Some information about the whole battery life thing.
For starters: It’s never under ANY circumstances called “battery backup”. NO. It’s not. Regardless what they tell you. “battery backup” or “backup battery” is a secondary help battery to a system (like a computer). Correct term is, and always will be, battery life.
When a phone is new
It will not immediately have great battery life, as you will play more with it the first days/week. And it takes a while for the battery to reach peak condition.
So, do not freak out when battery life isn’t stellar the first weeks. It’s as it should be pretty much. And whatever you do. PLEASE don’t start to troubleshooting this as you will then mess with the battery life MORE and possibly destroy it for all time.
Using a phone will use battery
Yes. As simple as that. If you use it more, it will use more. Use it as a toy and it will of course be have a “bad” battery life.
Where you use your phone matter
This assume you’re using it on mobile data. When moving around it will cause the phone to search for better cell towers, and it might up the power of the radio as well.
And, if you’re between two cell towers it might switch between those two. Which will cause it to use more battery. 4G LTE can be very power hungry at times. So, is there’s a wifi around that is what you should use.
And, if it’s warm (above 35°C) around battery life WILL suffer from this since the type of batteries used today gets less efficient when it is warm/hot. Some makers uses 35°C as the upper limit for when a phone should be used. Just avoid using your phone out in the sun on a hot day. Or even inside if it’s hot there.
What you install matters
A LOT even. If you install every app and game you see in play store. This might/will lead to more battery being used. And, it comes down to just WHICH apps you install as well.
Don’t assume it’s good just because it’s in Play store. And, oh: avoid installing apps from outside play store. Unless you REALLY knows where it comes from. And you really know what you’re doing.
No, updates doesn’t make it worse.
Most of the time.
Edit: i’ll rephrase this my point seemed to go out the window.
A regular update will NOT give you a bad battery life. Regardless what anyone will tell you. Sure, there might be issues with various things installed TO the phone already giving you issues. That’s another thing totally. Yes, some Android versions was a little “Odd” in the past but could differ greatly between phones.
And that assume that you did the regular things that you sometimes HAVE to do after a major update.