Why Dual-Motor Scooters Outperform Single-Motor Scooters in Acceleration, Hill Climbing, and Range
This article explains why dual-motor electric scooters accelerate faster, climb hills better, and have a longer range than single-motor scooters, even when they have the same total power output.
How Dual Motors Improve Acceleration
Dual-motor electric scooters accelerate faster than single-motor ones primarily due to differences in power distribution.
1. Better Traction Distribution Reduces Wheel Spin
A single-motor scooter (which typically drives one wheel) applies all its torque to that single wheel during acceleration, often leading to wheel spin, especially during startup. A dual-motor system, however, can distribute torque to both the front and rear wheels, significantly improving the efficiency of traction utilization.
Here's the underlying principle:
According to Newton's Second Law:
F=m⋅a
Where:
F: Net external force (in Newtons, N) ;
m: Mass of the object (in kilograms, kg);
a: Acceleration of the object (in meters per second squared, m/s²)
Therefore, when the load is the same, a greater net force (F) results in greater scooter acceleration. The net force propelling a scooter forward is mainly determined by the motor's driving force, air resistance, and rolling friction of the wheels. Among these, the motor's driving force is the most significant. This driving force is converted into static friction between the tire and the ground—it's this static friction that directly propels the scooter forward. Only the driven wheel(s) can provide this driving force.
Why does static friction propel the scooter forward? This might seem counterintuitive, as we usually associate friction with impeding motion. However, in this case, the opposite is true: during scooter acceleration, static friction is the crucial force that pushes it forward. When the motor drives the wheel to rotate forward, the point of the tire in contact with the ground has a tendency to slide backward. To prevent this sliding, the ground applies a forward static friction force. This force is the ground's reaction force on the wheel. Far from hindering the scooter, it provides forward traction, propelling the entire vehicle.
Simply put, the force transmission process is: Motor rotates wheel → Wheel pushes ground → Ground pushes scooter body forward via static friction. Static friction acts as the tractive force, while the motor provides the driving force.
Driving Force vs. Tractive Force:
Driving Force is the force generated by the motor's torque acting on the tire, attempting to make the tire roll on the ground. It is the fundamental source of tractive force.
Tractive Force is the static friction force exerted by the ground on the tire, preventing the tire from slipping while simultaneously pushing the scooter forward.
According to Newton's Third Law, action equals reaction. Thus, when the scooter is not slipping, the tractive force (static friction) that propels the scooter forward is equal to the thrust force exerted by the scooter's wheels on the ground, which is the motor's driving force (ignoring other losses during energy conversion).
Generally, a larger motor driving force leads to greater static friction and faster acceleration. However, there's a limit to the available static friction. Once this friction limit is exceeded, the tires will slip, the wheels will spin idly, and the scooter will no longer accelerate. When the wheel is not slipping, wheel driving force = tractive force; when the wheel is slipping, wheel driving force > tractive force.
The formula for calculating maximum static friction is:
F_static ≤ μs⋅N
Where:
F_static: Static friction force;
μs: Coefficient of static friction (between tire and ground);
N: Normal force exerted on the object (usually due to gravity)
Therefore, the difference between dual-motor and single-motor electric scooters is clear:
Single-motor, single-wheel: Regardless of how powerful the motor is, the maximum tractive force that can be converted into forward motion is limited by the maximum static friction between the single driven wheel and the ground. Once the motor's output torque exceeds this limit, the wheel will spin instead of providing greater thrust.
Dual-motor, dual-wheel: With two independent driven wheels, each wheel can utilize its static friction with the ground. This means the scooter can simultaneously use twice the tire contact patch to "grip" the ground. The available tractive force limit is generally higher than that of a single-motor system, allowing for a greater net force to propel the scooter forward without slipping, potentially approaching double the force in extreme conditions.
2. More Even Torque Distribution and Better Dynamic Response
Even with the same total power (e.g., both 1000W), a dual-motor system allows for more precise control over each motor's output, achieving smoother and faster torque response. Especially with advanced electronic control systems (like FOC), dual motors enable more intelligent speed regulation, optimizing the acceleration process.
