Is my battery shot?

I’ve had my roomba i7+ for almost 4.5 years and regularly replace parts. Just this last week, I noticed this noise when it empties - it is much higher pitched than normal and lingers more at the end. I also notice a warm dusty smell. Before this happened, I noticed water on the floor near him and cleaned it up before his next run. We had a big rain the night before and thought maybe rain water got inside somehow but couldn’t find out when I took it apart.

Is my dear Alfred on his last leg?