I ordered a foldable 26i Mountain Bike from Thunder Ebikes in Oct 2017 through Alibaba.
This is more of a warning than a review because it all went not well.
Thunder Ebikes are a typical example of a Chinese rippoff manufacturer. I was promised a 12.8 amp Samsung battery, of course I got a cheap Chinese one which has "chunk" written all over it. The rear rack could not be mounted because it was so out of spec. Need to modify it to make any use of it. Screws rusty within weeks. Then I had a problem with the electrical system. I contacted them, let them know about it described the problem in every detail and got this answer back: "you have not used your bike enough that is why we cannot cover the problem under warranty."
I then checked the components myself and found a little transistor which was between battery and controller to be blown. Replacement cost of a dollar or 2 but they simply did not respond any more. Be very careful when considering a deal with this company.
Ride SAfe, Gerry