What is battery thermal management and why does it matter?
Battery thermal management is the process of actively controlling a battery pack’s temperature to keep it within the operating range where it performs safely, efficiently, and reliably. Without it, lithium-ion cells degrade faster, lose capacity, and in extreme cases pose serious safety risks. For engineers and procurement specialists working on electrified heavy machinery or mobile industrial equipment, understanding how thermal management works is fundamental to specifying a system that will hold up in the field.
How does a battery thermal management system actually work?
A battery thermal management system, or BTMS, works by continuously monitoring cell temperatures and using heating, cooling, or both to maintain the pack within a defined temperature window. Sensors feed real-time data to a control unit, which activates the appropriate thermal circuits to add or remove heat as conditions demand. The system operates automatically and responds to both ambient conditions and the battery’s own heat generation during charge and discharge cycles.
In practice, a BTMS combines several subsystems: a thermal circuit carrying a coolant or refrigerant, heat exchangers, pumps or fans, electric heaters, and a control logic layer that ties everything together. The control unit typically interfaces with the vehicle’s or machine’s main control system, allowing the BTMS to respond not just to temperature readings but also to the operational state, ambient data, and fault conditions. This integration is what separates a well-engineered thermal management system from a simple cooling circuit bolted onto a battery pack.
What happens to a battery when temperature goes out of range?
When a lithium-ion battery operates outside its designed temperature range, both performance and lifespan deteriorate. At low temperatures, internal resistance rises sharply, reducing available power and making fast charging potentially damaging to the cells. At high temperatures, electrochemical degradation accelerates, capacity fades faster, and in severe cases thermal runaway becomes a risk. Either direction shortens the battery’s service life and can compromise operational safety.
The damage is not always immediate or visible. Repeated exposure to temperatures even slightly outside the optimal range causes cumulative degradation. A battery pack that regularly operates in cold conditions without preheating will lose measurable capacity over a relatively short number of cycles. In mobile machinery that operates year-round across wide climate ranges, this is not a theoretical concern but a practical engineering constraint that must be addressed in the system design from the outset.
What are the main types of battery thermal management systems?
The main types of battery thermal management systems are air-cooled systems, liquid-cooled systems, and refrigerant-based direct cooling systems. Air cooling is the simplest approach but offers limited heat transfer capacity. Liquid cooling using water-glycol circuits is the most widely used method in high-power applications because it provides significantly better thermal conductivity and more precise temperature control. Refrigerant-based systems are used where very precise temperature uniformity or active chilling is required.
Passive versus active thermal management
Passive systems rely on thermal mass and natural convection to buffer temperature changes, with no powered components. They are lightweight and simple but only suitable for low-power applications with mild ambient conditions. Active systems use powered components such as pumps, compressors, and heaters to maintain temperature regardless of ambient conditions. For heavy mobile machinery operating across wide temperature ranges, active thermal management is almost always necessary.
Heating versus cooling circuits
Many BTMS designs include both a cooling circuit and a heating circuit, because the system must perform in both summer heat and winter cold. In Nordic and sub-Arctic operating environments, the heating function is often the more demanding design requirement. Electric resistance heaters or heat pump circuits warm the battery before operation starts, ensuring the cells are within their optimal charge and discharge range even when the machine has been parked overnight in freezing conditions.
With over 50 years of experience in refrigeration technology, Lumikko offers proven, validated products designed to perform reliably in demanding conditions. When needed, we also design tailored solutions to meet our customers’ specific requirements. Find your right solution and discover how Lumikko’s flexible approach can seamlessly integrate with your product — without requiring additional design work on your part.
Why is thermal management especially critical for heavy mobile machinery?
Heavy mobile machinery presents a combination of challenges that makes battery thermal management significantly more demanding than in passenger vehicles. These machines operate across extreme ambient temperature ranges, generate high and variable power loads, face continuous vibration and shock, and are expected to run reliably for long service intervals in remote or harsh environments. A thermal management failure in a mining machine or a heavy construction vehicle does not just mean a breakdown; it can mean significant downtime and safety risk in a location where support is not immediately available.
The duty cycles of heavy machinery also place greater thermal stress on battery packs. A machine that draws high current during lifting or tramming, then regenerates energy during braking, creates rapid fluctuations in heat generation that the BTMS must absorb and manage continuously. Unlike a passenger car that spends much of its time at moderate load, heavy mobile equipment regularly operates near peak capacity. This demands a thermal management system with sufficient capacity margins and robust control logic, not a system sized for average conditions.
Lumikko has developed battery thermal management systems for electrified heavy machinery, including mining equipment for Sandvik, where the combination of underground ambient conditions, high power demands, and long service intervals defines the design requirements precisely.
How is a BTMS integrated with power electronics cooling?
A BTMS is integrated with power electronics cooling by sharing or interconnecting thermal circuits so that both the battery pack and the inverters, converters, and motor drives are kept within their respective temperature limits through a coordinated system. In many electrified machines, the battery and the power electronics have different optimal temperature ranges, which means the integration requires careful hydraulic and control design to manage each component independently while using shared infrastructure where possible.
The most common integration approach uses a single coolant loop with multiple branches and temperature zones, controlled by valves and separate heat exchangers. The control logic prioritizes based on criticality: if the battery needs cooling while the inverter needs warming, the system must handle both simultaneously without compromising either. This level of integration demands that the BTMS and the power electronics cooling system are designed together from the beginning, not as separate afterthoughts bolted together during integration.
In practice, this means the thermal management engineer must understand not just the battery chemistry and its limits, but also the thermal characteristics of each power electronics component, the machine’s duty cycle, and the ambient conditions it will face. Designing these systems in isolation and integrating them later typically results in compromises that affect either performance or reliability. We are praised for our ability to flexibly customize our solutions to seamlessly integrate with the customer’s product — and this approach also enables the modernization of existing equipment. Talk with our experts to explore how we can support your integration requirements.
What standards and certifications apply to battery thermal management systems?
Battery thermal management systems for mobile and industrial applications must comply with a range of standards depending on the application, market, and vehicle type. Relevant standards include IEC 62619 for safety requirements of lithium-ion cells and batteries in industrial applications, UN 38.3 for transport testing of lithium batteries, and the ISO 6469 series for electric vehicle safety. For defense applications, additional military standards such as MIL-STD-810 for environmental testing apply. Rail applications are governed by EN 45545 for fire safety and EN 50155 for electronic equipment in rolling stock.
Certification requirements are not uniform across applications, and the applicable standards depend heavily on where and how the machine or vehicle will operate. A battery system for an underground mining machine faces different regulatory and certification requirements than one for a military vehicle or a tram. This is one reason why thermal management systems for demanding applications need to be engineered specifically for the target application rather than adapted from a generic design.
Manufacturing quality systems also matter. ISO 9001 certification provides a baseline assurance that the design and production processes are controlled and documented. For customers in defense, rail, and heavy industry, traceability and documented quality processes are not optional extras but standard procurement requirements. Lumikko’s design and manufacturing operations in Seinäjoki, Finland, hold both ISO 9001 and ISO 14001 certification, supporting compliance documentation across the full product lifecycle.
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