Which phone are you using?
Open the Settings app and look for a category that has something to do with battery (on my LG Stylo 4, it's called, strangely enough, Battery). It should give you a list that details the amount of power consumed by running apps.
The Note 4 was released 4 years ago. That means battery production on them stopped long ago too. That battery you have now may have been sold as new, but chances are it was old stock and bad already from sitting on the warehouse shelf for who knows how long. Unless you can find a seller with fresh made batteries (which who knows if that's even possible), buying a replacement is going to be a crap shoot.It's a Samsung Note 4, but was bought just over a year ago. The battery is roughly 4 months old, as I bought it when I got my motherboard replaced. Bad files? Possibly, I have a few photos that on Quick Pic that say "Failed!", I don't know if it's corrupted or Quick Pic just isn't loading it. The phone + media card is 96gb total.
I could try a new battery, just wanted to avoid buying a new one and it's not the issue.
At this point, buying a newer phone may be the best bet simply due to performance issues and the amount of resources apps are using nowadays. If you do want to try another battery, maybe look into extended batteries if one is available. With a higher starting capacity, any degradation may still give you reasonable run time. I'd also try reaching out to any of those battery dealers and see if you can get an idea of the production date of their stock (which they may or may not have an answer for).Would one of the non Samsung batteries be of use? Like an Anker, or is buying a new phone my best bet? I still have an S7 Edge, but I prefer Notes, and my Edge has that pink line going down it. I'd probably buy pay as you go, I don't like phone contracts anymore.