Battery Management Systems and Lifespan in Electric Vehicles (EVs)

On the highways that crisscross the world, a transformation is taking place—from centuries of fossil fuel-powered cars to clean, efficient electric vehicles (EVs). The EV market is expected to grow tenfold over the next decade, and the need to monitor, manage, and maintain high-performance batteries to power millions of electric vehicles will grow.

Today’s battery market is driven not only by cost, but also by the need for vehicles with longer driving range, shorter charging times, and increased functional safety. In order to meet these stringent battery management system requirements, the highest standards must be adhered to and deviations minimized.

With 40% of the price of an electric vehicle dependent on the battery, performance and battery life have become major factors in the success of EV brands. As a leader in battery management systems (BMS), Analog Devices, Inc. (ADI) works with customers to find the best critical processes to monitor and manage electric vehicle batteries and ensure their safety, productivity, and lifespan.

Overview

• company

After ADI acquired Linear Technology, ADI's product portfolio included the first integrated high voltage battery stack monitor in 2008. Since then, we have been committed to providing the highest performance solutions. Today, we are developing our 5th generation of products.

• challenge

The growth of the EV market increasingly requires battery manufacturers, supply chains and automotive brands to deliver high-quality, reliable battery technology to meet demand.

• application

Battery monitoring and management.

• Matters of concern

OEMs are very concerned about battery safety, cost, efficiency and lifespan.

• Target

Improve BMS to ensure safety, improve reliability, enhance performance and extend the life of EV batteries.

Invest in a better battery management system
BMS that closely monitors, controls, and distributes reliable charging and discharging of the entire battery system over its service life. Accurate monitoring of current and voltage profiles is critical because overcharging a battery can cause a fire or explosion, while undercharging (or completely discharging) the battery can cause failure. The quality of the battery management system directly affects the number of miles an EV can travel per charge. A quality battery management system maximizes the overall life of the battery, thereby reducing the cost of ownership.

In this case, price level becomes less important and long-term value becomes the key metric. This is because you are looking for better performance over the life of the battery. “When it comes to accuracy, and accuracy over the life of the vehicle, there is no trade-off,” said Mike Kultgen, general manager of BMS at ADI. “The higher the accuracy, the better you understand the state of the battery cells, the more capacity you can extract from them, and the more reliable the battery pack will operate.” The value of BMS performance is obvious when considering the investment in the battery pack, and even more so as automotive designers consider warranty and lifecycle costs of the battery pack1.

The Rigorous Requirements of Battery Management
Batteries place high demands on design teams as they consider a range of priorities, including price, reliability and safety. When dealing with EV systems that deliver voltages from 48 volts to 800 volts, you can't take any chances.

To deliver more than 100 kilowatts of power the instant the driver presses the pedal, the battery system must operate efficiently at hundreds of volts. However, lithium batteries can only deliver a few volts. To get enough power, a large number of cells need to be connected in series to form a long battery stack. A typical electric vehicle might use 100 individual cells to deliver 350 volts at the top of the battery stack. But this poses some challenges.

In a long battery stack, if one fails, effectively all of them fail. So you need to monitor and manage all of them—charge and discharge them, every day of the vehicle’s lifecycle. Lithium batteries cannot operate at extreme charge and discharge conditions, but must be kept within a very specific range, such as 15% to 85%, or the battery performance will degrade.

Monitor and manage power
ADI's BMS provides accurate battery measurement information throughout the battery pack lifecycle, from production to end of life. Electronics are directly connected to each cell in the battery stack, reporting voltage and temperature corresponding to the cell current. The system provides state of charge and state of health. The current and temperature of each cell must be monitored by complex algorithms in the central processor. ADI has built in a powerful communication interface while supporting a modular design (architecture). It is fully scalable and suitable for our different customer groups.

“The BMS continuously monitors the battery, providing reliable measurement accuracy at all times and across a wide range of temperatures and operating conditions. The system knows what is happening at every moment and relies 100% on the information it receives from the ADI chip.”

