Battery drain issue in iPhone 12

Protect & Prolong life of your iPhone's Battery:

1. About the battery usage on your iPhone, iPad, and iPod touch ...
2. Batteries - Maximising Performance - Apple (IN)
3. iPhone Battery and Performance

Try some of these options too.

1. Avoid Screen Mirroring
2. Put on Low Power Mode
3. Put Auto Lock On (1 min):- with low power mode it will be 30 Sec
4. Put Auto Answer Off
5. Disable Push notifications for apps you do not use often
6. Keep your iPhone Face down to prevent notifications to light up screen
7. Enable Auto Brightness:- Settings > General > Accessibility > Display Accommodations > Auto-Brightness [Enable]
8. Manually lower brightness from Control Center
9. If you Want to watch continuous Video. Stream it on TV or a Monitor
10. Don't force close apps; Apps which are not on frontend screen are paused by the system to save energy. Apps require more energy to re-launch. Apps which are open in the background use large memory is a myth and quitting them is counterproductive
11. Location services to be allowed only while using the app
12. Set your iPhone to fetch email and calendar data from internet less frequently
13. Turning off Background App Refresh 
14. Charge before it drops below 20-30%
15. Try connecting to trusted Wifi where ever available in stead of Cellular
16. Enable Airplane mode in areas with bad cellular and wifi coverage. Your phone keeps trying for reconnection with the missing / weak network. This uses lot of energy
17. Switch off Wifi & Bluetooth while in Roaming or Not in Range
18. Enable "Wifi Assist" : Settings > Cellular or Settings > Mobile Data > Wi-Fi Assist [Enable]
19. Periodically Check your Battery Health (Settings > Battery > Battery Health)

Not sure if I have a faulty device and should replace it, or maybe it's 5Gs fault, what's your opinion? I'm really a light user. Full day only 2h Screen time.

On my iPhone 12 mini when I surfed the web on lunch break the phone got seriously hot and the screen dimmed noticeably. The battery took a large hit. But it went normal afterwards. Had the same thing once last week. I never faced this problem at home on WiFi.

I was connected to 5G because at work we're supposed to use the guest WiFi which is completely open to a huge complex with thousands of guests trying to register to eat in or compare prices, so I stay virtual miles away from it.

I know the password to connect to corporate WiFi but there I would leave footprints and I don't trust my personal device in there :)

But as 5G is like fibre on the move so at work it is better than any of their WiFis, though at home a fibre connection over WiFi offers still more reliability and less latency.

Now I'm really not sure if it's faulty hardware because I once had the same phenomenon on the OnePlus 8 Pro I had before the 12 mini only there it happened once in three months while it happened twice on the iPhone which I bought 4 weeks ago on launch day.

Does anyone else have this? Could it be fixed by an update? Should I try disabling 5G but I really don't want to because now I'm used to it, when commuting to work 5G gives me ultra fast web while 4G gives me loading bars and rotating wheels.

Also know for iPhone 11 and later models, battery performance --> About the battery and performance of iPhone 11 and later