In an electric vehicle, the main powertrain components include the battery system, power management system, inverter/converter, onboard charging system, drive system, and regenerative braking system. Because there are no tailpipe emissions, EVs have historically been excluded from formal California Air Resources Board (CARB) onboard diagnostic (OBD) regulations; however, this will likely change as the number of EVs on the road increases. In November 2023, CARB announced a road map for setting OBD requirements for EVs.
THE CHALLENGE
Battery and battery system technologies (e.g., battery chemistries, diagnostic sensors, control algorithms, pack configurations, etc.) are evolving rapidly to facilitate efficient and rapid electrification of the transportation sector. As technological advancements accelerate, the automotive industry must continually develop and improve upon methods to assess the impact of battery utilization on performance and safety across the entire EV lifespan. These methods that are being developed for EVs are in many ways analogous to the onboard diagnostic (OBD-II) tools used in vehicles with internal combustion engines to control emissions, ensure reliability, and routinely diagnose and communicate vehicle health.
EXPONENT'S MULTIDISCIPLINARY SOLUTION
How can we improve our understanding of battery diagnostics to create tools that will support vehicle electrification? For example, what are the most reliable techniques to accurately estimate the state-of-health (SOH) of the battery pack? Are those predictive tools designed to account for and evaluate different user profiles and environmental conditions? The ultimate objective is to optimize the total lifecycle management of the battery; accurate diagnostics can help establish effective secondary markets for EV batteries and support related sustain ability initiatives by assessing a battery's remaining life span and potential future uses.
Batteries & Energy Storage Technologies Consulting
Exponent has performed extensive battery safety, performance, and aging testing studies to understand the variation in battery behavior given different operating parameters, environmental conditions, and abuse mechanisms.
Electrical Engineering
Leveraging in-depth working knowledge of electronic control units in EVs as well as their communication protocols, controls, and implementation, Exponent has analyzed the accuracy of different sensors in a battery pack and execution of diagnostic protocols designed to assess battery life.
Data Sciences
Exponent has analyzed vehicle telemetry to develop proof-of-concept for data-driven diagnostic tools, providing parameters for in-depth data studies such as expected battery aging according to various aging conditions, including cycle count, vehicle mileage, balancing circuit activity, etc.
Thermal Sciences
Exponent has expertise in mitigation strategies that can help improve safety and decrease the likelihood of thermal runaway events in large-format EV battery packs, including tools involving onboard diagnostics and system controls.
Vehicle Engineering
By providing the legal requirements for onboard diagnostics tools and elucidating the implications for OEMs, drivers, and regulatory agencies, our experts have laid the groundwork for identifying and developing OBD-II indicators in EVs.
EXPONENT'S IMPACT
Through the execution of battery characterization studies, Exponent is helping our clients understand the influences of charge and discharge strategies, as well as environmental conditions, on the degradation of lithium-ion batteries and their consequential effects on safety and performance. The findings from these studies are instrumental in developing algorithms that enhance the precision of battery SOH predictions.
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