Battery Thermal Management Systems

Thermal management is vital for vehicle operation, range, and longevity when designing commercial zero-emissions vehicles. Navigating what you need for your commercial electric vehicle can seem daunting, so knowing what to look for is essential. The first thing to understand is determining what your battery packs need to stay operational for optimal vehicle performance. For optimal performance, the temperature of most Lithium Ion battery packs must be maintained in a narrow window – typically 20° C  to 45° C – regardless of ambient temperature during operation, charging, and discharging cycles. Since battery packs self-heat when the vehicle operates, charges, and discharges, the battery pack must be cooled. A battery thermal management system’s active or passive cooling loop will be activated depending on the battery packs and ambient temperature.

If the ambient temperature is far enough below the battery pack temperature, then a passive cooling loop can be used to reject heat from the coolant loop. This loop has a radiator to reject heat from the coolant to ambient air and an array of fans to increase airflow through the radiator to maximize heat transfer. The passive cooling loop comprises a radiator and smart electric components – an intelligent electric pump, coolant valve, and fans. When the coolant enters a battery thermal management system, the coolant is directed to the radiator based on the positioning of the coolant valve, which will direct the coolant to the passive cooling loop when the ambient air is far enough to the battery pack temperature during charging, discharging, and operation. The coolant will enter the radiator and reject the heat from the coolant to the ambient air, and an array of fans attached to the radiator are used to increase airflow through the radiator fins to increase heat transfer.

In the other instance, an active cooling loop with a refrigeration circuit will be required when the ambient temperature is above the battery pack temperature on a hot summer day. Heat is transferred from the coolant to a refrigerant in this loop through a chiller. Many chillers are vacuum-brazed layered-core heat exchangers with optional integrated expansion valves. These chillers are a heat transfer component. A chiller is part of a refrigeration circuit in battery thermal management systems. A chiller rejects heat from the coolant to the refrigerant. The compressor in the refrigeration cycle draws a lot of power during the active cooling operation. The passive cooling loop improves the COP (coefficient of performance) of the system 2-3 times generally.

On a cold winter morning, when the ambient temperature is -20° C and a vehicle sits idle, the battery will likely be cold-soaked. In freezing temperatures, the chemical reaction inside the battery slows down, raising the internal resistance. This, in turn, can reduce the battery pack’s charge, discharge capacity, and power capabilities. The battery may even stop functioning in extreme cold. In some cases, the battery pack can even see irreversible damage. In those instances, the battery must be heated for charging and starting vehicle operation. When a battery is cold-soaked, it needs to be pre-conditioned. Pre-conditioning a battery pack is comprised of warming up the battery packs to the optimal temperature range before the vehicle can be charged or driven.

To pre-condition the vehicle, an active heating loop must be activated to accomplish this process. The heating loop includes a high voltage (HV) electric heater to warm the coolant to the desired set point before the coolant routes back to the battery pack. When the heating mode becomes operational, the local CANbus network from the vehicle communicates to the battery thermal management system that it needs to heat the coolant that is not meeting the battery’s optimal temperature range. Coolant will flow out of the battery pack into the battery thermal management system, where it will fill up a surge tank. At this point, an electric pump will draw the coolant and control the speed of the coolant flow through the battery thermal management system. An electric valve will then route the coolant to the heating loop. That electric heater will activate and warm the coolant below the set point. It will flow out of the active heating loop, and egress from the battery thermal management system and go directly to the battery pack. This process does not happen instantaneously. Before the coolant flows to the heater, and after the battery thermal management system receives the command to heat the coolant from the vehicle CANbus network, the private internal battery thermal management system CANbus network communicates to the electric heater, informing it to activate to prewarm. This process applies to all the electric components the internal private battery thermal management system CANbus network communicates to. Once triggered, the coolant can flow through any electric component to achieve the right temperature.

