# Calculation method of energy consumption economy of pure electric vehicle

The evaluation index of AC energy consumption is not only related to the economy of the pure electric vehicle itself, but also affected by the power grid and charging equipment. Therefore, the direct current energy consumption rate of the power battery pack can be selected as an economic evaluation index.

The energy consumption rate per unit mileage of pure electric vehicles is

In the formula, Ep (kw-h/km) is the direct current energy consumption rate of pure electric vehicles; Pei (kW) is the power demand of the vehicle under operating conditions: ti (h) is the running time under operating conditions; Si (km) is the operating conditions The distance traveled.

For acceleration conditions, the driving power demand of the car is

In the formula, Pj (kW) is the power demand for the car to accelerate: v(t) (km/h) is the speed of the car at a certain moment; i is the slope; aj (m/s²) is the acceleration (deceleration) speed.
The driving speed of the car at a certain moment is

In the formula, v0 (km/h) is the initial speed of acceleration.
The distance traveled by the car under acceleration is

In the formula, Sj (km) is the distance traveled by the vehicle under acceleration conditions: vj (km/h) is the end speed of acceleration.
The acceleration time of the car is

Substituting formula (2) ~ formula (5) into formula (1), it can be obtained that the energy consumption rate per unit mileage of pure electric vehicle under acceleration conditions is

In the formula, Ej (kw.-h/km) is the energy consumption rate per unit mileage of the pure electric vehicle under acceleration conditions.

It can be seen that under acceleration conditions, the energy consumption rate per unit mileage of a pure electric vehicle is a function of the sum of the square of the start and stop speeds of the acceleration section. Under the same average speed, the small sum of the square start and stop speeds of the acceleration section has low energy consumption. Increasing the starting speed and increasing the speed interval will increase the energy consumption per unit mileage.
For uniform speed conditions, the driving power requirement of the car is

In the formula, Py (kW) is the power demand of the car at a constant speed: vy (km/h) is the driving speed of the car at a constant speed.
The distance the car travels at a constant speed is

In the formula, Sy (km) is the distance traveled by the car at a constant speed: ty (s) is the constant speed travel time.

Substituting formula (7) and formula (8) into formula (1), the energy consumption rate per unit mileage of pure electric vehicle under constant speed working condition can be obtained:

In the formula, Ey (kW.h/km) is the energy consumption rate per unit mileage of the pure electric vehicle under the uniform speed condition.

It can be seen that under constant speed conditions, the energy consumption rate per unit mileage of a pure electric vehicle is a function of the sum of the squares of the start and stop speeds of the acceleration section. Increasing the driving speed will increase the energy consumption per unit mileage.

For deceleration conditions, the deceleration of pure electric vehicles includes two situations: one is coasting deceleration or braking deceleration without regenerative braking. At this time, the drive motor is in the off state, the electric energy output is zero, and the pure electric vehicle has a unit mileage. The energy consumption rate is zero; the other is braking deceleration under the regenerative braking function, which means that the wheels drive the motor, and the motor is in the working state of the generator. The energy consumption of a pure electric vehicle is negative, and the power battery is in a charging state.

For parking conditions, the drive motor is in the off state, and the energy consumption rate per unit mileage of the pure electric vehicle is zero.

Therefore, the energy consumption of pure electric vehicles mainly occurs in acceleration and constant speed operation conditions, and the energy consumption in deceleration and parking conditions can be ignored.
The driving distance of the car under deceleration condition is