Electric vehicles are increasingly entering households, and various new domestic car manufacturers and traditional car manufacturers have launched cars with a range of up to 1,000 kilometers. In order to better understand the evaluation indicators of electric vehicle range, this article conducts a simple comparative analysis of electric vehicle range test standards, summarizes several technical indicators that need to be focused on for electric vehicles, and hopes to serve as a reference guide for evaluating electric vehicles.
1. Three main test standards for electric vehicle range. [1]
There are three range standards in the range test, NEDC, WLTP, and EPA.
NEDC: The full name is "New European Driving Cycle", which means the new European driving cycle, also known as the "New European Cycle Test". Although it is the European range test standard, my country's Ministry of Industry and Information Technology will use this standard when testing the comprehensive mileage of new energy vehicles. The main countries using it are Europe, China, and Australia.
During the test process, five working conditions were included, including 4 urban cycles and 1 suburban cycle (simulation) conditions. The specific test method is to put the vehicle on a test bench. Generally, the test will be carried out on a roller test bench. The roller in contact with the tire has a motor to simulate the resistance under different working conditions. A blower will be placed in front of the front of the car to simulate the airflow that matches the current vehicle speed. During the test, other loads such as air conditioning, headlights, heated seats and other applications will be turned off. During the test, the speed will not exceed 50km/h for urban conditions, the average speed will be 18.5km/h, and the test time will be about 195 seconds; in suburban conditions, the state of smooth traffic will be simulated, with a maximum speed of 120km/h, an average speed of 62km/h, and a test time of about 400 seconds.
WLTP: The full name is World Light Vehicle Test Procedure, which is jointly formulated by Japan, the United States, the European Union, etc. The test is divided into four parts: low speed, medium speed, high speed and ultra-high speed, with corresponding durations of 589s, 433s, 455s and 323s, and corresponding maximum speeds of 56.5km/h, 76.6km, 97.4km and 131.3km/h. The test incorporates the rolling resistance, gear position, vehicle weight (cargo, passengers), etc. of the vehicle into the test.
EPA: The full name is U.S. Environmental Protection Agency, which is the abbreviation of the United States Environmental Protection Agency. The test uses MPGe to equivalently represent its energy consumption, and records the vehicle's power consumption converted to MPGe in urban road conditions, highway road conditions and mixed road conditions, as well as the cruising range. MPGe is the abbreviation of Miles per gallon gasoline equivalent.
1 MPGe ≈ 0.04775 km/kW·h
The above table is the EPA test data of Tesla's standard range version.
Based on the actual mileage, the reliability of the three test standards is EPA>WLTP>NEDC. When talking about the range of electric vehicles, we must compare the range based on the test standards.
2. Example analysis of the range of electric vehicles
Fuel vehicles: Take the 2007 Passat 1.8T as an example. The capacity of the fuel tank is 62 liters. Ignoring the difference in gasoline specifications, the general urban fuel consumption is about 12 liters per 100 kilometers, and a full tank of fuel can run 500 kilometers; when driving on the highway, the speed is 100km/h, the fuel consumption will be about 9 liters per 100 kilometers, and it can run 650 kilometers; the same tank of fuel has a large difference in mileage under different working conditions.
Pure electric vehicles: Take the Tesla model 3 long-range rear-wheel drive version as an example. The motor power is 217KW, and the battery capacity is 75kwh:
EPA: 523 km combined; 534 km city; 512 km highway
WLTP: 600 km
NEDC: 675 km
Someone on Youbube tested the Tesla model 3 long-range rear-wheel drive version. On the unlimited speed highway in Germany, cruising at a speed of 200km/H, the power consumption per 100 kilometers is about 60kwh. At a speed of 200km/H, the actual cruising range of the vehicle is about 130 kilometers.
From the above, it can be seen that just as the cruising range of a full tank of fuel car is closely related to the driving road conditions, the cruising range of pure electric vehicles is closely related to the test conditions. The cruising range values under different test standards are quite different, and EPA is the closest to the actual driving mileage value.
3. Parameters related to the cruising range of electric vehicles
Battery capacity
Unit KWH, also called degree. This indicator is like the capacity of the fuel tank of a fuel car, indicating the amount of energy that can be stored;
Motor power
Unit KW. This indicator is like the engine displacement of a fuel vehicle, indicating the power of an electric vehicle;
Cruise range
The indicator for evaluating the cruising range must be linked to the test standard, and the difference between NEDC, WLTP, EPA and the actual driving conditions must be understood.
The temperature of the working environment of electric vehicles
The cooling and heating of electric vehicles consume the energy of the battery. The discharge capacity of the battery at different operating temperatures also varies, especially below zero. We often hear electric vehicle drivers complain that the cruising range decays quickly in the winter in northern regions. This is due to the low-temperature discharge characteristics of the battery itself, and the need for heating the battery. The heating in the car consumes the energy of the battery.
Summary
Based on the actual driving mileage, the reliability of the test standard is EPA>WLTP>NEDC. On the other hand, battery capacity, motor power, and operating temperature are also important parameters that affect the cruising range of electric vehicles.