A couple days ago I updated my Galaxy S7 to the new Android 8.0 Oreo update. Since the update my phone has been draining 1% of its battery after about every minute, the battery will still lose power even if the phone is charging. I have tried to look up similar problems, they do not seem to have the problem of this much of a power loss and I have tried what has been suggested for those kind of problems (checking for applications that can be draining power, changing phone settings to minimize phone usage, removing the GearVR applications, "wipe cache partition", doing a factory reset, and things similar), none of them have worked.
I also think something may have gone wrong while I updated my phone. It seems that there should be new applications added to the phone which I do not see listed. Also, when I do the steps to go to the location where the commands "wipe cache partition" and "factory reset" are located the phone shows a screen saying it's updating, the same screen was originally shown when I updated the phone to the new update, it would eventually go to a screen that shows a dead android icon with the text "no command", this would last a minute or two before finally showing the commands list. This is a problem that stays even after doing a factory reset and I have checked the phone's settings for any available updates, it shows that my phone is "up to date".
Sorry if there is any spelling or grammatical errors, any help would be amazing as it seems it would difficult to reverse the update and I can't really use my phone with the worry that its battery would be ruined from draining its power so quickly.
It could be worth just checking that your phone can support all the features that Oreo brings in relation to your phone not appearing to have all of them.
How old is your phone @Echos ?
As a factory reset has not helped and I assume a few days has elapsed to allow the phone to settle then I'd suggest to use a Samsung Service Centre or Samsung Experience Store who will be able to help you further with this situation.
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.1/ Android 11.
As a last resort I took my S7 to a Samsung service center only to be told there was nothing they could do. Phone is not the issue but the oreo update is the issue.
I am having the same issue with my S7 Edge. It is extremely annoying that now I have charge my phone twice during the day. It seems Samsung have deliberately introduced this bug because I have 2 Samsung S7 Edge and I only updated one phone. Of course the other one running fine. If Samsung doesn't fix this pretty soon I will write to the local regulator. I suggest all of you do the same.
I have been having the battery drain issue for a while. At some point, it just became unbearable that I wanted to buy a new phone. However, I found that turning on the power save (mid) setting helped me save some battery d
rain. At first, in the battery usage (where you can check the percentage of apps and phone systems that drain battery) it was 11-15% power drain from Andriod OS. After I turned on the power saver, it went down to 2-3% battery drain, next to the rest of the apps I use (1-2% drain).