Does battery need replacement even when using Wasserstein Power Supply?

I have been using a Ring Video Doorbell 2 for at least 2, maybe up to 4 years wired to a Wasserstein power supply. Until recently, the battery was always at a very high % - but now it's down to 19%. Do I need to replace the battery? Or just remove it and use the wired power exclusively? I guess I need to check the power supply to make sure it didn't go bad - just wondered if anyone else has seen this situation.