The battery is a key electrical component in a car, and its performance directly affects the start of the car. The current car start without exception uses the starter motor start method. During the starting process, especially at the moment of starting, since the starting motor speed is zero and no induced potential is generated, the starting current: I=E/(RM+RS+RL); where: E is the no-load terminal voltage of the battery, RM It is the armature resistance of the starting motor, RS is the internal resistance of the battery, and RL is the line resistance. Since RM, RB, and RL are all very low, the starting current is very large. For example, using a 12 V, 45 Ah battery to start a car with a 1.9 L diesel engine, the voltage of the battery drops from 12.6 V to about 3.6 V at the moment of starting. The battery voltage waveform during the starting process is shown in Figure 1. The instantaneous current at startup is 550 A, which is approximately 12C discharge rate of the battery> battery current waveform during startup. The current/voltage conversion ratio of the current sensor is 100 A/V. Although the car battery is a special battery for starting, it can discharge at a high rate, but the performance of the battery becomes very poor when the high rate discharge is more than 10 times, and the damage to the battery is very obvious when the high rate discharge is so high. The drastic voltage change during the start-up process is also a very strong electromagnetic interference, which can cause the electrical equipment to lose power, forcing the electrical equipment to re-energize after the generator starts, and the computer is very easy to crash during this process. Therefore, from the perspective of improving the electromagnetic environment of automobile electrical equipment, improving the starting performance and battery performance of the automobile, or extending the service life of the battery, it is necessary to improve the performance of the automobile power supply during the starting process. One of the solutions to the problem is to increase the capacity of the battery, but it needs to be increased a lot and its volume is increased, which is not a good choice. Parallel connection of super capacitors with batteries can solve this problem well.

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• Super capacitor characteristics

Compared with batteries and traditional physical capacitors, the characteristics of super capacitors are mainly reflected in:

(1) High power density. It can reach 102～104 kW/kg, which is much higher than the power density of the battery.

(2) Long cycle life. After a few seconds of high-speed deep charge and discharge cycles of 500,000 to 1 million times, the characteristics of the supercapacitor change little, and the capacity and internal resistance are only reduced by 10% to 20%.

(3) Wide working temperature limit. Since the adsorption and desorption speeds of ions in supercapacitors do not change much at low temperatures, their capacity changes are much smaller than those of batteries. The operating temperature range of commercial supercapacitors can reach -40℃～+80℃.

(4) Maintenance free. The supercapacitor has high charge and discharge efficiency, has a certain tolerance to overcharge and overdischarge, can be repeatedly charged and discharged stably, and theoretically does not require maintenance.

(5) Green and environmental protection. Supercapacitors do not use heavy metals and other harmful chemicals in the production process, and have a long life. Therefore, they are a new type of green environmental protection power supply.

• Super capacitor classification

For supercapacitors, there are different classification methods according to different contents.

(1) based on different energy storage mechanisms, supercapacitors can be divided into two categories: electric double layer capacitors and Faraday quasi-capacitors. Among them, electric double layer capacitors mainly generate storage energy through the adsorption of pure electrostatic charge on the electrode surface. Faraday quasi-capacitors mainly generate Faraday quasi-capacitors through reversible redox reactions on and near the surface of Faraday quasi-capacitive active electrode materials (such as transition metal oxides and macromolecule polymers), thereby realizing energy storage and conversion.

(2) according to the type of electrolyte, it can be divided into two categories: water-based supercapacitors and organic supercapacitors.

(3) according to whether the types of active materials are the same, they can be divided into symmetric supercapacitors and asymmetric supercapacitors.

(4) according to the state of the electrolyte, supercapacitors can be divided into solid electrolyte supercapacitors and liquid electrolyte supercapacitors.

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