Unveiling the hidden factor behind operating temperature, cooling technologies and fast charging of Lithium-ion battery packs

Introduction

Beneath the sleek exteriors and cutting-edge features of Lithium-ion battery packs, lies a complex challenge: ensuring these battery packs perform optimally, stay safe, and endure for the long haul. Amid this challenge, a technique known as impedance measurement has emerged as a crucial tool. In this blog, we delve into the depths of impedance measurement, exploring its significance, the untold stories it reveals, and the reasons why it should find its place in the datasheets of lithium-ion battery packs.

Understanding Impedance

At its core, impedance (Z) is a complex ratio—voltage (V) to current (I)—in an AC circuit. It's an amalgamation of resistance (R) and reactance (X), accounting for capacitive and inductive elements.

In the context of lithium-ion batteries, impedance holds the key to unravelling a battery's inner workings and health.

Z=R+jX, Where j is the imaginary unit.        

AC Impedance Measurement: Advancements and Insights

By applying alternating current and measuring the voltage response, AC impedance measurement provides a window into the battery's behavior. Recent strides have brought precision frequency sweep techniques, allowing researchers to extract intricate details about electrochemical reactions and ion transport processes. Modern analyzers, empowered with automation and advanced algorithms, fast-track battery diagnostics and real-time monitoring.

Ztotal=R internal+1/jωCtotal1+..., 

Where,
Rinternal is the internal resistance of the battery.
Ctotal represents the total capacitance.
ω is the angular frequency of the AC signal.        

DC Impedance Measurement: Beyond Resistance

While traditionally assessing internal resistance, DC impedance measurement has expanded its horizons. It now characterises parameters like cell health, enabling more accurate lifespan predictions.

Predictive Analytics: The Art of Foreseeing

Impedance measurement propels predictive analytics for battery health. Machine learning integration empowers algorithms to spot subtle patterns in extensive datasets—patterns that human eyes might miss. These algorithms then deliver more accurate battery health predictions, optimising battery management and maintenance strategies.

Cooling and Temperature: The Unseen Impacts

Impedance measurement also reveals insights about cooling technology. A cooling system's efficiency affects temperature distribution within the battery pack.

Temperature changes impact impedance: high temperatures enhance conductivity, lowering impedance, while low temperatures impede ion mobility, raising impedance.

Monitoring impedance fluctuations aids in detecting cooling system effectiveness and potential thermal imbalances.

Operating Temperatures: The Impedance Connection

Operating temperatures deeply influence impedance. Lithium-ion batteries have optimal temperature ranges for performance and safety. Extreme temperatures—either too hot or too cold—cause impedance fluctuations. Extremely cold conditions lead to higher impedance due to decreased ion mobility, whereas excessive heat reduces impedance through increased ion mobility.

Operating within the optimal temperature range is vital for maintaining stable impedance and ensuring battery longevity.

Impedance in Datasheets: The Missing Link

Despite its significance, impedance measurement often remains absent from lithium-ion battery datasheets. This omission arises from the complexity of impedance data and the challenge of simplifying it for non-experts. Datasheets usually spotlight straightforward specifications like capacity, voltage, and cycles.

The growing importance of impedance in assessing battery health and performance indicates a need for its inclusion in future datasheets.

Conclusion: Illuminating the Path Forward

Impedance measurement is far more than a diagnostic tool—it's a key driving force behind lithium-ion battery technology. As AC and DC impedance measurement techniques advance, as predictive analytics integrate machine learning, as real-time monitoring becomes feasible, and as cooling and temperature effects are unveiled, the role of impedance in shaping our electrified future is ever clearer.

As we stand on the brink of a battery-powered era, it's crucial to recognize impedance measurement's vital role. It's a tool that not only reveals hidden truths about battery behaviour but also guides us toward safer, more efficient, and longer-lasting battery solutions. Let's imagine a world where impedance measurement finds its rightful place in battery datasheets, where consumers and experts alike can gain insights into the heart of battery technology, and where this technique illuminates the path toward a sustainable and electrified future.

It's important to note that the views expressed in this newsletter are personal and do not necessarily reflect the views of any organisation or company mentioned herein.

I hope you found this newsletter informative and thought-provoking. If you have any questions or feedback, please don't hesitate to reach out.

Best regards,

GM

About the Author

Ganesh Moorthi

I am an accomplished Lithium-ion Battery Pack Expert and Energy storage Expert with over a decade of experience in designing and developing EV and ESS battery packs. Throughout my career, I have spearheaded the technology development of Battery Packs and Battery management systems with different AFE's and architectures. I have also led the development of Hardware, Firmware, Packaging, and Software for Energy Storage Systems. I possess a deep understanding of Lithium-ion chemistry and have demonstrated expertise in the production of LiB's with proprietary technologies. With my extensive educational qualifications and vast experience, I believe I can bring unique perspectives about the Energy Storage industry.

Image by Vectorjuice on Freepik