Aluminium or copper cables in DC charging infrastructure?

The discussion about aluminum or copper occurs at almost every larger DC charging station. That discussion often starts with the cable price. That is too limited. The choice of material also influences cable cross-section, voltage drop, heat development, bending radius, connection technology, space in power cabinets and ultimately the operational reliability of the charging site.

This consideration becomes extra relevant for heavy vehicles. A depot with electric trucks, buses or construction machines can charge at high power for hours. As a result, not only the cables, but especially the connections and connection points, are subject to long-term thermal stress.

The right question is therefore not: is aluminum better or worse than copper? The relevant question is: on which cable route does aluminum provide a technical and economic advantage, without deteriorating implementation or operational reliability?

Start with the cable route, not with the material

A DC charging site consists of various electrical parts. The cable between transformer and low-voltage distributor has different requirements than the connection between a power cabinet and a satellite. The available space, cable length and mechanical load also differ per route.

• Transformer to main distributor or power cabinet: often relatively long and clear routes with room for larger cable cross-sections.
• Main distributor to charging equipment: the applicability largely depends on the manufacturer’s terminals, input space and permitted cable cross-sections.
• Power cabinet to satellite: multiple positive and negative cables, limited space and often smaller bending radii. This is where installation becomes an important part of the decision.
• Internal cabling of the charger: falls within the manufacturer’s design and product responsibility. There, a project designer cannot independently choose a different conductor material.

That is why one choice of material for the entire charging site usually does not work. A combination of aluminum on longer fixed routes and copper in compact or mechanically sensitive parts may make more technical sense.

Electrical difference: aluminum requires a larger cross-section

Copper conducts electricity better than aluminum. At approximately 20 °C, the electrical conductivity of copper is around 58 MS/m and that of aluminum is around 35 MS/m. For a comparable electrical resistance, aluminum therefore requires roughly one and a half to more than one and a half times as much conductor cross-section.

Aspect	Copper	Aluminum	Consequence for design
Electrical conductivity	Approximately 58 MS/m	Approximately 35 MS/m	Aluminum requires a larger cross-section for comparable resistance.
Density	Approx. 8.9 g/cm³	Approx. 2.7 g/cm³	Despite its larger cross-section, aluminum remains considerably lighter.
Space required	Relatively compact	Larger diameter	More space needed in gutters, bends, glands and cabinets.
Mechanical behavior	Relatively robust	More attention to creep and thermal expansion	Connection technology and mechanical support are becoming more important.
Material price	Higher	Typically lower	Savings must be compared to installation and component costs.

That larger cross-section is not automatically a problem. Aluminum can be a good fit for a long cable route through a spacious cable duct. In a compact charging cabinet, the same choice can lead to excessively large bending radii, insufficient clamping space or an impractical mounting sequence.

Voltage drop and cable loss: compare at system level

The resistance of a conductor follows in simplified form from R = ρ × L / A. Where ρ is the resistivity, L is the conductor length and A is the cross-sectional area. The electrical loss follows from P = I² × R. At high charging currents the loss therefore increases quadratically with the current.

This makes a comparison based on cable cross-section alone misleading. Comparing an aluminum cable of 300 mm² with a copper cable of 300 mm² means little, because both do not have the same electrical resistance. You must compare cross sections that are sized for the same design purpose.

Calculation example: 600 kW over 50 meters

Take a simplified DC path of 50 meters at 800 V and 600 kW. The current is then approximately 750 A. For the positive and negative conductors together, the electrical loop is 100 meters.

• 300 mm² copper gives approximately 4.4 V voltage drop and approximately 3.3 kW conductor loss at 20 °C in this simplified calculation.
• 500 mm² of aluminum results in the same order: approximately 4.2 V voltage drop and approximately 3.2 kW conductor loss.

This example mainly shows that aluminum can perform similarly electrically when the cross-section is adjusted accordingly. It is emphatically not cable dimensioning. For an actual design, operating temperature, installation method, bundling, ground conditions, insulation material, short-circuit withstand capability and manufacturer data also count.

In heavy transport, the load duration is at least as important as the peak power

For passenger cars, the maximum charging power is often taken into account. For a truck depot, the usage profile is more important. Multiple vehicles can charge simultaneously for hours, causing cables and connections to reach high temperatures for a long time.

