Many battery pack engineers and purchasers ask early on: “Do you have an existing mould for flat tubes?” This question reveals deeper concerns—development cost, lead time, and whether the cooling efficiency meets thermal needs. Choosing the wrong cross-section design may lead to poor thermal contact, costly tooling changes, and project delays.
Below, you’ll find a detailed look at what moulds are available, how to evaluate cross-section logic, when customisation makes sense, and what data you’ll need to communicate clearly with suppliers like XD THERMAL.
It’s common for clients to ask whether there are ready-to-use moulds. This question often implies they have some familiarity with battery thermal systems or have explored flat tube solutions for energy storage or electric mobility applications.
XD THERMAL does maintain a library of extrusion dies for flat tubes—especially for cylindrical cell formats such as 4680 or 4695. However, many of these are protected by NDAs and are not reusable across projects. Due to the high variation in wall thickness, flow channel design, and thermal requirements, most tubes still require some degree of customisation.
For instance, while 70mm, 80mm, 85mm, and even 140mm wide profiles are sometimes reused in prismatic cell side-cooling setups, internal channels and wall structures vary widely. Flat tubes are often integrated into broader battery liquid cooling systems and must be compatible with enclosure layouts. Since extrusion moulds cost relatively little and can be delivered within two weeks, creating a custom tool often provides more flexibility than reusing existing ones—especially when minimum material orders (e.g., 200kg) are similar to the cost of new tooling.
Flat tube shape is directly tied to how well it can dissipate heat, distribute coolant, and integrate with battery layouts. Getting this right is critical for performance and reliability.
If you’re working on a cylindrical cell system using serpentine tube solutions, your flat tube may require a radius-optimised curvature for tight bending. In contrast, prismatic cell side cooling demands large, flat contact areas to maintain even pressure and thermal contact. Cross-sections influence coolant velocity, turbulence, and overall pack thermal gradient.
Designing for high thermal efficiency typically means widening surface contact and controlling flow channel depth. Some engineers prefer wider and thinner profiles to optimise surface area contact. Others reduce channel size to increase turbulence and improve heat transfer. At XD THERMAL, we also support CFD simulation services to optimise flow path and temperature balance in early design stages. Whether your platform needs a cold plate design, an integrated battery pack cooling plate, or standalone extrusions, the cross-section is the foundation of thermal performance.
Lack of a clear design doesn’t mean you’re stuck. In fact, many of our clients rely on our engineering team to develop cross-sections based on thermal needs, packaging constraints, and simulation inputs.
XD THERMAL provides full-cycle support—from section design and extrusion validation to coating and machining. We evaluate thermal loads, structural requirements, and production priorities to create suitable sections for your project.
Our team regularly works with EV startups, ESS manufacturers, and global OEMs who know their target cell types and platform layout but not how to convert that into a heat exchanger structure. For instance, if strength is critical, we increase wall thickness. If you want lower cost, we widen flow channels and reduce material mass. If coolant resistance is a concern, we may incorporate turbulence ribs. The earlier we’re involved, the easier it is to deliver a section that meets functional, financial, and delivery targets.
Many clients wish to avoid upfront tooling, but in most scenarios, new moulds are the best choice both financially and technically.
Tooling costs are low and turnaround is fast—typically two weeks. With aluminium extrusion, minimum orders often require 200kg of material, which is comparable to moulding costs. A custom tool allows exact fit to your pack and avoids redesign later.
Here’s when we recommend custom moulds:
Custom tooling ensures that once you validate samples, the same profile is ready for ramp-up. At XD THERMAL, we often co-develop extrusion with partners to streamline thermal validation and prevent mismatches during SOP phase.
Many early-stage projects lose weeks due to unclear technical communication. Getting your initial data straight can accelerate mould confirmation, sampling, and validation.
At minimum, share your target cell type, estimated dimensions, coolant strategy (top-side or side-cooling), and whether cost or performance takes priority. Provide target flow rate and temperature delta if possible.
We typically send a one-page form to help clients quickly provide basic info. If the project is under NDA, we guide them through the safest way to describe their needs. Visual diagrams of cell layout help us assess space constraints and suggest cross-section ideas. Also, designating a single technical contact on your side streamlines follow-ups and decision-making across the project lifecycle.
Choosing the wrong mould doesn’t just waste money—it can derail entire cooling system development timelines and create major engineering rework.
We’ve seen clients try to adapt standard tools, only to suffer from coolant leaks, connector mismatch, or bending defects. Some even had to rebuild their battery liquid cooling system after discovering incompatibilities with serpentine routing or flow uniformity.
For example, choosing too thin a wall may lead to flow channel collapse during bending. Too thick, and it won’t seal well under pressure. If the cross-section isn’t matched to your pack layout, you may lose 20–30% cooling efficiency or trigger thermal runaway zones. In severe cases, this results in delays of several months. Investing early in mould optimisation can save much more in the final SOP schedule.
Flat tubes are often compared to cold plates and serpentine tubing systems in ESS and EV thermal designs. Each has its own advantages depending on the cell arrangement and thermal requirements.
Flat tubes offer a lightweight, scalable alternative to full aluminum cooling plate setups and can outperform serpentine tubes in side-cooling applications for **prismatic cells**. They provide greater contact area while simplifying integration into enclosures.
While serpentine tube solutions work well for cylindrical cells in tight formations, they may require more complex bending and welding processes. Cold plate design offers the most uniform cooling but can be heavier and less space-efficient. Flat tubes bridge the gap—flexible, low-cost, and highly customisable. In mixed battery architectures (e.g., combining modules with both cylindrical and prismatic cells), flat tubes provide modular adaptability that reduces overall BOM complexity. This hybrid flexibility is one reason why so many advanced ESS and e-Mobility platforms are shifting toward flat tube-based thermal systems.
Choosing the right cross-section and mould for flat tubes is the foundation of a reliable battery liquid cooling solution. But more than that, it’s about working with a supplier who can help you design, validate, and deliver what your application needs—fast, flexibly, and flawlessly.
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