Nine factors affecting the health of new energy vehicle batteries
The Social Sciences Literature Press officially published the "Automotive Big Data Application Research Report (2021)". The report pointed out that the health impact factor of new energy vehicle batteries will gradually deteriorate with the increase in use and storage time. There are currently nine essential factors that commonly affect battery health.
The report shows that responding to user needs for high-frequency use of new energy vehicles is a big challenge for new energy batteries. Hence, battery health monitoring is a necessary skill for the company. In daily work, the working condition of the battery is not optimal, and battery health is often affected by many factors. Therefore, it is necessary to study the impact of influencing factors on battery health. It helps improve battery performance and prolong battery life—significant guiding significance.
The report pointed out that the nine major factors affecting battery health are:
(1) Current capacity
The battery's current capacity is one of the critical parameters that characterize battery health. When the battery's current capacity is less than 80% of the rated capacity, it indicates that the battery includes various aspects of performance ageing and degradation that are more serious. The degree of attenuation of the battery capacity directly affects the battery's health. When the battery's durability decreases, the battery's capacity also decreases, which makes the life of the energy battery continue to shorten, and the vehicle mileage becomes shorter.
(2) Internal resistance battery
The internal resistance will lose part of the electrical energy during operation, and the electrical energy loss is proportional to the battery's internal resistance. Regarding lithium-ion batteries, after repeated charging and discharging work, internal resistance will gradually increase due to their internal chemical changes, and the corresponding internal resistance loss will gradually increase, which results in a decrease in the battery's available energy.
(3) Depth of charge and discharge
Depth of discharge has apparent uses for battery health, and different depths of charge and discharge have other effects on the life of lithium-ion batteries. More active materials inside the battery are activated with the new account and discharge depth. The amount of electricity released by the storm is more significant, and the battery health decays more obviously.
(4) Charge and discharge rate
When using a battery, if the battery is not charged and discharged according to its charge and discharge rate, it will have a significant impact on the performance of the storm and even affect the battery's service life. Although high-rate charging can shorten the charging time, the battery temperature rises too fast due to the battery's internal resistance during high-rate charging, which adds difficulty to thermal management and deteriorates battery health. In addition, high-rate charging can easily cause battery overcharging, affecting battery health.
(5) Self-discharge rate
The self-discharge rate of a battery is one of the essential parameters of battery performance, and it is also one of the important influencing factors of battery health. The battery's self-discharge rate is also called the charge retention capacity of the storm, which refers to the length of time that the battery's internal storage power can be stored without connecting to an external load.
(6) Overcharge and over-discharge
The discharge cut-off voltage is closely related to the equivalent resistance of the lithium-ion battery. An increase in the discharge cut-off voltage means that the equivalent resistance becomes more extensive, and the heat dissipation of the lithium-ion battery increases, which accelerates the battery loss. In the same way, overcharging will also affect battery life.
(7) Number of cycles
There are reversible charge and discharge reactions inside the battery and some irreversible side reactions. As the number of battery cycles increases, the electrolyte becomes thinner, and the reduction of practical components leads to a decrease in the battery's available capacity. The ageing of the battery becomes more apparent.
(8) Charge and discharge current
The charge and discharge current factors also have different effects on battery health. Li Yan et al. studied the influence of varying discharge currents on the cycle capacity degradation of lithium-ion batteries and analyzed the degradation degree of internal battery materials under different discharge currents by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Research results show that the greater the discharge current, the faster the battery capacity declines, and the quicker the battery health declines.
(9) Temperature
Lithium-ion batteries' standard operating temperature range is (-20°C, 60°C), and the ideal operating temperature is 25°C. At this time, the battery performance is the best. The change of the battery temperature will cause the evolution of the battery's parameters, such as the increase of internal resistance and the jitter of the charge and discharge rate. When the ambient temperature of the lithium-ion battery is too high or too low, the battery's performance deteriorates, resulting in a decrease in battery capacity and battery health. Therefore, the temperature is a crucial factor affecting battery life.
Edit by Paco
