Shift Sensor for Bafang BBS middrive ebike engine.
In a recent BBS improvement Bafang added a shift sensor function
and cable, the motor will have an extra yellow head cable.
When user install BBS motor onto their bike, if the crank wheel is running
when they shift the SHIMANO gears, it is a high risky to destroy the derailleur.
With this function, motor will be stopped for a second when people shift the gears,
to help the derailleur. Especially for 350W+ motor, it is a must
to stop the engine before shifting the gers.