Dyanabook Battery Repair ノートPC用バッテリー復活させる?

I spent really busy days recently so I left the notebook PC (Dynabook R73/W6M) for one week without power hooked. Then, I found it didn't recognize the battery... Maybe, over discharged and some cells are dead... I bought the PC in 2016 and have replaced the battery once. I decided to repair it this time. From this movie clip, I am using Marantz MPM-4000U to improve the voice quality though, originally, my voice has noise...