After Update iOS 14.6 Battery drain and heating up device.

If your battery health is at 80% or below, learn about repair options: Get Support.

If not, Please read:

• About the battery usage on your iPhone, iPad, and iPod touch - Apple Support
• iPhone Battery and Performance - Apple Support
• Batteries - Maximizing Performance - Apple
• Batteries - Why Lithium-ion? - Apple

Cheers,

Jack

It is not clear here in your post about the ambient temperature in your area where you are using the iPhone. However --> Keeping iPhone, iPad, and iPod touch within acceptable ...

Store the device where the temperature is between -20º and 45º C (-4º to 113º F). Don’t leave the device in your car, because temperatures in parked cars can exceed this range.

Use iOS devices where the ambient temperature is between 0º and 35º C (32º to 95º F). Low- or high-temperature conditions might cause the device to change its behaviour to regulate its temperature. Using an iOS device in very cold conditions outside of its operating range might temporarily shorten battery life and could cause the device to turn off. Battery life will return to normal when you bring the device back to higher ambient temperatures. Using an iOS device in very hot conditions can permanently shorten battery life.

Before updating to the latest iOS 14.6 as told in your post what was your earlier iOS version. Then you can look into the iOS changes that have happened between the earlier version on your iPhone and this new version that you have updated now. 

This will give you a broader idea of the issue if it is directly linked to the iOS version or is triggered by something else.

I have the same problem on my iPhone 12 Pro. It’s relatively new & the battery is still at 100 percent and was lasting most of the day but not since update to 14.6. I listen to a lot of podcasts in the apple podcast app. Until they fix this I am going to try a different podcast app.

iPhone 11 and later models, battery performance --> About the battery and performance of iPhone 11 and later