Maintaining a battery pack’s optimal temperature levels in all ambient environments will always require a comprehensive battery thermal management system with cooling and heating loops. A system with some or none of the loops listed above may present challenges when attempting to offer zero-emissions commercial or industrial electric vehicles to customers in all climate conditions. Also, not having an all-inclusive battery thermal management system with intelligent electronic controls will complicate your design process and slow down the development process.

Battery Management Systems

In many instances, engineers will search for battery management systems. Battery management systems are entirely different than battery thermal management systems. Battery management systems work alongside a battery thermal management system. It is impossible for them to function without one another without negative consequences. They both support the regulation of the batteries’ temperature. However, they cannot regulate the batteries’ temperature without the other one. Battery thermal management systems are not directly affixed to the battery. Battery management systems are either a part of or affixed close to the battery. Battery management systems are required to support the maintenance of battery temperature. The battery management system is a mechanism that transfers heat to and from the battery cells with coolant either through direct immersion or conduction through a battery cooling plate or other structure.

The first type of battery management system is the battery cooling plate. This battery cooling plate stabilizes the battery cell temperature for optimal temperature uniformity. The cooling plate pulls heat from the battery cell through conduction in this construct. It transfers the heat to a coolant running along the channels of the battery plate. The cooling plate falls into the category of a heat exchanger but has some subtle differences. Instead of rejecting heat to the air, it extracts heat from lithium-ion battery cells. These battery cooling plates are often constructed with lightweight aluminum, which supports a lower payload. There are two prevalent cooling plate types: Serpentine Cooling Plate (SCP) or Regulatory Cooling Plate. The cooling plate is affixed directly to the battery pack to provide close contact for efficient heat transfer to regulate battery temperature to meet peak performance during operation.

The other primary battery management system construct is cell immersion. The direct liquid cooling method, also referred to as immersion cooling, is a thermal management system inside the battery pack. A sealed battery module is flooded with coolant, and the battery pack’s architecture allows coolant to flow directly through the battery pack to every individual cell. This small compact immersion system is efficient in cooling battery cells quickly.

Some battery manufacturers provide the battery management system integrated into the battery pack, while others will require OEMS to purchase the battery plate separately. However, if you are looking for a battery management system, you need a battery thermal management system to pair with it so that they can work together to condition the coolant and transfer the conditioned coolant to the battery pack.

Only the battery thermal management systems can pre-condition or cool the coolant that flows to the battery packs. Battery management systems do not change the temperature of the coolant that flows to and from the battery pack. They are a means to keep the temperature-regulated coolant in or around the battery. So it’s imperative to know the difference between the two to accurately look for them in the market.

Battery Chillers

Another common way people search for thermal systems to regulate the coolant that flows to the battery is by searching for and sometimes referring to a battery chiller. The term battery chiller may seem befitting because battery packs need to be cooled during operation, charging, and discharging to maintain their optimal temperature level. However, searching for a battery chiller can lead you down two different paths. Most battery chiller systems will only provide active, leaving the unmet thermal need for cold-soaked battery packs in colder ambient temperatures. A comprehensive battery thermal management system contains cooling and heating loops. In addition to having one less loop than a comprehensive battery thermal management system, you could find yourself having to design a heating circuit outside of the battery chiller with controls that connect to the battery pack and battery chiller system. Designing a heating loop and programming those additional controls adds complexity to the design process and could impact your design lead time. Sometimes, searching for a battery chiller in a search engine could also lead you down the path of finding a component versus a system. Occasionally, a battery chiller is confused with a heat exchanger, also referred to as a chiller.

