Why is facetime draining my battery even when my phone is charging?

Charged battery to 99% on FaceTime video call for an hour battery drained to 70%..

Background activity turned off for all apps.

any other suggestion?

Same here 5 hours of use of facetime went from %100 to %40 in a matter of 5 hours. I have a macbook air m2

Hey Chargingissuez,

As FaceTime can be resource intensive it may be using more battery than other apps on your device, or additional apps open in the background could contribute to the battery drain as well.

First, we'd recommend checking to see what apps are using the most battery life on your iPhone. This article explains how: About the battery usage on your iPhone, iPad, and iPod touch - Apple Support

"Check battery usage 

To see an overview of your battery level and activity for the last 24 hours and up to the last 10 days, go to Settings > Battery.

When you tap one of the time periods above the Activity graph (Last 24 Hours or Last [X] Days), you can see which apps contributed to your battery usage during that time period, and the proportion of battery used for the app.

To see how long each app was in use on screen (the dark blue bars) or in the background (the light blue bars), tap Show Activity. Under each app, you might see these usage types:

• Background Activity means that most of the app's battery usage — such as playing music or tracking location — happened while the app was in the background.
• No Cell Coverage and Low Signal means that your device was searching for a signal or being used with a low signal.
• Connected to Charger means the app was used only when your device was charging.

You can also see when your device was last connected to a charger and the last charge level. With iOS 16, you can see if charging paused because of Optimized Battery Charging, Clean Energy Charging, or temperature."

We'd also recommend checking your battery health and reviewing the information in this article to for additional steps to help improve battery life: iPhone Battery and Performance - Apple Support

"Your battery's maximum capacity

The Battery Health screen includes information on maximum battery capacity and peak performance capability. 

Maximum battery capacity measures the device battery capacity relative to when it was new. A battery will have lower capacity as the battery chemically ages which may result in fewer hours of usage between charges. Depending upon the length of time between when the iPhone was made and when it is activated, your battery capacity may show as slightly less than 100%.

A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions. The one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers battery service for a charge. Learn more about charge cycles.

As your battery health degrades, so can its ability to deliver peak performance. The Battery Health screen includes a section for Peak Performance Capability where the following messages may appear."

Thanks!