Mike Kultgen, General Manager, ADI BMS

Key Value: Accuracy, Reliability, and Stability
The benefits of working closely with ADI’s battery management system experts extend beyond access to a broad range of components and products. They provide OEMs with our system-level expertise, deep domain knowledge, and years of real-world BMS design experience. OEMs can increase efficiency in driving miles per charge, extend battery life, ensure safety, and improve brand trust.

“Customers tell us they need to trust our products to use them,” said Patrick Morgan, vice president of AUTG at ADI. “So we host technical summits at their site or in our factory and invite our key designers and application engineers to meet with their teams. We spend a day or two introducing our roadmap, understanding the problems they need to solve, and then discussing how we will solve their specific problems. We build trust by focusing on collaboration.”

Solving Problems, Finding Solutions
"A customer based in Asia asked us to design a new battery management system around their legacy battery management system," said Cuyler Latorraca, applications manager at ADI. "We looked at their assumptions, system requirements, and operating environment. We discovered that their grounding scheme was causing errors in the system's measurements, a common problem in the industry, and took steps to eliminate that error."

ADI High-Performance BMS Powers Supercars

The Rimac C_Two high-performance supercar has 1,914 horsepower, a 0-60 mph acceleration time of 1.85 seconds, and a top speed of 258 mph. This all-electric supercar showcases Rimac's technological prowess, using a battery pack consisting of 6,960 lithium-manganese-nickel cells, fully demonstrating the true spirit of innovation and passion.

Founded about a decade ago in a garage in Croatia by a 21-year-old inventor, Rimac Automobili has grown into a 600-employee technology giant that designs, develops and manufactures electric supercars and high-performance electrification systems for global automotive companies.

With ADI's high-precision BMS integrated circuits (ICs), Rimac electric vehicles can extract the most energy and charge from the battery by taking high-precision measurements of the cells. Sophisticated diagnostics enable the system to monitor the battery's characteristics, voltage, and temperature to determine the state of charge at any time. "High accuracy translates directly into fast charging times, maximized battery capacity, and range," said Patrick Morgan, vice president of Automotive Electrification and Infotainment at ADI.

“Rimac is a technological powerhouse in the field of high-performance electric vehicles. We develop and manufacture key electrification systems for many of the world’s automotive companies, while our own supercars are setting a higher bar for electric vehicle performance,” said Mate Rimac, CEO of Rimac. “The battery management systems we use are some of the most demanding applications in the world, requiring extremely high precision, large current and voltage changes in a very short time, and fast dynamic adjustments within the battery management control system. We decided to use Analog Devices’ portfolio of battery management ICs across our entire product line. We have compared and selected Analog Devices’ products based on their ability to provide high-precision measurements and product reliability over the entire lifecycle of the vehicle.”

Looking to the Future
“High-voltage battery system technology is advancing at a rapid pace,” said Greg Zimmer, BMS marketing manager at ADI, “and we are under a lot of pressure to increase capacity and extend service life. How will the industry achieve this? How do we get more power out of the battery pack, increase its range, support faster charging, and develop centralized and modular designs while building batteries that last 10 years?

ADI is not only focused on the problems our customers are facing today, but also on the future and the process of continuous improvement. We will continue to lead the industry with solutions that maximize range per charge, reduce overall weight, and lower the total cost of the battery system. Our extensive system-level experience and large portfolio of components (3 to 18 cells in one IC, supporting more battery options than any other competitor) set us apart from the competition.

We haven’t reached peak BMS yet.
ADI is working with OEMs to improve how power density, accuracy, and weight challenges will be addressed and communicated in the future through architectural innovations. We will continue to innovate, and our 5th generation BMS is on track to be in production vehicles next year.

BMS: ADI Advantages
ADI is a leader in battery management systems, meeting the growing demand for safe, high-quality, high-performance batteries in the EV market. With rich system-level experience and diverse component products, the partnership we provide will benefit customers greatly.