Battery draining when idle - Xiaomi Mi 10 Questions & Answers

Hello everyone, after struggling with the installation of a custom ROM, I've managed to have a decent setup with ArrowOS, I have a problem that I don't know how to fix after trying many battery saver apps.
Basically, it drains 2% of the battery when idle (no data either WiFi or mobile, no GPS, battery saver option enabled); apparently the cause is the launcher: I use Nova, but I have tried the Arrow one and Microsoft and they are even worsening the situation (>3%/h).
With MIUI I've never experienced such a draining, I don't know what to do.
I have tried Greenify but had to remove it because it crashes when accessing the settings (don't ask me why because I've no clues); Naptime but, ironically, it was draining the battery on its own as well (3%/h); now I'm using BatteryGuru but I didn't find anything yet that has a real effect.
Any recommendation/suggestion?

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A bit late but you'll never get a custom rom that is "better" than the stock rom. Miui has plenty of features to restrict apps under power saving.

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shivadow said:
A bit late but you'll never get a custom rom that is "better" than the stock rom. Miui has plenty of features to restrict apps under power saving.
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Actually, I am running PixelExperience with Greenify and it's better than the MIUI, the draining with Arrow was insane despite Greenify: I mean, during the night it was draining 14/20% of the battery with data turned off and battery saver enabled while with PE it was 3/4% as a standard and 1 or 2% with the battery saver enabled.
I didn't understand the reason though, I have sent the logs to the dev but never had any reply.

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I noticed your omitting the fact that running a custom rom means running more code which consumes more power?
Stock roms are as efficient as is gets because that code used is minimal and proprietary to Qualcomm. Ie made under license. Custom roms are open source and contain lots of moot code to get around instruction sets that aren't publicly available.

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PixelExperence IS a custom ROM... Unless you think that it is the official ROM of Xiaomi...
What am I omitting?

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You misunderstood. Custom roms are slower because they use open code which contains more lines of programming. Stock roms use proprietary code specifically for that chip which is shorter and less cluttered.

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Sorry, I don't get your point and why you are accusing me first of omitting information, which I didn't, and second to misunderstand what you wrote, which I didn't again: I have opened this thread to ask for help because I noticed an excessive battery drain even when idle, I wanted to know if someone had the same issue and how they have fixed it, in case. Apparently, I was the only one with this phone who had the problem, so I tried my ways to solve it and the "solution" has been avoiding ArrowOS.
I didn't open this post for lecturing about custom ROMs and the additional code that they execute.

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To be messing around with custom roms you need to understand what they are and how they work. Especially the basic differences of stock vs custom and how they'll never be equal.
I don't mean to scald you, lecture you or whatever you want to call it, my point is that all this information around custom roms is well documented yet people expect miracles when it simply isn't possible. All custom roms allow is customisation over stock, nothing more. If you want battery then you sacrifice performance. If you want performance you sacrifice battery. It's how the universe works. That is all the roms allow.
Custom roms use a LOT more code than stock because proprietary drivers for the chips aren't in the public domain. That is what Xiaomi and other OEM's pay fees to Qualcomm for. As developers don't have that kind of money lying around they have to make do with github open source drivers. These are NOT perfect and are basically emulators.
That is why you have unexplained battery drain on custom roms. That is why you void your warranty when you install custom roms..

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My impression is that I've asked how to find apples and you are explaining me why bananas are yellow...
I'm sorry, probably my first question wasn't clear enough: I've had excessive battery drain only on ArrowOS and I wanted to know if someone else had the same issue and how to fix it. As simple as that.
The thing you say about more code to run, customization, battery lasting time vs performance are true, but (and this will be my last reply on this thread because I feel stupid having to explain it over and over again) my current setup with Pixel Experience, a custom ROM I've tried, was OK already from the very beginning, it became even better with Greenify rooted, and, once again (I've already said that before), the battery lasts longer now than with MIUI.
I'm sorry if I seem upset, but it looks like I'm getting a lecture (that I don't need, mostly because I don't care) on custom ROMs and "their hidden secrets" when I have simply asked IF there was a solution of a specific problem I have had only with ArrowOS.
Closing note: I've tried Paranoid Android and the battery lasting time was great too, the same as MIUI.
My "simple and silly" deduction, considering that I've had this problem on ArrowOS but not with Paranoid Android nor Pixel Experience, simplifying dramatically, is still that it's an "ArrowOS thing" or my setup for it. I hope this clarify the situation.