Battery cells are placed inside a module where a dielectric fluid circulates andcomes into direct contact with the cell surfaces. A cell-spacer guides the fluidand insures the separation between the cell. This enables uniform, 360° heatextraction, even during high‑power demand or fast‑charging events. This fullyimmersive contact provides cooling performance that is not achievable withtraditional systems such as air or cold plates

Yes, but the battery is not filled like a tank. Arelatively small quantity of dielectric fluid circulates through an internal coolingloop, touching the cell surfaces only where needed. This ensures excellentthermal transfer while keeping fluid volume low

Automotive demonstrators show:

• Charging time divided by two on the Renault Mégane E‑Tech prototype equipped with an immersed battery.
• Increased driving range thanks to improved thermal stability.
• Up to 3× better thermal performance, and up to 7× more effective when normalized by cell surface area.
• Significantly improved safety against overheating (thermal‑runaway prevention).
• Lighter and simpler systems, as some components (cold plates, large glycol circuits, etc.) become unnecessary.

Yes. The dielectric fluid:

• Immediately removes heat in the event of a cell failure,
• Prevents the propagation of potential thermal runaway,
• Creates a natural thermal barrier between cells.

These safety benefits are among the main reasons why OEMs show strong interest

Absolutely. Thanks to direct fluid‑to‑cell contact, immersion:

• Supports very high charging power (up to 22 kW demonstrated on a modified PHEV),
• Enables projected recharge times under 10 minutes,
• Drastically reduces temperature rise, which normally limits charging speed.

TotalEnergies has conducted several real‑world integrations:

• Renault Mégane E‑Tech — immersion battery prototype, resulting in ×2 charging speed and better range.
• Volvo XC90 PHEV (Phosphor project) — conversion of a mass‑produced PHEV into an immersion‑cooled pack (22 kW charging capability).
• Swappable electric scooters — removable packs cooled by immersion.These results demonstrate compatibility with mainstream automotive platforms.

Uniform thermal control reduces:

• Premature cell ageing,
• Temperature imbalances between cells,
• Thermal stresses during fast charging.Internal demonstrations show greater long‑term stability and a potential increase in lifetime.

It is technically mature (working demonstrators, active OEM discussions), but large‑scale production depends on:

• Adoption by automakers,
• Adaptation of assembly lines,
• Standardisation of immersion‑ready battery modules.Experts anticipate OEM adoption well before 2030.

In several projects, immersion was integrated:

• Without modifying the vehicle, such as the XC90 PHEV conversion (original vehicle layout preserved),
• While keeping the overall pack structure intact,
• By adapting only specific parts (circuits, fluid reservoir, pump).This shows a high level of compatibility with existing EV platforms

Depending on the architecture:

• A prototype pack requires around 16 liters,
• Optimised versions use as little as 4.5–5 liters.These low volumes improve both industrial viability and environmental footprint