Will electrified vehicle thermal management move toward direct refrigerant contact?

BYD, the world’s largest electrified vehicle (EV) manufacturer, has unveiled its groundbreaking 1000kW Super e-Platform. The company claims to be the first to achieve a 10C charging rate, meaning the charging speed is 10 times the battery’s capacity per hour.

This allows vehicles to add up to 400km of range in only five minutes, with a theoretical full charge in just six, substantially outperforming the charging speeds of the fastest EVs on the market today and effectively addressing the widespread issue of ‘range anxiety’

Central to this innovation is a new 1000-volt architecture, enabling charging rates that were once considered impossible. “Our pursuit is to make the charging time of electric vehicles as short as the refuelling time of fuel vehicles,” said BYD founder Wang Chuanfu. This ambition, if realised on a large scale, could make electric vehicles as convenient as their petrol or diesel counterparts.

Conquering thermal demands

BYD’s ‘flash charging’ demands unprecedented energy delivery to the battery. With a peak charging current of 1000 amps at 1000 volts, the resulting power transfer of one megawatt generates significant heat.

To manage this, the 1000kW charging platform relies on advanced thermal management, which efficiently controls the heat to prevent battery degradation and ensure safety.

Traditional EV thermal management systems fall short in handling such extreme heat loads, making BYD’s solutions a fundamental rethinking of battery cooling architecture, rather than just an incremental improvement. 

Three-dimensional cooling

Crucial to BYD’s thermal management breakthrough is what executive VP Lian Yubo described as a
“three-dimensional flow path composite temperature control system”. Unlike conventional single-plane cooling systems, this design implements refrigerant flow paths on both the top and bottom surfaces of the battery pack.

The dual-plane approach creates a three-dimensional cooling envelope around the cells that, according to BYD’s technical presentation, delivers a dramatic 90 per cent boost in heat transfer efficiency over conventional cooling solutions.

By rapidly extracting heat from multiple surfaces at once, the system significantly enhances heat dissipation, making it well-suited to handle the immense thermal loads created by megawatt charging.

Direct refrigerant cooling

Another key innovation in BYD’s thermal management strategy is the direct refrigerant cooling system. Unlike the industry-standard glycol-water coolant systems, which require multiple stages for heat exchange, BYD’s approach uses refrigerants in direct contact with the battery pack.

This direct method improves cooling efficiency by eliminating thermal resistance from intermediate steps and offers a faster thermal response during rapid charging events. Additionally, this system is lighter, with a 90 per cent claimed weight reduction compared to conventional coolant-based systems, whole also being safer, thanks to the use of non-conductive refrigerant that further reduces the risk of electrical shorting in the battery system – an essential factor for the 1000-volt architecture.

Blade battery’s thermal advantage

BYD’s Blade battery design plays a crucial role in its thermal management strategy. Engineered with a unique prismatic cell structure, along with a symmetrical design and stacking process, the Blade battery maximises space utilisation and improves thermal conductivity by more than five times compared to traditional designs.

This efficient temperature management at the cell level helps reduce thermal gradients, particularly during high-power charging. When combined with the integrated cooling system, it not only keeps the battery cool in high-temperature conditions but also minimises the risk of thermal runaway and ensures long-lasting performance.

Thermal management for electric drive systems

The Super e-Platform features a new generation of high-speed motors capable of reaching up to 30,511rpm, delivering 778 horsepower (572kW) with a power density of 22 horsepower per kilogram (16kW/kg), setting a new industry benchmark.

However, the motor’s high speed presents significant thermal management challenges due to increased mechanical losses, which generate heat. To address this, BYD has integrated specially formulated high-performance oils while optimising the spray flow velocity and angle to ensure consistent lubrication and cooling.

This improves heat exchange efficiency by 78 per cent compared to lower-rpm designs, helping prevent thermal degradation and ensuring sustained high-performance operation.

