Mid-Drive Motor is located in the middle of an electric bicycle, around the area of the bottom bracket. Essentially, it resides inside the crank (the arm that connects to the pedals) and applies force directly to the mechanical transmission system,which is the traditional collection of components that propel the bike forward. However, drive hub motors are located in the front or rear hub of the bicycle, and despite working fundamentally in the same way, they feel quite different to the rider.
In most cases, the transmission system of a mid-drive e-bike consists of a traditional chain, chainring, and flywheel, which collectively drive the rear wheel and propel forward. Or, you may be looking for a belt drive system that works very similarly, driving the rear wheel. Either way, mid-drive motors increase the amount of pedal force you put in.
It can do this because the motor itself has sensors that measure your pedaling effort. The motor reads this data and responds by providing additional power directly onto the chain or belt, pushing you forward with greater force.
This can effectively making the motor ideal for enthusiasts who need very sensitive pedal-assist and some hybrid e-bike riders who may use their electric bike for multiple types of riding, such as daily commuting and weekend short trips.
This makes it the preferred mode for electric mountain bikes, where riders often need higher levels of assistance to deal with very challenging terrain. The downside to this direct connection is that you may experience increased wear and tear on the power transmission system as it has to deal with the force you apply through the pedals, as well as the typically higher force that the motor provides. Over the medium to long term, this may mean you need to replace some of the worn components more frequently.
Additionally, since Mid-Drive Motors typically are more powerful, as a compensation, you sometimes install larger batteries to provide good range, but they may be heavier and not fit neatly inside the frame. However, professional mountain bike brands will integrate the battery as much as possible to avoid negative impacts on handling, and an integrated design typically allows for easy removal.