Get the Apple battery case, it's a life changer.
I did, and it was okay until it died completely while I was on an out of town trip, forcing me to buy a mophie case instead. And I didn’t keep it on the phone all the time either, only when I needed it.
Plus it creates that big bump on the back, it’s definitely not a perfect solution.
Either way my 8 Plus arrives tomorrow so I won’t have to deal with this 7 and its tiny battery anymore.