How Intelligent Battery Management Drives EV Buyer Confidence

Precise battery management system monitoring improves range, extends battery life, and supports lithium-ion safety and reliability.

Figure 1. Increasing range, extending battery life, and ensuring the safety and reliability of lithium-ion batteries are the three key technical challenges addressable through rigorous testing of battery management systems. (Image: iStock)

The electric vehicle (EV) market globally is growing fast, and stunning growth is projected to continue through 2040 and beyond. While it’s the kind of growth that reflects strong customer enthusiasm, manufacturers recognize that for most drivers, purchasing an EV is a fundamental shift that may hinge on their concerns about the vehicle’s range and reliability.

At the upper limit, EVs can travel 350-plus miles on a single battery charge, creating real cause for excitement in the automotive industry — but also a nagging source of range anxiety for drivers. The fear that a driver will run out of battery power while on the road, without access to a charging station when they need it, is real.

In fact, range anxiety is credited as a leading factor in why consumers are not gravitating toward EVs as quickly as automotive manufacturers had projected. Some potential EV owners also have concerns regarding the safety and reliability of EV batteries, which have been amplified by media stories of EV fires. Battery lifetime is another issue for consumers, with fears of batteries needing to be replaced within a few years, at huge expense (Figure 1).

How can EV manufacturers effectively overcome the most common fears of drivers?

The semiconductor automated test equipment (ATE) sector can help. To meet this challenge, EV manufacturers must first embrace the critical role of battery management systems (BMS) and then demand the generation of highly accurate battery data for existing and future EVs.

By enabling more accurate cell-by-cell monitoring – a significant advance in overall EV battery monitoring – the ATE industry can drive improvements in the verification of the monitoring accuracy that’s essential for continued growth of the EV industry.

Increasing range, extending battery life, and ensuring the safety and reliability of lithium-ion (Li-ion) batteries are the three key technical challenges that automotive systems engineers can address more comprehensibly through rigorous testing of BMS.

The Impact of More Accurate and Functional BMS

Figure 2. The BMS market is expected to see significant growth over the next decade. Plug-in EV = plug-in hybrid electric vehicle (PHEV) + battery electric vehicle (BEV). (Image: Yole Group)

The BMS is a system for monitoring EV battery performance to ensure safety and reliability, and to maximize range. The BMS controls charging and balancing the charge on individual cells within a battery pack and integrates a multitude of semiconductors. Its multi-channel battery monitoring and balancing system ICs manage cell voltage, current, and temperature, to determine the state of charge (SoC) and health of the entire battery pack. These devices may be wired or wireless, communicating the information they gather to a central processing unit, which, for example, displays the battery status to the driver or sends alerts or warnings. The BMS market is expected to see significant growth over the next decade (Figure 2).

Battery packs are comprised of multiple cells. For ideal performance, the BMS must manage the charge and monitor the state of charge for each cell individually. The BMS must also manage temperature fluctuations and the health of the entire battery stack, where batteries of various voltages are stacked on top of one another.

Better Battery Management Systems Improve EV Range

Can a better BMS help alleviate range anxiety? There is reason for optimism. By providing a more precise measurement of the vehicle’s charge status, an improved BMS enhances battery utilization. This, in turn, extends the driving range and improves estimates, instilling greater driver confidence.

Improved BMS monitor accuracy aids battery pack performance, allowing the vehicle to manage its charge and discharge cycles more efficiently, ultimately resulting in extended battery life. In a cascade of benefits, this stands to open up additional driving miles, thus granting drivers greater mileage with fewer charging stops.

For instance, if the accuracy of measuring the SoC is increased, then the usable battery energy is also increased. SoC is determined by measuring the voltage across the cell, so accurate voltage measurement is crucial to obtaining an accurate figure for SoC.

