Coping with the user demand for high-frequency use of new energy vehicles is a big challenge for new energy battery health, so battery health monitoring is a necessary skill for companies. In daily work, the working condition of the battery is not the most ideal, and battery health is often affected by numerous factors, thus it is necessary to study the impact of the influencing factors on battery health, which is of great guidance to improve battery performance and extend battery life.
The report points out that the nine factors affecting battery health are.
(1) Current capacity
The current capacity of the battery is one of the main parameters characterizing the health of the battery, when the current capacity of the battery is less than 80% of the rated capacity, it means that the battery, including all aspects of aging and degradation of performance, is more serious. The degree of battery capacity decay directly affects the health status of the battery. When the battery durability decreases, the capacity of the battery also follows the decline, which makes the energy battery life is also shortening, and the vehicle range becomes shorter.
(2) Internal resistance battery
Work will be part of the power loss by the internal resistance, and the loss of power is proportional to the internal resistance of the battery. For lithium-ion batteries, after multiple charges and discharge work, due to its internal chemical changes, the internal resistance will gradually increase, the corresponding internal resistance loss will also gradually increase, which causes the reduction of the available battery energy.
(3) Charge and discharge depth
The depth of discharge has a very obvious effect on the health of the battery, and different charge and discharge depths have different effects on the life of lithium-ion batteries. Charging and discharging depth increases, the active material inside the battery activates more, the battery releases more power, and thus the battery health decay is more obvious.
(4) Charge and discharge rate
When using the battery, if it is not charged and discharged according to the battery's own charge and discharge rate, it will have a great impact on the performance of the battery, and even affect the life of the battery. Although the high rate of charging can shorten the charging time, but the high rate of charging due to the existence of internal resistance of the battery battery temperature rises too quickly, adding difficulty to thermal management, resulting in the deterioration of battery health. In addition, high rate charging is also easy to cause battery overcharge, which will also affect the battery health.
(5) Self-discharge rate
The self-discharge rate of the battery is one of the main parameters of the battery's performance, and also one of the main factors affecting the battery's health. The self-discharge rate of the battery is also known as the battery's charge retention capacity, which refers to the length of time that the battery's internal storage capacity can be preserved under the condition that no external load is connected.
(6) Overcharge and over-discharge
Discharge cut-off voltage is closely related to the equivalent resistance of lithium-ion batteries. An increase in the discharge cut-off voltage means that the equivalent resistance becomes larger, which increases the heat dissipation of the lithium-ion battery and accelerates battery loss. Similarly, overcharging will also have an impact on battery life.
(7) The number of cycles
There are not only reversible reactions inside the battery charging and discharging but also some side reactions that occur, which are irreversible. As the number of battery cycles increases, the electrolyte becomes thinner and the active ingredient decreases, resulting in a reduction in the available capacity of the battery, and thus the aging of the battery is more obvious.
(8) Charge and discharge current
The charge and discharge current factors also have different effects on the health of the battery. Li Yan et al. studied the effect of different discharge currents on the decline of the cyclic capacity of Li-ion batteries and analyzed the degree of decline of the internal materials of the batteries under different discharge currents by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. The results show that the higher the discharge current the faster the battery capacity decline and the faster the battery health degradation.
(9) Temperature
The normal operating temperature range of lithium-ion batteries is (--20℃, 60℃), and the ideal operating temperature is 25℃ when the battery performance is the best. Changes in battery temperature will cause changes in the battery's own parameters, such as the increase in internal resistance and charge/discharge rate jitter. When the ambient temperature of the lithium-ion battery is too high or too low, the battery performance deteriorates, resulting in lower battery capacity and reduced battery health. Therefore, the temperature is a key factor affecting battery life.
