@bigbuilder a bad battery can do that. Replace the battery and re-evaluate. Since iFixit does not yet have a guide for that, use something like [https://www.youtube.com/watch?v=9ZEVDeodA0Q|this video] to replace the battery.
While you work on your Roomba, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.
Repair is War on Entropy!