A Battery with MSMD model & NTGK E-chemistry CFD simulation is an essential engineering tool for understanding the performance of lithium-ion batteries, which power everything from electric cars to smartphones. The C-Rate effect on Battery Performance CFD is a critical area of study because it determines how fast a battery can be safely charged or discharged. A Battery fluent analysis using ANSYS Fluent provides a virtual window into the complex physics inside a battery cell.

This report details a lithium-ion battery CFD study that uses the advanced MSMD model fluent provides, coupled with the NTGK Fluent electrochemistry model. This powerful combination allows us to simulate the linked electrical and thermal behavior of a battery. By investigating different C-rates, this Battery CFD analysis shows designers exactly how demanding more power from a battery creates more heat. This understanding is crucial for designing effective cooling systems, preventing thermal runaway, and finding the perfect balance between fast performance and long-term battery health and safety.

Figure 1: A conceptual diagram explaining the meaning of Battery C-Rate.

Figure 2: A schematic showing the internal components of a lithium-ion battery cell, including the anode, cathode, and separator, which are modeled in this Fluent CFD simulation.

Simulation Process: A Transient MSMD-NTGK Model for C-Rate Analysis

The simulation process for this Battery C-rate study began with a 3D geometry representing a single, fundamental lithium-ion cell, complete with one anode and one cathode. To ensure both accuracy and speed, a fully structured mesh was created using high-quality hexahedral cells that are perfectly aligned with the internal layers of the battery. This type of mesh works exceptionally well with the MSMD battery model in ANSYS Fluent. The simulation physics was set up by activating the Multi-Scale Multi-Domain (MSMD) model, which was then coupled with the NTGK electrochemistry model. This crucial step allows Fluent to solve for the electrical current, chemical reactions, and heat generation all at the same time.

To investigate the core question of this study, three distinct discharge scenarios were simulated: a slow 0.5C rate, a standard 1C rate, and a very fast 5C rate. To simulate realistic cooling, a convective heat transfer condition was applied to all the outer surfaces of the battery. To ensure the simulation was realistic and safe, voltage limits were set between a minimum of 3V and a maximum of 4.3V, just like a real Battery Management System. The entire analysis was run as a transient simulation with the energy equation enabled.

Post-processing: CFD Analysis of the Electro-Thermal Penalty of High C-Rates

The simulation results tell a complete engineering story about the trade-off between power and performance. The data clearly shows that asking for a faster discharge (a higher C-rate) directly causes a penalty in both the battery’s electrical stability and its thermal safety. The analysis starts with the electrical performance, shown in Figure 3. The voltage plots reveal the “cost” of drawing current quickly. At a slow 0.5C rate, the voltage drops gently from 4.11V to 4.03V over a long period. At the standard 1C rate, the drop is slightly faster. However, at the aggressive 5C rate, the penalty is severe: the voltage starts lower at 3.97V and falls steeply to 3.82V in just 70 seconds. From an engineering viewpoint, this sharp voltage drop is caused by increased internal losses. The high electrical current demanded by the 5C rate magnifies the effects of internal resistance and polarization within the battery’s chemistry, making it less efficient at delivering its stored energy.

Figure 3: A combined plot and contour display from the MSMD-NTGK analysis. The plot shows the terminal voltage drop over time for each C-rate, while the contours illustrate the voltage distribution across the cell electrodes.

This high electrical current is also the direct cause of the thermal problems, as shown in Figure 4. The temperature plots are a mirror image of the electrical demand. At 0.5C, the temperature rise is tiny, only to 300.29K. At 1C, it’s a manageable rise to 300.61K. But at 5C, the temperature shoots up to 303.97K in just over a minute. This is a significant and potentially dangerous increase. The temperature contours explain why and where this happens. The heat is not generated evenly; it is concentrated at the cathode and anode tabs. This is because the tabs act as electrical bottlenecks where the current density is highest, leading to intense resistive heating (Joule heating). The simulation proves the direct link: higher C-rate means higher current, which means more intense localized heating.

Figure 3: A combined plot and contour display from the Fluent simulation. The plot shows the maximum cell temperature over time for 0.5C, 1C, and 5C discharge rates, while the contours visualize the temperature distribution inside the cell for each case.

The most important achievement of this simulation is the successful quantification of this electro-thermal penalty. We now have exact numbers that connect a specific C-rate to a specific voltage drop and a specific rate of temperature rise. For a battery designer or manufacturer, this data is invaluable.

1. Defining the “Red Line”: This model allows engineers to define a safe operational envelope. They can now tell the end-user that continuous operation at 5C is not recommended because it will rapidly heat the battery and reduce its effective voltage, providing a data-driven basis for product guidelines.
2. Smarter, Targeted Cooling: The simulation proves that the tabs are the problem areas. Instead of cooling the entire battery, designers can use this information to create a smaller, lighter, and cheaper cooling system that focuses its efforts directly on the battery tabs, where it is needed most.
3. Optimizing the Performance-Lifespan Balance: This CFD model is a powerful tool for finding the “sweet spot.” A designer can see that by reducing the maximum discharge rate from 5C to 3C, they might only lose a small amount of peak performance but could cut the heat generation in half. This leads to a battery that is safer, lasts for many more cycles, and is ultimately a better and more reliable product.