This is the sixth article in an 8-part series featuring articles on Innovations in Electric and Autonomous Vehicles. The series presents an insight into the developments and challenges in the automotive sector as it undergoes massive transformations with the arrival of electric and self-driving vehicles. This series is sponsored by Mouser Electronics. Through the sponsorship, Mouser Electronics shares its passion for technologies that enable smarter and connected applications.The cost of Li-ion, the leading electric vehicle (EV) battery chemistry technology, will soon settle at a mature market value due to market dominance.[1] With that, there is an opportunity for alternate chemistry innovation to gain a share of the battery segment. One such chemistry, solid-state batteries, is poised to emerge as the leading chemistry for EV batteries.In this article, we present a comparison between the commonly used Li-ion batteries and the (relatively) new solid-state batteries for EVs. We also analyze some barriers preventing the mass adoption of the new battery technology.<h1 dir="ltr">Li-ion vs. Solid-State Electrolytes for Battery Electric Vehicles</h1>Li-ion is still leading the market for liquid-state electrolytes. But Li-ion is not without challenges: The chemistry carries higher costs as skyrocketing demand outstrips supply. In addition, there is an opportunity to improve the top safety concern of flammable liquid catching fire. Safety is one of the most critical success criteria for EVs to inspire public confidence, so the industry and safety regulators are searching for how to reduce the flammability risk.Solid-state batteries (using lithium metal as one of its elements) address the most pressing safety challenges of Li-ion. They are more stable and contain a higher energy density than Li-ion. In addition, solid-state comes from readily available materials, which reduces the need to mine. It also offers lower flammability, faster charging, and extended range.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjc2MTMzMzE1MDgzLTE2NzYxMzMzMTUwODMucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" width="720" height="288" class="fr-fic fr-dii">Fig. 1: Li-ion vs. Solid State BatteriesBarriers to the Wide-Scale Adoption of Solid-state Electrolytes for Electric VehiclesWith the advantages of safety, charge time, performance, and availability, solid-state is the future of EV batteries. However, there remain a few barriers to wide-scale adoption for battery developers.&nbsp;First, solid-state batteries will carry a higher development cost due to a lack of existing capital to produce mass quantities.There are also gaps in the solid lithium electrolyte material that degrade battery performance and service life when implemented into Battery Electric Vehicles (BEVs).&nbsp;In addition, solid-state batteries are prone to cracking, and it is best to charge them at 60&deg;C for optimal performance.Solid-state EV batteries are not yet mass-produced. As with any development material, optimizing the manufacturing process to scale profitably is essential. As a result, manufacturing challenges through the lack of experience with solid electrolyte materials would substantially delay wide-scale adoption. In addition, these challenges could shut down the EV battery plant, negatively impacting the public&#39;s first interaction with the new battery chemistry.To address development costs, automakers could vertically integrate to cut development costs and decrease supply risks, creating resiliency between original equipment manufacturers (OEMs) in the face of supply shortages. Their goal is to find a better solution for Li-ion batteries while reducing solid-state manufacturing costs.Having said that, OEMs are already shifting development to solid-state, given all their benefits. Adoption has already started: Toyota announced it will invest $13.5 billion by 2030 into solid-state batteries, and a group including Volkswagen, Ford, and BMW announced solid-state initiatives in the coming years.