About a year ago, I posted this thread:
https://www.ar15.com/forums/outdoors/-/1-699848/I bought a Vivi S2 from Amazon in January of 2021. I really enjoyed it for the first few months that I had it. As an ebike, it wasn't overpowered, but adequate for my needs.
In June, I was riding up a long hill, pedaling with motor assist, when I suddenly lost all power. The bike was still under warranty (which was supposedly 6 months).
Took the controller box apart and found melted insulation and burned wires. Motor was taxed, amperage spiked, and apparently, no protections were built in to stop the surge. I let the smoke out.
So, I started trying to get warranty service for it.
Instead of detailing that entire process for you, I posted a video on Youtube following my harrowing experience.
Thinking of buying a VIVI ebike from Amazon or another retailer?
https://www.youtube.com/watch?v=MmgkSIDiA5M&ab_channel=squashpupTL;DW: There is no customer service, and they lie through their teeth. I am still getting messages from the seller who is adamant that he has shipped replacement parts, but he refers to a tracking number for a package that ended up in Texas months ago. He really wants me to remove my negative feedback. And, although he did issue a partial refund for less than half of the purchase cost of the bike, he didn't honor the warranty that was promised at the time of purchase.
In the end, my purchase price was $550, I got a $250 refund, and I sold the bike as being DRT on Facebook for $125. So, I lost $175 on the deal. Could have been worse, but bad enough.
The bad part is, after the fact, if I'd KNOWN that the bike itself had no overload protection, it would have been relatively easy to wire in a 10-15 amp fuse that likely would have prevented the problem.
So, if you order one of these bikes, understand that you are likely on your own. And if you possess any electrical knowledge at all, you'd best install a fuse to prevent a complete meltdown of the controller or motor.
For my second ebike, I ponied up the money and ordered from an American company with a good reputation for customer service. Just passed the 100 mile mark on the new bike and I'll post a review here shortly.