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 that sustains confidence in electric vehicles. This article thoroughly explores the safety of lithium batteries applied to automobiles, unraveling the crucial challenges and innovative solutions that are shaping the future of safe electric driving.
The finances of some large automotive companies were affected by problems related to defective batteries in electric vehicles during the years 2020 and 2021. Beyond the large losses caused by unforeseen events of this type, in today's post we offer the manufacturing and safety measures carried out by NCPOWER and how under strict control measures they maintain the safety of their batteries at 100%, free of incidents today.
1. Quality
To operate safely, batteries must be produced with the utmost care and precision, from active materials processing 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 important challenges: on the one hand, many intermediate companies do not have complete information, nor the ability to influence the quality of the cells and packages they acquire. In today's market, the simple ability to purchase batteries from a quality supplier can outweigh any quality management certification. Even the strictest quality management measures do not guarantee the detection of 100% of failures.
Given this fact, in addition to the aforementioned quality, we must design risk prevention systems that guarantee maximum safety.
2. System Design
Battery systems incorporate multiple layers of protection, which serve to:
- Maintain the battery in its intended operating period
- Protect it against external damage
- Minimize the impacts of possible individual cell failures
These measures include passive safety components, such as strong packaging to resist shocks and hermetic sealing against the entry of fluids, which act as final resources to reduce damage in critical situations. In turn, the Battery Management System (BMS) works as the brain of lithium-ion battery systems, ensuring that no cell is over or under charged, and bring with them basic health estimation functionalities, including state of charge (SOC) and state of health (SOH). However, BMSs also have shortcomings that we must address: the BMS only sees the cells within the corresponding battery pack, they have little or no access to historical data or data from other battery systems, and they have limited computing power.
Hence, at NCPOWER we carry out preventive analyzes by monitoring the technical functioning of the batteries.
3. Cloud-based battery analysis
This approach employs more advanced methods than traditional battery management systems, allowing electric vehicle manufacturers and owners to identify potential critical faults at an early stage.
Implementing 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 EV owners, allowing them to take preventive measures before any damage is done. These diagnostics, based on existing field data streams, can be applied to any lithium-ion battery system without requiring product changes.
We scan sensor data for anomalies such as rapidly changing impedances or sudden voltage drops, as precursors to thermal events, the lack of reference data and continuous comparisons with similar systems strongly limits the value of such analyzes.
An example of risk detection thanks to the BMS
Let's consider a hypothetical situation where an electric car is equipped with an advanced Battery Management System (BMS) intended to monitor and manage the health 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. You can adjust the charging current, alert the driver, or even temporarily interrupt charging until the situation is resolved. In addition, the system has the capacity to store detailed data on this irregularity. In this way it can be continually improved at the level of security and design.Find out more about battery design and BMS at NCPOWER here.
An example of analytics-based risk detection
There are several ways cloud-based analytics can identify critical battery safety behavior early. Specifically, a robust battery analysis 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. By way of 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 condition.
Model-based security diagnostics monitor the decline of active lithium over time. Thus, they generate automatic alerts when certain thresholds are reached (indicated by red and yellow dotted lines).
Lithium plating is a phenomenon that primarily manifests itself when a battery is charged at high current rates and low temperatures. It can also occur under operating conditions considered "normal." What does this phenomenon consist of? In the accumulation of metallic lithium on the anode surface, which has represented a significant challenge in the lithium-ion battery field for many decades.
This issue not only leads to rapid degradation of battery capacity but can also pose a security threat. The accumulation of metallic lithium can lead to the formation of metallic dendrites and trigger secondary reactions, such as the release of gases. This situation results in a decrease in 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.
With 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 the safety of electric vehicles does not become another obstacle to overcome. Instead, the benefits of cloud-based software that examines battery operational data go beyond providing an additional layer of security. In addition, business risks and supply chain costs decrease. At the same time, they increase sustainability and accelerate innovation.