[2]<h1 dir="ltr">Conclusion</h1>Solid-state batteries address the flammability safety concerns with liquid-state batteries, charge faster, and provide a more extended driving range. Commissioning the capital and ramping supply of the batteries will aid the transition from liquid- to solid-state, preparing EVs for long-term success and massive consumer adoption.This article is based on an e-book by Mouser Electronics. It has been substantially edited by the Wevolver team and Electrical Engineer <a href="https://www.wevolver.com/profile/ravi.rao" target="_blank">Ravi Y Rao</a>. It&#39;s the sixth article from the Innovations in Electric and Autonomous Vehicles Series. Future articles will introduce readers to some more trends and technologies transforming the automotive sector.The <a href="https://www.wevolver.com/article/innovations-in-electric-and-autonomous-vehicles" target="_blank">introductory article</a>&nbsp;presented the different topics covered in the Innovations in Electric and Autonomous Vehicles Series.The <a href="https://www.wevolver.com/article/autonomous-and-electric-vehicles-the-future-of-mobility/" target="_blank">first article</a>&nbsp;discussed the present state of autonomous vehicles.The <a href="https://www.wevolver.com/article/cutting-down-emissions-with-mobility-as-a-service/" target="_blank">second article</a>&nbsp;explains MaaS and how improvements in automotive technologies are speeding up its adoption.The <a href="https://www.wevolver.com/article/a-deep-dive-into-the-new-v2x-and-cellular-v2x-architectures-based-on-5g/" target="_blank">third article</a>&nbsp;takes a look at how the 3GPP intends to use 5G in V2X applications with significant advantages over current dedicated short-range communication or other Cellular-V2X proposals.The <a href="https://www.wevolver.com/article/driver-monitoring-systems-for-ensuring-driver-alertness/" target="_blank">fourth article</a>&nbsp;explains Driver Monitoring Systems (DMS) and their role in reducing the possibility of mishaps due to human errorsThe <a href="https://www.wevolver.com/article/the-state-of-electric-vehicles-in-2023-trends-in-the-development-and-adoption-of-electric-vehicles/" target="_blank">fifth article</a>&nbsp;examines some of the ways EV technologies will evolve, and some of the obstacles they need to overcome before the automotive industry can transition to fully electricThe <a href="https://www.wevolver.com/article/solid-state-vs-li-ion-which-battery-tech-is-better-for-electric-vehicles/" target="_blank">sixth article</a>&nbsp;discusses solid-state batteries, a promising alternative to conventional Li-ion batteriesThe <a href="https://www.wevolver.com/article/active-noise-cancellation-in-electric-and-autonomous-vehicles/" target="_blank">seventh article</a>&nbsp;explains active noise cancellation and why it&rsquo;s a very effective solution for eliminating noises in automobilesThe <a href="https://www.wevolver.com/article/next-generation-vehicles-need-safe-human-machine-interfaces/" target="_blank">final article</a>&nbsp;focuses on Human Machine Interfaces, the sleek and stylish dashboards that are changing the way we interact with cars<h1 dir="ltr">About the sponsor: Mouser Electronics</h1>Mouser Electronics is a worldwide leading authorized distributor of semiconductors and electronic components for over 1,200 manufacturer brands. They specialize in the rapid introduction of new products and technologies for design engineers and buyers. Their extensive product offering includes semiconductors, interconnects, passives, and electromechanical components.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjc2MTMzMzM3OTk1LWltYWdlMi5qcGciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 300px;" class="fr-fic fr-dib"><h1 dir="ltr">References</h1>[1] David L. Chandler, &lsquo;The reasons behind lithium-ion batteries&rsquo; rapid cost decline&rsquo;, MIT News, 22nd November 2021, [Online], Available from: <a href="https://news.mit.edu/2021/lithium-ion-battery-cost-1122" target="_blank">https://news.mit.edu/2021/lithium-ion-battery-cost-1122</a>[2] Tim Kelly, &lsquo;Toyota to spend $13.5 bln to develop electric vehicle battery tech by 2030&rsquo;, Reuters, [Online], Available from: <a href="https://www.reuters.com/business/autos-transportation/toyota-spend-over-135-bln-ev-batteries-by-2030-2021-09-07/" target="_blank">https://www.reuters.com/business/autos-transportation/toyota-spend-over-135-bln-ev-batteries-by-2030-2021-09-07/</a>

