Motor and drivetrain

The electric drive of the C5 runs:

12 V motor → epicyclic gearbox → toothed drive belt → drive gear → rear axle, driving the left-hand rear wheel only.

The overall reduction is 13:1. The pedal drive is a separate system; see Pedal drive.

How it works

The motor is a 12 V permanent-magnet DC motor rated at 250 W continuous, made by Polymotor (Italy, part of the Philips group). It isn't a washing-machine motor, despite the legend.
There is no speed control. The power button simply switches the motor on or off through a relay, and the motor's own maximum speed (4,100 rpm) limits the C5 to about 15 mph.
The motor draws about 15 A on the level, about 50 A climbing a 1-in-15 hill, and up to 140 A when stalled. It is protected by a thermistor in the armature shaft, a thermal trip on the case, and stall detection in the control box. See Electrics.
The motor sits in an eccentric clamp. Rotating it is how you set the drive belt tension.

Pedal off from rest, then use the motor. Starting on the motor alone strains the gearbox, belt and motor.
Pedal on hills. The motor overheats on long climbs and cuts out.
Don't push the C5 backwards quickly. The motor acts as a generator and can destroy the control box's protection diode.

Clicking or slipping under power: see Drive belt and Motor support.
Motor runs but no drive: check the belt, and whether the gearbox has come off its lip.
Motor cuts out on hills: thermal protection doing its job. See Electrics.
Never-serviced gearbox: regrease it before regular use. See Gearbox.

Chassis (motor support) · Electrics (thermal trip, heat sensor, control box) · Pedal drive · Wheels and tyres