Is it a big injustice to buy a new energy electric vehicle now? Let's take a closer look at how long an electric vehicle lasts. The general view tends to be based on the warranty period provided by the manufacturer, such as 8 years or 120,000 kilometers. However, a true understanding of EV battery life should focus on the cycle life of the battery and how it behaves in real-world use.
The so-called cycle life refers to the minimum capacity standard that a battery can maintain after a specific number of charge-discharge cycles. This criterion is often to maintain % or 70% of the original capacity. For example, if the capacity of a ternary lithium battery drops to 80% after 800 charge-discharge cycles, its cycle life is defined as 800 cycles.
There are two important dimensions to consider in the cycle life of a battery: one is the full cycle, which is the entire process of the battery from full discharge to full charge to full discharge. In this process, the active material inside the battery completes a complete chemical transformation. On the other hand, the so-called equivalent cycle refers to partial charge and discharge, such as a battery charged from 50% to 100% and discharged back to 50%. This is considered a half-cycle. Since lithium batteries rarely undergo full discharge in practical applications, we are usually talking about equivalent cycles.
The country's minimum requirement for electric vehicle batteries is 8 years or 120,000 kilometers. However, battery life cannot be evaluated based on time and mileage alone. Although the concept of "calendar life" exists, it is greatly affected by cycle life, and its reference value is relatively weak. The key to evaluating battery life is its actual cycle life performance. For example, the typical cycle life of ternary lithium batteries is about 840 cycles, and lithium iron phosphate batteries can reach 2400 cycles, although these figures are only approximate reference values.
It is important to note that the cycle life of lithium-ion batteries is not fixed and is affected by a variety of factors, including differences in test conditions. Even for the same type of battery, the lifetime performance may vary under different processes and battery management system (BMS) technologies from different manufacturers.
According to the requirements of the national standard GBT31484-2015, the remaining capacity of pure electric passenger car batteries after 500 cycles should not be less than 90%, and not less than 80% after 1000 cycles. This suggests that even ternary lithium batteries with a shorter life should be able to reach 1,000 cycles while maintaining 80% capacity. This standard applies to the entire battery pack, not just a single cell, so users don't have to worry about cell inconsistencies.
Importantly, 1000 cycles does not mean that the battery can only be charged 1000 times. In fact, cycling refers to the complete process by which the active material inside the battery completes a single charge and discharge. According to the test conditions of the national standard, charge to the cut-off voltage with a current of 1C at 25, and then discharge to 20% with the same current, this process is usually carried out in the range of 20% to 100% of the electric power, which is equivalent to 084 full cycles. Therefore, to reach 1000 cycles, it actually takes about 1250 repetitions of charge and discharge.
Depending on these rigorous test conditions, the actual service life of the battery may well exceed 1,000 cycles. Assuming that one charge and discharge is carried out once a week, and each charge and discharge is equivalent to a full cycle, then there will be about 50 charge and discharge times a year. Based on this calculation, 1000 cycles can last for about 20 years, which means that after about 20 years, the battery capacity will be reduced to 80%. At this point, the battery is not scrapped, but the range has been shortened and the performance has decreased slightly.
Considering that an average of 20,000 kilometers are driven per year, the total mileage in 20 years will reach 400,000 kilometers. Assuming a range of 400 km on a single charge, 1,000 cycles over 20 years would provide enough range. Therefore, even according to the minimum requirements of 1000 cycles according to the national standard, the electric vehicle battery can meet the needs of daily use.
Overall, the longevity and maintenance of EV batteries is crucial. Proper usage and charging habits can effectively extend battery life, making it a worthwhile long-term investment. With proper management and maintenance, the battery of an electric vehicle can not only meet the needs of long-term use, but also rival or even surpass the performance of traditional fuel vehicles. On the way home is the New Year