I had a surge this morning that sent me backwards onto the asphalt when my Pint went full-speed ahead. I was riding on my new Hoosier wet-weather treaded tire, just logging some kms to get used to it, so I had my upper body pads on, in addition to the wrist guards and helmet that I always have. Lucky thing – tore my coat on the elbow, but the pads did their job. Hopped up and rode another 6km* in a mild state of shock. lol.
I was at 38% battery, and I never felt any surge like that on the stock tire on that much battery (2400 km on that one). OTOH, this new tire is very soft and very energy inefficient compared to the stock slick tire. May well be that I won't be able to ride it like the old tire due to the additional drag all the time. I'm 85 kilos and run with it at around 22 psi, so far.
Headwind; soft tire, cold temperatures, low battery – it all seems to play into the possibility for drama in the form of surges/nosedives.
*Note: Yep. Range extender, but I've got 1000 km riding with that, too, and it's never been an issue.