Article #6 of Innovations in Electric and Autonomous Vehicles Series: Getting the capital equipment in place and ramping up the supply of batteries will help transition the market from liquid- to solid-state. Industry and consumers will both benefit.

Solid-State vs. Li-ion: Which Battery Tech is better for Electric Vehicles?

Article #6 of the "Why Edge?" Series. A short guide to how Edge AI can boost electric vehicle performance and safety when applied to the Battery Management System (BMS).


Why Edge AI for EV Battery Management

Formula Student Team from the Instituto Superior Técnico, University of Lisbon.

This year, Murata is sponsoring the Formula Student Team from the Instituto Superior Técnico, University of Lisbon, with a mixture of funding and electronic components. 


Keeping it cool while on track

Solid-state batteries could play a key role in electric vehicles, promising faster charging, greater range and longer lifespan than conventional lithium-ion batteries. But current manufacturing and materials processing techniques leave solid-state batteries prone to failure. Now, researchers have uncovered a hidden flaw behind the failures. The next step is to design materials and techniques that account for these flaws and produce next-generation batteries.In a solid-state battery, charged particles called ions move through the battery within a solid material, in contrast to traditional lithium-ion batteries, in which ions move in a liquid. Solid state cells offer advantages, but local variations or tiny flaws in the solid material can cause the battery to wear out or short, according to the new findings.&ldquo;A uniform material is important,&rdquo; said lead researcher <a href="https://engineering.princeton.edu/faculty/kelsey-hatzell" target="_blank">Kelsey Hatzell</a>, assistant professor of mechanical and aerospace engineering and the Andlinger Center for Energy and the Environment. &ldquo;You want ions moving at the same speed at every point in space.&rdquo;In an article published Sept. 1 in the journal Nature Materials, Hatzell and co-authors explained how they used high-tech tools at Argonne National Laboratory to examine and track nano-scale materials changes within a battery while actually charging and discharging the battery. The research team, representing Princeton Engineering, Vanderbilt, and Argonne and Oak Ridge National Labs, examined the grains made up of crystals in the battery&rsquo;s solid electrolyte, the core part of the battery through which electrical charge moves. The researchers concluded that irregularities between grains can accelerate battery failure by moving ions faster to one region in the battery over another. Adjusting material processing and manufacturing approaches could help solve the batteries&rsquo; reliability problems.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1662688715599-Argonne-National-Labs-by-ANL-gov-aps_header_0-768x432.jpg" style="width: 766px;" class="fr-fic fr-dib">Argonne National Laboratory, Argonne, Illinois, USA&nbsp;Batteries store electrical energy in materials that make up its electrodes: the anode (the end of a battery marked with the minus sign) and the cathode (the end of the battery marked with the plus sign). When the battery discharges energy to power a car or a smartphone, the charged particles (called ions) move across the battery to the cathode (the + end). The electrolyte, solid or liquid, is the path the ions take between the anode and cathode. Without an electrolyte ions cannot move and store energy in the anode and cathode.In a solid-state battery, the electrolyte is typically either a ceramic or a dense glass. Solid state batteries with solid electrolyte may enable more energy dense materials (e.g. lithium metal) and make batteries lighter and smaller. Weight, volume and charge capacity are key factors for transportation applications such as electric vehicles. Solid-state batteries also should be safer and less susceptible to fires than other forms.Engineers have known that solid-state batteries are prone to fail at the electrolyte, but the failures seemed to occur at random. Hatzell and co-researchers suspected that the failures might not be random but actually caused by changes in the crystalline structure of the electrolyte. To explore this hypothesis, the researchers used&nbsp;<a href="https://www.anl.gov/msd/synchrotron-studies-of-materials" target="_blank">the synchrotron</a> at the Argonne National Lab to produce powerful X-rays that allowed them to look into the battery during operation. They combined X-ray imaging and high-energy diffraction techniques to study the crystalline structure of a garnet electrolyte at the angstrom scale, roughly the size of a single atom. This allowed the researchers to study changes in the garnet at the crystal level.A garnet electrolyte is comprised of an ensemble of building blocks known as grains. In a single electrolyte (1mm diameter) there are almost 30,000 different grains. The researchers found that across the 30,000 grains, there were two predominant structural arrangements. These two structures move ions at varying speeds. In addition, these differing forms or structure &ldquo;can lead to stress gradients that lead to ions moving in different directions and ions avoiding parts of the cell,&rdquo; Hatzell said.She likened the movement of charged ions through the battery to water moving down a river and encountering a rock that redirects the water. Areas that have high amounts of ions moving through tend to have higher stress levels.&ldquo;If you have all the ions going to one location, it is going to cause rapid failure,&rdquo; Hatzell said. &ldquo;We need to have control over where and how ions move in electrolytes in order to build batteries that will last for thousands of charging cycles.&rdquo;Hatzell said it should be possible to control the uniformity of grains through manufacturing techniques and by adding small amounts of different chemicals called dopants to stabilize the crystal forms in the electrolytes.&ldquo;We have a lot of hypotheses that are untested of how you would avoid these heterogeneities,&rdquo; she said. &ldquo;It is certainly going to be challenging, but not impossible.&rdquo;The article,&nbsp;Polymorphism of Garnet Solid Electrolytes and Its Implications on Grain Level Chemo-Mechanics, was published in the journal Nature Materials. Besides Hatzell, authors included lead author Marm Dixit, of Vanderbilt University and Oak Ridge National Laboratory; Wahid Zaman of Vanderbilt University and Princeton University; Jonathan Almer and Jun-Sang Park of Oak Ridge National Laboratory; Partha Mukherjee of Vanderbilt University; Peter Kenesei of Argonne National Laboratory; Bairav Vishugopi of Purdue University. Support for the project was provided in part by the National Science Foundation and the U.S. Department of Energy.