A chiller’s function is only part of the refrigeration circuit, which is part of the process of cooling the coolant in an active cooling loop. A chiller is a heat exchanger in the first phase of a refrigeration circuit. After the chiller rejects heat from the coolant to the refrigerant, the refrigerant will be in a vapor state. As the refrigerant passes through the compressor, it will compress the refrigerant vapor, raising its pressure and temperature. At this point, the pressurized, hot refrigerant gas passes through the condenser, where heat is rejected to the cooler ambient air. Due to the compressor, the refrigerant vapor’s higher temperature improves heat transfer by creating a more significant temperature differential than what you’ll find in the passive cooling loop. In the battery thermal management system, the fan array also covers the condenser, increasing airflow through the condenser and further improving heat transfer.  This refrigeration circuit is part of active cooling, which is only one of the three coolant loops needed to cool and pre-condition the coolant that flows to the battery. If you have a system that only supports hot batteries, the vehicle won’t be able to maintain optimal temperature ranges in cold environments, impacting battery life and vehicle performance.

EV Battery Cooling Systems

Many people often search for an EV battery cooling system and find themselves at a dead end. Because many EV battery cooling systems are only comprised of an active and passive cooling loops like the battery chiller system, having only these cooling loops addresses the cooling needs for a battery during charging, discharging, and when the ambient air temperature is high. This again leaves the unmet need for the temperature-optimized coolant flowing to the battery packs in colder climates. Similar to the battery chiller system,  pre-conditioning is required in a commercial electric vehicle during cold weather, and there isn’t a means to warm up the battery packs. Searching for an EV battery cooling system will only address part of the need to maintain battery packs at the optimal temperature range. Similar to the battery chiller system, you will need to design a heating coolant loop and program controls outside of the system, creating complexity and could impact development lead times.

When searching for a system to regulate your commercial electric vehicle’s battery pack temperature, remember to search for a battery thermal management system. The battery thermal management system comprises cooling and heating loops containing heat exchangers – like a “battery chiller” or “chiller” – smart electric components and smart electronic controls. To maintain the battery packs’ temperature, you need a complete system that can cool and pre-condition battery packs in all environments. Looking for an EV battery cooling system, battery chiller, or battery management system will only take you down the wrong path or get you part of what you are looking for. Be vigilant in your search and find a battery thermal management system to regulate the temperature of your commercial electric vehicle’s battery pack.

Thermal Management for Power Electronics

Another thermal need to be addressed when designing a commercial electric vehicle is temperature regulation for power electronics – including inverters, DC-DC converters, traction motors, and on-board chargers. Heavy-duty electric vehicles demand and consume more power-driven by far higher torque during operation than the average light-duty electric vehicle or passenger car, requiring a deeper consideration of thermal management for the power electronics. All of these power electronic components can have varied derating temperature requirements ranging from 50 – 65° C. If the power electronic component temperatures creep above their recommended derating temperature, it could significantly reduce output power capability. Each power electronic has its own derating temperature requirement specified by the manufacturer. Additionally, if the component temperature is allowed to rise above the operating range, it can result in a failure, making the vehicle inoperable. The power output will rely on the derating temperatures of the power electronics. Also, the power electronics run the risk of overheating and shutting down if the temperature rises above the manufacturer’s recommended operating range.

Each one of these power electronics will have an integrated cooling architecture, in which a coolant is flown through to allow heat transfer from the internal components to the coolant.

This coolant is routed through the cooling package to reject the heat to ambient air before circulating back through the power electronics. Often, a cooling package comprises electric fans, smart electronic controls, wire harnesses, and heat exchangers. The cooling package should be sized for the worst-case combined heat rejection requirement while maintaining a coolant temperature below the lowest derating temperature among the power electronic components in the loop. Positioning each of the power electronics in the coolant loop is an equally critical consideration when designing the power electronics coolant loop. The speed of the fans will be modulated depending on the cooling needed to minimize power draw with intelligent electronic controls. In addition to the Electronics Cooling Package (ECP), coolant pumps and a surge tank may be added to the coolant loop to help manage the flow of the coolant to and from the vehicle’s power electronics and the power electronics cooling package.

