Dell XPS 15z laptop battery issue - Upon removing AC adapter, charge of battery drops from 100% to about half

Hi all,

I have an XPS 15z laptop. The problem I have is the laptop appears to be completely charged, but when I disconnect the AC adapter, the charge drops to about 47% within a minute of removing AC power.

This is a Dell refurbished laptop that I've owned for a little over 2 years. Neither the AC adapter nor the battery have been replaced in that time.

All software and hardware updates are current, including the BIOS.

My inclination is that the battery is going dead, but I wanted to get some other input before purchasing and replacing the battery.

Thanks for any and all assistance!