As the electric vehicle (EV) industry grows, two main charging methods are shaping the conversation: battery swapping and fast charging. At Swapp Design, we believe battery swapping offers a more sustainable and scalable solution. However, we recognize that a well-designed fast charging station may be the right fit for certain user categories. Similarly, a poorly designed swapping station could fail to meet expectations. Ultimately, responsible utilization through responsible design is key to success in both approaches.
Let’s compare swapping with fast charging, focusing on sustainability and technology.
Sustainability and Responsible Resource Use
Power Variance Demand and Infrastructure Design
A fundamental difference between fast charging and swapping is the demand placed on the grid. Fast charging stations tend to have 14% higher peak power when compared to battery swapping. However, the critical difference lies in power demand's variance (fluctuation). Despite reaching a steady demand, swapping stations results in almost no variance, maintaining a stable, flat power demand. On the other hand, fast charging stations induce significant fluctuations, with power demand swinging by 35%—rising 14% above and falling 21% below the steady state value seen in swapping stations. This makes the fast-charging power graph resemble a toothsaw, while swapping presents a flat and operationally efficient power curve.
While the total energy deployed is the same for both methods, the peak power demand for fast charging places a higher burden on the grid. Infrastructure must be designed to handle this peak load, not just continuous power, meaning fast charging stations need larger, more complex systems to function effectively, also influencing capital and operational efficiencies. But it’s not just the infrastructure that gets oversized; components inside the battery, such as busbars and harnesses, are also scaled up to accommodate fast charging. These oversized components add weight, complexity, and cost to the overall design, leading to a less efficient solution.
In comparison, swapping stations distribute their power requirements more evenly, reducing the infrastructure burden and eliminating the need for oversized components.
Depth of Discharge (DoD)
Fast charging systems often rely on Depth of Discharge (DoD) to maintain fast charging speeds. This technique involves virtually limiting the battery's max and min threshold. While enabling fast speeds, this technique underutilizes the battery’s full capacity. It’s like carrying a 20-liter water bottle but only using 16 liters. This synthetically increases battery cycles, creating an illusion of longevity but wasting resources.
Battery Longevity
The general trend of fast charging affecting battery longevity is very well documented. This is evident even in innovative battery chemistries like lithium-titanate oxide (LTO), which are designed for longevity but still experience quicker degradation under rapid charging conditions. In contrast, swapping stations charge batteries under optimal conditions, using their full capacity and replacing them only when necessary. This responsible design leads to more efficient resource use and longer battery life.
Power Loss and Heat
Fast charging systems suffer from power loss due to high currents, manifesting as heat. The heat is proportional to the square of the current. So, if you are charging ten times faster, the heat is 100 times more. It is even greater as the battery ages because the internal resistance of the battery system also contributes to how much the battery heats up while charging. While cooling systems are commonly used to mitigate this, these measures only address the symptoms, not the root cause. The issue is significantly muted for swapping stations, as the charging rates are much lower. They’re designed to be more energy-efficient, without costly and complex cooling systems.
Technology and Grid Impact
Peak Power vs. Energy Consumption
In an apples-to-apples comparison, where the same number of EVs with the same battery capacity are to be catered by fast charging and swapping stations, it is obvious that both deploy the same amount of total energy. The critical difference lies in the peak power and the power variance/fluctuation. Fast charging demands a high variance in power, which leads to spikes in grid demand and requires the infrastructure to be designed for these peak loads. They must serve the EV in real-time as they draw the power from the grid. They cannot act according to how the grid is doing at any given time. Studies show that fast charging also contributes to voltage fluctuations, harmonic instability, harmonic emissions, and supraharmonics, all of which degrade the reliability of power systems and can negatively impact the power quality and shorten the lifespan of electrical distribution systems. These effects, compounded over time, reduce overall grid efficiency and increase maintenance costs.
In contrast, swapping stations offer a steadier energy draw. Unlike fast charging, which can cause disruptive power fluctuations, swapping stations can monitor the grid’s strength and adjust power draw accordingly. This flexibility allows swapping stations to minimize their impact on the grid, making them a more stable and predictable option in terms of grid management.
