How to Determine if the Battery of a New Energy Electric Vehicle is Faulty in the Simplest Way

The batteries of new energy electric vehicles are composed of individual battery cells. The commonly used model for these battery cells is typically 18650, which are cylindrical in shape with a diameter of 18mm and a height of 65mm. The voltage of each individual battery cell typically ranges between 3.5 and 4.1V, and under no circumstances should it drop lower than 3.2V. If the voltage of a cell falls below this threshold, the vehicle is at risk of malfunctioning at any given moment.

The faults that can occur within the battery are numerous and diverse. These typically include excessive voltage differences between individual cells, leakage of liquid, issues with the harness contact, insulation faults, BMS (Battery Management System) system faults, temperature sensor faults, and more. Among these, the problem of excessive voltage difference between individual cells is one that is most frequently encountered.

So, what are the manifestations when the voltage difference between individual cells of the battery in an electric vehicle is overly large? Such a voltage imbalance does not directly render the electric vehicle incapable of driving. However, it does lead to a significant and often sudden reduction in the vehicle’s cruising range. For instance, if under normal circumstances the vehicle is capable of running approximately 200 kilometers, but within a short period, the cruising range drops to 150 kilometers, it could be an indication of a voltage difference issue among the individual cells.

The individual battery cells in an electric vehicle are typically arranged in a parallel + series configuration and exhibit what is known as the “barrel effect.” To illustrate, consider a scenario where within an entire set of batteries, the voltage of one cell is 3.8V while the others are all at 4.1V. Then, when the voltage of this particular problematic cell drops to 3.2V, regardless of the voltages of the other cells, the vehicle is likely to experience a breakdown.

In most cases, the dashboard of an electric vehicle provides displays of the highest and lowest voltages of the individual cells. How, then, can one determine the quality of the battery based on the voltage difference? The most straightforward approach is to closely examine the disparity between the highest and lowest voltages. If this voltage difference exceeds 0.2V, it is a strong indication that a battery cell is likely damaged. As demonstrated in the provided image, the highest unit voltage is 4.11V, while the lowest individual voltage is 3.85V. With a voltage difference reaching 0.26V, it can be confirmed that one individual cell has sustained damage. In the event of an individual cell failure, the battery requires disassembly and replacement of the affected battery cells. It’s important to note that battery cells usually cannot be replaced on an individual basis but rather in small groups. One such small group typically consists of approximately over a hundred battery cells.

The battery of a new energy electric vehicle is currently covered by a warranty provided by the state for either five years or up to 200,000 kilometers. If any problems arise within this warranty period, it is imperative to have the battery replaced promptly at the designated service station.

Let’s take a closer look at the significance of these voltage differences. A small variation in voltage among individual cells may not initially seem critical, but over time, it can have cumulative effects. Even a seemingly minor voltage imbalance can disrupt the overall performance and efficiency of the battery pack. The cells within the pack operate in a coordinated manner, and when one cell falls behind in voltage, it places additional stress on the others. This can accelerate the degradation of the entire battery system and ultimately lead to a shorter lifespan and reduced performance.

The BMS system plays a crucial role in monitoring and regulating the voltages of individual cells. It is responsible for ensuring that the charging and discharging processes are evenly distributed among the cells to prevent excessive voltage differences. However, even with an efficient BMS, external factors such as extreme temperatures, rapid charging, or deep discharging can still contribute to voltage imbalances.

When a battery cell is damaged and needs replacement, the process is not as simple as swapping out a single component. The disassembly and reassembly of the battery pack require specialized skills and equipment to ensure the safety and integrity of the entire system. Moreover, the quality and compatibility of the replacement battery cells or groups are of paramount importance to maintain the performance and longevity of the battery.

In conclusion, understanding and monitoring the voltage differences of individual battery cells is essential for identifying potential faults in the battery of a new energy electric vehicle. Regular checks and prompt action during the warranty period can help ensure the reliable and efficient operation of the vehicle, prolong the battery’s lifespan, and provide a seamless driving experience for the owner.