It's a small, but real risk. What makes our batteries any better than the several dozen hover board units that caught fire in North America last year? I guess they're not getting knocked around. Technology is the same. BMS. 18650 cans. Maybe the resellers do a better job picking quality makers.

I put my charger on a timer, in case I forget, leave the house or fall asleep. I also charge in a clear space on the floor of my garage. I've got three dolphins and two shrink wraps. The latter go in a metal tool chest when not on a bike.

On the other hand, I've go two Ryobi's for my lawn tools that I will leave on the charger. I trust the UL label.

Keep in mind that one of the largest ebike dealers in the Midwest had a battery catch fire in their showroom a year ago.