Batteries are the centerpiece of modern technology, powering electric vehicles (EVs) and driving a more sustainable future. However, extreme temperature changes result in a loss of battery efficiency, lifespan, and performance.

This is where battery pack thermal management systems (BTMS) come in. They aim to stabilize temperatures within a certain range, usually from 20°C to 40°C.

Popular lead-acid and lithium-ion batteries’ optimal performance and safety depend heavily on effective thermal management, which directly impacts battery capacity and charging rate.

The EU has declared its intention to have at least 30 million zero-emission vehicles in operation by 2030, so it is a priority to tackle thermal management issues and maximize battery life.

To achieve such goals, renowned brands like Tesla and Chevrolet have already adopted this passive and active thermal management approach.

In this blog post, we’ll explore the challenges of battery pack thermal management and how advanced simulation techniques can help optimize performance, prevent failures, and ensure safe operation.

Battery Pack Thermal Management Issues: Heat Generation

The primary challenge in battery pack thermal management stems from the inherent heat produced during essential battery functions, such as:

• Heat Generation During Charge/Discharge: Chemical reactions within battery cells convert electrical energy to chemical energy (charging) and vice versa (discharging), generating heat as a byproduct.

• Impact of Charge/Discharge Rates: Faster charging and discharging rates produce more heat, posing a greater thermal management challenge.

• The Role of Ambient Temperature: High external temperatures can worsen heat buildup within the battery pack or limit the effectiveness of cooling systems.

Dangers of Inadequate Battery Pack Thermal Management

The effects of poor electrical management in electric vehicles can be dire. Overheating the battery can cause thermal runaway, which can lead to explosion or combustion. For example,

In October 2021, a thermal runaway caused two Pure EV ePluto e-scooters to  burst into flames, highlighting the severe safety risks associated with thermal management.

Here are some issues it may cause:

1. Thermal Runaway

As noted above, this is one of the most terrible outcomes. This event occurs when a battery starts to heat up, triggering a self-reinforcing reaction that can result in an explosion or fire.

Thermal runaway is a dangerous problem for both the vehicle’s passengers and people nearby. Therefore, adequate thermal control systems are necessary to prevent it.

For example, LG Chem introduced a new flame retardant material designed to significantly delay thermal runaway in electric vehicle (EV) batteries, potentially by up to 20 minutes, even at extreme temperatures of 1,500°C.

2. Performance Degradation

The heat-induced premature aging of batteries results in compromised capacity and life, which leads to performance degradation. High temperatures speed up chemical reactions occurring in the battery cells, leading to the electrolyte’s deterioration and eventually resulting in shorter battery life.

This is also known as ‘capacity fade,’ which leads to the loss of storage capacity. Eventually, detrimentally affects the long-term performance of EVs.

3. Safety Hazards

Improper thermal management might be a real threat to the safety and can cause fire and explosion. Prolonged heat may cause the battery elements to fail or degrade over time.

The safety issues that arise from battery thermal control underline the importance of using advanced cooling and heating systems to prevent hazards and ensure the safe use of electric vehicles.

Leveraging Simulation for Optimal Battery Pack Thermal Management

With simulation, engineers can virtually test different battery pack designs and cooling strategies. This allows them to identify potential thermal issues early on, optimizing performance and safety without the need for costly physical prototypes.

Here are some advantages of simulations in battery pack thermal management:

1. Virtual Prototyping

 Virtual prototyping through simulation can help with the following:

• Time and Cost Savings: Rapid iteration in the virtual world significantly reduces development time and expenses.

• Exploration and Optimization: Engineers can quickly evaluate various design variations and carefully optimize thermal management strategies for peak performance.

• Risk Reduction: Potential issues are identified early, minimizing the risk of failures and delays later in the development process.

2. Optimizing Heat Transfer

The test can be designed to cover different cooling systems, including air cooling or liquid cooling, which will serve to verify their ability to cool down the battery cells.

Thermal gradient and heat diffusion rate evaluations help engineers determine the most optimized cooling mechanism to match different battery pack configurations.

3. Predicting Thermal Behaviour

Modeling establishes temperature distribution within the pack at different operating conditions.

Engineers can predict areas of the highest temperature and thus develop the most efficient thermal management strategies through simulating heat creation, thermal conductivity of the substances, and airflow.

Battery Pack Thermal Management: How is the Thermal Simulation Performed? 

Performing Computational Fluid Dynamics (CFD), thermal analysis on lithium-ion battery packs for electric vehicle performance enhancement involves:

1. Geometry preparation structuring a 70-cell module with inlet and outlet sections.

2. Mesh generation to divide the geometry into small elements, selecting a medium-sized grid for efficiency.

3. Applying boundary conditions for fluid flow and heat transfer, including inlet/outlet specifications and thermal characteristics of the working fluid (air).

4. Initializing the simulation consistently from the inlet.

5. Running the simulation to calculate fluid flow and temperature distribution over specified time steps.

6. Post-processing and visualization to analyze variables like temperature and velocity, identifying areas for design improvement.

Some Use Cases of Applying Simulation

Here are some areas where battery pack thermal management simulation analysis may come in handy:

1. Cell Placement Optimization 

Simulations help evaluate heat generation based on different cell arrangements within the battery pack. Engineers can optimize cell placement by analyzing temperature profiles to minimize thermal gradients and prevent localized overheating.

2. Material Selection

Simulations measure the thermal conductivity of materials for battery housing and cooling systems. This allows engineers to evaluate the thermal properties of different materials and select the most appropriate ones to enhance heat dissipation and overall thermal management efficiency.

3. Control System Design

Simulating battery management systems (BMS) optimizes charging and discharging protocols for thermal stability.  Dynamically adjusting charging rates and discharge limits based on predicted thermal behavior helps BMS prevent overheating and ensure the safe operation of the battery pack.

Innovating Battery Pack Thermal Management with CFD Simulation

Simulation is indispensable in designing battery packs for electric vehicles, ensuring both safety and efficiency. By conducting CFD thermal analysis, potential overheating risks can be identified and mitigated, preventing battery failures and enhancing performance.

Future advancements in battery thermal management technology may include advanced cooling systems, phase change materials, and active thermal management strategies to optimize temperature control.

Mechartes’ expertise in CFD analysis, as demonstrated in our case studies can help design innovative solutions for battery pack thermal management, ensuring reliable and safe operation.

Explore our case studies on CFD simulation and more.