By CheolJoong (CJ) Kim, Asia-Pacific Sales Director, SemiQ.

The importance of shifting from ICE-based to electric vehicles is recognized by the majority of both governments and car manufacturers. Following the Glasgow Climate Pact, which was reached at COP26, over 100 countries and companies have signed a declaration to phase out internal combustion engine (ICE) vehicle sales in advanced economies by 2035 and globally by 2040.

Countries like Norway are almost there, with 90% of new vehicles sold being EVs. But the average is still below 20% and much needs to be done.

The shift to EVs is fundamentally tied to advances in battery technology. Consumers still have hesitancies relating to range anxiety (more accurately charging anxiety) and governments need to increase public charging infrastructure, and OEMs need to enable both faster on-board chargers (OBCs) and larger-capacity batteries.

For EV manufacturers, the ability to rigorously evaluate battery performance, durability, and efficiency is essential in developing longer-range and longer-life power sources. And core to this evaluation process is the battery cell cycler, a critical piece of test equipment whose performance relies heavily on the power electronics within.

SemiQ is a supplier to this industry – announcing its work supplying a leader in this field earlier this year. As a result of this deal, the technology is already being integrated into advanced cell cycling systems used by several of the world’s leading battery manufacturers, and in this article, we’ll examine in more detail how we’re helping these organizations to meet the demands placed on them.

The Function and Challenges of Battery Cell Cyclers

A battery cell cycler is a high-precision power electronics system designed to repeatedly charge and discharge battery cells under controlled conditions. This process is essential in the evaluation of SEI layer formation and in performance and safety analysis.

Taking each in order, a stable and well-formed SEI is critical for the battery’s long-term performance and longevity, with the initial charging cycles for lithium-ion cells forming the Solid Electrolyte Interphase (SEI), a passivation layer on the anode surface and the cell cycler is crucial in this process.

And for performance and safety analysis, cyclers enable manufacturers to conduct degradation tests and subsequent analysis over many thousands of cycles, as well as the undertaking of temperature and stress testing, and screening for manufacturing defects or performance anomalies.

To perform these tasks effectively, the cycler’s power stage needs to precisely control current and voltage and simulate real-world conditions without causing damage from overcharging or discharging. High switching frequencies are therefore needed as this allows for finer levels of control.

This naturally places the high-speed switching MOSFETs under significant pressure, forcing them to endure immense thermal stress from repeated power cycling. Tests can run for several weeks or even months and a MOSFET failure would not only disrupt the test, but also compromise the integrity of the collected data.

Furthermore, with hundreds or thousands of cells being tested simultaneously, the overall power conversion efficiency is a major factor in operational cost. Thermal management challenges are compounded as any inefficiencies in the system are emitted as heat (P_LOSS=I²R).

A SiC-Based Solution for a 100 kW System

To meet these demanding requirements, designers of a new 100 kW cell cycler system have integrated SiC MOSFET modules from SemiQ. The cycler has been developed using ten 10 kW cells connected in parallel, with each 10 kW cell unit integrating twelve QSiC™ half-bridge modules (120 modules per 100 kW cycler system).

Fig 2: Assembling the power conversion stage of an advanced battery cell cycler utilizing SemiQ QSiC™ modules.

Key Technical Advantages of the QSiC™ Modules

The inherent material properties of silicon carbide provide a distinct advantage in high-power, high-frequency applications. The SemiQ SiC modules (specifically the GCMX003A120S3B1-N and GCMX003A120S7B1 1200 V half-bridge modules) were chosen for their ability to deliver the required precision, reliability, and efficiency.

The modules are engineered for high-speed switching with exceptionally low switching losses. This is critical for achieving the precise current and voltage control needed for battery characterization. The lower energy loss during switching transitions contributes significantly to higher overall conversion efficiency, reducing both operating costs and the thermal load on the system.

These modules also feature a rugged design that is capable of withstanding the thermal stress of continuous power cycling and have been tested to over 1350 V, giving a greater than 10% margin over their 1200 V.

Of course, a reliable body diode is crucial for performance in a half-bridge topology, particularly during freewheeling operation. This also enables systems based on the SemiQ modules to use simpler designs that remove the need for external anti-parallel diodes.

Fig 3:  The SemiQ GCMX003A120S3B1-N is a 1200 V QSiC™ half-bridge module offering low switching losses and high reliability for demanding power conversion applications.

According to IMF figures, transportation accounts for 36% of greenhouse gas emissions in the U.S., 21% in the European Union, and 8% in China. According to the Center For Climate And Energy Solutions (C2ES), the majority of this isn’t aircraft, it’s road vehicles, with these responsible for 83.5% of all transport emissions.

The electrification of transportation is therefore among the most important steps that can be taken to reach net-zero, with the IMF stating the “move toward EVs … is seen as a key way to help countries achieve climate goals.”

For this, the evaluation of battery performance, durability, and efficiency plays a vital role in enabling the development of longer-range, longer-life EV batteries and the successful integration of SemiQ’s SiC modules into these advanced cell cyclers demonstrates the technology’s capacity to meet the rigorous demands of modern EV battery testing.

For detailed specifications, datasheets for the GCMX003A120S3B1-N and GCMX003A120S7B1 modules are available at SemiQ.com here.