My understanding is brushed have lower RPM more torque Brushless High RPM low torque
Brushed will run longer periods like hours where LIPO's are short run times for Brushless.
Brushed usually use Lead acid which are heavier and give more Ballast for boats.
Scale boats tugs brushed Speed boats Brushless
Brushed and Brushless Motors: Advantages and Disadvantages Depending on your application, there are reasons why you might choose to use a brushless motor over a brushed motor. The following table summarizes the main advantages and disadvantages of each motor type:
Brushed motor Brushless motor
Lifetime Short (brushes wear out) Long (no brushes to wear)
Speed and Acceleration Medium High
Efficiency Medium High
Electrical Noise Noisy (bush arcing) Quiet
Acoustic Noise & Torque Ripple Poor Medium (trapezoidal) or good (sine)
Cost Lowest Medium (added electronics)
As previously mentioned, one of the disadvantages of brushed motors is that there is mechanical wear of the brushes and commutator. Carbon brushes in particular are sacrificial, and in many motors they are designed to be replaced periodically as part of a maintenance program. The soft copper of the commutator is also slowly worn away by the brushes, and eventually reach a point where the motor will no longer operate. Since brushless motors have no moving contacts, they do not suffer from this wear.
Speed and Acceleration
Brushed motors rotational speed can be limited by the brushes and commutator, as well as the mass of the rotor. At very high speeds, the brush to commutator contact can become erratic, and brush arcing increases. Most brushed motors also use a core of laminated iron in the rotor, which gives them large rotational inertia. This limits the acceleration and deceleration rates of the motor. It is possible to build a brushless motor with very powerful rare earth magnets on the rotor, which minimizes the rotational inertia. Of course, that increases the cost.
The brushes and commutator form a kind of electrical switch. As the motor turns, the switches are being opened and closed, while significant current is flowing through the rotor windings, which are inductive. This results in arcing at the contacts. This generates a large amount of electrical noise, which can get coupled into sensitive circuits. Arcing can be somewhat mitigated by adding capacitors or RC snubbers across the brushes, but the instantaneous switching of the commutator always generates some electrical noise.
Brushed motors are “hard switched” – that is, current is abruptly moved from one winding to another. The torque generated varies over the rotation of the rotor as the windings get switched on and off. With a brushless motor, it is possible to control the winding currents in a way that gradually transitions current from one winding to another. This lowers torque ripple, which is a mechanical pulsation of energy onto the rotor. Torque ripple causes vibration and mechanical noise, especially at low rotor speeds.
Since brushless motors require more sophisticated electronics, the overall cost of a brushless drive is higher than that of a brush motor. Even though a brushless motor is simpler to manufacture than a brushed motor, since it lacks brushes and a commutator, brushed motor technology is very mature and manufacturing costs are low. This is changing as brushless motors become more popular, especially in high volume applications like automotive motors. Also, the cost of electronics, like microcontrollers, continues to decline, making brushless motors more attractive. Summary Due to declining costs and better performance, brushless motors are gaining in popularity in many applications. But there are still places where brushed motors make more sense. Much can be learned by looking at the adoption of brushless motors in automobiles. As of 2020, most motors that are running whenever the car is running – things like pumps and fans – have moved from brushed motors to brushless motors for their increased reliability. The added cost of the motor and electronics more than makes up for the lower rate of field failures and decreased maintenance requirements. On the other hand, motors that are operated infrequently – for example, motors that move power seats and power windows – have remained predominately brush motors. The reasoning is that the total run time over the life of the car is very small, and it is very unlikely that the motors will fail over the life of the car.