Just wanted to share that I had some battery issues (draining too fast, often draining the entire battery within 1 day) with a OnePlus Nord N10 5g. The phone I purchased was an old refurbished one and I'm not sure if the battery was refreshed or if it was the original battery.
Nonetheless, my battery issues have seemed to resolved and thought I'd share. It may help others or not. So, take it or leave it.
By default, the screen brightness was quite high (to the far right on the slider) and I can't recall if "Adjust automatically" was enabled or not. I manually selected the screen brightness to the lowest level I could tolerate without feeling like I couldn't see the screen. Surprisingly for me, I can move the slider almost all the way to the left. I also unchecked the "Adjust automatically". So, now the screen brightness is using the minimal battery. (I believe this was the biggest gain for me).
Furthermore, I am fairly conscious to disable WiFi unless I am actively using it for internet access.
That is all I did and now the battery lasts a couple days without charging (vs completely drain in 1 day) and does not drain much at all.
One last thing I am mindful of is to only use the charging cable that came with the device. I think the fast chargers that are more modern may easily cycle/overcharge older batteries and reduce the battery's long term life. With all batteries, there is a limited number of charging cycles and you'll notice that each 100% full charge may not last as long as when it was brand new. Overcharging (while at 100%) and/or letting the battery drain completely to 0% may reduce the life of the battery a bit. So, being mindful to unplug when at 100% and to start charging before it gets too low may help in maximizing its life.
Hope this helps.
Good luck maximizing your device's battery life!
