Breakthrough in EV Battery Heating Unveiled by Shanghai Jiao Tong University Team
As winter approaches and temperatures plummet across northern regions, electric vehicle (EV) owners brace themselves for a familiar challenge: reduced driving range and sluggish performance in the cold. This seasonal frustration stems from a fundamental limitation of lithium-ion batteries—their sharp decline in efficiency and power delivery at low temperatures. At -20°C, many EVs can lose up to 40% of their usable energy, rendering them impractical for daily use in colder climates. For years, researchers and automakers have sought solutions to this critical barrier to widespread EV adoption. Now, a team of engineers from Shanghai Jiao Tong University has introduced a groundbreaking self-heating strategy that could redefine how electric vehicles manage battery temperature in freezing conditions.
Published in the Journal of Power Supply, the research led by Jingbo Han, Chong Zhu, Jia Li, Yansong Lu, and Xi Zhang presents a novel approach that leverages existing vehicle components—specifically the traction motor and inverter—to warm up the battery pack without requiring any additional hardware. This innovation not only promises faster heating times but also addresses long-standing concerns about energy consumption, battery longevity, and passenger comfort during the heating process.
The core of the new method lies in a clever reconfiguration of the vehicle’s powertrain architecture. In standard operation, the inverter converts direct current (DC) from the battery into alternating current (AC) to drive the electric motor. However, during cold starts, the system can be switched into a self-heating mode. By activating a simple relay connection between the battery and one phase of the motor winding, the entire drivetrain is repurposed into an internal AC heating circuit. In this mode, the motor windings act as energy storage elements, and the inverter facilitates a controlled exchange of energy between the battery and a filter capacitor, generating an alternating current directly within the battery cells.
This internal alternating current produces resistive heating, warming the battery from the inside out—a process far more efficient than external heating methods that rely on thermal conduction through battery casings. The team’s experiments demonstrated that their method can raise the temperature of a lithium-ion battery pack from -20°C to above 0°C in just 403 seconds—under seven minutes—without causing permanent damage to the battery’s lifespan. This rapid warm-up time is a significant improvement over many existing preheating systems, which often take 10 to 15 minutes or more to achieve similar results.
What sets this technology apart is not just its speed, but its integration and efficiency. Unlike previous approaches that required dedicated heating elements or external power sources, this strategy uses only components already present in most electric vehicles. There is no need for auxiliary heaters, resistive coils, or extra DC-DC converters. By eliminating the need for additional hardware, the solution reduces both cost and system complexity, making it highly attractive for mass production.
The researchers achieved precise control over the heating process through an adaptive fuzzy PI controller, a sophisticated algorithm that dynamically adjusts the heating current and voltage to maintain optimal conditions. This controller continuously monitors the battery’s voltage and current peaks, ensuring they remain within safe operational limits—between 2.7 V and 4.2 V per cell in their tests. By doing so, it prevents overvoltage and undervoltage conditions that could lead to lithium plating, a dangerous side reaction that degrades battery performance and poses safety risks.
Lithium plating occurs when lithium ions are forced to deposit as metallic lithium on the anode surface instead of intercalating into the graphite structure, typically under high current or low-temperature conditions. Once formed, these deposits can grow into dendrites that pierce the separator, leading to internal short circuits. The adaptive control system developed by the Shanghai Jiao Tong team effectively mitigates this risk by regulating the amplitude of the alternating current based on real-time feedback, balancing heating speed with long-term battery health.
One of the most innovative aspects of the research is its solution to a previously overlooked problem: motor noise and vibration during self-heating. When alternating current flows through the motor windings—even when the vehicle is stationary—it generates electromagnetic torque pulses. These pulses can cause audible humming, buzzing, or even mechanical vibrations felt inside the cabin, undermining passenger comfort and potentially accelerating wear on drivetrain components.
To address this, the team introduced a torque ripple suppression technique based on rotor position clamping. By precisely aligning the rotor of the permanent magnet synchronous motor with the stator winding connected to the battery—specifically positioning it at 0° electrical angle relative to the energized phase—the net electromagnetic torque is minimized. In this configuration, the opposing magnetic forces cancel each other out, effectively neutralizing the torque pulsations that would otherwise occur.
Experimental validation confirmed the effectiveness of this approach. When the rotor was aligned with the A-phase winding, the peak electromagnetic torque during heating remained as low as 0.4 N·m, even at high current amplitudes. In contrast, misalignment—such as positioning the rotor at 120° or 240°—resulted in torque peaks exceeding 2.2 N·m, a fivefold increase. This dramatic reduction ensures that the heating process remains silent and vibration-free, preserving the quiet ride quality expected in modern EVs.
The team conducted extensive testing using a scaled-down battery pack composed of six LG 18650 lithium manganese cobalt oxide (LiMnCoO₂) cells, a 2.8 kW surface-mounted permanent magnet motor, and a power module simulating a real-world traction inverter. All experiments were performed inside a climate-controlled chamber set to -20°C to simulate extreme winter conditions. Temperature sensors monitored the battery surface throughout the heating cycle, while a real-time control system logged voltage, current, and PWM signals.
