What is the maximum battery life? What elements have an impact on the battery’s lifespan? How can the battery life be increased? All cars, whether they run on fuel cells, pure electricity, or hybrids, will have battery devices, and how long a battery lasts directly affects how long an automobile will last. Let’s examine the national regulations pertaining to pure electric vehicle warranties.
Understanding battery cycles
The number of battery cycles determines how long a new energy vehicle’s battery can last. There is a 5–20 year average usage period. For instance, ternary lithium batteries, which are used in new energy vehicles, have a 1,000–2000 charging cycle limit and an endurance mileage of 400–400,000 kilometers. Family cars, on the other hand, have an annual car mileage of 20,000 kilometers, which is usable for 20 years, and even if the battery weakens, it gradually reduces to 32 kilometers. Depending on how well the battery performs, a 0 km battery can also be used for approximately 5 years. The fundamental ideas behind battery attenuation and life are:
Battery life is defined as the service life or the battery life as determined by driving, which takes into account various driving-related factors such as temperature, terrain, and traffic. “Cycle life” and “storage life” are the two primary measurement dimensions for working life:
1) Storage life: Once the battery has reached its full capacity, it will be kept in storage under specific guidelines until its health drops below the predefined level, or, to put it another way, “the time the battery has experienced from service to decommissioning in the idle state”.
2) Cycle life: The number of cycles before 80 percent of the total charge, or “the number of cycle tasks performed by the battery from service to decommissioning,” is the number of times the battery cycles under specific charging and discharging conditions until the battery attenuates to a certain capacity.
How many cycles does the battery have? The process of using a battery from 100 percent to 0 percent is referred to as a cycle, and it can be finished in a single day or a shorter amount of time. This is only 0.5 cycles, for instance, if it is charged with 50 percent of the vehicle’s remaining power. Battery attenuation is the tendency for the battery’s actual available capacity to progressively diverge from its theoretical capacity value, or factory-rated capacity, as a result of chemical consumption and aging of the internal physical structure. Battery attenuation can be classified as “irreversible attenuation” or “reversible attenuation” based on the reason for the loss. Both types of attenuation will have an impact on the battery’s lifespan when in use.
1) Irreversible attenuation: Because of the presence of chemical side effects, the battery’s active lithium ions are irreversibly consumed.
2) Reversible attenuation: When temperature, current, and internal chemicals diffuse uniformly within the battery, the capacity lost due to different forms of polarization internal resistance within the battery can be recovered.
What are the primary determinants of battery life?
Power battery charging and discharging is a complicated physical and chemical process. The attenuation speed is influenced by the features of the battery itself, the external environment, and the end user’s usage habits; these factors will also have an impact on the battery’s life.
There are two main categories of factors that affect power battery life: internal factors and external factors. The power battery’s material properties, thermal management system, BMS strategy, and other internal factors are the main examples of external factors summing up as variables that affect charging and discharging as well as the environment in which the battery is used.
The categories are as follows:
1) Internal components
(a) The material properties of the actual power battery
Electrolytes, diaphragms, positive and negative electrodes, and other components make up power batteries in general. The battery’s performance is greatly dependent on the selection of diaphragms and positive and negative electrodes. Power batteries with a range of common chemical systems are currently available on the market, including ternary, lithium iron phosphate, lithium manganate, and lithium cobaltate. Each of these materials has unique qualities. Lithium iron phosphate has the longest battery life due to its sequential olivine structure, which closely combines oxygen (O) and phosphorus (P). The longer battery life is due to the crystal structure’s good reversibility, stability, and safety, which prevents damage even in the event of internal heat buildup in the battery.
(b) The BMS control approach
The task assigned to BMS as the “nanny” of the battery system is challenging. In the event that the battery pack malfunctions, it initially looks into the possibility that the BMS is broken. Battery pack data is constantly gathered by BMS. It is simple to create extreme conditions like overcharge, overplay, overtemperature, overcurrent, etc., which have a fatal effect on battery life if its control accuracy is low or there are algorithmic errors.
(c) System for managing temperature
Both the BMS and the thermal management system are passive and active. The thermal management system analyzes pertinent data and outputs commands to carry out BMS passively. The thermal management system regulates the battery pack’s temperature when it is too high or too low. It also ensures that there is an even temperature difference between the battery pack and its surroundings. It is highly detrimental to battery life if the thermal management system does not perform the aforementioned tasks.
2) External Factors
- Factors influencing the charging process
The internal electrolyte will boil violently as a result of the reaction when the battery is overcharged, which will cause the active material on the positive and negative surfaces to fall off and reduce the battery’s capacity. It will also produce a lot of heat, which increases the risk of thermal runaway with the battery. Additionally, overcharging will result in excessive migration resistance of lithium ions, insufficient space for lithium to be embedded in the negative electrode, and a premature release of lithium ions from the positive pole that is unable to be equally embedded in the negative electrode. The battery life will gradually decrease because lithium ions that are unable to become embedded in the negative electrode can only acquire electrons on the electrode’s surface, where they will form a silvery-white lithium element. This process is called the Analysis of lithium.
(b) Factors influencing the discharge process
The internal stored power is discharged by the power battery. Overdischarge will result from continuing to discharge after the voltage reaches the cut-off voltage. The electrolyte’s density will be significantly decreased, the lithium battery’s internal pressure will rise, and the reversibility of the positive and negative active substances will be harmed when the battery voltage falls below the limit under-voltage value. It can only be partially recovered even when charging, and the capacity will be greatly decreased.
(c) Ambient temperature influencing factors
Given that power batteries are chemical devices, the surrounding temperature has a significant impact on their cycle life. Among these, excessively high or low ambient temperatures can seriously shorten the battery’s cycle life. Only within a specific temperature range can the power battery operate at its peak efficiency.
In general, the temperature is between 25 and 45 degrees Celsius. The power battery’s discharge capacity and lifespan will both be impacted if the ideal temperature range is exceeded. The electrolyte will experience a side reaction in a high-temperature environment, which will further irreversibly attenuate the battery. The activity of the positive and negative electrode materials, the electrolyte’s passability, the binder’s properties, and the chemical characteristics of the power battery will all be significantly diminished in a low-temperature environment, leading to irreversible attenuation.
There are a few ways we can postpone battery deterioration during regular use:
- Routine maintenance: Check the power battery’s condition promptly. If anomalies are discovered, they ought to be fixed quickly. Simultaneously, complete charging ought to be carried out no less than once per month, and BMS will adjust SOC (remaining power) promptly to prevent SOC jumping as a result of persistent discontent with charging.
- Have good charging habits: Generally speaking, daily cars should aim to maintain the SOC between 20 percent and 80 percent. To prevent overcharging, do not wait until the power is completely out before charging while using it. Control the charging time throughout the process; there’s no need to charge the power battery to 100 percent all the time. This will prevent overcharging, which could shorten the battery’s lifespan and harm its internal reversible materials.
- Sufficient parking for electric cars: In order to prevent cars from being exposed to the sun for extended periods of time during summer’s high temperatures, it is advised to find a shaded or well-ventilated area. In addition, charging ought to be avoided in extremely hot weather. It is advised to park the car indoors during cold winter days to prevent the vehicle from becoming unusable due to the low temperature.
In general, batteries are still considered “pretentious” products, but we don’t need to worry about how long they will last as long as we use them responsibly and take care of them on a regular basis. Ultimately, we still want to use it.
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