It is essential to find a power electronics cooling package with the proper cooling capacity to optimize the coolant temperature flowing to and from the power electronics. In addition to finding the right thermal management system, it is crucial to find a service provider offering technical support to design the cooling package to ensure adequate airflow. Without thermal expertise, you could integrate the system in a part of the commercial electric vehicle that will not allow optimal cooling capacity. In addition, it creates complexity in the design process and impacts the design lead time for your commercial electric vehicle.

Thermal Management for Hydrogen Fuel Cell Stacks

In recent technology, hydrogen fuel cell commercial electric vehicles require a comprehensive thermal eco-system to ensure proper vehicle operation. Like a commercial battery electric vehicle, hydrogen fuel cell electric vehicles contain power electronics and lithium-ion battery packs but also include fuel cell stacks that need thermal management. Hydrogen fuel cell stacks convert hydrogen gas into electricity through an electrochemical reaction with oxygen, emitting only water vapor and heat as byproducts. This process generates much heat, and the temperature needs to be regulated to ensure proper fuel cell stack operation. If a fuel cell stack generates an extensive amount of heat, it could lead to various issues, affecting the performance, efficiency, and safety of the fuel cell system. High temperatures will accelerate the degradation of the catalyst used in the fuel cells. This will reduce the efficiency of the electrochemical reactions and diminish performance. Excess heat can also deteriorate the membrane and electrolytes of a fuel cell stack. This will impact conductivity and performance, which in turn affects efficiency. Voltage instabilities are another risk, leading to fluctuations in electrical output, negatively impacting the performance of electrical components and systems. The most significant safety risk is thermal runaway. To ensure the safety of people and vehicle longevity, integrate a fuel cell stack cooling package that can regulate fuel cell stack temperature.

The fuel cell stack coolant loop will comprise a fuel cell stack cooling package with high voltage fans – to maximize energy efficiency, heat exchangers, smart electric components, and intelligent controls.   A coolant circuit will flow around the fuel cell stack, transferring heat from the stack to the coolant. The coolant then flows to a cooling package to reject heat to the ambient air before returning to the stack.

Typically, the fuel cell stack roughly run 50-60% efficiently, generating waste heat during the electrochemical process. At this point, waste heat will managed to keep the fuel cell stack safe. The passive cooling loop coolant will flow around the fuel cell stack, transferring heat from the stack to the coolant. The stack cooling package will be located away from the fuel cell stack and used to reduce the coolant temperature. The coolant then flows to a cooling package to reject heat to the ambient air before returning to the stack. There will be a liquid charge air cooler and potentially another heat transfer device to reject the heat from the fuel cell stack. A high-capacity coolant pump will be between the fuel cell stack and the fuel cell stack cooling package to drive fluid flow. The heat exchanger will be at the start and hottest part of the coolant loop, exiting the fuel cell stack to channel the waste heat. The excess heat is sent into a second coolant loop that can be used for cabin heating.

Fuel cell stacks also require low-conductivity coolant. As conductivity increases, a fuel cell stack cooling loop will need a heat exchanger with a clean surface, solder, and flux residue. Not having a stack cooling package that does not meet the fuel cell stack’s stringent conductivity requirements could cause short-circuiting, induce galvanic corrosion, electrolyze the coolant, reduce efficiency, and increase the safety risks of the fluid in the vehicle. This is critical in selecting a stack cooling package for your fuel cell electric vehicle.

Modine EVantage™ Thermal Management Systems

Thermal management is imperative in commercial hybrid, battery, and fuel cell electric vehicles. Batteries and power electronics for hybrid and battery electric vehicles ensure safety, reliability, and vehicle longevity. These are also vital considerations for fuel cell electric vehicles and managing the thermal requirements for fuel cell stacks. You can trust Modine EVantage™ thermal management systems to adequately regulate commercial electric vehicle lithium-ion batteries, power electronics, on-board chargers, and fuel cell stacks. The EVantage product suite is a comprehensive set of thermal solutions for your commercial hybrid, battery, and fuel cell electric vehicles. Modine designs Evantage products with the highest quality standards and experienced thermal engineers that can guide you through your thermal system integration journey.

