What speed electric vehicles and related parts

Maximum speed of the electric car depends on the rated motor speed , you can limit the output voltage to limit the output speed , can be transferred to the output terminal plus two resistor divider in the Hall , if accuracy is not required , you can also signal line plus one to two diodes ( with controller sensitivity related to the Cargo bike experimentally determined ) . How can we know the brush motor brushes changed ? Generally when the brushes wear to 1/ 3 of the time, he should be replaced, the motor does not turn bad brush Fortunately , afraid of bad is good sparks serious damage commutator segments , then more harm than good , so the motor carbon brush should be life management . With a 240 -watt motor, battery is 36V20Ah, but the car Folding electric bikes starts, the power indicator pointer will point to the lowest level , but the car is not enough power, I ask this question about where is not just with a controller on the line of ? What kind of controller like this should be used , there is no good controller is recommended . Common causes of this phenomenon in general , there are two : the line impedance is too large, there may be various circuits joints bad .