In addition, BYD applies a refrigerant-based direct cooling solution to manage the heat from both the motor and its 1500-volt silicon carbide (SiC) power modules. BYD’s decision to use 1500-volt silicon carbide (SiC) power modules is driven by this material’s exceptional thermal conductivity and higher thermal breakdown voltage.

These features allow the chips to function at higher temperatures and voltages while generating much less heat compared to traditional silicon chips.

As a result, more power can be transferred to the vehicle’s battery while maintaining system stability, ensuring long-term efficiency. This innovative approach helps to keep temperatures under control, ensuring the system can function at its peak without overheating.

As BYD chief scientist Lian Yubo explains, this technology enables engineers to “control the electric drive temperature as low as we want”, which is essential for maintaining high performance and preventing thermal derating.

BYD says the success of this thermal management system was confirmed through durability testing. In these tests, the vehicle was able to complete “over 70 consecutive 0-100km/h sprints without performance degradation”, demonstrating the thermal management system’s effectiveness at maintaining consistent performance.

Minimising heat build-up

BYD’s thermal management strategy not only focuses on removing heat but also on minimising its generation at the source. One key innovation is the introduction of “dual electron flow channels” in the Blade battery. These channels expand the pathways for electron movement, essentially creating wider “highways” for current to flow through the battery.

This design significantly reduces heat generation, cutting cell heating by 50 per cent during high-current operations. By addressing heat at its source, BYD’s approach lessens the overall thermal management burden, shifting the focus from cooling down heat to preventing it from forming in the first place.

BYD’s 1000kW vehicle line-up

BYD’s expansion plans extend beyond the charging infrastructure; the company is also committed to advancing its own vehicle line-up to accommodate the new 1000kW charging capabilities.

As part of this, the company’s updated Han L sedan and Tang L SUV models, set for delivery in China later this year, will feature the new Super e-Platform.

These vehicles will showcase the platform’s capabilities, with dual-motor variants offering up to 1084 horsepower (797kW) and claimed 0-100km/h acceleration times as low as 2.7 seconds for the Han L and 3.6 seconds for the Tang L.

A unified approach to cooling

BYD’s thermal management strategy is distinguished by its integrated approach across the battery, motor, and power electronics, employing a unified refrigerant-based system that allows for dynamic thermal load sharing between components, optimising cooling efficiency.

This integration incorporates predictive control algorithms to anticipate thermal events, ensuring proactive temperature regulation rather than reactive responses to heating.

Shaping the future with direct refrigerant systems

As the EV industry progresses towards greater charging capabilities and more compact, power-efficient drive systems, innovations in thermal management are expected to grow in importance.

BYD’s strategy could indicate a wider trend in the industry moving away from liquid cooling and towards more advanced direct refrigerant systems, particularly for high-performance applications where thermal management plays a crucial role.

BYD’s response to infrastructure limitations

While the 1000kW charging system represents a significant leap forward, being almost twice as fast as existing systems, it also highlights challenges within the EV industry. One key issue is its incompatibility with current infrastructure, such as in Australia, where the Combined Charging System (CCS) standard supports rates of up to 350kW for DC fast charging, while many stations offer just 50-150kW.

To optimise the charging process, the Super e-Platform features dual charging ports, allowing vehicles to draw power from multiple sources simultaneously. This enables existing public chargers to be quickly upgraded to accommodate its ultra-fast charging speeds, where infrastructure supports it, significantly reducing the time required for a full charge.

It is part of BYD’s broader strategy to push the boundaries of high-speed charging, address infrastructure limitations and accelerate the global adoption of electric vehicles.

Additionally, BYD plans to establish more than 4000 liquid-cooled megawatt flash-charging stations across China, each capable of delivering 1360kW and incentivising the global adoption of high-speed charging and strengthening the EV ecosystem.

Charge anxiety in the rearview

Experts are already calling BYD’s new charging system a major milestone in the EV revolution. 

“Concerns surrounding range anxiety are dwindling as new models can travel further with a single charge,” said Octopus Electric Vehicles public policy director James Court. “BYD is now putting charge anxiety to rest, which should further accelerate mass adoption of electric driving.”