Solid-state batteries offer advantages for electric vehicles over traditional lithium ion versions, shown above. Photo by Bumper DeJesus/Princeton University

Solid-state batteries could play a key role in electric vehicles, promising faster charging, greater range and longer lifespan than conventional lithium-ion batteries. But current manufacturing and materials processing techniques leave solid-state batteries prone to failure.

Fixing a hidden flaw could unlock better batteries for electric vehicles

This student article shows the synergetic effects of a furfuryl polymer coating and subsequent calcination leading to improved electrochemical performance of nickel-rich NMC622.

High-Performance Amorphous Carbon Coated Lithium-Nickel-Manganese-Cobalt-Oxide (NMC622) Cathode Material with Improved Capacity Retention for Lithium-Ion Batteries

Using public electricity and solar panels for the easy and hassle-free charging of Electric Vehicles is an interesting solution to combat the problem of the unavailability of Electric Vehicle Charging Stations.

Electric Vehicle Charging Station from Public Electricity and Solar Panels

As climate concerns increase, electric vehicles are growing in popularity. In Switzerland, some 5.5% of passenger cars have a battery, and more than half of all new registrations in Q4 2021 were for electric or hybrid cars, according to the Swiss Federal Office of Energy. But what will happen to these vehicles&rsquo; lithium-ion batteries once the cars reach the end of their useful lives? &ldquo;Even when the batteries are no longer suitable for electric vehicles, they still have 70%&ndash;80% of their capacity left,&rdquo; says Mario Paolone, a professor at EPFL&rsquo;s Distributed Electrical Systems Laboratory (DESL).<iframe src="https://www.youtube.com/embed/x06x5D3Wqcc?&wmode=opaque&rel=0&enablejsapi=1&origin=https://www.wevolver.com" frameborder="0" allowfullscreen="" class="fr-draggable" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" style="width: 767px; height: 434px;"></iframe>The CircuBAT initiative, which officially kicked off today, aims to turn the production, use, and recycling of electric-vehicle lithium-ion batteries into a closed-loop process. The project will run for four years and be carried out by a consortium of seven Swiss research institutions and 24 companies, with the goal of making batteries last longer by optimizing each stage of their lifecycle. The research will focus on three areas: extending a battery&rsquo;s lifespan, finding them a second life, and recovering and recycling materials.DESL will be involved on the topic of second-life battery applications of the project. One avenue that the lab&rsquo;s engineers will explore is using the batteries to store power for regulating grid frequency and other parameters. &ldquo;We&rsquo;ll investigate the best ways to implement recycled batteries in power grids,&rdquo; says Paolone. &ldquo;We&rsquo;ll take into account the state of the battery when it starts its second life, as well as how it ages as it&rsquo;s used.&rdquo; The engineers will test second-life batteries (supplied by other project members) on DESL&rsquo;s full-scale microgrid, under real-world yet controlled conditions.<h2>Aging rather than dying</h2>Based on the results of their tests, the DESL team will develop a model for characterizing the batteries&rsquo; aging process. Their model could then be applied to any battery, regardless of how it was treated during its first life. &ldquo;A battery is characterized by its energy capacity &ndash; i.e., how much energy it can store at different charge and discharge rates &ndash; and by the power at which it can be charged and discharged,&rdquo; explains Paolone. &ldquo;These macroscopic characteristics change as a battery age and are affected by its operating cycle. Our goal is to model precisely how these characteristics shift over time, so they can be controlled effectively during the batteries&rsquo; first and, crucially, second life.&rdquo; The engineers&rsquo; model should help operators make optimal use of batteries in their second life.Ultimately, the DESL team hopes to develop a method for certifying batteries for second-life applications, attesting to the battery&rsquo;s capacity both at the beginning of its second life and over several years of use. The later a lithium-ion battery is recycled, the smaller its carbon footprint. And reducing the carbon footprint is one of the key aims of CircuBAT: &ldquo;Our goal is to minimize the overall environmental impact of electric vehicles. That will include expanding batteries&rsquo; storage capacity in order to support the energy transition and developing designs that require fewer resources,&rdquo; says Andrea Vezzini, who heads the CircuBAT project team at Bern University of Applied Sciences.<hr><h2>About CircuBAT</h2>CircuBAT is a joint initiative of the Swiss Federal Laboratories for Materials Science and Technology (Empa), the Swiss Center for Electronics and Microtechnology (CSEM), the University of St. Gallen (HSG), the Eastern Switzerland University of Applied Sciences (OST), the Switzerland Innovation Park Biel/Bienne (SIPBB) and EPFL. It is being managed by Bern University of Applied Sciences (BFH). 24 companies are also involved in the initiative as partners. CircuBAT has received funding from Innosuisse, the Swiss innovation agency, as part of its first Flagship Initiative call for proposals.

