When it comes to keeping heavy vehicles and stationary power applications running efficiently – whether it’s a battery-electric bus, a fuel-cell-powered truck, or even a hydrogen combustion excavator – thermal management is one of the most critical systems. And at the heart of that system? The electric water pump.
Gone are the days when water pumps were purely mechanical, driven by engine belts. In modern battery-electric (BEV), fuel-cell electric (FCEV), hybrid, and even internal combustion engine (ICE) vehicles, electric water pumps play a crucial role in moving coolant where it’s needed to regulate temperatures and protect components.
In this article, we’ll explain how electric water pumps work, why they’re growing in popularity, and their role in powertrain cooling, cabin HVAC, and complete systems.
The Rise of Electric Pumps
Whether it’s BEVs, FCEVs, or traditional ICE vehicles, powertrain components need cooling and cabins need HVAC. Cooling batteries, fuel cells, motors, and power electronics while ensuring effective cabin heating is just as important today as it was decades ago. What has changed, however, is the type of water pump being used.
For years, mechanical water pumps have been the cornerstone of vehicle cooling systems – and they’re still widely used today, especially in ICE vehicles, thanks to their simplicity and affordability. However, with electrification on the rise, electric water pumps are becoming the preferred choice, particularly in BEVs, FCEVs, and hybrids.
In the next section, we’ll take a look at how electric water pumps work and why they are in such high demand.
How Electric Water Pumps Deliver Precision Cooling and Heating
A thermal management system in a heavy vehicle or industrial application typically consists of multiple closed-loop coolant circuits, each serving a specific function:
- Cooling Circuit: Absorbs heat from powertrain components (batteries, motors, inverters, fuel cells) and transfers it to a radiator or cooler for heat dissipation.
- Heating Circuit: Transfers heat from the coolant to the cabin via the cabin HVAC system or other components, often with the help of a PTC heater.
At its core, an electric water pump is a compact, electronically controlled pump that moves coolant (typically a water-ethylene glycol mix) through these heating and cooling circuits, regulating heat transfer.
Unlike belt-driven mechanical pumps, electric water pumps are not tied to engine speed, meaning they can operate precisely when and where needed, improving efficiency across all types of vehicles—from fully electric buses to hybrid construction machinery.
Flow Rate and Pressure: The Key to Effective Cooling and Heating
Two key factors determine how well heat is transferred in a cooling or heating circuit: Flow and pressure.
Flow rate (measured in litres per minute, or LPM) determines how much coolant moves through the system, while pressure (measured in bars or psi) ensures it reaches every component effectively. Electric water pumps excel at balancing these factors for optimal heat transfer.
In particular, there are two major advantages that electric water pumps offer that make them superior in modern thermal management systems.
Balancing flow rate and pressure is critical to system performance. It is a topic we’ll explore in more detail when we explore how to choose the right electric water pump for your BEV or FCEV, covering key specifications and application requirements. Sign up to our Thermal Academy newsletter and be the first to find out when it's available.
1. Operate Independently of the Powertrain
Traditional mechanical water pumps are belt-driven, meaning their performance is tied to engine RPM. This simple design, however, can lead to significant inefficiencies:
- At high engine speeds: The pump may run faster than necessary, wasting energy.
- At idle or low speeds: The pump may not circulate enough coolant, causing overheating risks in high ambient temperatures
Electric water pumps eliminate this issue by running independently of the engine, which is why many modern ICE vehicles opt for them. And, in BEV and FCEV applications, where no engine is present and efficiency directly impacts range and performance, electric water pumps are essential.
2. Adjust Flow Rate Dynamically for Precision Regulation
Beyond operating independently, electric water pumps enable real-time, dynamic control of coolant flow – delivering just the right amount of cooling or heating when needed.
This is achieved through two common control methods:
- CAN Control: The pump communicates with the vehicle’s ECU, adjusting flow rate based on real-time cooling demand and sharing pump information such as rpm and fault feedback.
- PWM Control: The pump speed is modulated through Pulse Width Modulation from the vehicle ECU, varying speed input to fine-tune coolant flow.
This ability to control flow dynamically ensures that every cooling and heating circuit operates at peak efficiency, supporting battery longevity, powertrain reliability, and passenger comfort.
The result? More energy-efficient, complex thermal management systems that only circulate coolant where and when it is needed.
Grayson’s Magnetic Drive Electric Water Pump features either CAN or PWM control, enabling dynamic flow rate control.
Now that we understand the fundamentals and advantages of electric water pumps, let’s dive into how electric water pumps work within powertrain cooling, cabin HVAC, and multi-circuit systems.
Electric Water Pumps and Powertrain Cooling
One of the core functions of an electric water pump is powertrain cooling. In EVs and FCEVs, this means maintaining optimal temperatures for:
- Battery packs: Using a Battery Thermal Management System (BTMS) to regulate temperatures via a heat exchanger or chiller.
- Electric motors and power electronics: Transferring excess heat from motors, inverters, and DC-DC converters to a cooler for dissipation.
In some systems, a single pump may handle both battery and motor cooling, while in more advanced setups, like our Vehicle CTMS, dedicated cooling loops provide independent temperature control for each component.
Electric Water Pumps and Cabin HVAC
Beyond powertrain cooling, electric water pumps are essential for cabin climate control, ensuring efficient heating and defrosting. In cabin and passenger HVAC systems, they:
- Deliver heat to the cabin via a heater core, often supplemented by a PTC heater when extra warmth is needed.
- Support defrosting and demisting, ensuring warm coolant reaches the demisting unit quickly.
- Assist heat pump-based HVAC systems, where coolant loops play a role in both heating and cooling functions.
The Role of Heat Exchangers and Multi-Circuit Cooling
In some advanced systems, thermal energy can be transferred between circuits via heat exchangers and intelligent control software to optimise efficiency and performance. This gives the opportunity for waste heat to be recycled and redistributed to other areas of the vehicle, reducing the need to rely on auxiliary heat sources that consume more energy.
For example, in our Vehicle CTMS, one coolant circuit handles battery heating whilst another is responsible for powertrain, and a third refrigerant circuit manages the cabin HVAC. By dynamically controlling the flow of this coolant and through the clever use of heat exchangers and indirect condensing, heat is efficiently transferred to different circuits, providing efficiency and packaging flexibility to OEMs designing new applications.
We’ll explore direct vs. indirect condensing in more detail in our next article, but for now, it’s important to recognise that electric water pumps play a key role in managing these interconnected systems.
Looking Ahead
Electric water pumps are more than just a component – they’re the backbone of modern thermal management systems, ensuring efficiency, reliability, and comfort in heavy vehicles and stationary power applications. Whether it’s cooling a battery pack, heating a cabin, or managing multi-circuit systems, their precision and adaptability make them indispensable in today’s electrified world.
In our next article, we’ll take a closer look at direct vs. indirect condensing and how these methods shape thermal efficiency. Until then, why not explore how Grayson’s electric water pumps can elevate your thermal management system or get in touch with our team to learn more.
