Building Better EV Batteries

Article By : Hwee Yng Yeo, Keysight Technologies

Creating the ideal cell chemistry requires an understanding of various parameters affecting battery performance, at the cell, module, and pack levels.

Battery makers face intense competition to get a slice of the pie in the electric vehicle (EV) battery market, which is poised to grow by $44.2 billion1 between 2020 and 2024. While technology has reduced the cost of an average Li-ion EV battery by 80% over the past decade, the battery remains the most expensive part of the electric car. Bringing down this cost component will help EVs win over more drivers.

What does the industry need to balance, in formulating the ideal, and affordable battery? The answer lies in understanding what causes the gaps between design goals and real-life performances (see example in Figure 1).

Creating the ideal cell chemistry requires an understanding of various parameters affecting battery performance, at the cell, module, and pack levels, depending on different intended applications.

Figure 1: Different cell characteristics must be considered when developing a new cell, as cell characteristics depend on their applications.

To complicate matters, each battery cell exhibits different characteristics, depending on their applications. In designing and testing batteries, the battery cell design manager must consider how to juggle various test parameters for multiple cell types under development, with available test resources.

In EVs and hybrid EVs, fast charging and extended range are important, hence the battery design must prioritize tests to achieve higher capacity, efficiency, and energy density goals. To manage and meet these requirements efficiently, battery cell manufacturers need to anticipate the types of tests that must be carried out throughout the entire battery development chain (see Figure 2). Furthermore, the rapidly evolving EV battery market also means manufacturers must adopt future-proof, design-for-test solutions to ensure attractive return on investments in their design and test solutions.

Figure 2: Each stage of the battery development cycle, from cell, to module, and pack, requires rigorous testing to meet design criteria.

Recently, ElringKlinger AG2, a global leading developer of automotive drive systems and volume manufacturer for battery components, decided to collaborate with Keysight Technologies to further accelerate the development of batteries. Their aim is to deliver highly efficient and reliable battery systems to their customers in a fast, consistent, and cost-efficient way.

ElringKlinger will test their cells to identify the most effective combination of cells for their targeted end-customer applications, using Keysight’s Scienlab Battery Test Solution.

Battery modules consisting of several of those cells are used to develop battery systems including a battery management system (BMS), thermal management, and necessary mechanical components.

In their use model, ElringKlinger established a highly customized turn-key laboratory that includes the full range of Keysight’s Scienlab Battery Test Systems, including safety environment for testing battery cells, modules and packs.

Software – Key to Success

While technology is helping EV batteries achieve greater energy density and longer life, the laboratories developing them are also getting bigger.

For many other smaller battery manufacturers with modest laboratory operations, it is possible to manually manage and coordinate the few test systems with rudimentary tools, like a spreadsheet.  But in recent years, these battery makers find themselves with a “good problem” as their business expands rapidly, putting pressure on lab managers to find productive ways to manage workflows and efficiently coordinate testing assets.

This trend towards huge test labs with thousands of test channels presents new challenges:

  • Increased number of cell types under test, leading to demand for more test resources to fulfill higher testing volume.
  • Greater time to market pressure, with demand for more efficient battery life cycle testing.
  • Management of test data and projects across different sites.

In addition to these requirements, the battery test lab manager must ensure the devices under test (DUT), in this case, the battery cells, modules, and packs, can perform as designed in what is known as “time-synchronous” testing.

Some common yet important parameters include durability, range, and efficiency; function, aging, environment, and performance; compliance to industry standards such as ISO, DIN EN, and SAE; temperature behavior and mechanical resistance; and electrochemical analysis.

Multiply these parameters by the number of different customer DUTs, sometimes across different sites, and it becomes obvious that the manual data tracking methods no longer suffice to help the battery laboratory managers.

The use of Big Data, which made inroads into the world of high-volume electronics manufacturing with the advent of Industry 4.0, is picking up speed across the EV battery industry. Battery makers up-scaling their operations are working with solution providers like Keysight, using automation tools like the PathWave Lab Operations for Battery Test, and battery analytics software like Energy Storage Discover to quickly set up their laboratory operations and deploy their test plans.

Figure 3 illustrates how these two software form an integral ‘backplane’ to the entire battery development and test process. While tests are controlled by the Energy Storage Discover software, the cloud-based PathWave Lab Operations for Battery Test allows visibility and management across the entire end-to-end lab workflow.

Such a platform allows the lab manager to easily manage test orders, plan and optimize test capacities and sequences, and share data for analysis more efficiently.

Figure 3: Computing and communications architecture for PathWave Lab Operations for Battery Test.

Optimizing the Battery for Performance and Reliability

No matter how well a single battery cell is designed, its performance is dependent on its interconnection in the module and pack, and the real-world conditions of the electric vehicle. Battery health is affected by extreme temperatures, energy cycles (usage) and how fast it’s being charged. Smooth energy conversion at various charging interfaces, both onboard the vehicle and with external EV supply equipment (EVSE) are also important. Figure 4 shows the complex environment to which the EV battery is connected.

Figure 4: The high-voltage (HV) Li-ion battery is at the heart of powering the EV and its various systems (Image Source: Keysight Technologies).

Holistic Battery Testing

EV power is determined by how battery cells, modules, and packs work together to provide better power and range. As seen from Figure 5, even as the journey of the single cell starts from the design lab, each step of its development, manufacturing, and integration into the vehicle has multiple interfaces.

Figure 5: From the single cell, to module, and pack, right to its usage in the electric vehicle – each step requires rigorous testing to ensure safety and reliability. (Image Source: Keysight Technologies).

Holistic design and test at each step of this journey ensures safety and reliability for both the vehicle and its drivers and passengers, and these qualities will continue to provide economies of scale to make batteries more affordable.

And the vision goes beyond enabling longer range for EVs. Ultimately, well-designed batteries will be at the heart of the global movement towards truly clean and renewable energy sources for our planet.

 

References

  1. Technavio: Global Electric Vehicle (EV) Battery Market 2020-2024
  2. Press release: Keysight and ElringKlinger AG Collaborate to Advance E-mobility

 

About the Author

Hwee Yng Yeo is Industry Solutions Manager, Automotive and Energy, at Keysight Technologies.

 

 

 


 

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