How to implement smart battery ecosystem solutions

The electrification of passenger cars and commercial vehicles is entering a new phase of market penetration. The shift from technical feasibility demonstration to mass production of premium vehicles is evident. The commercialization of technology leads to more optimized and affordable vehicles.

Nevertheless, most of the latest generation of electric vehicles (EVs) are still considered expensive or less attractive than conventional internal combustion engine vehicles. Therefore, reducing costs and improving performance are key to ensuring successful and sustainable market growth. Reducing size, weight and cost will affect the competitive advantage of battery systems throughout the vehicle's life cycle. On the other hand, extending the driving range will also have a significant impact on its market attractiveness and competitiveness. In addition, as more and more electric vehicles reach the end of their life, automakers will even compete for the value of second-hand batteries recovered from scrapped vehicles.

Because of this demand, news about battery innovations tend to highlight new battery packaging concepts and new materials that may one day be able to store more charge than today’s lithium technology. Another part of the battery – the battery management system (BMS) that monitors the state of charge (SOC) and state of health (SOH) of the battery – is often not well known but is needed to track and support battery innovation.

Here, new wireless BMS (wBMS) technology developed by Analog Devices and pioneered by GM in its modular Ultium battery platform is now being released to volume production. wBMS offers automakers a new competitive advantage over the entire lifecycle of a battery – from when the battery module is first assembled, through operation in an electric vehicle, to disposal, and even into the battery’s second life when needed.

Wired battery connection - expensive, cumbersome and complex approach

The intention of developing wBMS technology is based on an analysis of the shortcomings of communication wiring in today's traditional electric vehicle battery packs. This analysis draws on ADI's expertise: it provides the most accurate BMS ICs on the market for wireless communication. ADI also develops the world's most powerful mesh network technology for industrial environments.

In a traditional EV battery pack, each battery cell is measured by a battery management IC. Data from the battery management IC is then transmitted back to the battery pack ECU via wiring. This requirement for intra-battery communication reflects the complex architecture of a large battery pack: it is typically composed of modules, each containing multiple cells. Natural production variations mean that each cell has individual characteristics that vary within specified tolerances. To maximize battery capacity, life, and performance, the key parameters of battery operation—voltage, charge/discharge current, and temperature—need to be monitored and recorded individually for each module.

That’s why an electric vehicle’s battery needs a way to transmit data from each module or unit that measures voltage and temperature to the ECU processor (see Figure 1). Traditionally, these connections have been made with wires: The advantage of wired connections is familiarity and ease of understanding.

Figure 1. A typical multi-component wired BMS network (left) and a simpler arrangement enabled by wBMS technology (right).

Disadvantages of Wired BMS

However, there are a host of disadvantages associated with wires: copper wiring harnesses add extra weight and take up space that, if filled by batteries, would provide additional energy capacity. In addition, the wiring needs to be fixed to the battery housing structure, and the connectors can be subject to mechanical failure, especially under vibration and shock conditions.

In other words, wires increase development effort, manufacturing cost, and weight, while also reducing mechanical reliability and available space. This results in reduced driving range. By removing the wiring harness, automakers gain new flexibility to meet vehicle design requirements for their battery pack form factor.

The complexity of the battery harness also makes assembly of the battery pack difficult and expensive: the wired pack must be assembled and the connections must be terminated manually. This is an expensive and dangerous process as the high-voltage EV battery modules are charged. To maintain the safety of the assembly process and protect the production line workers, strict safety protocols are employed.

For these reasons, OEMs have strong reasons to introduce powerful wireless technologies into new EV battery system platforms.

wBMS — A new smart approach

The wBMS is a complete solution that is easy for automakers to integrate into battery pack designs. It includes a wireless cell monitoring controller (wCMC) unit for each battery module and a wireless manager unit for controlling the communication network that wirelessly connects multiple battery modules to the ECU. In addition to the wireless part, each wCMC unit also includes a BMS that performs high-precision measurements of various battery parameters so that the application processing unit can analyze the battery's SOC and SOH.

While wBMS technology takes full advantage of eliminating wiring harness design and assembly issues, there are further areas in the battery lifecycle where additional value will be generated:

Battery Assembly - The only connection required for a battery module is the power terminal, which can be easily accomplished through a highly automated process. This also avoids safety risks for assembly line workers by eliminating manual labor for assembly and testing. In addition, the modules can also be tested and matched before being installed inside the battery.

Repair—The secure wireless feature means that the condition of the battery pack can be conveniently analyzed by diagnostic equipment in authorized garages without touching the battery pack. If a fault is detected, the faulty module can be easily removed and replaced. The wireless configuration simplifies the installation of new modules in the battery system.

Second life - As the number of vehicles increases, a market for second life batteries that are recovered from scrapped electric vehicles and reused in applications such as renewable energy storage systems and power tools is emerging. This also creates a new source of value for electric vehicle manufacturers who are responsible for recycling or disposing of batteries from scrapped electric vehicles, as wBMS allows for simpler integration of modules for second life applications.

Disposal – Recyclable metals and potentially hazardous materials within the battery pack require approved and regulated disposal arrangements. Simple connections and no communication harnesses make battery module removal easier and faster than with wired batteries.

Data Management – ​​wBMS technology makes it easy to read key battery data from each smart module: this means the condition of the battery can be determined individually. For example, this data can provide information about the SOC and SOH of the module. Combined with the data from when the module was originally produced, this allows for its second life application and provides a detailed set of specifications for each module sold. The ready availability of this data increases the resale value of the module.

ADI's complete wBMS solution

The wireless network protocol implemented by ADI in the wBMS system meets the automotive industry's requirements for reliability, safety and security under all operating conditions based on full network time synchronization technology. The use of wBMS in GM's mass-produced electric vehicles has proven its reliability in the harshest environments: batteries based on wBMS have traveled hundreds of thousands of kilometers in more than 100 test vehicles, on-road and off-road, and in conditions from the desert to the frozen north and the harshest.

With wBMS, ADI also supports automakers’ initiatives to comply with the ISO 26262 functional safety standard. The radio technology and network protocols are developed in such a way that the system is resilient in noisy environments and uses sophisticated cryptography to provide secure communications between monitoring units and managers. The security measures prevent unintended recipients such as criminals or hackers from spoofing the data transmitted on the wireless network. In addition, the transmitted data is received without modifying the content, and the intended recipient knows exactly which source sent the message.

Lifetime management of battery value

Throughout the lifecycle of a battery pack, from initial assembly to disposal and into its second life, wBMS functionality embedded in the battery pack ensures that vehicle manufacturers and their owners can easily track the condition of the battery, maintain performance and safety, and maximize value. The entire system, including the interaction between the battery module’s cell monitoring unit and the ECU, is handled by ADI’s technology, with configuration settings defined by the manufacturer.

wBMS technology is also backed by ADI's Battery Lifecycle Insight Service (BLIS) technology. This provides edge-based and cloud-based data software to support traceability, production optimization, storage and transportation monitoring, early fault detection, and life extension. Together, wBMS and BLIS technologies enable automakers to achieve a higher return on their investments in battery pack development and production, improve the economics of their electric vehicle business strategy, and help accelerate the market's transition to a low-carbon, sustainable future for personal mobility.

The key to designing and enabling such battery solutions using wBMS is system understanding as well as the methods and tools that support the above designs and technologies. AVL provides a full range of simulation, testing, engineering capabilities and experience to successfully drive these innovations together with customers and bring them to market by preparing for mass production. AVL is currently working heavily on battery ecosystem solutions by developing data analysis methods, predictive capabilities supported by virtual development, and vehicle and battery data to improve the life and performance of batteries.