iPad Battery drain fast

Hello everyone, this is y mom's iPad (Device model iPad Air 2 16GB) and since the last week she's been experiencing some battery performance issues, basically it drains very fast even when is not used. I already turned off the background refresh to see if it helps but made no difference, then restore and updated the iPad with the software version 15.8.1 (it was already in the last iPadOS version when restored) and yet no difference once again. I checked using coconutBattery and shows 86% battery health. I had a similar issue with my iPad (9th Generation) a time ago, and was fixed just by turning off background refresh, so I thought it would help this one too. There is the picture of the battery draining by itself, and the iPad is completely clean, no Apps, no Apple ID, no files, nothing but the default apps.