Why is my new iPhone 12 Pro's battery draining so quickly?

By "84%" are you referring to battery health? That certainly is not a "new" iPhone but a used one which has already seen a lot of use and the battery is getting to the point where it won't last an entire day. I have an iPhone SE(1) with 84% battery life and if I leave home with it fully charged I am lucky to arrive back home a few hours later with more than 30%. In my case it really isn't worth buying a new battery for an iPhone that is that old.

"Normal use" is not a very precise term. For me "normal use" is leaving my iPhone untouched for several day on end.

To learn about maximizing (and the difference between) battery life and lifespan, read this support document --> Batteries - Maximizing Performance - Apple

Read this support article about iPhone battery and performance to learn about the battery health feature and what is considered normal performance --> iPhone battery and performance - Apple Support

To see the feature go to: Settings > Battery > Battery Health

"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." A degraded battery may display the notice: "Your battery’s health is significantly degraded. An Apple Authorized Service Provider can replace the battery to restore full performance and capacity." If it is not at or above 80% "normal", consider contacting Apple about a battery replacement. --> iPhone Battery Replacement - Apple Support Frankly though, from what you say and my own experience with an "84%" battery health iPhone, even 84% health is a a real nuisance.

Hello, I bought a new iPhone 12 Pro.

The iPhone 12 Pro was discontinued in September 2021. If your phone really is "new".....as you report.....it has been sitting in a warehouse somewhere for almost 4 years. This would have been terrible for the battery.

Maybe you could clarify on whether your phone really is "new"?

Tap Settings > General > About on your iPhone and report back on the warranty Coverage information that you see there. Is there any info when you Tap Settings > General > About > Parts & Service History?

That behavior is normal for an iPhone with battery health at 84%. Batteries do not last forever. While Apple nominally says replace at 80% health, in my experience anything at or below 84% means you really have to charge it multiple times per day. If it has gotten to the point where you feel it is a nuisance then either get a new battery or perhaps even think about getting a newer iPhone.

sadeghnajafi81 wrote:

It’s my mistake in writing

I mean I bought an iPhone 12pro earlier

the battery health is 84% and I must charge it twice in one day is it normal?

Yes it's normal. You bought an iPhone which was released in 2020, which is nearly 5 years old and the battery health is close to needing to have the battery replaced at 84% battery health.

What is claimed is:

You downgraded to an older (out of production) model with older components (including the battery).

No one here knows what specifically is happening, but here are some examples:

Learn why ⇢ the battery in your iPhone drains too quickly for detailed information.

Good luck! 👋🏼😉

sadeghnajafi81 wrote:

For example, today from 10 am until now, it has gone from 70% to 15% in about four hours with normal use. Is this normal with a battery health of 84%?

For me it is normal. My iPhone SE1 with 84% battery health can easily drop from 100% down to 10% in a couple of hours. All I have turned on is Bluetooth. Cellular data is off and during those 4 hours I many not even wake it from sleep. While I do charge it to 100% again, 100% these days is not what 100% was when I got the iPhone from somebody 5 years ago. Back then battery health wasn't all that much more (maybe 89%?) but for me 84% basically means I can't leave the iPhone off the charger for more than a couple of hours.

For what I am mostly using the phone for, I need Bluetooth turned on all the time so I don't really have an option other than buying a new battery (not worth it for a phone that old) or getting a newer iPhone. You could try using Low Power Mode to save battery life on your iPhone or iPad - Apple Support

Incidentally, my wife has an iPhone 8 with 84% battery health. Used under the same conditions as mine a 4 hour outing only results in a drop to 80% charge, so things can apparently vary between models. Her iPhone likely has a larger battery than mine so doing the same tasks over the same amount of time only results in a smaller % drop in charge.

How often you charge the battery will be determined by the apps that you are running. At 84%, your battery has used up most of its expected life, so it is certainly going to require more attention at this point.

You are going to need to replace the battery in another 3-4 months, so I imagine that a new battery will perform significantly better than a 4 year old battery that is nearing the end of is life.

Don't try to babysit the battery, just replace it at 80%, or Apple might be willing to install a new battery before it reaches 80% if you want to explore that potential option.