‘Thanks for starting this thread.
‘Mine is doing the same, even with a 5 watt charger plugged in. i have never had a phone continue to heat up after charging was complete. If heat is bad for batteries, Apple has turned our phones into a toaster to kill our batteries. I only use about 20% of my battery everyday so when I plug my phone in at bed time it reaches the 80% in less than an hour. So why is my phone so warm in the morning when it has been fully charged for hours!!!
I have done chat and even called Apple and the techs give ridiculous excuses including me having a case on the phone. I have owned every iPhone since the 3G and never had one of the turn into a toaster after charging was complete! I have resorted to just charging for like 30 minutes at a time and no longer charging overnight.
it is the 80% charge limit that does this as if you turn it off, the phone is not even slightly warm in the morning. I have posted a bug report with Apple.