Results showed a clear correlation between heating current amplitude and warm-up speed. At a peak current of ±6 A, the battery took 912 seconds to reach 0°C. Increasing the current to ±9 A reduced the time to 402.5 seconds, and at ±12 A, it dropped further to 349.2 seconds. However, the researchers also observed a trade-off: while higher currents delivered faster heating, they also increased the risk of capacity fade over repeated cycles.
After 60 heating cycles, batteries subjected to ±12 A current showed a measurable decline in capacity—from 3.182 Ah to 3.047 Ah—indicating early signs of degradation. In contrast, those heated at ±6 A and ±9 A maintained stable capacity, suggesting that moderate current levels offer the best balance between speed and longevity. The team attributes the degradation at higher currents to localized lithium plating, likely triggered by excessive overpotential despite voltage regulation.
Interestingly, the total energy consumed per heating cycle was lower at higher currents. At ±6 A, each cycle consumed 7.9% of the battery’s state of charge (SOC), whereas at ±9 A and ±12 A, consumption dropped to 4.4% and 4.3%, respectively. This counterintuitive result is explained by the shorter duration of high-current heating, which reduces heat loss to the surrounding environment. In essence, faster heating means less time for thermal dissipation, leading to higher overall energy efficiency.
These findings have important implications for automakers designing thermal management systems. Rather than simply maximizing heating speed, the optimal strategy may involve dynamically adjusting the current amplitude based on ambient temperature, battery SOC, and expected driving patterns. For instance, a vehicle preparing for immediate departure might use a higher current for rapid warm-up, while one scheduled to start in an hour could use a gentler, longer cycle to preserve battery life.
The research also highlights the importance of frequency selection in AC heating. Previous studies have shown that lithium-ion batteries exhibit lower impedance at higher frequencies, allowing for greater heat generation per unit current. However, excessively low frequencies can lead to polarization and lithium plating, while very high frequencies may require impractically large current amplitudes due to capacitive effects. The team selected a heating frequency of 170 Hz—within the previously identified optimal range of 100 to 3,000 Hz—achieving a balance between efficiency and safety.
Unlike earlier high-frequency heating methods that required currents of 3C or 4C (three to four times the battery’s rated capacity), the Shanghai Jiao Tong team’s approach operates at more moderate levels, reducing stress on the inverter and extending component lifespan. Their system’s ability to generate controlled AC current using the existing inverter topology eliminates the need for specialized high-frequency power supplies, further enhancing its practicality for automotive applications.
From a systems engineering perspective, the proposed method represents a paradigm shift in vehicle electrification. Instead of treating the battery, motor, and power electronics as separate subsystems, the researchers demonstrate how these components can be intelligently reconfigured to serve multiple functions. The same inverter that drives the wheels can also act as a battery heater; the same motor windings that produce propulsion can store energy for thermal management.
This level of integration reflects a growing trend in automotive design: maximizing functionality through software-defined reconfiguration rather than adding hardware. As vehicles become more electrified and software-centric, such multi-functional architectures will become increasingly valuable, enabling new capabilities without increasing weight, cost, or complexity.
The implications extend beyond passenger cars. Commercial fleets, delivery vans, and electric buses operating in cold climates could benefit significantly from rapid, efficient battery heating. For logistics companies, minimizing downtime during cold starts translates directly into improved operational efficiency. For public transit agencies, reliable winter performance ensures service continuity even in the harshest conditions.
Moreover, the technology could play a crucial role in expanding the viability of EVs in regions like Scandinavia, Canada, Russia, and northern China, where winter temperatures regularly fall below -20°C. By ensuring consistent performance regardless of ambient temperature, this self-heating strategy removes one of the last major objections to EV ownership in cold-weather markets.
The research team, based at the School of Mechanical and Power Engineering at Shanghai Jiao Tong University, is now exploring ways to further optimize the heating protocol. Future work will focus on developing a frequency-adaptive model that calculates the ideal heating frequency at each temperature point, maximizing thermal efficiency while preventing side reactions. They are also investigating predictive algorithms that could initiate heating based on weather forecasts and driver schedules, further improving energy efficiency.
In an era where sustainability and performance are equally important, innovations like this represent the cutting edge of clean transportation technology. By turning a fundamental limitation of lithium-ion batteries into an opportunity for smarter system design, the team has opened a new pathway toward truly all-climate electric mobility.
As the global transition to electric vehicles accelerates, technologies that enhance reliability, efficiency, and user experience will be key to winning consumer trust. This self-heating strategy, rooted in elegant engineering and rigorous experimentation, exemplifies how academic research can deliver practical solutions to real-world challenges. It is not just a technical achievement—it is a step toward making electric vehicles a viable choice for everyone, everywhere, regardless of the weather.
Jingbo Han, Chong Zhu, Jia Li, Yansong Lu, Xi Zhang, School of Mechanical and Power Engineering, Shanghai Jiao Tong University, Journal of Power Supply, DOI: 10.1324/j.issn.2095-2805.2024.6.179