The main purpose of the battery is to power the motor. This might sound strange since your cycling is powering the motor. But remember, despite what some brands have you made believe, on the road you don’t generate force in the dead points (pedals vertical). So at those moments the motor needs (a little) power to keep going through your dead point. This is part of the smooth feel. Also, when you keep your legs still, the motor needs to keep itself going for the smooth rolling effect.
Also, TrueForce Technology is a robot and has a 'brain' that needs the power to run. If you have a TrueKinetix product with a display or you connect a display to your TrueKinetix product, then the power level required for a smooth experience is greater than you can deliver in a workout.
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