We currently offer two battery thermal management system architectures. An air-cooled, direct battery thermal management system, which we call the A-CON BTMS. This system provides three loops to heat or cool your battery to the appropriate temperature specifications. Our system is robust and can cool an entire bank of batteries. Our system’s private CANbus network communicates with the electric components’ firmware to inform them when and how to operate. The A-CON system is designed for plug-and-play and customizable solutions. Our experienced thermal management engineers could design an A-CON BTMS that meets your commercial electric vehicle needs. We can provide 3 – 10 kW systems with varying models for active cooling circuits. Our A-CON BTMS is a versatile system that can be used for many applications.

Our other battery thermal management system is the liquid-cooled condenser, indirect battery thermal management system- L-CON BTMS. Our system offers two loops, both active heating and cooling. This system was designed to operate well in dirty, rugged environments. Designed to ensure debris and dirt intrusion does not clog the system. This system is a plug-and-play solution for any heavy industrial or off-highway vehicles. With its compact size, this battery thermal management system makes integrating this system into the smallest chassis easy. So, from small-sized vehicles like street sweepers to large rugged excavators, the L-CON BTMS is an excellent solution. This system is also connected to a private CANbus network that communicates to the electric components’ firmware: small space, dirt, dust, no problem with the L-CON BTMS.

Modine EVantage thermal systems offer the Electronics Cooling Package or ECP for power electronics. The ECP is a complete solution designed to effectively cool down your power electronics and traction motor. The ECP is an adequate power electronics cooling solution with minimal power draw and multi-zone cooling. Its easy plug-and-play solution allows for fast integration. It also has a private CANbus network that speaks directly to the components in and around the ECP. Our ECP is built to your specifications with small to large fan arrays with low-voltage and high-voltage fans.

The Modine EVantage Fuel Cell Stack Cooling Package is designed to intelligently meet the thermal management needs of a fuel cell stack while ensuring conductivity requirements are also met. Comprised of heat exchangers, smart electric components, wire harnesses, and intelligent controls, our flux-free heat exchanger is designed to fulfill the strictest conductivity requirements. Enabled with predictive cooling, the Fuel Cell Stack Cooling Package will allow a 10 to 15° C temperature swings at the fuel cell stack. This mitigates strong temperature spikes during vehicle operation. The state-of-the-art all-aluminum coolant-to-coolant heat exchanger effectively manages waste heat and channels it to the cabin heating operating points, which the vehicle’s HVAC system can use. This plug-and-play solution can meet your fuel cell stack performance requirements.

Modine EVantage thermal systems offer preventative maintenance and diagnostics software with every application. With our software, you can download DM1/DM2 diagnostic message data logs, monitor status, troubleshoot potential problems, monitor system response in real-time, and offer manual override mode, which allows you to control all the major components. Our software has an intuitive, graphical interface to thermal management solutions that make viewing your vehicle’s status easy.

In addition to our products, Modine has a state-of-the-art testing facility. We offer validation testing in-house. We have vibration and vehicular wind tunnel testing for your commercial electric vehicles. Our tech lab is ISO-compliant. Our products are designed and tested in Racine, WI, and manufactured in Lawrenceburg, Tennessee, US and Pontevico, Italy. EVantage thermal systems are buy-America compliant.

In your search for a comprehensive thermal management solution for your commercial electric vehicle, consider Modine Evantage thermal management systems. Modine’s 100-plus-year legacy in thermal management has propelled us into the zero-emission vehicular market. Our dedicated team of thermal engineers will guide you through the thermal management system integration process. Modine’s Evantage quality thermal management systems, thermal management legacy, and a trusted team of engineers are what you need when designing your commercial battery, hybrid, or fuel cell electric vehicle.