It’s important to avoid the myth that swapping stations only charge during non-peak hours. While it’s true that some charging can take place during off-peak times, charging during peak hours is inevitable to meet user demand. Otherwise, the number of batteries required at each station would increase significantly, which would be impractical. The responsible approach is how these stations are designed to manage power dynamically and align with grid conditions.
Oversized Investments: Infrastructure and Battery Components
Fast charging systems not only require oversized infrastructure investments—like larger transformers and heavy-duty electrical components—but also affect the components inside the battery itself. To accommodate the higher power demands of fast charging, internal components such as busbars, battery management systems (BMS), and harnesses are also oversized. This oversizing increases complexity, weight, and cost, ultimately leading to a less efficient overall system. Moreover, these bulky components are seldom used during the drive of most vehicles; discharge rates are significantly lower.
In contrast, swapping stations don’t require such heavy-duty components inside the battery. By operating at lower, controlled power levels, swapping stations can utilize the right-sized infrastructure and battery components, which results in lower costs and more efficient design. This leads to a better balance between performance and resource use, making swapping a more responsible economic and environmental solution.
Moreover, swapping stations act as floating assets. When the grid is in distress, algorithms detect it and refrain from overburdening it while serving EVs continuously. Therefore, there is isolation between the demand from EVs and the supply from the grid, helping to mitigate power fluctuation risks while stabilizing energy use.
Interoperability Challenges in Fast Charging
When considering fast charging, one crucial question is: Can a fast charging station cater to any EV with a compatible fast charging system or advanced cell? The reality is that EVs come in a wide variety of shapes and sizes—there are two-, three-, and four-wheeled vehicles, each with vastly different battery capacities. Even within the four-wheeled category, battery capacities can range from as low as 12 kWh to as high as 120 kWh. For which vehicle must we design the fast charging station?
If the goal is to get vehicles back on the road with a full charge in 30 minutes, do we aim to serve the smaller 12 kWh EVs or design for the larger vehicles with 120 kWh batteries? Designing for the smaller ones would leave the larger EVs unable to charge quickly. Conversely, designing for the large EVs—which are far fewer—would be irresponsible and inefficient for most vehicles, leading to oversized infrastructure. Building separate fast-charging networks for different vehicle categories seems impractical, and such an approach would be complex to scale effectively.
The answer to this dilemma would be a full-stack solution in which a fast-charging company also designs a standardized battery. However, the idea that all EVs would eventually adopt the same standard battery is unscalable—each vehicle type has its own unique needs.
By contrast, Swapp Design’s swapping approach faces no such issues. Our solution is fully scalable and can serve all 4-wheelers, whether large or small, using the same infrastructure. This flexibility allows for responsible resource utilization and ensures that no segment of the EV market is left behind.
Conclusion
For specific user groups, fast charging may be a practical choice. However, fast charging stations are subject to unpredictable factors, such as grid instability, temperature, and the EV battery’s state of charge. These can alter charge times and introduce variability into the user experience.
Swapp Design’s battery swapping offers a predictable and consistent experience. Drivers remain seated in their vehicles while the battery is swapped in 3 to 5 minutes. Moreover, we are on track to reduce this swap time to under 1 minute—a significant advantage made possible through our innovation, independent of external dependencies such as cell technology or the grid’s capacity.
And here’s a fun fact: The peak power of a 10-minute fast charging station would be 170% of that of a 1-minute swapping station. This staggering figure shows the strain fast charging could place on a single station level. This makes swapping a sustainable and scalable solution, in the limit.
At Swapp Design, we believe responsible utilization through responsible design is the cornerstone of a sustainable future for EV charging. While fast charging may be appropriate for certain users, battery swapping offers a more scalable, sustainable, and user-friendly solution. As the world moves toward electric mobility, we remain focused on building a future where responsibility is embedded in every design layer, from the grid to the vehicle, without compromising on a frictionless user experience.
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