iPhone 16 loses 7–8% battery overnight with no activity

7-8% a night is much less than average. You don’t just have a battery. While it is called an iPhone, it is actually a very powerful pocket-sized computer that can incidentally make phone calls. And like all computers, it uses power continuously, even in low power mode. If it wasn’t in low power mode it would probably lose 15% to 20% overnight.

But you should be charging overnight, every night. The absolute best way to get maximum use on a charge, as well as slow the decline of battery capacity long term is to enable Optimized Battery Charging (Settings/Battery/Battery Health) and charge the device overnight, every night leaving it powered on. The battery will fast charge to 80%, then pause. During the nighttime pause the phone will use mains power instead of battery power, allowing the battery to “rest”, and thus reducing the need to charge the battery quite as often. The phone will resume charging to reach 100% when you are ready to use your phone; it will “learn” your usage pattern. If you enable iCloud Backup (Settings/[your name]/iCloud - iCloud Backup) the phone will back up overnight also, assuring that you can never lose more than the current day’s updates. Here's more information→About Optimized Battery Charging on your iPhone - Apple Support

tttppp15 wrote:

Thanks for your reply - appreciated. Well yes, I have read about optimized battery charging, but I have also read about charging the phone up to 80-90% and just sometimes to 100%. I am charging during the day, leaving it on wi fi to allow icloud backup to happen. Last night I left it with 81% and woke up with 77%. This night I didn't turn on low power mode, that is the only difference.

The night before (and some nights before it also) I left it with 35% and woke up with 28%, which just sounded like too much for the phone which is activated 1.5 months ago. Any opinions appreciated.

My opinion is also to charge at night, all night, every night. They even have a night stand/bedside mode to use it as a clock. That is how they were designed.

I’ve also read that the earth is flat, and aliens kidnap humans.

But I have already told you the absolute best way to manage your battery by charging overnight, and letting the automatic backup take place overnight.

There is no other charging protocol that is better for the battery than overnight charging, and most other “advice” actually reduces battery capacity faster in the long run because it essentially means that all energy to run the iPhone comes from the battery, and no from external power.

Here’s the long answer→When to charge your iPhone or iPad | Communities