The Ultimate Guide to Extending the Lifespan of EVs Lithium battery
(Last Updated On: 21/06/2023)
The Ultimate Guide to Extending the Lifespan of EVs Lithium battery
With the growing demand for electric vehicles, battery project managers are on a quest to ensure their lithium battery projects stand the test of time. While an average EVs battery can last anywhere from 5-20 years, several factors can greatly impact its longevity. In this informative blog post, we’ll uncover the secrets behind battery life, discuss the importance of cycles and discharge rates, and delve into the environmental factors that can affect your battery’s health. Don’t miss our practical tips on how to prolong your lithium battery’s life for optimum performance.
The lithium battery life refers to the working condition life, which is the calculated lithium battery life during actual driving and needs to consider factors such as temperature, terrain, and traffic conditions during the driving process. The working life mainly includes two measurement dimensions: “storage life” and “cycle life”.
The time required for a lithium battery to be stored under certain conditions after completion of production until it decays below a predetermined level of health. It can be understood as the time it experiences from service to retirement in an idle state.
The lithium battery is cycled under certain charging and discharging conditions until the lithium battery capacity decays to a certain level. Usually, the number of cycles before 80% of the total power, can be understood as the number of cycle tasks performed by the lithium battery from service to retirement. A cycle refers to the process of lithium battery consumption from 100% to 0%, which can be completed in a day or over a period of time. For example, if the vehicle is charged with 50% remaining lithium battery, this is only considered as 0.5 cycles.
2. What is Lithium battery decay?
It refers to the trend in which the actual usable capacity of a lithium battery gradually deviates from the factory rated capacity (i.e. theoretical capacity value) as the internal physical structure ages and chemical substances are consumed. According to the reasons for loss, lithium battery decay can be divided into “irreversible decay” and “reversible decay”, both of which can have an impact on the lithium battery life in actual use.
a. Irreversible decay: The active lithium ions inside the lithium battery undergo irreversible loss due to the presence of chemical side reactions.
b. Reversible decay: The capacity consumed by various types of polarization resistance inside a lithium battery can be restored with temperature, current, and uniform diffusion of internal chemicals.
The charging and discharging cycle of the power lithium battery is a complex physical and chemical process. The characteristics of the lithium battery itself, the external environment and the use habits of the end user will affect the decay rate, thus affecting the lithium battery’s life.
The factors affecting the lifespan of power batteries are mainly divided into two aspects: internal factors and external factors. Internal factors mainly include the material characteristics of the power lithium battery itself, thermal management system, BMS strategy, etc. External factors can be summarized as influencing factors during the charging and discharging process and the usage environment.
a. Material characteristics of power batteries themselves
Power batteries are generally composed of positive and negative electrodes, electrolytes, separators, etc. The selection of positive and negative electrodes and separators is crucial for the performance of the lithium battery. At present, there are various mainstream chemical systems of power batteries on the market, such as NCM, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, etc., each of which has its own unique performance. When it comes to lithium battery life, lithium iron phosphate is the most superior mainly because it has an ordered olivine structure, with phosphorus (P) and oxygen (O) tightly combined. Even if the lithium battery’s internal heating occurs, the crystal structure is not easily damaged, and it has good reversibility, stability, and safety, resulting in a longer lithium battery life.
b.BMS control strategy
As the ‘nanny’ of the lithium battery system, BMS carries a critical mission. As long as the lithium battery pack cannot function properly, the first consideration is whether the BMS has malfunctioned. BMS constantly collects lithium battery pack data. If its control accuracy is not high or there are algorithm logic errors, it is easy to cause extreme situations such as overcharging, over-discharging, over temperature, and over current, all of which have a fatal impact on lithium battery life.
c.Thermal management system
The relationship between the thermal management system and BMS is passive and active. BMS analyzes relevant data, outputs commands, and is passively executed by the thermal management system. When the temperature of the lithium battery pack is too high or too low, the thermal management system cools or heats the lithium battery pack; When the temperature difference of the lithium battery pack is too large, the thermal management system conducts balanced coordination. If the thermal management system does not do the above work well, it is very detrimental to the lithium battery life.
a. Factor affecting the charging process
Overcharging is a fatal factor affecting lithium battery life. When the lithium battery is overcharged, the internal electrolyte will undergo intense boiling due to reactions, causing the active substances on the positive and negative electrode surfaces to fall off, and the lithium battery capacity will decay. At the same time, it will generate a large amount of heat, making the lithium battery more prone to thermal runaway. Overcharging can also cause insufficient lithium intercalation space in the negative electrode, resulting in excessive resistance to lithium-ion migration. Lithium ions quickly detach from the positive electrode but cannot be equally embedded in the negative electrode. Lithium ions that cannot be embedded in the negative electrode can only obtain electrons on the surface of the negative electrode, forming a silver-white lithium element, which gradually reduces the lithium battery life. This process is called lithium precipitation.
b. Factor affecting the discharge process
The power lithium battery will discharge the internal stored power. If the voltage reaches the cutoff voltage, continuing to discharge will cause over-discharge. When the lithium battery voltage is below the limit Undervoltage value, it will significantly reduce the density of the electrolyte, increasing the internal pressure of the lithium battery, and damaging the reversibility of the positive and negative active substances. Even if charged, it can only partially recover, and the capacity will also have a significant decline.
c. Factors affecting the ambient temperature during use
Due to the fact that power batteries are chemical equipment, the operating environment temperature is crucial for their cycle life. Among them, low or high ambient temperatures can have a fatal impact on the cycling life of the lithium battery. Power batteries can only perform best within a certain temperature range, usually above 25 degrees Celsius and below 45 degrees Celsius. Once the optimal temperature range is exceeded, the discharge capacity of the power lithium battery will decrease and its lifespan will be affected. In high-temperature environments, the electrolyte will undergo side reactions, causing more irreversible decay in the lithium battery; In low-temperature environments, the activity of positive and negative electrode materials, electrolyte permeability, and the properties of binders will all decrease, leading to a sharp decrease in the chemical properties of power batteries and irreversible decay.
a. Regular maintenance: Timely check the status of the power lithium battery, and if any abnormalities are found, they should be repaired in a timely manner. At the same time, perform a full charge at least once a month, and BMS will promptly correct the SOC (remaining lithium battery) to avoid SOC jump caused by long-term insufficient charging.
b. Maintain good charging habits: It is generally appropriate to maintain a SOC of 20% -80% for daily use. During use, do not wait until the lithium battery is depleted before charging to avoid over-discharge. During the charging process, control the charging time and do not have to strive to charge the lithium battery to 100% every time to avoid overcharging, which can damage the reversible substances inside the power lithium battery and damage its lifespan.
c. Reasonable parking of electric vehicles: In hot summer environments, it is recommended to choose a location with good shading or ventilation to avoid long-term exposure to the scorching sun. At the same time, charging should be avoided in extremely high-temperature environments. In low-temperature winter environments, it is recommended to park the vehicle indoors to avoid the possibility of the vehicle being unable to function properly due to low temperatures.
In conclusion, understanding the complexities of lithium battery life is vital for battery project managers seeking to optimize their projects’ performance and longevity. By applying the insights and tips provided in this ultimate guide, you can make informed decisions that will significantly impact your EV battery projects. If you require further assistance or have any questions regarding your lithium battery projects, don’t hesitate to reach out to Bonnen Battery, your trusted partner in delivering exceptional lithium battery solutions.
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