What is a pure electric car?

Pure electric cars are cars that are powered entirely by rechargeable batteries (such as lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries or lithium-ion batteries). Pure electric cars are composed of six parts: chassis, body, battery pack, electric motor, controller and auxiliary facilities. Because the electric motor has good traction characteristics, the transmission system of a pure electric car does not need a clutch and a transmission. car speed control can be realized by the controller changing the speed of the motor through the speed regulation system. Now the development of pure electric car technology is quite mature, and some models are put into mass production and commercial operation all over the world. Pure electric cars have the following advantages:

(1) Reduce dependence on petroleum resources and achieve diversification of energy utilization. Since electricity can be obtained from a variety of primary energy sources, such as coal, nuclear energy, water power, wind power, light, heat, etc., it can relieve people’s worries about the depletion of oil resources.

(2) Reduce environmental pollution. Pure electric cars themselves do not emit harmful gases that pollute the atmosphere. Even if the power consumption is converted into emissions from power plants, in addition to sulfur and particulates, other pollutants are also significantly reduced. Most power plants are built far away from densely populated cities, which do little harm to humans. Moreover, the power plants are fixed and emit concentrated smoke and dust. It is easier to remove various harmful emissions, and related technologies are available.

(3) High energy conversion efficiency. The energy efficiency of pure electric cars surpasses that of gasoline-powered cars, especially when running in cities, where the cars go and stop, and the driving speed is not high, pure electric cars are more suitable. The same crude oil is crudely refined and sent to the power plant for power generation. The electricity generated is charged into the battery, and then the battery drives a pure electric car. Its energy utilization efficiency is higher than that of refined into gasoline and then driven by a gasoline engine to drive the car.

What is a pure electric car?
pure electric car

At the current level of electricity and oil prices, the operating cost of pure electric cars is lower than that of traditional cars, which has better economic efficiency. However, current pure electric cars still have shortcomings such as shorter cruising range and higher battery prices.

Although pure electric cars have a history of more than 100 years, they have been limited to specific applications and the market is small. The main reason is that various types of batteries are generally expensive, short in life, large in size and weight, and charging time. Long and other serious shortcomings. Currently used lead-acid batteries, nickel-metal hydride batteries and lithium-ion batteries, based on their actual cycle life and market prices when installed in cars, can estimate the cost of each lkWh of electricity that a pure electric car must pay from various power batteries.

What is a pure electric car?
Electric car battery

When estimating the cost that a pure electric car must pay for every 1kWh of electric energy taken from various power batteries, it is assumed that the highest rechargeable state of charge (SOC) of the battery is 0.9, and the discharge SOC is 0.2, that is, the actual available battery capacity only accounts for 70% of the total capacity; the price of power supplied by the grid is 0.5 yuan/kWh, and the average charging and discharging efficiency of the battery is 0.75. According to the rough calculation of the above data, it can be seen that although it only needs 0.5 yuan/kWh to get electricity from the grid, it is charged into the battery and then taken out from the battery. The price of the lead-acid battery provides 1kWh of electricity at about 3.05 yuan, of which 2.38 yuan is the depreciation cost of the battery , 0.67 yuan is the grid power supply fee, and the cost of each lkWh of electricity provided from the nickel-hydrogen battery is 9.6 yuan, and the lithium-ion battery is 10.2 yuan. That is, the cost of electric cars using the latter two advanced batteries is more than three times that of lead-acid batteries. .

At present, in the Chinese market, the price of diesel engine power generation is roughly 3 yuan/kWh, and the price of gasoline engine power generation is estimated to be 4 yuan/kWh, that is, the price of electricity supplied from lead-acid batteries is roughly the same as the price of diesel power generation, and only energy is obtained from Considering the cost, the use of lead-acid batteries has a certain price advantage over gasoline engine drives. Because lead-acid batteries are too heavy and take a long time to charge, they are only widely used in various track cars, golf carts, garbage trucks, forklifts and electric bicycles with a speed less than 50km/h. Practice has proved that lead-acid batteries have strong competitiveness and practicability in this low-end product market.

Compared with lead-acid batteries, nickel-metal hydride batteries have a three-fold increase in energy volume density and a 10-fold increase in specific power. Although the nickel-hydrogen battery has the advantages of higher specific energy and specific power, and relatively long life, the price of nickel-hydrogen battery remains high because nickel metal accounts for 60% of its cost. Ni-MH battery is not an ideal storage battery for electric cars, it may only be a transitional battery. At present, nickel-metal hydride batteries are still the first choice for electric cars in the near and mid-term. With the large-scale production of lithium-ion batteries and the reduction of costs, nickel-metal hydride batteries will eventually withdraw from the electric car power battery market.

Lithium-ion battery technology has developed rapidly. In the past 10 years, its specific energy has increased from 100Wh/kg to 180Wh/kg, its specific power can reach 2000W/kg, its cycle life can reach more than 1,000 times, and its operating temperature range has reached -40℃ ~55℃. . In recent years, due to a major breakthrough in the research and development of lithium iron phosphate batteries, the safety of lithium ion batteries has been greatly improved. At present, many developed countries have taken lithium-ion batteries as the main direction of power batteries for electric cars. China has advantages in lithium resources. The output of lithium-ion batteries accounted for 37.1% of the global market in 2004. The current price-performance ratio of lithium-ion batteries is expected to reach a level that can compete with lead-acid batteries and become the main power battery for electric cars in the future.

The technical difficulty of pure electric cars is less than that of plug-in hybrid electric cars. At present, the performance indicators of pure electric cars to be launched in China can already meet the needs of ordinary users, and the technology is basically mature. In the low-end market, the economic advantages of pure electric cars are very obvious. The lag in the construction of the charging network affects the convenience of the use of pure electric cars, and is currently the most important factor restricting the development of pure electric cars. It is expected that in demonstration pilot cities, with the gradual improvement of the charging network construction, the development of pure electric cars will be relatively fast, especially the share of pure electric cars in the low-end market will increase significantly.