I think that size of battery would move it into requiring a motorcycle license here in Switzerland, just based on the size alone. And if it goes faster than 45km/h then definitely.
I have my motorcycle license and have been considering getting something that I can ride all day. Only problem is that if it's classified as a motorcycle license I don't think I can take it in the train like a bike if I run out of juice far away.
I know we all carry fully charged batteries in our pockets and sometimes keep them in our ears too.
But something about travelling in crowded and closed space like train with a fully charged diy (or even commercial) battery pack sounds risky.
This is one of the reasons I didn't go for a diy replacement of TWS pair with dead batteries.
While I don’t think anyone should be allowed to take a 2150Wh home made battery on a train, I’m not sure why battery capacity should affect classification. Limiting power delivery makes much more sense.
Quite common for Bosch powered cargo bikes to allow fitting two 800Wh batteries and you can always carry spares. They’re just horribly expensive.
I’m very glad my US spec e-bike is 28mph/45kmph rather than 15mph/25kmph limited as I feel much more comfortable taking the lane closer to car speeds on residential roads even if I rarely go above 20mph.