Figure 3. A more accurate State of Charge (SoC) increases usable battery capacity. (Image: Teradyne)

A typical cell might need to be kept between 10 percent and 90 percent of its theoretical capacity, giving a usable energy of 80 percent. If the BMS has an error rate of +/-1 percent, the practical limits will be 11 percent and 89 percent, and usable energy is therefore 76 percent, while a BMS accuracy of +/-5 percent gives limits of 15 percent and 85 percent, and usable energy is 70 percent. Overall, the lower the accuracy of the BMS, the lower the usable energy. Figure 3 provides a look at how accuracy increases usable battery capacity.

This, coupled with emerging battery architectures and chemistries and other vehicle improvements, would enable automotive manufacturers offering 300 miles on a single battery charge today to offer 500 to 600 miles, a notable competitive differentiator to attract hesitant buyers.

As battery packs become more densely integrated and support higher voltages, IC testing is essential for guaranteeing device quality — both ensuring longevity of EVs in the field and delivering differentiators for new EV models. The test challenge is to be more precise than the device, by a factor of 10× or more.

Managing Complexity of Testing Multiple Li-ion Battery Technologies

While accurate measurement of an EV’s battery cells is vital to alleviating range anxiety, the safety and reliability of lithium-ion batteries in EVs are equally important. Smaller and lighter than conventional rechargeable battery technologies, Li-ion devices deliver high energy efficiency, high energy and power density, and long life cycles.

Yet because Li-ion batteries can ignite, it’s crucial to thoroughly monitor the storage and release of energy inside the system’s battery cells. A state-of-the-art BMS enables charge and discharge cycles to be managed more safely, which extends battery life and minimizes the risk of catastrophic failure and fire.

Lithium batteries are dominating the EV market space and are currently available in a variety of chemistries, including Nickel Manganese Cobalt (NMC) and Lithium Iron Phosphate (LFP). Both options have their advantages and disadvantages; for example, NMC batteries are susceptible to dangerous thermal runaway, which can cause fires, while LFP options may be adversely affected by very cold temperatures.

Furthermore, the market is dynamic with continuously changing cell chemistries. There is a general shift away from NMC and toward LFP, due to LFP’s voltage vs. state of charge curve being typically flatter than that of NMC. A near-future chemistry, Lithium Iron Manganese Phosphate (LMFP), may bridge the gap between the pros and cons of NMC and LFP, but could require more complex test and monitoring devices.

But what is the impact of multiple technologies on the BMS sector? As battery manufacturers face a widening array of options, determining a battery’s SoC is becoming more challenging. Multiple evolving technologies define this as a dynamic market and BMS manufacturers require a flexible ATE test solution to handle the challenge and future-proof their BMS investments.

In response to this need, the ATE industry is delivering technology to support temperature-stable, multi-channel instrumentation, requiring less calibration and offering higher throughput. Multichannel ATE technology is optimized to get precise measurements quickly.

New Challenges for Battery Management

As the EV industry continues to grow and mature, battery voltage and architecture changes manifest in the form of higher battery capacity and the capability for faster charging. The resulting increase in cell count leads to larger packages and higher voltage, creating test challenges. As a capital expenditure, test equipment must not only meet current technological requirements but also be future proof as technology advances.

The anticipated exponential growth of EVs requires higher throughput and economic scalability for test. This growth is predicated upon testing devices quickly at automotive quality levels.

Voltages are now spiking upward, ranging from 400V to 800V, which requires increasingly more battery cells. This steady stream of advancements means automotive manufacturers must lean harder on BMS innovation and functionality to keep auto buyers satisfied with their purchases. Potential buyers will always care deeply about range and battery health, considerations just as important as automotive safety systems.

In any case, these requirements demand more stringent testing. The semiconductor ATE industry is rising to the challenge, with advanced instrumentation that supports more accurate testing of higher voltage in the BMS. This includes committing to future preparedness by creating long-term product road-maps to support the throughput needed for increasingly higher voltages.

Battery management systems are poised to become a key competitive differentiator in an EV market that is seeking to grow and thrive on a global level. And by tapping into smarter BMS, automotive manufacturers are future-proofing their resources by embracing, even anticipating, trends in EV battery design.

This article was written by Thomas Koehler, Product Marketing Manager for the Automotive and Complex Power Device segment at Teradyne (North Reading, MA). For more information, visit here .