In Electric Vehicle (EV) and Energy Storage System (ESS) applications, thermal management has become a decisive factor for safety, lifetime, and usable power. For battery packs based on cylindrical cells—such as 18650, 21700, and emerging 46-series formats—custom liquid cooling tubes, commonly known as snake tubes, serpentine tubes, or ribbon tubes, have proven to be one of the most efficient and scalable solutions.
Unlike flat liquid cold plates typically used for prismatic or pouch cells, snake tubes are designed to follow the cylindrical geometry of the cells themselves. This structural difference leads to several practical engineering advantages:
① Maximized Surface Contact: The serpentine geometry conforms to the curved cell surface, increasing effective heat transfer area. In tightly packed cylindrical modules, contact area can be significantly higher than side-mounted cooling plates.
② Structural Contribution: When manufactured from aluminum alloys such as the 3003 series, snake tubes act as semi-structural elements. They stabilize cell positioning while managing heat, reducing the need for extensive plastic bracketing.
③ Lightweight Efficiency: Micro-Port Extrusion (MPE) technology enables thin wall designs—typically in the 0.3–0.6 mm range—while maintaining sufficient burst pressure. This supports higher pack energy density.
Engineering boundary: Snake tubes are particularly effective for side-cooled cylindrical packs with liquid cooling loops. They are less suitable for low-power systems or architectures relying solely on bottom cooling.
Challenge: High discharge rates caused internal temp gradients, forcing BMS derating.
Solution: Optimized serpentine routing to shorten flow paths.
Result: Cell-to-cell ΔT stabilized within 2–3 °C; system pressure kept under 10 bar.
Why it matters: Improved thermal uniformity enabled more sustained power output under dynamic driving conditions.
Challenge: Prioritizing 15-year service life over peak cooling power.
Solution: Enhanced sealing grades and corrosion-resistant alloy selection.
Result: Met IP67/IP69K standards; verified for -40°C to 125°C operation.
Why it matters: Long-term reliability and reduced maintenance risk are critical for stationary energy storage assets.
(Note: These guidelines are based on typical aluminum extrusion and bending standards to ensure manufacturability and cost-efficiency and are typically referenced during early-stage DFM reviews.)
To speed up the transition from concept to prototype, we recommend adhering to the following Design for Manufacturability (DFM) parameters:
Every battery pack presents unique geometric and thermal requirements. A structured customization workflow helps convert these requirements into manufacturable hardware.
1. Thermal Simulation & DFM: We use CFD to balance channel count and dimensions against allowable pressure drop.
2. Micro-Port Extrusion (MPE) Selection: Utilization of existing open molds for MPE profiles to reduce tooling costs.
3. Precision Bending: CNC bending technology shapes the serpentine profile to match 21700 or 4680 layouts without compromising the micro-channels.
4. Validation: Every prototype undergoes Helium Leak Testing and Burst Pressure Testing.
This workflow allows performance-cost-manufacturability decisions to be made before committing to hard tooling.
| Specification Parameter / Capability | Details |
|---|---|
| Material Alloy | Aluminum 3003, 3003 Mod, 6063 |
| Tube Structure | Micro-Port Extrusion (MPE) / Harmonic Tube |
| Typical Wall Thickness | 0.3 mm – 0.6 mm (customizable) |
| Cell Compatibility | 18650, 21700, 4680 / 46-series cylindrical cells |
| Flatness Tolerance | Typically ±0.5 mm (process dependent) |
| Burst Pressure | > 30 bar (dependent on design) |
| Helium Leak Rate | ≤ 2×10-8 Pa·m³/s (Standard for automotive) |
Understanding what drives cost can help engineers design more economical solutions. Based on DFMA (Design for Manufacture and Assembly) principles, consider the following:
Scaling from prototype to mass production often exposes weaknesses invisible at the concept level. XD THERMAL operates three manufacturing plants with a combined annual capacity of over 1,489,200 units. With IATF 16949 certification, we ensure design intent is carried through to volume production with higher predictability.
A: We can manufacture continuous serpentine tubes up to 3,000mm (3 meters) in unfolded length. This capability is particularly important for large-scale Commercial Vehicle (Truck/Bus) battery packs and ESS (Energy Storage System) modules where reducing connection points is vital for leak prevention.
A: Yes. If you provide the flow rate (L/min) and coolant type (e.g., 50/50 Water-Glycol), our engineering team can simulate the pressure drop based on your designed flow path. We can suggest optimizing the hydraulic diameter of the MPE tube to keep the total pressure drop within your pump’s capability (typically < 30-50 kPa for module-level loops).
A: Designed in accordance with automotive standards (like USCAR), XD Thermal’s snake tubes, when used with inhibited glycol-water coolants, are engineered for a service life exceeding 10–15 years. We use corrosion-resistant 3003 Mod alloys to prevent pitting over long operational cycles.
A: Yes. Since the tube is in direct contact with the battery cells, electrical isolation is critical. We offer two main insulation solutions:
PET Film Wrapping: A cost-effective solution (typically blue or black) that provides >3000V dielectric strength and abrasion resistance.
Epoxy Powder Coating: A premium solution (typically 80-150µm thickness) that covers the entire tube surface with high uniformity, ideal for complex 3D shapes where film wrapping is difficult.
A: Yes. While we primarily manufacture based on customer prints, our engineering team provides DFM support to optimize tube paths for pressure drop and thermal uniformity.
A: Yes. We offer rapid prototyping services (2-3 weeks) using soft tooling to help you validate thermal performance before hard tooling investment.
A:
Prototypes: 2–3 weeks (using soft tooling).
Hard Tooling (PPAP): 4–6 weeks for mold creation and trial production.
Mass Production: Standard lead time is 3–4 weeks after order confirmation.
A: Not always. XD Thermal has a library of “Open Dies” (existing MPE profiles) with various widths and heights. If you can adapt your design to use one of our existing profiles, you can avoid extrusion tooling costs. You would only need to pay for the Bending Fixture and Check Fixture (Gage), which are significantly cheaper than creating a new extrusion die.
A: Snake tubes are flexible and wrap around cylindrical cells for direct side cooling. Cold plates are rigid flat surfaces, typically used for bottom cooling or prismatic cells. Snake tubes generally offer better surface area coverage for cylindrical formats.
By combining close-to-cell cooling geometry, quantified engineering data, and a transparent customization workflow, XD Thermal provides a robust and scalable thermal management path for cylindrical battery packs in EV and ESS applications.
