Electric vehicle (EV) battery packs must charge faster, deliver more power, and hold more energy, all without much additional room inside the pack. Much of that engineering challenge now centers on the cooling interface between the cell and the coolant path, where every additional layer adds thermal resistance.
Advanced battery cooling systems must manage heat generated during charging and discharge while maintaining temperature uniformity across the pack.
Freudenberg Sealing Technologies is addressing these demands with AB-Chillcore, an advanced battery cooling platform built around one idea, which is to put the cooler in direct contact with the cell and remove the thermal interface materials in between.
Traditional liquid-cooled packs rely on a cooling plate paired with thermal interface materials (TIMs) or gap fillers to move heat away from the cells. The approach is common and it works, but each layer introduces thermal resistance and raises cost and assembly complexity.
“The biggest architectural shift is that more designs are moving from ’cool a plate’ then ’conduct through layers’ to ’cool the cell surface directly,’” says Sumir Kakkar, new product introduction manager with Freudenberg Sealing Technologies.
The direct cooling interface is engineered to contact the cell surface rather than rely on a thick stack-up of TIMs or gap fillers. This change does more than strip out a layer. It turns the cooler into part of the mechanical structure of the pack.
“When you go to direct contact, the cooling solution stops being a passive plate and becomes a mechanically compliant thermal component,” he explains. “It must conform to small height and shape variations and maintain contact across the active area.”
The mechanical problem behind direct contact
Battery cells are not dimensionally fixed. They expand and contract with temperature, shift under load, and swell as they age. Manufacturing tolerances introduce additional variation, meaning no two cells sit in precisely the same position.
“As packs push higher energy density, the allowable space for thermal compliance shrinks, yet the need for compliance grows because real cells aren’t dimensionally static,” Kakkar says. A cooler pressed against the cell must absorb all of that and still hold even contact across the surface.
That makes contact pressure one of the defining variables in the design. Too little, and gaps open between the cooler and the cell. Too much, and the cell takes on mechanical stress.
Exploded view of an EV battery pack showing the relationship between the cells, cooling layer, and structural components. Direct-contact cooling seeks to improve heat transfer by reducing the number of layers between the cell and coolant path.
“If the contact pressure window is too low, you lose contact and create thermal bottlenecks,” he adds. “Too high, and you risk mechanical damage, swelling constraints, or accelerated degradation.”
Freudenberg’s approach builds the compliance into the structure, using flexible designs and tolerance-compensation features that follow the cell surface instead of filling the gap with cured material.
How direct contact compares with TIM-based systems
The differences between direct contact and TIM-based systems tend to fall into four areas:
- Thermal performance and uniformity. Removing intermediate layers lowers thermal resistance and helps hold cell temperatures steady under demanding operation.
- Hotspot reduction. More even contact limits local hot spots, which matters most at the high currents seen in fast charging and high discharge.
- Cost and manufacturability. Cutting gap fillers and TIMs simplifies the bill of materials and removes assembly steps tied to dispensing and bond-line thickness.
- Serviceability. Without large amounts of cured bonding material, packs can be easier to service or rework.
Hotspot control grows more important as charging currents climb. Localized temperature differences accelerate cell aging and can push the battery management system to throttle power to protect the pack, so spreading heat evenly across the cell face has a direct effect on the power the pack can sustain.
Matching the method to the constraint
AB-Chillcore is less a single part than a set of configurations, and Freudenberg is evaluating several through the platform.
Top and bottom cooling targets direct contact with a primary cell face and tolerance compensation across it. Side cooling manages cell breathing through controlled compression on the side walls and can provide applications that need more cooling capacity, such as fast charging. Immersion cooling carries its own requirements around dielectric fluids, oil compatibility, and flow control, with a simpler assembly.
“Different cooling approaches can all work, but they don’t solve the same constraints. They have to be evaluated based on contact, tolerance, compression, flow, and packaging,” he says.
Direct-contact cooling systems must maintain consistent thermal contact despite cell swelling, thermal expansion, and manufacturing variation. Freudenberg’s AB-Chillcore platform incorporates compliant structures designed to accommodate those changes.
Holding the cooler against the cell solves half the problem. The coolant still has to carry heat away evenly, and at fast-charge rates the system is fighting peak heat generation and tight cell-to-cell uniformity at the same time.
Freudenberg tunes that behavior through channel geometry, flow-profile adjustments, and inserts that deliberately create turbulence within the coolant path.
“Turbulence boosts convective heat transfer by disturbing boundary layers and increasing mixing, particularly useful when heat flux spikes during fast charging,” Kakkar says. Steering the flow, he adds, is aimed at uniformity rather than peak cooling, which reduces the temperature gradients that build along long channels and leave some cells better cooled than others.
The platform’s demonstrator hardware, a flex cooler, shows the combination at work. It uses multi-layer, 3D-patterned elements that handle compression and fluid mixing across a flexible surface backed by rigid areas. Water-glycol remains the expected coolant for most designs, with dielectric oils used for immersion concepts.
Freudenberg describes the concepts as pre-development and is targeting functional demonstrators by the third quarter of 2026. The direction it is building toward, Kakkar says, is one of higher integration, better contact, and smarter flow.
“The future compact cooling system isn’t necessarily smaller because of different fluids,” Kakkar says. “It’s smaller because it uses geometry and contact mechanics more effectively, and it controls coolant distribution more precisely.”
Filed Under: Featured Contributions, Tech Spotlight, Thermal Management