The DESL team hopes to develop a method for certifying batteries for second-life applications. © Alain Herzog/EPFL

EPFL has joined six other Swiss research institutions in CircuBAT, an initiative selected for the first Innosuisse Flagship program, in order to develop a circular business model for lithium-ion batteries.

Electric car batteries could soon get a second lease on life

More security, larger storage capacities, shorter charging times - solid-state batteries are expected to outperform conventional lithium-ion batteries in almost all performance parameters in the future.&nbsp;The basis for this has been developed by the FestBatt battery competence cluster with the participation of researchers from the Karlsruhe Institute of Technology (KIT).&nbsp;In a second funding phase, complete battery systems and methods for production are now being developed.&nbsp;The Federal Ministry of Education and Research (BMBF) is funding around 23 million euros.A further development of the lithium-ion battery could give electromobility the decisive impetus in just a few years.&nbsp;Professor Helmut Ehrenberg, coordinator of the characterization platform in the FestBatt competence cluster at the Institute for Applied Materials (IAM) at KIT, is convinced of this: “Solid-state batteries do without liquid and flammable electrolytes, their chemistry enables higher energy densities and shorter charging times.&nbsp;In addition, toxic and rare materials such as cobalt can be dispensed with. ”The FestBatt competence cluster, which was launched in 2018, is developing this key technology on behalf of the German government and is now starting the second funding phase.&nbsp;The work takes place in strong international competition - in order to open future markets for Europe as quickly as possible,&nbsp;the federal government has bundled the competencies of 17 scientific institutions with FestBatt.&nbsp;These include universities, Helmholtz institutes as well as institutes of the Fraunhofer Society and the Max Planck Society; the work is coordinated as a whole by the Justus Liebig University of Giessen (JLU).<h2>First steps towards mass production</h2>The focus of FestBatt's new funding phase will be the development of cell components and entire solid-state battery cells based on promising electrolytes, and material and process technologies for their production will also be developed.&nbsp;However, there are still a number of scientific and technological challenges to be solved before solid-state batteries can be mass-produced.&nbsp;The characterization platform coordinated by KIT with the participation of the University of Marburg, Forschungszentrum Jülich and JLU will, among other things, characterize contact and interfaces with X-ray, synchrotron and neutron radiation as well as various microscopy techniques on complex multiphase systems.<h2>Advantage through systematic characterization</h2>In the first funding phase of FestBatt, more than 100 researchers worked in transdisciplinary thematic platforms to identify suitable materials and to synthesize different solid electrolytes.&nbsp;The characterization platform systematically examined the materials: The most important influencing variables in the synthesis of solid electrolytes and critical material changes in composites were identified.&nbsp;The further development of solid-state batteries in FestBatt's second funding phase is now building on this.&nbsp;It was only through the development of standardized measurement protocols that it was possible to reliably determine the performance characteristics and classify the very different cell concepts that are being developed with great intensity around the world.<hr>Original publicationRandau, S., Weber, DA, Kötz, O. et al .: Benchmarking the performance of all-solid-state lithium batteries.&nbsp;Nature Energy, 2020.&nbsp;DOI:&nbsp;<a href="https://doi.org/10.1038/s41560-020-0565-1" target="_blank">https://doi.org/10.1038/s41560-020-0565-1</a>About FestBattThe Federal Ministry of Education and Research (BMBF) has been funding the second round of the BMBF competence cluster for solid-state batteries (FestBatt) since November 2021 with around 23 million euros for three years. In the second phase, FestBatt consists of an accompanying project and nine joint projects: three cell and four cross-sectional platforms, including the characterization platform coordinated by KIT. FestBatt is closely networked with the other BMBF competence clusters funded in parallel (including ProZell and ExcellBattMat). The competence cluster is also being coordinated in the second funding phase by Professor Jürgen Janek from the Center for Materials Research (ZfM) at the Justus Liebig University in Giessen.

