Long Range E-Bike

Cool project! Scary one, too; kudos on pulling it off successfully!

I wonder, am I scared shitless because I do or because do not know enough about electronics?

This is as amazing than frightening. I remember looking at Lion chemistry and DYI when vaping was trending and agreeing that I will not know enough to be safe. On the other end, that is also why when we chose our cargo bike (bakfiets), we short listed models that accept two batteries by default. We found a Riese&Muller Packster 70 second hand. It is another 700 - 800 EUR to buy one but it is fully integrated. It would not cover the same range but we probably get +200km out of ECO mode without issue and probably 100-110km in full assist. In the Netherlands, this works very easily (infrastructure already available, common and known to other drivers, flat).

Terrifying! I worry sometimes about how much home-made LIon circuitry there is floating around. The quality of some mass-produced stuff is hardly any better.