This article by Electric Bike .com is well worth reading by anyone interested in mid drive e-bikes. These bikes will become more common in the more expensive bikes and conversion kits.
There are many factory mid drive e-bikes appearing now. Many of the best e-bike brands now have or will have models with a mid drive. These are highly priced e-bikes…because the mid drive motors that are installed are much more expensive than a hub motor, and because the factory takes one of the top models and modifies the frame to incorporate the mid drive motor.
Almost all of the mid drive motors replace the usual bottom bracket. The frame tubing is cut back from where it would join a bottom bracket and is welded to the case of the much larger motor.
The factories making the bikes will have a supply contract with one of the factories making the mid drive motors. For instance Cannondale and Trek and many european bike brands choose a Bosch motor.
E-BIKES WITH MID DRIVE MOTORS INTEGRAL WITH FRAME
By that I mean that the e-bike has been designed around the motor.
MID DRIVE MOTORS REQUIRING MODIFICATION OF THE FRAME.
That is almost all of them.
Bosch, Kalkhoff, eProdigy, Continental (the tyre maker), Panasonic, MPF 5.0, Electrgil Acron, Conway, TranzX, Yamaha, Cevedale, Evation, Bionicon, and Protanium Diavelo.
MID DRIVE MOTORS REQUIRING MODIFICATION AT THE CHAINWHEEL
There are factories in China making large numbers of a cylindrical motor with a worm reduction gear that drives a chainwheel. This is a much cheaper arrangement than the integral mid drive motor and chainwheel incorporated into the frame. The brands with this arrangement of mid drive motor include HiTek, Evelo and Aseako.
MID DRIVE MOTORS REQUIRING NO MODIFICATION OF FRAME.
These motors have integrated motor and chainwheel and can directly replace the pedals and chainwheel of most bikes. The motors are made by AEG and Bafang. Bafang BBS02 is being made in thousands and will appear in some brands and is available singly for individual e-bike conversion.
PS . I have a 250Watt and 350Watt BBS02 that I am trying. I’ll sell them soon. See Conversion Kits