Schematic structure of a solid-state battery. (Graphic: JLU / Elisa Monte)

The BMBF competence cluster for solid-state batteries (FestBatt) is starting the second funding phase - the characterization platform will be continued under the coordination of KIT

FestBatt: The next step in solid-state batteries

This is the fourth article in a <a href="https://www.wevolver.com/article/how-to-select-the-right-reinforced-transformer-for-high-voltage-energy-storage-applications" rel="noopener noreferrer" target="_blank">5-part series</a> exploring power conversion. The series will provide insight into how the rapid electrification of vehicles and the switch to renewable energy is driving the demand for safe and reliable power conversion and electronic components.&nbsp;The articles were originally published in an&nbsp;<a href="https://www.mouser.com/news/bourns-power-ebook/mobile/index.html" rel="noopener noreferrer" target="_blank">e-magazine</a>, and have been substantially edited by Wevolver to update them and make them available on the Wevolver platform. This series is sponsored by&nbsp;<a href="https://www.wevolver.com/profile/mouser.electronics" rel="noopener noreferrer" target="_blank"></a><a href="https://www.wevolver.com/profile/mouser.electronics" rel="noopener noreferrer" target="_blank">Mouser Electronics</a>, an online distributor of electronic components. Through their sponsorship,&nbsp;Mouser Electronics&nbsp;supports engineers in designing sustainable and efficient applications for a greener future.&nbsp;<h1>Introduction</h1>The need to monitor the state of health of lithium-ion cells in battery packs during charging and discharging is a key requirement for Battery Management Systems (BMS) in high-energy applications such as hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs). Maintaining performance and safe operation is of paramount importance, as lithium-ion chemistries are prone to degradation and aging issues. A dangerous thermal runaway condition can occur if the ambient temperatures are out of specification or if the batteries are undercharged or overcharged, possibly causing cracks in the carbon and lithium plating.The three parameters measured by the BMS (Figure 1) to determine the state of a cell&rsquo;s health are cell voltage, temperature, and current. The traditional solution employed to measure these parameters has been the use of shunt resistors. These passive components feature a relatively high absolute tolerance of 5 percent. However, the overall accuracy, when combined with a current sense module, can be reduced to as low as 0.01 percent. This article provides helpful BMS design information on the accuracy level that can be obtained using Bourns&reg; Model CSM2F Series shunt resistors combined with a current-sense module designed for this purpose.<div class="fr-img-space-wrap"><img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjE2NTgwNjQ0Mjk4LUlNQUdFIDEtMDEuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 788px;" class="fr-fic fr-dib">Figure 1: Block Diagram of Battery Management System.<h2 class="fr-img-space-wrap2">Bourns&reg; Shunt Resistors for Battery Current Measurement</h2></div>Bourns offers three shunt resistor models qualified by Bourns for harsh environment energy storage applications. The resistive element in all three models consists of large copper terminals as can be seen in the examples of the CSM Series on the left. Given that the resistivity of copper is 1.72 x 10-8 &Omega;m and that the resistance will increase by 0.393 % for every extra degree Celsius in temperature, the overall coefficient of resistance between the two points will be higher than the resistivity of the resistor alloy (max. 50 ppm/˚C or 0.05 %/˚C). If the distance between the two measurement points in copper is 3 mm in total as is the case with CSM2F-8515, the temperature coefficient of resistance, or TCR, will increase from 50 ppm/˚C (TCR of element) to 150 ppm/˚C (TCR of combined element plus copper terminal). The maximum current these shunts can carry is quite high. The Bourns&reg; Model CSM2F-7036, for example, using Ohm&#39;s Law can carry 1000 A, DC/DC at a maximum power 50 watts. A typical battery pack for an HEV is 24 kWH. This is equivalent to 500 ampere hours in a 48 V vehicle. Therefore, the current can be very high, especially during periods of high power such as acceleration when moving or fast charging when stopped.