Is there a battery health viewer in settings?

@cinnamoncat1001 see if this works for your version. Open its Settings app, select Device Care, scroll down to the bottom, and tap Diagnostics, then tap the Battery status option. If that won't work try this

Open the app » Phone »Of your Samsung Galaxy S7

type * # * # * # * # 4636

In the menu that appears go to » Battery information »

Look at the figure indicated in the category » Battery level ", It must be greater than 80 , otherwise it announces that your battery starts to tire

Finally, compare the value in » Battery voltage ”With the value on the box of your Samsung Galaxy S7. If it is lower it also indicates that the battery is tired from here

The S7 is around 6 years old and if you have not charged or used your battery for a while, it is pretty likely that it is coming to its End of Life. I suggest you replace it. 三星 盖乐世 S7 电池更换