My Apple Care has expired. My Battery Health under Settings says Maximum Capacity is 79%. It also says "Your battery's Health is significantly degraded" and my research says that it's recommended to be replaced when it gets below 80%. If my battery was working great, I wouldn't worry about it, but I think it should be lasting longer.
There are a few options:
Apple store or authorized like
Best buy all the same price more than likely close to 200 all in the price is listed online at Apple.
You can buy a battery and replace yourself from apple direct - They will rent you the tools as well also listed online little to no savings with tool rental.
Most likely you will need to tell apple you are replacing the Battery as they need to authorize for the phone to work no matter how - I think this can be done online now.
You can take it to a mall or like repair shop should easily be under 100 or buy a battery from many online like Ebay
amazon to battery stores for most likely under 50 or less and replace yourself (it can be done with a little bit of effort and care with no issue plenty of videos and or picture instructions on
youtube or apple site direct and many other) both will void Apple from ever buying this phone back from you as it is not a genuine apple battery - although it is not worth much now so consider that as well before you say this is a bad option.
lastly buy a new phone.
Apple batteries from 12 up are absolutely garbage..... Buy an XR or 11 with a new battery from a reputable seller... Or like others switch to Samsung that is easier to work with. Yes I have a Crapple phone as does my son and my wife for work but personal she has a Samsung and I can say without a doubt it works just as good as an apple and in some cases better with a longer battery life as in daily use and longevity at least compared to the new apple phones. - Samsung runs amazing pricing specials from time to time before saying retails..........
My XR was at 93% when I gave it to my son 4 years old... he traded it in at 6 years at 90% his new 15 is at 89% in a year. The XR easily outlasted the new phones when it was traded..... Mine did the same 89% after a year... % slows down dropping a lot after that.