&nbsp;<h1>Recommendations for Signal Processing</h1><div class="fr-img-space-wrap"><img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjE2NTc5ODcwNzQ3LUlNQUdFIDMtMDEuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 788px;" class="fr-fic fr-dib">Figure 2: Block Diagram of Signal Processing Circuit and Photo of Experiment.&nbsp;Bourns developed the typical current source module block diagram (Figure 2) to evaluate a shunt-based current measurement system&rsquo;s accuracy. The module consists of an Analog Front End (AFE) with a current sense amplifier with analog buffer, 24-bit ADC and Serial Peripheral Interface (SPI). Several high-voltage bidirectional current-sense amplifiers from ADI, such as the model <a href="https://www.mouser.com/Analog-Devices-Inc/Current-Sense-Amplifiers/AD8210-Series/_/N-1yyh4l4Z6o48gZ1yyhna8" target="_blank">AD8210</a> or <a href="https://www.mouser.com/Analog-Devices-Inc/Semiconductors/Amplifier-ICs/Current-Sense-Amplifiers/AD8211-Series/_/N-6o48g?P=1yyhna6Z1yyh4l4&gclid=CjwKCAjw34n5BRA9EiwA2u9k3-Sp4U4oA9MaKwWJwe3JEK-By0AiM23RZUkK8CTQqzRjiXoNY98kHxoCTzsQAvD_BwE" target="_blank">AD8211</a>, have gains of 20 and common-mode voltages of up to 65V.</div>To evaluate the shunt, Bourns tested its Model <a href="https://www.mouser.com/new/bourns/bourns-csm2f-resistors/" target="_blank">CSM2F-8518</a> (100&mu;ohm nominal resistance), as shown in Figure 2. A single-board microcontroller kit is programmed to communicate with the module over an SPI connection. The current for the measurement was generated using a precision current source.The first measurement to be determined is the resistance of the shunt. This is done using the known current from the current source and a precision 4-wire voltmeter. Once the actual resistance of the shunt is measured, then the voltage across the shunt using the current sense module can be compared with the actual resistance value.The current sense amplifier has a common mode voltage of 80V maximum, allowing for the module to be placed at the high end in 48V battery systems. The module also contains a surface-mount temperature sensor with a PWM output proportional to the ambient temperature. Figure 3 shows the temperature sensor output at room temperature. The amplifier power is supplied by a DC supply of +5V. This experiment&rsquo;s power comes from a Low Drop Out (LDO) regulator with the original supply coming from the USB interface. For an isolated 5V supply, a low-power micro converter using the <a href="https://www.mouser.com/new/linear-technology/adi-lt8301-lt8302-converters/" target="_blank">ADI LTC8301</a> (flyback or push-pull) can provide the necessary isolation with the required safety level.Figure 4&nbsp;shows the data points collected from the A/D input terminals with an average of 22.44364mV and peak-to-peak variation of 0.007mV over the sampling period.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjE2NTgwMjA4NTY1LUlNQUdFIDQtMDEtMDEuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 788px;" class="fr-fic fr-dib">Figure 3: Data in Degrees Celsius Recorded by the Module.<h1 class="fr-img-space-wrap2">Determining Measurement Accuracy</h1>The accuracy of the measurements at room temperature can be calculated using the following formula.The accuracy:<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjE1Mjg4MzgxMDk4LXRlc3QgNC5qcGciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 300px;" class="fr-fic fr-dib">The data at several DC currents ranging from 10mA up to 20A was recorded, and the accuracy calculated (Figure 5). The accuracy tends to degrade once the currents increase beyond 10 amperes, and the shunt starts to heat up. The resistance value used to calculate the current will drift as a result, which has a negative impact on the accuracy of the measurements. To further assist designers, Bourns has developed a look-up table that shows the normalized increase or decrease of the resistance with temperature. With this data, the original value used for the resistance can be modified by the factor shown in Figure 6 and correlated with the temperature sensor reading.