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Emily Newton

Innovation

Why Do EV Batteries Need Better Performance Tests?

Consumers want to know that EVs are safe and reliable

Published: Tuesday, October 12, 2021 - 11:03

Electric vehicles (EVs) are becoming more popular. The consumers interested in buying them generally want to know answers to questions such as: Is the car’s battery an explosion or fire risk? Will its useful life match or exceed the vehicle’s? Will the battery charge as fast as promised? Can it consistently perform within the stated range?

EV battery tests can determine those things and more, giving potential purchasers and current owners more peace of mind. However, researchers, engineering professionals, and manufacturers must continually develop better battery tests. Here are some specific reasons why.

Better battery tests could bring standardization

Lithium-ion battery usage spans far beyond electric cars. It extends to products ranging from power tools to laptops and many other familiar products. When researchers examine a battery’s electrochemical performance, they usually focus on three parameters:

Open-circuit voltage: The battery’s maximum voltage with no current flow
Resistance: How much a battery’s materials interfere with the current flow, causing voltage drops
Capacity: The total charge a battery stores

Beyond those three areas, there’s a significant degree of variation, largely due to a battery’s intended application. Researchers may test batteries at different temperatures or measure resistance with either alternating or direct current. That variability makes it difficult for the people conducting battery tests to know with confidence how the results stack up compared to other investigations. The outcomes might seem positive in the lab environment, but the lack of standardization prevents direct evaluation of those results to what other batteries achieved.

A team from multiple organizations, which included Argonne National Laboratory, University of Warwick, OVO Energy, Hawaii National Energy Institute, and Jaguar Land Rover aimed to help testers select the best examination methods for particular situations. Their work compared eight test methods and specified the equipment needed for each. The content also mentioned what information each assessment would show and detailed the advantages and disadvantages.

This work could bring much-needed standardization for all lithium-ion battery tests. As it stands, stakeholders often develop internal processes without concern for whether those examinations have compatibility with the tests carried out elsewhere by fellow academic researchers, engineering professionals, and automakers. Even the internationally recognized standards have numerous suggestions for testing cells that cause substantial differences in test preparation and results, despite two parties or groups using one framework for their assessments.

More robust testing could shape future recommendations

When manufacturers conduct EV testing, it’s crucial to consider all the various situations a car owner might encounter. The results could prompt automakers to suggest certain strategies for safety, including making new consumer recommendations. For example, should car owners always replace batteries that reach a certain age, even if they still work well? Must they invest in new batteries after minor road accidents due to the risk of concealed damage that could affect the vehicle’s safe operation?

Researchers at Austria’s Graz Institute of Technology have engaged in long-term work to improve EV batteries. In 2017, they announced a study to determine what happens to a vehicle’s traction batteries during a crash. The team examined new power sources, as well as older ones or those that had already been in minor road accidents.

More recently, a group from the same institution assessed whether a battery gets more dangerous as it ages. The results showed significant electrical and mechanical changes due to charge and discharge cycles. More specifically, the group confirmed a higher stiffness under mechanical load. However, they clarified that the change doesn’t necessarily make it riskier to drive a car with an older EV battery.

Instead, project manager Christian Ellersdorfer from The Institute of Vehicle Safety says that, “The sum of the influences makes them safer over time because they also lose electrical energy.” The research showed that older cells were less likely to have thermal runaway events after short-circuiting because of their reduced energy potential.

Another phase of this research could also repurpose EV batteries after they’re too old for continued use in a car. “Used batteries with a power capacity of 80 percent are no longer suitable for electric vehicles, but they are very suitable for stationary energy storage or for machine tools. For the first time, we are determining generally valid parameters in the area of safety,” says Ellersdorfer.

Consumers and automakers will likely take new guidelines more seriously if they know the outcomes of specific tests to see how EV batteries perform under real-life stresses. For example, members of the public often wonder if manufacturers recommend things primarily to relieve the liability burden. That’s certainly part of it. However, if those entities specify that stringent research from an outside source led to the change, it brings credibility.

Testing could help fire risks associated with EV batteries

EV batteries tested in the lab are subject to built-in precautions to extinguish a blaze when necessary. One shaker system has a chamber that douses batteries with up to 1,000 liters of water after sensing thermal runaway conditions. Exposing EV power sources to shocks and vibrations through such tests helps determine how they’d perform in real-world situations.

Plus, if the batteries catch fire in a controlled environment, it’s crucial to figure out the reason as soon as possible to target and remedy the matter. However, it’s not always possible to notice the issue before a car reaches the public. That’s why Anders Gulliksson from Dafo Vehicle Fire Protection was involved in a European Union-funded project to build technology to stop such incidents in electric vehicles.

“When the commonly used Li-ion batteries fail through short-circuiting, overcharging, high temperatures, mechanical damage and overheating, this might cause thermal runaway and the release of a flammable electrolyte, which makes fire extinguishing very difficult,” says Gulliksson. Additionally, these blazes may release toxic gases, including hydrogen fluoride. It can cause serious skin and respiratory tract damage.

EV fires are relatively rare but real threats. GM recently recalled batteries for the Chevy Volt due to a fire hazard caused by two manufacturing defects. The company recommended that owners not let their cars get below 70 miles of remaining range or charge them in an enclosed area overnight until the issues get fixed.

Improved testing to curb fires benefits manufacturers and consumers alike. Recalls are expensive for companies due to the costs associated with parts replacements and the reputational damage these events can cause. Similarly, people preparing to buy a certain electric vehicle model may think twice about it if they hear the car has a life-threatening battery-related problem. Testing enhancements reduce the chances of fire risks becoming widespread problems that only become apparent after vehicles reach the market.

Improved EV battery tests should increase consumer confidence

Keeping an EV going through a long trip is not as straightforward as researching the nearest gas station and pulling up to an unoccupied pump. However, numerous efforts are underway to remove the so-called range anxiety that can make people balk at buying EVs. An Irish project involves turning empty phone booths into charging stations. Each one gives a car up to 100 kilometers of range in only a half-hour.

Researchers continually look for ways to enhance existing battery tests, whether by running them differently to determine more information or finding practical ways to boost the overall efficiency of the assessments. When customers know a battery has been thoroughly tested, they should feel more open to buying a car that has it.

One recent example involved a Stanford University team that used machine learning to accelerate the usual pace of battery testing. That approach caused nearly a 15-fold reduction in the typical times for examining them, which can take months or even years to achieve. Since EV battery tests must occur at every design phase, this achievement could result in products that boast longer ranges or other performance enhancements customers want.

The goal at Stanford was to find the best method of charging an EV battery in only 10 minutes while also maximizing its lifespan. Machine learning allowed shortening the length and number of trials. The testing took almost two years without the technology, but the team accomplished it in a mere 16 days. Machine learning also suggested a new and unexpected charging protocol.

These outcomes could pioneer new, more efficient battery testing methods by drastically cutting down how much experimentation teams must do to reveal the most promising areas of focus for their work. If machine learning rules out the options that almost certainly will not provide the hoped-for results, researchers can quickly identify and devote their time to the possibilities most likely to push battery technologies forward.

EV battery tests connect to green vehicles’ success

Battery capability is certainly not the only thing that makes a person want to buy an electric car. However, many consumers understandably care about the power source because it’s a main factor in the vehicle’s performance.

These examples show there’s no single way to make EV tests better. However, researchers are making significant progress in enhancing the future of what happens to ensure the batteries are road-ready.

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About The Author

Emily Newton’s picture

Emily Newton

Emily Newton is the Editor-in-Chief of Revolutionized, and online magazine exploring the innovations disrupting the scientific and industrial sectors.