# SK On and GS Caltex Advance Immersion Cooling Packs for High-Voltage EV Fleets *South Korean battery makers and refiners accelerate direct dielectric fluid testing to suppress thermal runaway and shorten charging cycles for next-generation platforms.* **Published:** August 30, 2026 **By:** Seung-min Park **Section:** Batteries & Electric Vehicles — South Korea **Format:** Why It Matters **Confidence:** high **Source:** https://eastasiabrief.com/batteries-ev/sk-gs-caltex-advance-immersion-cooling-packs-high-voltage-126 **Publisher:** East Asia Brief (https://eastasiabrief.com/) --- ## What to know - SK On and SK Enmove unveiled on March 8, 2026, an integrated cell-to-pack platform using dielectric immersion cooling fluids, targeting commercial pouch pack production by 2027. - The technical disclosure at the InterBattery 2026 exhibition in Seoul marked the latest step in South Korea's supply-chain push toward direct liquid thermal management for high-voltage electric vehicles. - Automotive battery systems rely on indirect cold plates that circulate water-glycol mixtures beneath cell modules. ![Researchers examine an immersion cooling battery system showcased inside a transparent tank at the InterBattery exhibition. (AI-generated image)](https://eastasiabrief.com/media/2026-08-30-c19382b0e1e9.webp) *Researchers examine an immersion cooling battery system showcased inside a transparent tank at the InterBattery exhibition. (AI-generated image)* SK On and SK Enmove unveiled on March 8, 2026, an integrated cell-to-pack platform using dielectric immersion cooling fluids, targeting commercial pouch pack production by 2027. The technical disclosure at the InterBattery 2026 exhibition in Seoul marked the latest step in South Korea's supply-chain push toward direct liquid thermal management for high-voltage electric vehicles. Automotive battery systems rely on indirect cold plates that circulate water-glycol mixtures beneath cell modules. That architecture leaves contact resistance between cells and cooling plates, creating localized thermal gradients during ultra-fast direct-current charging. Direct immersion submerges cells, busbars and control boards in non-conductive dielectric fluid. By eliminating air gaps, the fluid absorbs heat directly from cell surfaces and prevents cascading cell-to-cell thermal propagation. SK On scheduled commercial production of its pouch cell-to-pack design for 2027. The company set a 2028 target for a pouch-integrated prismatic pack that places pouch cells inside rigid aluminum cases, company executives said. The pack designs combine high-nickel cathode chemistry with synthetic hydrocarbon fluids supplied by SK Enmove, an in-house operating unit of SK On. The arrangement removes conventional intermediate module housings to raise volumetric energy density. Vehicle testing began in early trial programs. Hyundai Motor Company and SK On evaluated an immersion-cooled pack prototype fitted to a modified Ioniq 5 electric crossover on July 18, 2025. The road trial measured cell temperature uniformity during repeated 350-kilowatt charging sessions. Direct dielectric contact reduced peak cell temperatures and suppressed thermal spikes that degrade cathode active materials, according to project engineers. Eliminating high-voltage wiring inside fluid-filled enclosures presented an early manufacturing challenge. Metal harnesses and connectors increase fluid displacement volume and create potential electrical leakage paths over extended vibration cycles. SK On addressed the wiring hurdle on March 3, 2025, by introducing a wireless battery management system. The design attaches sensor chips directly to cell tabs, transmitting voltage and temperature telemetry across radio frequencies to an external module antenna. Removing copper harness assemblies lowers pack weight and minimizes mechanical fluid turbulence. The wireless setup allows dielectric liquid to circulate unobstructed across cell faces, SK On said in a technical presentation. Specialty chemical refiners are adjusting base oil refining assets to supply the emerging vehicle thermal fluid sector. GS Caltex Corporation expanded its immersion cooling lineup on June 26, 2025, releasing four specialized formulations for vehicle packs, charging stations and stationary storage. The refiner manufactures polyalphaolefin dielectric fluids under the Kixx Immersion Fluid brand at its Yeosu refining complex. The synthetic hydrocarbon fluid has a flash point exceeding 250 degrees Celsius to prevent vapor combustion under electrical arcing. GS Caltex supplied its fluid to LG Uplus Corporation on June 26, 2025, for data center cooling trials while conducting secondary qualification tests with domestic battery cell makers. The fluid maintained dielectric breakdown voltage and volume resistivity during 12-week stress tests, GS Caltex said. Marine energy storage systems provided early commercial validation for dielectric submersion hardware. Hanwha Aerospace and SK Enmove presented their SEAL marine storage module on Sept. 10, 2024, during a technical demonstration in Pangyo. The marine module received design safety certifications from DNV and the Korean Register of Shipping. The Korea Research Institute of Ships and Ocean Engineering installed the system on an electric propulsion test vessel to monitor marine salt tolerance. Submersion systems add liquid mass compared with dry pack cavities. High fluid viscosity at low ambient temperatures also increases parasitic power draw from circulating pumps, requiring low-viscosity base oil formulations. Refiners use catalytic hydrocracking and oligomerization to produce isoparaffinic and polyalphaolefin fluids with low pour points. The custom molecular structures maintain pumpability at minus 30 degrees Celsius while preserving flash-point margins, chemical engineers said. Vehicle pack assemblers must also redesign elastomer seals and enclosure gaskets. Synthetic hydrocarbon fluids can soften standard ethylene propylene diene monomer rubber over multi-year operational lifetimes. Tier-one suppliers have shifted qualification testing toward fluorosilicone and fluoroelastomer sealing compounds to prevent fluid seepage across underbody enclosures. Sealing validation remains a critical prerequisite for production platform sign-offs, automotive suppliers said. Cost structures continue to influence deployment timelines. Dielectric synthetic fluids carry a price premium over standard ethylene glycol coolants, limiting initial adoption to premium electric vehicles and high-utilization commercial fleet platforms. Automakers project that savings from simplified firewalls and reduced module hardware will offset higher fluid expenses. Eliminating aluminum cooling plates and thermal interface gap fillers reduces raw material part counts in cell-to-pack architectures. Automotive standards committees have not established standardized flammability and disposal rules for vehicle immersion fluids. South Korea's Ministry of Trade, Industry and Energy has not published national certification standards dedicated to automotive dielectric coolants. Industrial testing programs continue across regional proving grounds. SK On plans to install prototype pilot lines at overseas manufacturing hubs to prepare cell-to-pack immersion tooling for global automotive customers. ## Impact map | Event | Korea | China | Japan | Global impact | | --- | --- | --- | --- | --- | | Immersion cooling commercialization | cell makers and refiners develop fluid packs | pack makers test direct liquid designs | thermal chemical suppliers compete on fluids | EV platforms shorten ultra-fast charging times | ## In this story - **Companies:** SK On, SK Enmove, GS Caltex, Hyundai Motor Company, Hanwha Aerospace - **Tickers:** 005380.KS, 012450.KS - **Exposed:** LG Energy Solution, Samsung SDI, DNV - **Policy:** Subsidies, Economic Security - **Impact:** Supply Chain, Capex, Cost Structure, Compliance ## Primary sources 1. petroleum.or.kr 2. sk-on.com 3. dailyt.co.kr 4. einfomax.co.kr 5. batterydive.com --- Cite as: East Asia Brief, "SK On and GS Caltex Advance Immersion Cooling Packs for High-Voltage EV Fleets," August 30, 2026. https://eastasiabrief.com/batteries-ev/sk-gs-caltex-advance-immersion-cooling-packs-high-voltage-126