<h1>Helping Ensure BMS Safety and Long Life</h1>Currents of several hundred amperes are measured by BMS in various e-mobility applications during battery charging and discharging. The ability to measure current accurately provides critical information for safety and ensures long battery pack life. Using an ultra-low resistance shunt resistor, and a precision AFE, can provide very accurate readings from very high to very low current levels with accuracy tolerances of less than 0.01 percent. Also, temperature sensing, and look-up tables from Bourns, can improve measurement accuracy as the temperature increases.This article has provided a proven methodology to measure the cell voltage, temperature, and current to determine the state of health of a battery cell. Key in this process are Bourns&reg; current-sense amplifiers featuring low offsets and high common mode voltages that enable high accuracy with the shunt being placed at the high end in 48V applications.Bourns&reg; <a href="https://www.mouser.com/new/bourns/bourns-csm2f-resistors/" target="_blank">Model CSM2F Series</a> shunt resistors are manufactured in an International Automotive Task Force-approved facility certified to build components for harsh environment applications such as in high-energy BMS used in HEVs and BEVs.This article was originally written by Mouser and Bourns in an&nbsp;<a href="https://www.mouser.com/news/bourns-power-ebook/mobile/index.html" rel="nofollow" target="_blank">e-magazine&nbsp;</a>and substantially edited by the Wevolver team.&nbsp;It&#39;s the fourth article of a 5-part series exploring power conversion. Future articles will dive into power conversion solutions for critical applications such as automotive and renewable energy. &nbsp;Article 1 explored <a href="https://www.wevolver.com/article/how-to-select-the-right-reinforced-transformer-for-high-voltage-energy-storage-applications" rel="noopener noreferrer" target="_blank">how designers can make design decisions when working with high-voltage energy storage systems. &nbsp;</a>Article 2 <a href="https://www.wevolver.com/article/rechargeable-batteries-for-greener-solutions" rel="noopener noreferrer" target="_blank">discussed the potential of rechargeable batteries.&nbsp;</a>Article 3 <a href="https://www.wevolver.com/article/selecting-battery-management-systems-transformers-for-isolated-communications-in-high-voltage-energy-storage" rel="noopener noreferrer" target="_blank">examined the method for selecting transformers for Battery Management Systems (BMS).&nbsp;</a>Article 4 <a href="https://www.wevolver.com/article/accurate-measurements-using-shunt-resistors-and-current-sense-modules-in-high-energy-storage-applications" rel="noopener noreferrer" target="_blank">explained the necessity of shunt resistors to deliver accurate Battery Management Systems.&nbsp;</a>Article 5 <a href="https://www.wevolver.com/article/innovative-transformer-solution-addresses-traditional-challenges" rel="noopener noreferrer" target="_blank">provided an overview of innovative transformer solutions for power conversion.</a><hr><h1>About the sponsor: Mouser</h1><a href="https://eu.mouser.com/" rel="nofollow" target="_blank"></a><a href="https://eu.mouser.com/" rel="nofollow" target="_blank"></a><a href="https://eu.mouser.com/" rel="nofollow" target="_blank">Mouser Electronics</a>&nbsp; is a worldwide leading authorized distributor of semiconductors and electronic components for over 1,100 manufacturer brands. They specialize in the rapid introduction of new products and technologies for design engineers and buyers. Their extensive product offering includes semiconductors, interconnects, passives, and electromechanical components.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjE4NTY0Njg3ODM2LU1vdXNlciBiYW5uZXIgYXJ0aWNsZS5qcGciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 300px;" class="fr-fic fr-dib">

Article 4 of the Power Conversion Series. Shunt resistors combined with a current-sense module can deliver highly accurate battery management systems in high-energy applications.

battery management system (BMS)