Let me tell you, the added weight is nothing... On a hub motor when you don't have a connected battery, say because the BMS tripped as you ran dry, the motor converts a signficant amount of your kinetic energy into electrical energy and then to heat. You can really feel it cogging. I could swear the two weeks I ran it without a batteris saw my thighs get significantly bigger!

Thankfully in my city there are plentiful subway stations with elevators, so when I did run dry once, I was able to pedal my bike into the subway and take it home.