TotalEnergies trials immersion-cooled battery in EV field test

Changing the battery cooling technology in an electric vehicle (EV) represents a considerable step. The cooling of lithium batteries by immersion is regarded as the optimum solution to the challenges posed by ultra-fast charging. The most powerful charging stations (up to 350kW DC) generate heat fluxes that existing cooling systems struggle to handle.

The paradigm shift in technology has an impact on future design, development guidelines, energy strategy and cooling control, as well as safety. Test projects are already underway, but to-date this technology has only been trialed in prototypes. 

In order to support the development of this technology, TotalEnergies has applied it for the first time in a road-going car, replacing the battery cooling system in a Volvo XC90 plug-in hybrid with an immersion alternative. In performance terms, the result was immediate: faster charging, better cooling, enhanced safety and lower cost and mass, without in any way needing to modify the design of either the battery or the vehicle.

This allowed a direct comparison between the advantages offered by immersion cooling and by more conventional cooling methods, supported by data collected for the first time from a mass-produced vehicle rather than relying solely on simulations. 

The cooling system was replaced with minimal mechanical modifications. The architecture of the vehicle was respected, and the battery remains the same. The only differences to be found were in the components needed for immersion cooling, or where it was necessary to make them compatible with the dielectric fluid. The potential of the on-board charger, by contrast, increased from 3.7kW to 22kW.

The data collected during the field trial revealed that cooling capability was seven times more effective when using the technology developed by TotalEnergies, the French company said. A more easily integrated system can reduce mass by 4% and cost by 5.6 % on the vehicle, the company said. The overall safety and durability of the lithium cells are also enhanced by the high performance of TotalEnergies fluids, it added.

After the trial, TotalEnergies said “we can confidently predict that immersion cooling for lithium batteries will be a key technology of the future. It perfectly addresses the challenges of the next generation of electric cars, whose batteries are expected to be more powerful, safer and longer lasting.”