfortunately, none of these resolved the issue.

The shutdown test

I completely shut down the iPhone before going to sleep and left it untouched for approximately 6 hours.

Before shutting it down, I checked the battery percentage.

When I checked it again after those 6 hours, the battery had dropped by more than 20% even though the iPhone had been completely powered off.

I also noticed that the phone was still noticeably warm when I picked it up before turning it back on.

This is what makes me think this may be more than normal post-update background activity.

The phone did not have any apps running because it was completely shut down.

Device information

• Model: iPhone 17 Pro
• Software: iOS 27
• Phone's Battery Health: 99%
• Charge Cycles: 92
• Problem started: Approximately 2 days after the iOS 27 update
• Battery drain: Very high during normal use
• Temperature: Consistently warm even during light use
• Shutdown drain: More than 20% over approximately 6 hours while completely powered off
• Factory reset: Already performed, but the problem remains

* I Have NEVER DROPPED my iPhone once, so There are NO ANY PHYSICAL DAMAGES!!!

Has anyone else experienced significant battery drain and warmth like this after iOS 27, particularly battery loss while the iPhone is completely powered off?

Could this indicate a battery, power-management, or hardware issue rather than normal post-update indexing?

Any advice would be appreciated.

(I'm so scared because I'm from Sri Lanka. I bought this phone from Sri Lankan reseller. We don't have Apple Stores in Sri Lanka to Claim remaining 6 months of Apple Care Warranty here)