>>1926825bafang kits are good
the major cost is getting a decent battery though, those are really expensive and easy to get ripped off with.
The downsides are the cadence sensing pedal assist isn't amazing, the motor needs an aftermarket stabilizing arm to avoid pivoting around the bb, the chain retention isn't amazing without a narrow-wide lekkie ring or the like, and you will eat drivetrain components.
Actually the major downside imo is that you're putting it on a bicycle which probably sucks. Most conversions i've seen ridden neglect the bike part of e-bike project.
The HUGE plus over the cheaper rear hub motors is ease of changing tubes/tires.
>>1926846it's chinkshit batteries which will explode into flames not the motor kit.