How Dual Motors Improve Hill Climbing Ability
The essence of hill climbing is that the tractive force (static friction between the ground and tires) must be greater than or equal to the component of gravity acting down the slope (when climbing, gravity can be considered to have two components: one perpendicular to the slope and one diagonally down the slope).
Because dual motors can drive two wheels simultaneously, they provide greater total tractive force, allowing them to overcome a larger gravitational component and achieve steeper climbing angles.
How Dual Motors Increase Range
While the superior acceleration and hill-climbing performance of dual-motor scooters might be easy to understand, the idea of a longer range might seem counterintuitive—many people assume two motors would consume more power, leading to a shorter range. This is not the case. Let's analyze in detail why dual-motor scooters can offer a longer range:
1. Dual Motors Are More Efficient Under Low Load
Each motor has an optimal efficiency operating range. When a motor operates within this range, energy conversion efficiency is highest, and losses are minimized.
During steady cruising, the power required by the scooter (e.g., to overcome air resistance, rolling resistance, and slight inclines) is often much lower than the motor's rated power, perhaps only 300W. In this scenario, there's a clear difference in operating efficiency between single-motor and dual-motor systems:
Single-motor model: A single high-power motor (e.g., 1000W) outputs 300W on its own, often operating outside its optimal efficiency curve, leading to higher energy consumption.
Dual-motor model: Two motors (e.g., 2 x 500W) can share the load, with each outputting only 150W. This power point is likely closer to their respective peak efficiency ranges, resulting in higher overall drive efficiency and lower energy consumption.
Furthermore, many dual-motor systems support an economy mode where only one motor is activated for light-load cruising, further conserving energy. In contrast, single-motor systems can easily deviate from their optimal efficiency range under low-speed, light-load or high-speed, heavy-load conditions, leading to reduced electrical energy utilization.
Therefore, dual-motor systems generally exhibit higher drive efficiency during daily cruising, acceleration, or uphill conditions, thereby reducing overall energy consumption and extending range.
2. Lower Copper Loss (I2R Loss)
When a motor converts electrical energy into mechanical energy, some energy is lost. Copper loss typically accounts for the largest proportion of total losses.
What is copper loss? Copper loss is the heat generated when current flows through the winding resistance. Essentially, it's a portion of the motor's electrical energy "wasted" as heat. This process significantly impacts motor efficiency.
Pcopper_loss=I²⋅R
Where:
I: Current;
R: Resistance
Single-motor and dual-motor systems differ significantly in terms of copper loss:
Single-motor scooter: The total current is concentrated in one motor, leading to higher current and greater loss.
Dual-motor scooter: At the same total power output, because the current is shared, the current in each motor is halved. This means the copper loss in each motor drops to 1/4 of the single motor's loss, and the total copper loss for both motors combined is 1/2 of a single-motor scooter's.
So, for the same power output, dual motors have lower total loss.
3. Higher Traction Reduces Additional Energy Loss
Easier Startup and Acceleration: Dual motors provide greater instantaneous torque and traction during startup. This means they can reach the target speed more quickly and "effortlessly," reducing the time the motors operate at high current during inefficient startup phases, thereby minimizing energy loss.
Hill Climbing Capability: Dual motors are more efficient when climbing hills. A single motor might require higher current and rotational speed to overcome slope resistance, leading to more heat generation and greater loss. Dual motors can share the load, allowing each motor to operate in a more efficient state, thus reducing total energy consumption.
Overall, with the same battery capacity, dual-motor electric scooters utilize battery energy more effectively due to higher energy conversion efficiency and optimized traction distribution, resulting in longer range and extended riding time.
Conclusion
At the same total power, dual-motor electric scooters generally outperform single-motor models in acceleration, hill-climbing ability, and range. Their core advantages stem from more rational torque distribution and traction utilization, a higher energy-efficient operating range, and lower motor losses.
Faster Acceleration: Dual motors share the driving force, providing greater and more evenly distributed traction, reducing the risk of wheel spin and improving acceleration.
Stronger Hill Climbing: Dual driven wheels provide greater total tractive force, overcoming the gravitational component on slopes with less effort.
Longer Range: Dual motors are more efficient under light or moderate loads, exhibit lower copper loss, and utilize energy more effectively.