In the evolution towards electric mobility, lithium batteries have assumed a leading role as the engine of the automotive revolution. However, beyond efficiency and performance, safety stands as the fundamental pillar underpinning confidence in electric vehicles. This article explores the safety of lithium batteries in automobiles in depth, unravelling the crucial challenges and innovative solutions that are shaping the future of safe electric driving.
The finances of some major automotive companies were affected by problems related to defective batteries in electric vehicles in 2020 and 2021. Beyond the heavy losses caused by such unforeseen events, today's post looks at the manufacturing and safety measures taken by NCPOWER and how they are keeping their 100% batteries safe and incident-free to date under strict control measures.
To operate safely, batteries must be produced with the utmost care and precision, from the processing of active materials to cell manufacturing and pack assembly.
Rigorous quality management, from goods receipt to final testing, is the only solution to control manufacturing defects.
In the field of electric vehicles there are two major challenges: on the one hand, many intermediate companies do not have the complete information, nor the ability to influence the quality of the cells and packs they purchase. In today's market, the simple ability to purchase batteries from a quality supplier may outweigh any quality management certification. Even the most stringent quality management measures do not guarantee 100% detection of faults.
In view of this fact, in addition to the aforementioned quality we must design systems risk prevention measures to ensure maximum safety.
2. System design
Battery systems incorporate multiple layers of protection, which serve to:
- Maintain the battery in its intended period of operation.
- Protect it from external damage
- Minimise the impacts of potential individual cell failures
These measures include passive safety componentsas robust packaging to withstand knocks and bumps. hermetic sealing against fluid ingress, which act as final resources to reduce damage in critical situations.
In turn, the Battery Management System (BMS) functions as the brain of lithium-ion battery systems, ensuring that no cell is over- or under-charged, and they bring with them basic status estimation functionalities, including state of charge (SOC) and state of health (SOH). However, BMSs also have shortcomings that need to be addressed: the BMS only sees the cells within the relevant battery pack, has little or no access to historical data or data from other battery systems, and has limited computing power.
Therefore, NCPOWER carries out preventive analyses by monitoring the technical performance of the batteries.
3. Cloud-based battery analysis
This approach employs more advanced methods than traditional battery management systems, allowing manufacturers and owners of electric vehicles to identify critical potential failures at an early stage.
The implementation of cloud-based analytics represents an effective strategy to prevent critical failures and raise safety standards in lithium batteries. This approach not only empowers vehicle manufacturers, but also electric vehicle owners, enabling them to take preventive action before damage occurs. These diagnostics, based on existing field data streams, can be applied to any lithium-ion battery system without the need for product changes.
We scan sensor data for anomalies such as rapidly changing impedances or sudden voltage drops as precursors to thermal events, but the lack of baseline data and ongoing comparisons with similar systems severely limits the value of such analyses.
An example of risk detection thanks to BMS
Consider a hypothetical situation in which an electric car is equipped with an advanced Battery Management System (BMS) designed to monitor and manage the status of each cell in its battery. At a certain point, the BMS identifies an unusual temperature rise in one of the cells during the charging process. This could signal a possible risk of overheating and, ultimately, a fire hazard.
This early detection allows the BMS to take immediate action to reduce the risk. It can adjust the charging current, alert the driver or even temporarily interrupt charging until the situation is resolved. In addition, the system has the ability to store detailed data on this irregularity. This allows for continuous improvement in terms of safety and design.
Find out more about the battery design and BMS on NCPOWER here.
An example of analysis-based risk detection
There are several ways in which cloud-based analytics can identify safety-critical battery behaviour in advance. Specifically, a robust battery analytics solution should monitor at least 20 safety indicators on a daily basis.
The algorithms capture electrochemical interactions and processes, providing insights into the internal states of the battery. As an illustration, the figure below presents an analysis of lithium inventory loss, a phenomenon closely related to lithium plating. The yellow dotted line indicates a warning period identified by NCPOWER's Safety Manager battery analysis solution, while the red line indicates a critical state.
Model-based safety diagnostics monitor active lithium depletion over time. They generate automatic alerts when certain thresholds (indicated by red and yellow dotted lines) are reached.
Lithium plating is a phenomenon that occurs mainly when a battery is charged at high current rates and low temperatures. It can also occur under what are considered "normal" operating conditions. What is this phenomenon? It is the accumulation of metallic lithium on the anode surface, which has been a significant challenge in the field of lithium-ion batteries for many decades.
This problem not only leads to a rapid degradation of battery capacity, but can also pose a safety threat. The accumulation of lithium metal can lead to the formation of metallic dendrites and trigger secondary reactions, such as outgassing. This situation results in a depletion of lithium reserves, which are no longer available to participate in the main reaction. Cloud-based safety algorithms, among other functions, must closely monitor the loss of active lithium to accurately predict safety-critical events.
Using this methodology and evaluating various safety indicators, NCPOWER's Safety Manager has successfully prevented more than 50 fire incidents.
What is the next step?
There are several challenges we must overcome to make electric vehicles significantly safer. Cloud-based battery analysis ensures that public perception of EV safety does not become another hurdle to overcome.
In contrast, the benefits of cloud-based software that examines battery operational data go beyond providing an additional layer of security. They also lower business risks and supply chain costs. At the same time, they increase sustainability and accelerate innovation.