Wide multi-port extrusion (MPE)
A flat, thin extrusion with a row of small parallel channels, sometimes called a harmonica tube. Placed under or between prismatic and pouch cells, it gives a large, flat contact area with low weight.
Battery thermal management
Battery Cooling Aluminium Profiles and Cold Plates
Battery cooling profiles are aluminium extrusions with internal channels that carry coolant under or between battery cells, keeping the pack in its safe temperature window. They range from wide multi-port extrusions and serpentine tubes to extruded cold-plate sections joined by friction-stir welding. Metline supplies these profiles in 3003, 6063 and 6061, extruded to drawing and leak tested, for EV and energy-storage projects worldwide.
- Types
- MPE, serpentine tube, cold plate
- Alloys
- 3003 · 6063 · 6061 · 1100
- Joining
- Brazing, FSW, laser welding
- Tests
- Leak, burst, flatness
Why lithium-ion batteries need liquid cooling
Lithium-ion cells age fastest and lose power when they run hot or unevenly. Most pack designs aim to keep cells within roughly 15 – 35 °C and to hold the temperature difference across the pack to a few degrees. Fast charging and high-power driving generate heat that air cooling cannot remove, so most electric vehicles and many stationary storage systems use a water-glycol loop running through aluminium cooling plates or tubes.
Aluminium dominates this job because it combines high thermal conductivity, low density and the ability to be extruded into long, thin-walled sections with many small internal channels. A single extrusion can provide the flat contact face for the cells, the coolant passages and sometimes structural strength, at a fraction of the weight of copper.
The cooling profile is only one part of the system. Heat flows from the cell through a thermal interface material and often an electrically insulating layer into the profile, then into the coolant. Contact flatness, channel geometry and the manifolds at each end decide how evenly the pack is cooled, so the profile has to be designed with the cell layout and the coolant circuit together.
Types of battery cooling profile
Serpentine cooling tube
A flat multi-channel tube bent in a wave that snakes between rows of cylindrical cells, contacting the side of each cell through a thermal pad.
Extruded cold-plate profile
Thicker extrusions with larger channels, joined side by side by friction-stir welding (FSW) and closed with end caps to form a cold plate. Can also act as the floor of the battery tray.
Stamped and brazed cold plate
Two pressed sheets of clad brazing sheet with formed channels, brazed together. Not an extrusion, but often compared with MPE designs.
Integrated tray profile
Structural 6xxx extrusions for the battery tray with cooling channels built into the floor section.
Manifolds and headers
Round or rectangular tubes and machined blocks that distribute coolant to the channels, brazed or welded to the profile ends.
Alloys for battery cooling profiles
| Alloy / temper | Thermal conductivity (typical) | Why it is used | Typical product |
|---|---|---|---|
| 1050 / 1100 | ≈ 220 – 230 W/m·K | Highest conductivity, very easy to extrude thin walls | Thin MPE, low-pressure plates |
| 3003 (and modified 3xxx) | ≈ 160 – 190 W/m·K | Good strength after brazing, corrosion resistant, brazeable | MPE and serpentine tubes in brazed coolers |
| 6063-T5 / T6 | ≈ 200 – 210 W/m·K | Good conductivity with more strength; fine surface for flat contact faces | Cold-plate profiles joined by FSW |
| 6061-T6 | ≈ 167 W/m·K | Higher strength for plates that also carry structural loads | Structural cold plates, tray floors |
| 6005A / 6082 | ≈ 170 – 190 W/m·K | Structural strength and crash performance | Battery tray frames with integrated channels |
Conductivity values are typical published figures and vary with temper. 6xxx alloys are not normally furnace brazed, because their solidus is close to the brazing temperature; brazed designs use 1xxx and 3xxx alloys, while 6xxx profiles are joined by FSW, laser or MIG welding or by adhesives.
Design points and acceptance tests
What to define on the drawing
- Contact face
- Flatness over the cell footprint, surface finish and any insulating coating or film
- Channel geometry
- Number, size and wall of ports; minimum wall governed by extrusion limits and burst pressure
- Pressure
- Operating pressure, proof and burst pressure required, including pressure cycling
- Leak tightness
- Helium leak test or pressure-decay test with the acceptance leak rate
- Cleanliness
- Internal particle limits so that debris cannot block channels or damage the pump
- Corrosion
- Coolant type (water-glycol with inhibitors) and external environment; galvanic isolation from copper and steel
- Electrical isolation
- Dielectric strength between cells and plate, by coating, film or insulating pad
Typical failures in service are pinhole leaks at joints, erosion or corrosion inside channels when the coolant inhibitor is depleted, and poor thermal contact where the plate is not flat. Ask for flatness to be measured after any joining step, because brazing and welding can distort thin profiles.
How cooling profiles are made
- Die designPorthole or bridge dies form the internal channels; thin-wall MPE needs precise die design and a soft, clean alloy.
- ExtrusionBillet is extruded, cooled and, for 6xxx alloys, aged to T5 or T6. MPE is often coiled or cut to length in-line.
- Cutting and formingProfiles are cut, bent (serpentine tubes) or machined for ports and manifolds.
- JoiningControlled-atmosphere brazing for 1xxx/3xxx assemblies; friction-stir or laser welding for 6xxx cold plates.
- TestingDimensional and flatness checks, leak and burst testing, cleanliness inspection, certificate of conformity.
References and standards
- EN 755-2 – Extruded rod/bar, tube and profiles: mechanical properties
- EN 573-3 – Chemical composition and form of wrought products
- ASTM B221 – Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- ASM International – Properties of Wrought Aluminum and Aluminum Alloys (thermal conductivity data)
- Hydro – Battery cooling and multi-port extrusion information
Battery cooling aluminium (aluminum) profiles: frequently asked questions
What is a multi-port extrusion for battery cooling?
It is a flat aluminium extrusion with many small parallel channels. Coolant flows through the channels while the flat face contacts the cells through a thermal interface material.
Which alloy is best for a battery cold plate?
3003 and 1xxx alloys are used for brazed MPE and serpentine coolers. 6063 suits extruded cold plates joined by friction-stir welding, and 6061 or 6082 is used when the plate also carries structural loads.
How are cold plates tested?
Usually by helium or pressure-decay leak testing, burst and pressure-cycle testing, flatness measurement and internal cleanliness checks against the customer specification.
Can 6063 profiles be brazed?
Generally no. 6xxx alloys melt too close to the brazing temperature. They are joined by friction-stir welding, laser welding or adhesive bonding instead.
How is the plate isolated electrically from the cells?
With a dielectric coating, an insulating film or a thermally conductive but electrically insulating pad. The dielectric test voltage should be stated on the drawing.
Do you supply custom cooling profile sections?
Yes. Send the profile drawing, alloy, length and quantity; we review extrudability and supply cut-to-length profiles with inspection reports.
Need battery cooling profiles?
Send the section drawing, alloy, length, quantity and test requirements. We will review the design and quote.
