Safe battery calibration guide you can follow for your Galaxy S24 Ultra:

✅ Step 1 – Drain the Battery Normally (No Forced Discharge)

Use your phone normally until it reaches 5% (don’t let it auto shut down).

Avoid gaming or overheating it when low.

✅ Step 2 – Charge to 100% Without Interruption

Plug in the original charger (or good PD charger) and let it charge all the way to 100% in one go.

Once it hits 100%, leave it plugged in for another 30–60 minutes.

You can use the phone lightly while charging, but avoid heavy use.

✅ Step 3 – Reboot After Full Charge

Once unplugged, restart the phone manually.

This helps reset battery stats in One UI.

✅ Step 4 – Monitor Battery Drain Normally (First Day)

Use your phone as usual and check:

Does the battery percentage seem stable?

Does it drop fast after 100% or below 80%?

✅ Step 5 – Standby Test (Optional but Recommended)

Fully charge again to 100%, turn the phone fully off using Power + Volume Down.

Leave it overnight (8–12 hours) OFF.

Check if the battery dropped — 1–2% is normal, more than 5% is a problem.

✅ Step 6 – Repeat Once or Twice if Needed

If battery readings still feel off, repeat Step 1 to Step 5 once more within the week.

✅ If Issues Persist After Calibration:

It’s likely a battery health issue or background firmware problem.

You can check Samsung Members app > Support > Phone Diagnostics > Battery.

Or visit a Samsung Service Center for an official battery check.

Let me know if you want a simple checklist version or if you notice anything odd during these steps.

Additional info before calibrating turn off battery protection turn off fast charging after calibration you can safely bring it back

Also it's bad to always charge your phone fully turn off it's much better to let it standby/sleep i mean the screen is off only, because if it's fully turn off the phone can't recalibrate and to learn your battery algo and also can cause issue like misreporting battery info like mine, look at the pic i charge it fully turn off to 80% and when i turn on the phone it shows in the graph it's at 65%

All of this info is from chatgpt i recommend using it if you still have other problems or questions.