What types of batteries are commonly used in electric vehicles

APR 16, 2019   Pageview:48

Lead acid batteries and lithium batteries.

 

Among them, lead-acid batteries are the cheapest, but they are large in size, heavy in weight, and short in life.

 

Lithium batteries can also be divided into two types. The monomer voltage is 3.7 V and 3.2 V, respectively, of which 3.2 V polymer batteries are said to be safer than the other.

 

The disadvantage of lithium batteries is that they are expensive, but they are light in weight, small in size, and have a long life (according to my understanding, the life span of lead-acid batteries should not be less than lithium).

 

There are also research capacitors. Its life is relatively unlimited, but even with a large capacity of super-capacitors, its volume and weight are several times larger than those of lead-acid batteries, and individuals feel that it is basically impossible.

 

Electric vehicle batteries are divided into two categories, batteries and fuel cells. The battery is suitable for pure electric vehicles, including lead-acid batteries, nickel-hydrogen batteries, sodium-sulfur batteries, secondary lithium batteries, and air batteries.

 

Fuel cells are dedicated to fuel cell electric cars, Including alkaline fuel cells (AFC), phosphate fuel cells (PAFC), molten carbonate fuel cells(MCFC), solid oxide fuel cells(SOFC), proton exchange membrane fuel cells(PEMFC), direct methanol fuel cells(DMFC).

 

Depending on the type of electric car. In pure electric vehicles equipped only with batteries, the role of the battery is the only power source for the car drive system. In hybrid vehicles equipped with traditional engines (or fuel cells) and batteries, batteries can play both the role of the main power source of the car drive system and the role of auxiliary power source. It can be seen that at low speed and starting, the battery plays the role of the main power source of the car drive system; When the full load is accelerated, it acts as an auxiliary power source; It is the role of storing energy when driving or decelerating or braking normally.

 

The fuel cell is oxidized by the fuel at the anode and the oxidant is reduced at the cathode. If gaseous fuel(hydrogen) is continuously supplied on the anode (ie, the negative electrode of the outer circuit, also known as the fuel electrode), and oxygen (or air) is continuously supplied on the cathode (ie, the positive electrode of the outer circuit, also known as the air pole), Electrochemical reactions can occur continuously on the electrode and generate electric currents. It can be seen that unlike conventional batteries, fuel and oxidants are not stored in the battery, but are stored in storage tanks outside the battery. When it works (output current and work), it needs to continuously transport human fuel and oxidants to the battery and expel the reaction product at the same time. Therefore, in terms of working methods, it is similar to conventional gasoline or diesel generators. Since fuel cells are continuously fed with fuel and oxidants during operation, the fuel and oxidants used in fuel cells are fluids (gases or liquids). The most commonly used fuels are pure hydrogen, various hydrogen-rich gases (such as reforming gas) and certain liquids (such as methanol aqueous solutions). Commonly used oxidants are pure oxygen, purified air and other gases and certain liquids (such as hydrogen peroxide and nitric acid. Water solution, etc.).

 

The role of the fuel cell anode is to provide a common interface for fuel and electrolytes, and to catalyze the oxidation of fuel. At the same time, the electrons generated in the reaction are transmitted to the external circuit or transferred to the assembly plate before being transmitted to the external circuit. The role of the cathode (oxygen electrode) is to provide a common interface for oxygen and electrolytes, to catalyze the reduction of oxygen, and to transmit electrons from the external circuit to the reaction site of the oxygen electrode. Since the reaction on the electrode is mostly a multi-phase interface reaction, in order to increase the reaction rate, the electrode generally uses a porous material and is coated with an electric catalyst.

 

The role of the electrolyte is to transport the ions produced by the reaction of the fuel electrode and the oxygen electrode in the electrode and to prevent the direct transfer of electrons between the electrodes.

 

The role of the diaphragm is to conduct ions, prevent electrons from transmitting directly between the electrodes and separate oxidants and reducing agents. Therefore, the diaphragm must be resistant to electrolyte corrosion and insulation and have good moisture resistance.

