iPhone 12 battery draining fast

It's very easy. Just connect your iPhone to your Mac via cable. Your iPhone will show in finder, you might need to trust if it's the first sync. Then click on restore, the system will download a whole new copy of iOS and install fresh. I recommend setting up as new and not from back up after the software install. Here the support document:

https://support.apple.com/guide/mac-help/back-up-and-restore-your-device-mchla3c8ed03/mac

Good luck!

Thanks. Will do that if the issue comes back. Last night it only drained 6%. Will conduct another observation tonight and see if it's going to be consistent by tomorrow if not then will have to resort to your suggestion. Thanks

I have the same problem with Iphone 12 Pro. It updated to 14.2 during the first setup, and I loose 20-30% battery over night.

I tried to reset the phone and restored it from icloud backup, but that didn't fix it.

Can you please tell a little bit more about the steps that helped for you? Did you restore it from an old backup, or did you make a clean install after restoring it from finder?

Ok, I think I made a mistake. I made a backup of 14.2 yesterday on mac, then I updated to 14.3 beta 2. This does not fix it for me. Then I have connected the 12pro again and it started a backup, overwriting the 14.2 backup :-( So right now, I have a finder backup of 14.3b2, but none of 14.2. (Yes, I read the manual after that and found the "...archive the backup.." part)

Is there any possibility, that I can switch back to a clean 14.2 now? Finder says "cannot find firmware" when I start to reset the 12pro. I think it is trying to load the 14.3, but there is no 14.3 yet.

I just got my 12 Pro Max and experiencing the same thing. Just turned in my Pro Max 11 and regretting it. Battery fully charged overnight and by 3 PM I was at 20%. And that i without a lot of usage....

No more problem after restore and set up as new. Look at the nice and normal battery curve. Though, just using single sim now. Dual sim is not fixed but I’ve bought a Pixel 4a for the second sim, back to two phones again but actually works nice for me distinguish work from personal lines 👍🏼

I think there are 2 different problems that people are experiencing.

• One is the battery drain regardless of Dual-sim or not - Personally I think this might be a bug or something with those peoples installations, so a fresh re-installation and with NO restore will probably fix that.

• Two is the one which also a lot of people are having, including me, which is that as soon as you enable the second sim the drain becomes constant regardless of how you use it.

I have two colleagues that have the exact same issue as me, when work sim is enabled (eSIM) we get really bad battery life. One of my colleagues used this on his iPhone 11 and there it worked fine (now he has the 12 mini).

I myself have the regular iPhone 12 and my 3rd colleague have the 12 pro.

One difference is as mentioned before in this thread, is the new 5G modem and I think there might be a firmware bug or a oversight. This might be on the carrier end since now on the 12 you cannot choose 3G as data source for the eSIM. You get locked to 4G only, and I think the 5G Auto has replaced this "3G" option (this is maybe the oversight I am talking about) but since ALL the 5G options are unavailable since this is not compatible with dual sim we are in a tough situation.

Picture bellow shows Dual sim drain between the yellow lines and a full day with single SIM used (physical SIM) between the green lines.

That’s not quite right, a clean installation without restore does not resolve the issue for all users.

The only thing (workaround) is that enabling airplane mode at night stops the drain. Regardless of WiFi etc. being enabled or not...

Oh hmm... I only saw ppl writing that they restored also after. Would be VERRY interessting to know if these ppl that have made re-installations without restores and still has the issue if they are using eSIM or physical. I think it might be eSIM related also.

I’m not sure what you mean “without restore” I did a restore using finder on my Mac which is the only way you will get a fresh copy of iOS 14.2 and then set up as new. Just resetting or wiping your iPhone won’t get you a clean OS. After the restore no more problems and I’m using eSIM as well.

So after doing a lot of messing with the iPhone and checking things out. I’ve actually located what is draining my iPhone 12 pro Max at an alarming rate when idle

Ive been watching the battery slowly deplete when the phone is in idle. Especially over night as I don’t use it as much.

what I’ve since learned is that the dual sim mode is the cause of it,

if I use one SIM card only and the dual sim is off, the battery behaves pretty normal and also the battery graph represents the exact same.

so where the circles are dual sim is active and you can see the battery deplete rapidly. As soon as you turn of the dual sim, the battery acts normal and the phone seems ok as you can clearly see and battery use is normal.

the red line was when iOS 14.2.1 was installed and yes it depleted a little. But when I switched the dual sim on. Look at that. The battery depletes rapidly yet again.

So for me, the Dual sim activation is the biggest culprit and is a massive drain on the battery and the phone never feels cool to touch. Not hot, just not cool.

so the modem is the biggest issue. Bad drivers or something really bad in the iPhone

while writing this which is on the iPad, the phone has dropped 1% in 10 mins doing zilch with dual sim on.

I believe iOS 14.2.1, released today, has the updated modem drivers. What iOS version are you one? I was having the same idle battery drain issue and I moved to version 14.3 beta 2 and no issues since then. 14.3 beta 2 has updated modem drivers as well.

Interestingly, after an update of 14.2.1 83% from 9 p to 12 was no bits at all ! And after 12, the beginning gradually drops to 73% to 4 am, then I turned off the sim, leaving only e-sim and power saving mode ... Flight smooth to 9 am ( the modem firmware became 1.14.06 )

He guys, PROBLEM SOLVED! Just turn off the New Live Background that came with the iPhone 12 Pro and Bluetooth in the settings. I am a power user and I have a physical Sim and eSim at the same time and that setup I had on my previous Xs Max so the only difference was the new live background and just in case I turned off Bluetooth (it was always on for me before)... I will turn it on and see tonight if it’s that or both together.

I have this iPhone for a week and that was the only problem I had! Another than that it’s fantastic and has a better battery life than my Xs Max and it’s charging way faster because of the smaller battery. Love it!

Good luck!

So after a little more investigation.

I’m running IOS 14.2.1 which does have a little modem update but has made zilch difference in the battery drain area.

i have Dual sim active here in the UK.

2 different networks. 1 on ESIM and 1 normal sim, this is now my findings,

Set the normal physical sim as default and ESIM as 2nd sim.

8 hours in stand by, battery drain 6%.

Now set the ESIM as default and the physical sim as 2nd,

1 hour standby. Battery drain 5%

The ESIM in dual mode as being active is draining the battery at an astonishing rate.

Master Reset done

Network connection reset done

phone charged cycle done

no apps running done

no app on done

it make no difference what you do.

when ESIM is set as master, the draining happens at an alarming rate