My iPhone 12 Pro Max battery drains with my SIM card in

Why aren't you charging your phone at night while you sleep. It's the recommended way to charge your iPhone. You should make sure Optimized Battery Charging is turned on in Settings > Battery > Battery Health > Optimized Battery Charging. And if you have iCloud backup enabled, your phone when on the charger at night, with the screen locked and connected to Wifi, will backup every night to protect the data on your phone.

Any phone will lose 20% overnight because unless you power them right off they use power.

That is why they are designed to be charged overnight every night so that optimised charging kicks in after a while.

Fo not leave them off charge overnight!

LOL......there's a lot of garbage on YouTube. Why would you trust people who have nothing to do with Apple over what Apple itself recommends?

I've given you the best advice available. Choose to use it or don't. I'm done here.

Well, that's just not going to happen. If the phone is on, even unused, the battery will deplete. It's your phone, so do as you please, but if you don't want to do what Apple recommends, what we know works and what will actually preserve the health of your battery, then you can't complain that your watch cannot do what you want.

Yes, that's why you are supposed to charge overnight, irrespective of what you wanna do.

If you think your battery has a problem

Battery Self-Discharge - User Tip

Check iphone battery for self discharge

Of course it does. Batteries discharge. It's normal. It's expected. Which is why it's recommended to charge your phone at night while you sleep.

No. Not only does it NOT effect the battery adversely, it helps maintain its health long term.

You're welcome.

and I drew a picture of optimised charging, should have shot a video.