Automotive
Wireless battery management systems - enabling smart battery ecosystems solutions through higher battery performance, greater lifetime, and cost value
By Stephan Prüfling, product manager, battery management systems at AVL, and Norbert Bieler, director, business development e-mobility at Analog Devices
E
lectrification of passenger cars and commercial vehicles is entering a new phase of market penetration. The shift away from technology feasibility demonstration to the mass production of premium vehicles is obvious. The commercialisation of technology leads to more optimised and affordable vehicles. Nevertheless, most current generation electric vehicles (EVs) are still considered as expensive or less attractive when compared to conventional combustion engine cars. Consequently, cost reduction and improved performance are key to ensure a successful and sustainable market growth. Reduction of size, weight, and cost impacts the competitive edge of battery systems over a vehicle’s complete lifecycle. On the other hand, the extension of the driving range will also have a significant impact on their market attractiveness and competitiveness. Furthermore, as the increasing numbers of EVs
reach the end of their life, car manufacturers will even be competing for the value to be derived from second life batteries recovered from scrapped vehicles.
Out of this demand, news about battery innovations tends to highlight the new battery packaging concepts and new materials that might one day be able to store more charge than today’s lithium technology. A different part of the battery - the battery management system (BMS), which monitors the state of charge (SOC) and state of health (SOH) of the battery - tends to go under the radar but needs to follow and support battery innovation. Here, the new wireless BMS (wBMS) technology, developed by Analog Devices and pioneered by General Motors in its modular Ultium battery platform, is now released to mass production. The wBMS gives car manufacturers a new competitive edge across the whole of a battery’s life - starting from when battery modules are first assembled, to
operation in an EV, beyond to disposal, and even, if needed, into the battery’s second life.
Wired battery connections - the costly, heavy, and complex approach The intention for the wBMS technology development was based on an analysis of the drawbacks of the communications wiring in today’s conventional EV battery packs. This analysis drew on ADI’s expertise: it supplies the market’s most accurate BMS ICs in the wireless communications field. ADI also developed the world’s most robust mesh networking technology for industrial environments. In a conventional EV battery pack, each cell is measured by a battery management IC. Data from the battery management IC are then communicated back to the pack ECU through wiring. This requirement for communications inside the battery reflects the complex architecture of a large battery pack: it is typically made up of modules, each
Figure 1. A typical multicomponent wired BMS network (left) and the simpler arrangement made possible by wBMS technology (right).
of which contains multiple cells. Natural production variations mean that each cell has individual characteristics that vary within a specified tolerance range. To maximise battery capacity, lifetime, and performance, the key parameters of battery operation - voltage, charge/discharge current, and temperature - need to be monitored and logged individually for each module. This is the reason why an EV’s battery requires a means to transfer data from each module or cell, where voltage and temperature are measured, to the ECU processor (see Figure 1). Traditionally, these connections have been made with wires: wired connections have the advantage of being familiar and well understood.
The disadvantage of a Wired BMS However, there is also a list of disadvantages related to wires: a copper wiring harness adds additional weight and occupies space that,
14 February 2023
Components in Electronics
www.cieonline.co.uk.uk
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