 

Batteries

 

Electric vehicle batteries consist of multiple cells in series. A typical battery pack has about 96 cells, and for lithium ion cells charged to 4.2 V, such batteries can generate a total voltage of more than 400 V. Although the automotive power supply system treats the battery as a single high-pressure cell, charging and discharging the entire battery each time, the cell control system must consider the situation of each cell independently. If one cell in the battery has a slightly lower capacity than the other cells, the charging state will gradually deviate from the other cells after multiple charge/discharge cycles. If the battery's charging state is not periodically balanced with other cells, it will eventually enter a deep discharge state, resulting in damage and eventually a battery failure. In order to prevent this from happening, the voltage of each battery must be monitored to determine the charging state. In addition, there must be a device that allows the battery to be charged or discharged separately to balance the charging state of these batteries.

 

An important consideration for battery surveillance systems is the communications interface. For communication within the PC board, commonly used options include a serial peripheral interface (SPI) bus and an I2C bus. Each bus has a low communication overhead and is suitable for low interference environments. Another option is the controller LAN(CAN) bus, which is widely used in automotive applications. CAN bus is very good, with error detection and fault tolerance characteristics, but its communication cost is very large, the material cost is also high. Although the connection from the battery system to the car owner CAN bus is desirable, there are advantages to using SPI or I2C communication in the battery pack.

 

Electric vehicle batteries are divided into:

 

A. Alkaline batteries. That is, the electrolyte is an alkaline aqueous solution of the battery;

 

B. Acid batteries. That is, the electrolyte is an acidic aqueous solution of the battery;

 

C. Neutral batteries. That is, the electrolyte is a neutral aqueous solution of the battery;

 

D. Organic electrolyte solution batteries. That is, the electrolyte is a battery of an organic electrolyte solution.

 

According to the mode of existence of the active substance, it is divided into:

 

A. Active substances are stored on electrodes. Can be divided into primary batteries (non-renewable, primary batteries) and secondary batteries (regenerative, batteries);

 

B. Continuous supply of active substances to electrodes. Can be divided into non-renewable fuel cells and renewable fuel cells.

 

According to certain characteristics of the battery, it is divided into:

 

A. High-capacity batteries;

 

B. Maintenance free batteries;

 

C. Sealed batteries;

 

D. Flame batteries;

 

E. Explosion-proof batteries;

 

F. Button batteries, rectangular batteries, cylindrical batteries, etc.

 

Although due to the wide variety of chemical power sources, the wide range of uses, and the large differences in appearance, it is difficult to unify the above classification methods. However, according to the nature of their work and storage methods, they are generally divided into four categories:

 

A primary battery, also known as a "primary battery," is a battery that can not be restored by charging after discharge. In other words, the battery can only be used once, and the battery can only be abandoned after discharge. The reason why such batteries can not be recharged is either the battery reaction itself is irreversible, or the conditions are limited to make the reversible reaction difficult. Such as:

 

Zn-Mn dry battery Zn│NH4Cl·ZnCl2│MnO2(C)

 

Zinc mercury battery Zn│KOH│HgO

 

Silver zinc battery Zn│KOH│Ag2O

 

A secondary battery, also known as a "battery," is a type of battery that can be recharged after discharge and can be recharged to restore the active material and can be discharged again and again, and can be reused repeatedly. This type of battery is actually a chemical energy storage device. The battery is fully charged with direct current. At this time, electrical energy is stored in the battery in the form of chemical energy. When discharged, chemical energy is converted into electrical energy. Such as:

 

Lead acid battery Pb│H2SO4│PbO2

 

Nickel cadmium battery Cd│KOH│NiOOH

 

Nickel-metal hydride battery H2│KOH│NiOOH

 

Lithium ion battery LiCoO2│ organic solvent│6C

 

Zinc air battery Zn│KOH│O2 (air)

 

Storage batteries, also known as "activation batteries," are batteries that are not in direct contact with positive and negative active substances and electrolytes, temporarily injected with electrolytes before use, or activated by other methods. The chemical deterioration or self-discharge of positive and negative active substances in such batteries is basically eliminated due to isolation from the electrolyte, allowing the battery to be stored for a long period of time. Such as:

 

Magnesium silver battery Mg│MgCl2│AgCl

 

Calcium heat battery Ca│LiCl-KCl│CaCrO4(Ni)

 

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