Acculon Energy

Chemistry Comparisons: A Use Case in Driving Efficiency via Designing Optimized Energy Storage Systems For Golf Cars

Today, we are going to embark on a journey to compare various battery cell chemistries within the context of a specific use case: golf cars. Join us as we aim to explore the value proposition offered by an energy storage system tailored to meet the unique requirements of GS2-size solutions commonly employed in golf cars.

Contact: Betsy Barry
Communication Manager

Some key drivers behind the electric vehicle movement are its potential to significantly slash greenhouse gas emissions, curb pollution, and lessen the impact of climate change.  Shifting to electric applications also unlocks economic opportunities, including stimulating growth and driving innovation, while creating a competitive edge in the global marketplace. That said, transitioning fleets or updating equipment requires an upfront investment. When considering this investment, we’re analyzing options based on the total cost of ownership (TCO) for the vehicles and equipment we electrify.  A focal point of these comparisons is the energy storage system that powers these applications.

Today, we’ll dive into a comparison of different battery cell chemistries. We’ll frame this comparison within a specific use case to explore the added layers of value an energy storage system can offer beyond a single TCO calculation. By taking a broader view, we can uncover other significant benefits that come with a safe, reliable, and optimal energy storage system designed specifically for your application’s needs.

However, before beginning to evaluate how different battery chemistries impact cost, it’s important to examine the variables and upfront assumptions that will influence a true “apples-to-apples” comparison. For this exercise, we will focus on golf cars as our “use case” application to create a practical point of reference.

So, our task at hand is to design a dependable and efficient battery system, specifically tailored for a GS2-size energy storage solution commonly used in golf cars. Several key factors demand consideration to ensure the device meets its intended purpose.

First and foremost, sizing is critical. The battery system must be the right geometrical size, store sufficient energy, and match the application’s voltage. This ensures it seamlessly integrates into the intended application without sacrificing performance or efficiency. Achieving the nominal voltage dictates the selection of a specific in-series cell arrangement, with 16s for LFP and SiBs and 14s for NMC-based chemistries being typical industry standards for 48V systems.

After analyzing available cell form factors, cylindrical cells emerged as the best choice for this particular application. Prismatic cells are typically big and intended for use in electric vehicles or stationary storage systems, meaning there are very few prismatic cells available in the required dimensions that can also meet the requirement needed for a 14s or 16s configuration within the constrained GS2 size dimensions. Geometrically suitable pouch cells are easier to find for this application, but they lack the structural robustness needed and require complex mechanical design to manage their expansion and guarantee long cycle life properly. Additionally, they lack a crucial safety feature: the current interruption device (CID). Only cylindrical cells offer enough flexibility in terms of geometrical cell orientation, a self-contained casing, and built-in safety components. Also, the fact that cylindrical cells come in common standard sizes forces cell manufacturers to compete on cost and quality, giving pack designers the ability to choose the very best cell based on a variety of factors from a selection of suppliers.

When designing a dependable & efficient battery system, considering variables & upfront assumptions is crucial for achieving an accurate comparison
& true TCO. Thorough evaluation during this process can also reveal the broader benefits of safety, reliability, & optimization.

The duty cycle plays a vital role in ensuring the device/equipment can handle the expected workload. In this case, the battery must support roughly 1-2 rounds of golf per day, with each round requiring 960Wh of energy. Standard practice dictates charging overnight without interruptions between rounds to maintain operational efficiency. Therefore, a 2kWh battery pack is the best choice, as the 48V nominal capacity of the pack needs to be about 45 Ah.

The table below outlines the impact of the selection of different chemistries for the GS2-size battery pack we are considering. We use normalized cost factors here based on real quotations and pack manufacturing costs.

This table nicely illustrates that the best chemistry might be different depending on the user application scenario. If you have a huge field and your drive is more than 2x of the average, the only chemistry that will last long enough might be NMC, or a user will need to use LFP/SiB in parallel. If the cost of operation (per drive) and/or cost per battery unit is the most critical factor, then SiB is the best choice. The LFP option is probably the most balanced. With the anticipated decrease in costs for SiB batteries as manufacturing ramps up and/or if lithium prices surge again, the cost advantage of SiB batteries for appropriate usage scenarios might become even more significant. Taking into consideration the safety and low-temperature performance of SiB makes the choice even more complicated; but currently, LFP is the top choice, with SiB emerging on its heels as an interesting option as well.

Effective heat management is crucial to prevent overheating and battery damage during operation. In this scenario, passive thermal management is preferred for its simplicity. Therefore, minimizing heat generation is a key design consideration.

Comparing heat generation rates between different battery pack capacities and chemistries within the same size constraints can be a complex topic to address concisely. However, it’s important to note that all three chemistries considered (LFP, NCM, and SiB) are suitable for passive thermal management in this application. LFP chemistry is known for its better tolerance of moderately high cycling temperatures compared to NMC cells. While data on SiB degradation at elevated temperatures is less established than for lithium chemistries, initial testing suggests that passive thermal management might also be sufficient for SiB in this application.

Safety remains paramount. The battery system must adhere to strict safety standards to safeguard both users and the environment from potential hazards. This includes measures to prevent overheating, overcharging, and short circuits, as well as ensuring compliance with relevant regulations and certifications.

By carefully addressing these considerations, the resulting battery system will be well-equipped to meet the demands of its intended application, providing reliable and efficient power for golf cars while prioritizing safety and longevity. 

Our exploration into the comparison of various cell chemistries and form factors shows the multifaceted advantages inherent in selecting the right energy storage solution. By contextualizing this evaluation within the specific gold car use case, we not only establish a practical benchmark but also highlight the importance of tailoring solutions to meet precise application needs. As we explored designing a dependable and efficient battery system, it was evident that considering variables and upfront assumptions is crucial for achieving an accurate comparison and true TCO. Beyond cost calculations, a thorough evaluation reveals the broader benefits of safety, reliability, and optimization, underscoring the strategic significance of investing in a custom energy storage solution that meets the requirements of your commercial or industrial application. Through this approach, we not only ensure operational efficiency but also pave the way for sustainable and cost-effective energy management practices.