EV Thermal Management System

The Thermal Management System (TMS) is the vehicle hardware that controls temperatures of critical components and fluids, primarily the battery pack, power electronics, electric machines, and the cabin HVAC (Heating, Ventilation, and Air Conditioning) subsystem. In EVs, TMS is both a battery-supply-chain subsystem (pack-level thermal design and components) and a core HV/LV (High-Voltage / Low-Voltage) electrical subsystem because it contains high-power electrical loads and directly influences battery safety, performance, charging rate, and lifetime.

There are two ways the industry uses the term TMS:

• Battery TMS (BTMS, Battery Thermal Management System): the subset dedicated to battery pack heating/cooling and pack temperature uniformity
• Vehicle thermal system (sometimes referred to as a vehicle thermal system, integrated thermal system, or thermal management architecture): an integrated set of loops that may couple battery, power electronics/motor, and cabin HVAC via shared heat exchangers and valves

Many modern EVs implement an integrated thermal system where the battery loop is one part of a broader vehicle thermal architecture.

Why TMS matters in EVs

• Battery safety: avoids operation outside safe temperature ranges
• Battery performance: temperature affects available power and regen capability
• Fast charging: charging rate is often thermally limited; preconditioning improves charge time
• Battery lifetime: temperature uniformity reduces uneven aging
• Efficiency and range: heat pumps and integrated thermal architectures can reduce energy consumption

What TMS controls

• Battery pack temperature and temperature uniformity
• Power electronics temperature (inverter, DC-DC, OBC where liquid cooled)
• Motor and gearbox temperature (where liquid cooled)
• Cabin comfort (HVAC)
• Defrost/defog functions that affect visibility and sensor operation (architecture dependent)

Battery vs vehicle thermal management

This table clarifies the partition.

Subsystem	Primary purpose	Main components	Interfaces	Typical naming
Battery thermal management	Keep battery within safe and optimal temperature range; enable fast charging	Coolant plates/paths, pumps, valves, chiller interface, heaters, sensors	Strong coupling to BMS; interacts with charging and VCU	BTMS, battery loop, pack thermal system
Vehicle thermal system (integrated)	Optimize overall vehicle heat flows and efficiency across battery, powertrain, and cabin	Heat pump or AC compressor, condensers, evaporators, radiators, chillers, valves, pumps, manifolds	Interfaces with BMS, VCU, HVAC controller, sometimes central compute	Integrated thermal system, vehicle TMS, thermal architecture

Common EV thermal architectures

EVs typically use multiple fluid loops. The exact number and coupling strategy varies by OEM.

• Coolant loop(s): carry heat between components and radiators/chillers
• Refrigerant loop: used by AC compressor/heat pump for cabin conditioning and battery chilling via a chiller
• Coupling strategy: shared heat exchangers and valves can transfer heat between loops

Key TMS hardware

TMS BOM content includes both mechanical and electrical components.

Component	Function	Battery relevance	HV/LV relevance
Coolant pumps	Circulate coolant through loops	Moves heat in/out of battery cooling plates	LV electrical loads; reliability-critical
Valves (solenoid and multi-way)	Direct coolant/refrigerant flow paths	Controls battery cooling/heating routing	LV actuation and control; enables integrated architectures
Heat exchangers (radiator, chiller, condenser, evaporator)	Transfer heat to/from air or between loops	Battery chilling via chiller interface in many designs	Defines cooling capacity and efficiency
AC compressor / heat pump	Moves heat via refrigerant cycle	Enables strong battery cooling and preconditioning	Often HV load; significant power draw at peak demand
Heaters (PTC heaters and/or other)	Adds heat for cabin and battery heating	Battery heating improves winter performance and fast charging	Often HV load; impacts range
Thermal interface hardware (cold plates, channels, TIM)	Moves heat from cells/electronics into coolant	Pack-level design driver for uniformity and safety	Mechanical integration within pack and power electronics
Sensors (temperature, pressure, flow)	Measure loop conditions	Enables safe pack control and derating	Feeds controllers for diagnostics and protection
Reservoirs, lines, quick-connects	Fluid containment and routing	Packaging and serviceability	Leak reliability and manufacturing quality drivers

Thermal Control Unit (controller) and control partitioning

Thermal control logic can live in multiple places depending on OEM architecture.

• Dedicated Thermal Control Unit (sometimes called a thermal controller ECU): controls pumps/valves and coordinates loops
• BMS involvement: sets battery temperature targets, charging limits, and safety derating
• VCU involvement (Vehicle Control Unit): coordinates vehicle-level energy and operating modes
• Infotainment/HVAC controller involvement: cabin comfort control and user requests

Interfaces to other EV systems

• BMS (Battery Management System): battery temperature targets, safety limits, preconditioning requests
• Charging systems (OBC/DC fast charging): thermal limits often gate charging rate
• HV power electronics: inverter/DC-DC/OBC temperatures and cooling demand
• PDU/HVJB (Power Distribution Unit / High-Voltage Junction Box): power feeds for compressors and heaters
• IVN (In-Vehicle Network): CAN/CAN-FD common for thermal controllers; Ethernet appears in newer centralized designs

TMS as an HV/LV electrical subsystem

TMS includes multiple electrical loads and control paths that sit across HV and LV.

• HV loads (common): AC compressor, PTC heaters, some high-power pumps (varies)
• LV loads (common): valves, sensors, control electronics, many pumps and fans
• Design focus: ensure stable power delivery and fault handling for safety-critical cooling and heating functions

Battery supply chain relevance

From a battery supply chain perspective, thermal management is a pack-level performance and safety differentiator.

• Pack thermal design (plates/channels/contact) influences fast charge capability and cycle life
• Component sourcing impacts reliability and cold-weather performance
• Manufacturing quality drives leak rates, air entrapment risk, and long-term service outcomes

List of U.S.-based vendors for TMS:

Manufacturer	State
3M	AL
3M	MN
ADA Technologies	CO
Borgwarner
Calogy Solutions	QC
Calsonic Kansei
CapTherm Systems
Continental
Dana
Gentherm
Hanon System
HotStart Thermal Management	WA
HYLIION	TX
KULR Technology	CA
Latent Heat Solutions	OH
Latent Heat Solutions	CO
LG Energy
MAHLE
Morgan Advanced Materials	IL
Morgan Advanced Materials	GA
Morgan Advanced Materials	KS
Morgan Advanced Materials	IN
Nanoramic Laboratories	MA
Parker LORD	IN
Robert Bosch
Samsung SDI
Senior Flexonics	IL
Senior Flexonics	Coahuila
SGL Carbon	CA
SGL Carbon	NC
SGL Carbon	PA
SGL Carbon	PA
Valeo
VOSS Automotive