High-voltage batteries in electric and hybrid commercial vehicles operate within defined temperature ranges. Charging, discharging and high power demand generate heat, while low ambient temperatures can also affect battery performance.
The battery thermal-management system is responsible for keeping temperatures within the operating range intended by the vehicle manufacturer.
For workshops, this means that reduced vehicle performance or charging limitations can sometimes originate in the thermal-management system rather than in the battery cells themselves.
Why do high-voltage batteries need thermal management?
Battery cells generate heat when electrical current flows through them. The amount of heat depends on factors such as battery design, power demand, charging rate and operating conditions.
Excessive battery temperature can accelerate degradation and may cause the battery-management system to limit charging or available power. Very low temperatures can also restrict charging and power output.
Temperature uniformity within the battery pack is important as well. Large temperature differences between battery areas can affect performance and ageing.
How are commercial vehicle batteries cooled?
The exact architecture varies between manufacturers and vehicle platforms.
Many high-voltage battery systems use liquid thermal management. Coolant circulates through channels or cooling plates associated with the battery modules and transfers heat away from the cells.
Depending on the design, the circuit can include:
- coolant pumps
- valves
- temperature sensors
- heat exchangers
- cooling plates
- coolant lines
- chiller or refrigerant interfaces
Some systems can also heat the battery when operating conditions require it. Battery thermal management is therefore not always simply a cooling system.
How does the battery management system interact with cooling?
Temperature sensors provide information about conditions within the battery system. The vehicle’s control systems can then regulate pumps, valves and other thermal-management components according to operating requirements.
Thermal conditions can also influence how much power the battery is allowed to deliver or accept.
If battery temperature moves outside the intended operating range, the system may reduce propulsion power or charging performance to protect the battery. A vehicle with reduced power therefore does not necessarily have a defective battery.
What can cause battery cooling problems?
Thermal-management faults can have several causes.
Reduced coolant flow can result from pump problems, restrictions, leakage or air within the circuit. Valves can affect coolant routing, while incorrect temperature information can cause the control system to respond improperly.
Heat exchangers and refrigerant-related components may also influence battery cooling in systems where the battery thermal circuit interacts with the vehicle’s HVAC system.
Diagnostics should therefore consider the complete thermal-management circuit rather than replacing the battery or coolant pump solely on the basis of a temperature-related fault.
What about thermal runaway?
Thermal runaway is a serious battery-cell failure process in which heat generation becomes self-sustaining and can propagate beyond the affected cell.
Battery systems use multiple measures to reduce and manage this risk, including cell monitoring, electrical protection, thermal management and battery-pack design.
Normal cooling-system operation is an important part of maintaining suitable battery temperatures, but thermal runaway should not be reduced to a simple cooling-system failure. Cell damage, internal electrical faults and other conditions can also be involved.
High-voltage battery faults therefore require the procedures specified by the vehicle manufacturer and appropriately qualified personnel.
Why component compatibility matters
Pumps, valves and sensors within battery thermal-management systems can be application-specific.
A replacement pump, for example, may need to meet particular electrical, hydraulic and control requirements. Similar external dimensions or connectors do not necessarily establish compatibility.
The same applies to valves and sensors that form part of electronically controlled thermal circuits.
Conclusion
Battery thermal management helps keep high-voltage batteries within suitable operating temperatures during charging and vehicle operation.
Coolant pumps, valves, sensors, heat exchangers and control systems work together to manage heat and, in some systems, battery heating.
When temperature-related problems occur, diagnostics should therefore consider the complete thermal-management system rather than assuming that the battery itself is defective.
FalkePro – Commercial Vehicle Spare Parts
FalkePro specializes in the sourcing and B2B trade of spare parts for trucks, buses and commercial vans. We support workshops, parts distributors, fleet operators and transport companies with commercial vehicle spare parts sourcing across international markets.
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