Acculon Energy

The Energy-Power Equation: A Balancing Act for Optimizing Energy Storage Systems

This week, we’re rounding out our 3-part series on cell selection & its importance in battery module & pack design. Join our discussion on both energy & power density & what they mean when considering your application’s requirements. 

Contact: Betsy Barry
Communication Manager

Achieving optimal performance and range in electric vehicle (EV) applications hinges on the capabilities of the energy storage system. The key challenge lies in meeting both the maximum power and energy requirements in a proportional manner. However, this feat is not easily accomplished due to the characteristics of most Lithium chemistries. Although Lithium chemistries are widely used in battery systems for their high energy density, these chemistries often exhibit a tradeoff between power and energy capabilities. Typically, a given chemistry excels in either providing high power or extended energy storage, making it challenging to strike a complementary balance between the two.

A common issue in the process of designing a battery pack is focusing solely on the energy requirements, which translates to how long the EV should run. Consequently, this approach may neglect the crucial aspect of power requirements, leading to potential setbacks in performance and creating a bottleneck in the overall design process. For example, if a battery pack is sized only for energy, it may encounter higher currents than it is capable of safely handling. This, in turn, can result in accelerated aging through mechanisms like increased heat generation. 

When designing an optimal energy storage system, it is important to consider the power and energy aspects cohesively. Identifying the true power requirements can be a challenging task, especially in applications where current spikes are sporadic and unpredictable. Herein lies the significance of understanding the duty cycle of the application and adopting a systems approach during battery pack design.

The duty cycle, representing the operational characteristics of the application, plays a pivotal role in sizing the battery pack correctly. Oversizing is a common pitfall, often driven by a lack of insight into how the pack will be utilized in real-world scenarios. By accurately understanding the duty cycle, the overall cost of the battery system can be reduced without compromising performance.

By taking a systems approach to battery pack design, should a scenario arise where the pack is undersized for power, proactive measures can be taken to mitigate accelerated aging. Implementing an appropriately sized, active thermal management system can effectively reduce the temperature of the battery, preserving its longevity. Similarly, intelligent control strategies further enhance the adaptability of undersized packs. These strategies can rate-limit the current, preventing the pack from exceeding its power capabilities and ensuring a more controlled and sustainable operation. In rare cases where the pack is undersized for energy, the overall system efficiency can still be optimized by selecting and controlling other components within the system or vehicle in an appropriate manner. This holistic approach ensures that, even in less-than-ideal scenarios, the system operates optimally and performance is not compromised.

When designing a battery pack, it is essential to consider both energy & power density to ensure
your energy storage system can proportionally meet
both the power & energy requirements of your application.

It’s crucial to acknowledge that there is no silver bullet in Li-Ion technology. Every choice involves a tradeoff, whether it be between power and energy, cost and performance, or a range of other considerations. Successful EV applications demand a nuanced understanding of these tradeoffs and a thoughtful, integrated approach to system design.