iPhone 12 battery draining fast

I don't know if it's solely related to modem.

I tried many different configuration on 14.3, here are my results for a 7 to 9hr night:

• Wifi on / BT on / dual SIM 4g ==> 30% lost
• Wifi on / Bt off / cellular data disabled + low power mode==> 20% lost
• Wifi off / BT off / 4g + low power mode ==> 10% lost
• Wifi off / BT off / 3g + low power mode ==> 10% lost

ColinFromSussex wrote:

Does anyone know what what other functions flight mode turns off ??

Flight mode completely disables the modem. Turning off mobile data merely prevents the modem being used for data; it leaves the modem enabled for voice and network registration. The power drain is caused by the modem remaining in a high-power state when registered to a 4G/5G network.

For me it helps to reset the Network Settings and keep the wifi turned off complete ( crossed wifi sign in controllcenter )

5G is turned auto and Not testet with lte only yet

DND and bedtime is on ( 21:00 - 7:00 )

flightmode off

BT is on

iOS 14.3

when wifi is on it drained 20% overnight. No aktiv app screen in the battery setting

when wifi is off ..... just ~4-6

test it 👍🏾

So a summary of what’s happening here is that people on O2 network are facing the issue. I have switched network from giffgaff (O2) to virgin (EE) and the battery drain is gone. While I was on giffgaff (O2) I tried installing the latest version of iOS 14 which isn’t out yet and the drain was gone. Make of it what you like, but I can also tell you in mobile data settings, while giffgaff has 5G as an option, virgin doesn’t.

Well I tried what apple support suggested -and some on here have said has already been tried.

Backed up phone. Gave it a full reset. Did not restore, but just re-entered my Apple ID and reloaded a few apps.

charged to 100% at 23:00 last night

left with WiFi, mobile data and Bluetooth all OFF.

08:30 this morning battery 87%.

So not as bad as it was but still not good.

apple said they would get me an advance replacement where they send new phone to me before I send old one back, but then said no. Next support person trying again.

I can’t go back to store I collected it from as store is closed due to Covid restrictions!

IF the next version of IOS after 14.3 does have a fix, why won’t apple tell us ??

Whatever ios version, whatever modem version: if you leave it at night idle, it will loose about 10% with Wifi on. Turn Wifi off, so the modem connects, it will drain about 30% in just 8 hours idle. Turn on 5G (or Auto) it will drain about 90% to empty.

It IS the hardware...

Contacted apple support 3 times regarding this issue this time they asked me to do factory reset again and set it up as new phone without sync with old phone I noticed there is a change last drained only 11% it was 25-35% still not happy contacting them again today,I think I will have to send it back.

One observation I made is that there was no battery drain with eSim from EE. But the drain is present with physical SIM card from EE (as well as any other major UK provider). Not sure about eSim from other providers, currently with O2 and they don’t offer eSim to pay as you go customers.

So, something to do with the physical SIM card for sure. Dual sim is buggy in iPhone 12 lineup

Hi @helder33 @user0197

Yes I agree. Its all good. It wasnt the intention here.

I do have a separate thread on the O2 support page, but they are really useless.

Apple support suggested to erase the phone again. Not the restore from backups but set it up as a new iphone, this way we can know if the old backup is causing issues.

even I had same issue but resetting the device without restore and switching off background app refresh , push notifications for most of the apps and WiFi calling fixed the problem. Now battery is stable.

I updated to 14.4 and the previous 50% drain is completely gone. Now it’s only 5% in 12 hours.

So 14.4 may also solve your problem, too.

I also set Siri to - don’t listen. Not sure if this may also be the solution. I’ll switch it back on and report soon.

What do you mean by 'linked to battery discharging'?

I am very familiar with the drain curve of the iPhone 12, how absurd and seemly unexplainable it is. If you have the option to connect to Wi-Fi a lot and your carrier supports Wi-Fi calling, just enable airplane mode. You may have to re-enable Wi-Fi the first time but it will memorize the setting and leave it turned on in the future when you enable airplane. Everything will continue to work, but the drain will be gone. Refer to the post I made recently. Hope this helps you out. We are all desperate and people have found airplane mode to be the only solution until, god forbid, the issue is officially fixed. As I said, if Wi-Fi calling is an option for you, airplane doesn't mess with calls/texts etc.

I hear ya. My 2018 iPad Pro (bought it in 2019) has magnificent battery life as well. Running same version as the phone. Tbh I have no idea (besides speculations that it is a software bug) what is really causing it. Even weirder that people report a fix one day and then the next day the issue appears again. It just seems so arbitrary.

Even weirder that I had superb battery life while on cellular the other day and then it makes me question wether it is really a cellular/modem issue. When Cellular Data is on and I am home connected to Wi-Fi it drains again. Other phones in my house, 6s and XR all running same version and on the same carrier, their drain is also normal. It's just weird. Did everything the average end consumer can do (and even more). Full dfu restore, without restoring from any backup. Nothing besides putting the thing in airplane mode helped. I understand some people don't want to mess with their phone so much and think its too much to ask for them to go into settings and start changing settings and experimenting and I agree. However a few do actually have extra time and want to be a little proactive to mitigate the drain, or at least try to. A thing you can try, which is pretty radical. Basically go into each and every setting, and I mean EVERY setting that can be turned off and turn it off. Things that update or download automatically etc. I think it's easier to disable everything, see if it improves anything and head back in and enable one by one again instead of going the other way by slowly turning this off and that off. You know what I mean? I was surprises how much I was able to turn off without noticing it being off, like all those Siri/Search Settings. I don't really use Spotlight at all nor do I rely or ever did get useful Siri suggestions, so turning off where Siri is checking when I am using an app and what I do within it makes total sense to me. All these processes run in the background all the time (Spotlight indexing which happens all the time doesn't even show up in the battery chart) and it could make the difference between losing 2 percent in an hour with the phone seemingly off or only using 0.2% in an hour. Couple that with mail push or frequent fetching and add another 1% every hour, Services updating location and the list goes on and on. However still, I have no doubt that in the iPhone 12 there is essentially one process that is essentially the culprit.

I haven't followed the discussion in a while but wanted to give you guys an update. I had the battery drain issue with my 12 Pro since day one especially in dual sim mode. Have tried everything and by battery drain I refer to abnormal drain in idle. Around 6% per hour.

Now I bought an iPhone 12 Pro Max last week and the problem is gone. Even in dual SIM mode the battery is perfect. Idle use around 0.5% per hour. Exact same SIM setup and settings.

Below you see the idle drain at night with cellular on and both lines active. Of course during the day I'm using my phone but battery performance is great!

This leads me to the conclusion that it's not a firmware but a hardware problem with the modem. Unless they use different firmware between 12 Pro and 12 Pro Max which I doubt.

Well there is one difference, which should not make a different but I just want to mention. The 12 Pro was the US model A2341 and the 12 Pro Max is the EU model A2411.

After the lack of adequate support from Apple, I tried using a second carrier in my country (had a backup sim). Just like the O2/EE case people have described here, I did not see the battery drain on the second carrier (Jio). Surprisingly while I use this carrier, I dont see the option Voice & Data under the Cellular (Mobile) Data Options whereas this was where I could switch between 4G and 3G in my previous carrier. The new carrier also shows up as LTE in place of 4G (previous carrier) on the top next to the signal bar. The problem seems to be lurking somewhere in here.

I am now considering to switch to the second carrier after a few weeks of testing using the backup sim. Unfortunate for my previous carrier to lose out on me due to Apple's bug.