As an ebike dealer who has sold a limited number of these self balancing scooters, it is UL, Underwriters Laboratories, for the Charger that is best, and CE/ UN 38.3 that you look for on the battery. Which is primarily found on LG/Samsung batteries with a good BMS along with a few other Asian brands who have taken the time to get certification. There are no US manufacturers of these scooters, NONE. Any bearing a US branding label were contracted and built in China. Take a close look at the pattern on the wheels and the body panels and you see that any claiming to be US made are the same as those in China. With that said, it is no different than with other inexpensive ebikes; if all you look at is the pricetag and go super cheap then somewhere a corner is cut.
As I have stated before, there are distinct differences in the quality of Lithium Ion cells coming from China, so looking for better quality cells along with a decent BMS is worth the few dollars difference in price. Also, it makes a difference if the manufacturer is willing to communicate with the buyer. Mine has provided certification and I opened up a couple of the scooters to verify what battery, etc. was actually inside. Did my homework before purchasing for my customers. Can't prevent folks from doing foolish things that might cause a problem; however, did what was possible to get a quality product and more importantly, EDUCATE people about proper charging protocols...let the batteries cool before charging and don't leave the unit on a charger 24/7. These particular packs are small and will be fully charged in 2 hours or so. Use a timer and a surge protector...all standard info from our shop.
What Amazon did helps create a rapid push back on the scooter manufacturers that inferior product will not be tolerated. That's good feedback which will help weed out the Asian brokers looking for a quick buck in the US market. Reminds me of the trendy cheap scooters that used to be sold in parking lots and street corners 15 years ago. Some people got hurt and US Customs, along with CPSC, stepped in and whole container loads of inferior product were being detained/refused. That altered the manufacturers process within a couple of years.