Mobility scooters generally operate at 24v and have a legal top speed of 4 mph on the pavement, road vehicles can have a top speed of 8 mph. 4QD controllers can be wired with a ‘top speed switch’ to restrict speed to either 4 or 8 mph.
4QD controllers are often used as replacements for broken oem controllers, or when re-purposing an old scooter or motor for some other application. As always the choice depends on the motor current and the application but it usually comes down to a choice between the DNO-10, Pro-150, or 4QD-200 [in increasing capacity].
A common motor for mobility scooters is the EMD PM50 (about 250w rating), up hills and kerbs this can draw up to 50 amps peak, although it will draw less on the level. It is quite common to see two motors used, one on each rear wheel.
Controllers for mobility scooters have become very complex and sophisticated, in part this is because the earliest vehicles were designed for very disabled people with poor motor control, the controllers therefore became very sophisticated to cope with the user’s disabilities. The second reason for this complexity is that early power semiconductors were temperamental and unreliable, so designs added more and more fail-safe protection circuitry. 4QD’s controllers started life for the Golf industry, which has started from the other end – very low technology gradually improving with time but always very price conscious. Golf vehicles need 100 to 200 amps which is much more than most mobility aids, except for high performance dual purpose machines.
The DNO-10, Pro-150, and 4QD-200 all have fail safe mechanisms built in and an uncontrolled failure to high speed is extremely unlikely. Even so, for passenger carrying vehicles we always recommend fitting a battery contactor or isolator switch within easy reach of the driver.