Date:2025.10.27
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The Source: Heat Generation Inside the Cell
To manage heat, we must first understand its origin. Within a battery cell, heat generation stems from two primary sources:[1]- Irreversible Heat (Ohmic Heating): This is the dominant source of heat during operation and is caused by the battery's internal resistance. As current flows through the cell, it encounters resistance, which generates heat—much like a standard electrical resistor. A key takeaway for system designers is that a cell with lower internal resistance will inherently generate less heat under the same load, making it a safer and more efficient foundation for the entire pack.
- Reversible Heat (Entropic Heat): This refers to the heat generated or absorbed by the electrochemical reactions themselves. Depending on the specific chemistry and the direction of the current (charging or discharging), these reactions can either release or absorb a small amount of thermal energy. While less significant than ohmic heating, it is still a factor in the overall thermal profile of the pack.
Passive Cooling Techniques
Passive battery thermal management involves dissipating heat without consuming additional power from the system. These methods are ideal for lower-power applications or as a supplementary part of a more complex system.- Heat Sinks and Conduction: The most common approach is to use thermally conductive materials to draw heat away from the cells. This is often achieved with aluminum or copper heat sinks or cold plates that provide a large surface area to dissipate heat into the surrounding air or a chassis component.
- Thermal Interface Materials (TIMs): To ensure efficient heat transfer from the cells to a heat sink, TIMs like thermal pastes, pads, or adhesives are used. They fill microscopic air gaps between surfaces, dramatically improving thermal conductivity.
- Phase Change Materials (PCMs): These advanced materials absorb significant amounts of heat at a specific temperature by changing their physical state (e.g., from solid to liquid). PCMs can effectively absorb heat spikes during high-load events, keeping the cell temperature stable.
Active Cooling Systems
For high-power applications like EV battery thermal management, passive methods are insufficient. Active systems, which consume energy to function, are required to remove heat more aggressively.- Forced Air Cooling: The simplest active method involves using fans to blow air over the battery modules. While cost-effective, it is generally less efficient than liquid cooling.
- Liquid Cooling: This is the predominant method for high-performance systems. A coolant (typically a water-glycol mixture) is circulated through channels or cooling plates integrated into the battery pack. The liquid absorbs heat from the cells and transports it to a radiator, where it is released into the ambient air.
- Direct Refrigerant Cooling: The most powerful active method uses the vehicle's air-conditioning refrigerant to directly cool the battery pack. This offers superior cooling performance, enabling faster charging and better performance in extreme climates.
System-Level Strategies for Preventing Thermal Runaway Propagation
Even with a robust thermal management system, the risk of a single cell failure—due to a manufacturing defect or physical damage—must be contained. A well-designed battery pack thermal management system includes multiple layers of defense to prevent a single cell failure from cascading into a full-pack thermal runaway event.- Fire-Retardant Barriers: Placing physical barriers made of fire-retardant materials between cells or modules can slow or stop the spread of heat and flames from one cell to its neighbors.
- Pack Venting Design: In the event of a cell failure, a large volume of hot gas is released. A carefully designed pack enclosure with dedicated vents can safely channel these gases away from the pack, preventing a dangerous pressure buildup.
- Advanced BMS Shutdown Protocols: The Battery Management System (BMS) is the intelligent brain of the pack. Beyond its core functions of monitoring temperature and voltage, an advanced BMS uses predictive algorithms to detect the early warning signs of a cell fault. If an anomaly is detected, the BMS can take proactive measures, such as isolating the faulty cell block and initiating a controlled shutdown to prevent a catastrophic failure.
Conclusion
A comprehensive battery thermal management system is a complex integration of mechanical design, thermal science, and intelligent electronics. However, the effectiveness of any cooling system is ultimately dependent on the quality and thermal stability of the individual cells within it.At Great Power, we understand that a battery pack is only as strong as its weakest cell. With over two decades of specialized R&D, we have mastered the art of engineering cells that form a reliable foundation for any safety strategy. Our nine global production facilities leverage advanced automation to produce cells with exceptional consistency and low internal resistance, minimizing the primary source of heat from the very start. By integrating advanced safety components like ceramic-coated separators and partnering with clients to ensure our cells work seamlessly with their BMS, we provide the building blocks for safer, more reliable energy storage solutions.
Learn how our advanced cell technology can be the foundation of your safety strategy. Schedule a technical consultation with our engineering team today.
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