This is where I start thinking self defense. By that I mean from 4 legged critters like stray dogs. I spent a month on "wheels" and remembered thinking the business end of my German Shepherds was a lot closer than I realized. Maybe some good "dog" pepper spray. 2 legged critters need attention also, but that becomes mental first, purchase second. I really don't want to kick off a "best" concealed handgun discussion.

Batteries like the folks before said.

Maybe some form of reflectors for the back of your wheels. A guy I know uses one of the "racing" chairs and it is all black. Kinda hard to see at night.