Battery drops suddenly and iPhone 15 Pro reboots

That is a symptom of high internal resistance in the battery; batteries have more than one failure mode. Reduced capacity is only one of several. Have the battery checked out by Apple→iPhone Battery Replacement - Official Apple Support

Jerkalerka wrote:

last 4 days my phone has been acting strange. It can suddenly just go dark and restart, and when it comes back on it has 10% battery.

i tried charging to 100% and it helped somewhat.

it normally restart when it would go below 60% battery, but when i charged it full it would go down to 40% once, and now it turn off when it reach 75%.

battery health says 83% and everything normal, but its far from normal. Why doesnt it log the weird battery outage?

i have the latest version of OS. Everything up to date.

That’s a symptom of a failing battery, probably high internal resistance. Loss of maximum capacity is just one of several possible failure modes. Contact Apple Support and they can do a remote diagnostic.

When you go to settings/battery/battery health is there a message about health?

Bulging screen is a definite battery failure, and a dangerous one; it can result in a fire. Don’t use or charge the phone until the problem is fixed.

Too late now, but if you had purchased AppleCare+ when you bought the phone the repair would be free.

If you turn it off, and don’t try to open it, then it will be safe. The bulge is a normal failure mode for Lithium ion batteries. The battery has an airtight case enclosing it, so if the internal chemical reaction generates gasses (which are toxic) as the result of a failure they are contained in the airtight case. Lithium is also flammable when exposed to air, so the case keeps air out also. The only danger is if you puncture the case.

Other users have reported that Apple repaired their device with a swollen battery for the cost of a replacement battery. YMMV.

Jerkalerka wrote:

If i turn it off, is it safe to keep inside? Or should i keep it closed off? In a jar?

You want to have Apple look at it as soon as possible. If the bulging should cause screen damage, you'll also need to get that repaired, most likely out of pocket.

Thank you for replying with your concerns, Jerkalerka. 😉

Here at the Apple Support Community, we are volunteers (thoughtful Apple users) who share knowledge in an effort to help others, such as yourself.

I recommend that you contact Apple Support for assistance.

Good luck! 👋🏼😉

Before that, but after i asked about it here, i noticed the phone screen began budging outward.

i can see into the phone from the right side. They told me that the entire backside, everything but the camera, has to be changed. Is that accurate?

Sounds about right. Chances are, you might decide that the money would be better spent on a new phone.