IOS 13.5 battery drains!!

At least you proved 13.5 was not the problem. Something on your phone is.

The next step would be to restore your device, and setup the device without restoring a backup, to see if the issue is replicated. I would first make sure you have a backup so your data is saved.

Here is a guide for those steps:

How to back up your iPhone, iPad, and iPod touch

Restore your iPhone, iPad, or iPod to factory settings and see how it goes

If no improvement arrange for repair or replace

If it works well restore from backup but be prepared to wipe again without restore from backup. 

https://support.apple.com/en-us/HT204184

OK. So for all people who have the same issue. There is quite simple resolution. You MUST install the system via iTunes from the IPSW files. After just restore the backup from icloud and the issue should be fixed.

Download IPSW for Your device. You could do that from apple developer account or from https://ipsw.me

Installation of IPSW:

1. Connect your iPhone or iOS device to your PC/MAC via lightning cable.
2. Open iTunes and select Your phone.
3. On a Mac, press and hold down the “Option” key and then click on “Update”
4. On a Windows PC, press and hold down the “SHIFT” key and then click on “Update”
5. Select the IPSW file (for Your device) that you downloaded and click “Choose”
6. Let the iOS device update as usual.

I wound up uninstalling the mail app. I reinstalled it and my battery drain issue is gone. Reinstalling the IOS via iTunes made no improvement to the battery drain issue as I did a restore after. Go to your battery in settings and see what the biggest draws are on the battery uninstall and reinstall the apps with the biggest drain.

You just need to make iCloud backup. After that wipe Your phone and install iOS 13.5 from iTunes as In my instruction. And during configuration restore the backup from iCloud. That should help.

You can do also backup via iTunes in case something goes wrong during restoration the backup from iCloud and to be sure that You will be able to get Your data back.

"...And then I wiped it again, reinstall iOS again, and instead of restoring from backup I set it up as a new phone, but everything is still the same. 10% drain in 3 minutes without any app running after 1 day stay in idle, low power mode on, and location service turned off...."

In that case your phone or battery needs replacing.

"... i kept air mood, background off, power off ..."

if you lose charge when powered right off (the gap in your photo) then the battery is faulty in my opinion. You should be able to store a powered off phone at 50% charge for months. It's how Apple tell you to store them long term. No iOS is running when powered off.

See if any of the steps in this thread helps:

https://discussions.apple.com/thread/251394122?login=true

I got my battery drain and heating problem solved.

Azuzbhimanimax, If a phone of any age set up as new with no extra apps and no icloud connections drains battery that badly then yes arrange for Apple Genius Bar to inspect it.

You can:

Contact Apple for support and service - Apple Support 

Have same problem with iPhone 8. Fresh install via itunes (not an update You need connect phone in DFU), resolved my problem.

13.6 is available now

My 6s is draining as well on iOS 13.5, it has a battery with 91% health and I can barely squeeze out 3 1/2 hours of light usage before it's in the 10% area.

-push notifications off

-location off

-Apple ID/iCloud logged out

-app refresh off

with all that stuff off I get a little better maybe pushing 4 hours but I noticed when I was logged into Apple ID/iCloud it was draining while using and I mean not 98,97,96 it was skipping from 94 to 88 etc.

I think we should all be clear here on phone models.

I see the iPhone 6s and Xs Max in this thread.

Even before iOS 13.5, our backup 6s (purchased ~5 years ago - and battery 1.5 years old - genuine Apple Store replacement) was having battery drain issues - with only a handful of "essential" apps (lock screen/home screen was draining).

Second, the iPhone Xs and Xs Max are awful. We went through three of these (wife phone).

It's a fact - the antenna is flawed (liquid crystal polymer). Apple replaced with a modified polyamide antennae on the 11 Pro / 11 Pro Max). The liquid crystal polymer antenna (designed to work with the first OLED phones) is garbage.

Note that LED-based devices use a different antenna, like my wife's iPhone 11 and my old iPhone 8 Plus (which, incidentally, has the best battery life and WiFi speeds - 400Mbps+ on WiFi 5).

After following this thread, I just restored an iPhone 6s for my daughter (she was using my old iPhone 8 Plus previously, but it's too big). The battery (non-scientifically) has been tracking about ~70% of when the phone was new (2015).

The battery was replaced in December, 2018, and is showing 97% of design capacity.

There is no SIM in the phone (no phone service). There aren't many apps on the phone - she mostly watches YouTube Kids and iMessage with friends. She has less than 50 photos in iCloud (I have 60,000 for reference).

In general, this thread perplexes me because people are having battery drain issues on newly cleansed devices.

However, a word of caution - even after factory-restore, battery usage spikes due to background tasks (notably iCloud Photos and other apps preparing themselves). This was more severe prior to the iPhone 8 which added the two "low-power" CPU cores (six total cores).

Finally, the tip above re: restoration (boilerplate) isn't really helpful at all. Copy/paste of the same stuff without thinking/analysis is unprofessional.

You must be right as I have changed my dad's Iphone 6s battery and have replaced it with a new one as its not draining overnight now (It got below 80% battery health) but what about people having new phones why its draining battery in them after all functions turned off?

My battery is still 96% of maximum capacity. It may have started aging but not that bad. I’d say it’s the result of multiple causes:

1. A possible bug in iOS “background processing” that global disable/enable doesn’t actually affect individual apps. It happens on my other phones and iPads.
2. Other unknown OS related bug that keeps network accessing. Set to Flight significantly reduced battery drain.
3. New “Smart charging” that won’t charge battery to full when plugged overnight, so it dropped from 100% to 99% much faster than before.
4. Inaccurate battery % presentation that mislead people to think that the phone has 90% charge, but in fact it’s already dropped to 86%. This is the only viable explanation why my battery dropped 6% in 1 minutes.