For depot charging, the design must therefore take into account the actual simultaneity factor and charging duration. An installation that processes a short peak without any problem may react differently under long-term high thermal loads.

For underground cables, ground temperature, thermal resistance of the ground, mutual distance and the number of loaded cables also play a major role. A cheap cable choice may therefore require additional trenches, larger conduits or other route distances.

On the DC route, I²R loss remains the starting point. With parallel conductors, differences in cable length, connection or contact resistance must also be prevented from leading to unequal current distribution.

The connection often determines whether aluminum is practically feasible

In practice, the greatest risk is not in the aluminum conductor itself, but in the transition between cable and component. Aluminum quickly forms an oxide layer, expands more strongly with temperature changes and is more sensitive to creep under prolonged mechanical pressure.

It must therefore be determined in advance whether the clamp, cable lug, gland and connection rail are suitable for the selected aluminum cable type and cross-section. Only use connection techniques that the cable and component manufacturer supports for that combination.

• Check the permitted conductor materials of each terminal.
• Check the maximum conductor cross-section and outside diameter, not just the rated current range.
• Use suitable aluminum-copper connections or bimetallic cable lugs where necessary.
• Follow the prescribed stripping method, surface treatment, crimping die and tightening torques.
• Include mechanical support and strain relief in the cabinet design.

Trying to retrofit a standard copper connection for aluminum is not a good design strategy. The choice of cable must be linked to the selected power cabinets and distribution boards in the sketch and final design.

Would you like to have a cable calculation performed or an existing calculation independently reviewed? Green Fellows can assess the sizing, assumptions and feasibility. For cable issues we work with, among others Paul Borghouts, our specialist in the field of cables and electrical dimensioning.

Bending radius and cabinet layout become part of the cable calculation

An electrical calculation can show that an aluminum cable can technically carry sufficient current. This does not yet prove that the cable also physically fits into the installation.

The larger cable diameter affects the minimum bending radius, entry angle, distance to connecting rails and required free space for mounting tools. Especially with multiple parallel conductors, a cabinet that seems large enough on paper may turn out to be too small during implementation.

In a good design, cable calculation and spatial development are therefore carried out side by side. Check not only the cable length, but also every bend, entry and connection for the actual dimensions of the chosen cable.

Satellite system: aluminum especially interesting for the compact charging points

In a satellite system, the power electronics and the charging points are physically separated. This creates longer fixed cable routes to the power cabinets and shorter, more compact routes to the satellites.

Aluminum can be financially interesting, especially on longer fixed routes. There is often more space for larger cross-sections and the cables do not have to pass through compact bends or small connection spaces as often.

From the power cabinet to a satellite the situation changes. There, several DC conductors often run next to each other, while the available space in the satellite remains limited. The charging point can also be mechanically loaded due to a collision or displacement.

In such a situation, a stiffer aluminum cable can transmit greater forces to the connection points. Copper is often the more logical choice due to more compact cross-sections and practical workability, unless the manufacturer has demonstrably designed the system for aluminum.

Integrated chargers: look especially at the manufacturer boundary

With an integrated charger, power electronics and charging output are in one housing. The project designer then mainly chooses the power cable to the charger. The internal DC cabling and output to the vehicle are subject to the manufacturer’s product design.

Aluminum can be an option on the power side if the manufacturer specifies suitable connections. If the connection terminal is designed exclusively for copper, this option is eliminated regardless of the theoretical savings on cable material.

Maintenance: Check the connection, not just the cable

A properly installed aluminum connection can function reliably. However, the maintenance approach must be appropriate to the connection type, load and manufacturer’s instructions.

Thermography under representative loads is valuable, because increased contact resistance can become visible as a local temperature increase. Preferably record a baseline measurement upon delivery, so that later inspections can be compared with the same connection.

Routinely re-tightening every connection is not automatically the correct measure. Some connection techniques are designed to maintain their contact pressure. Therefore, follow the component manufacturer’s maintenance and tightening instructions and base additional inspections on intensity of use and risk.

Costs: compare total construction costs and lifetime costs

Aluminum is usually cheaper per meter than copper. With long, heavy power cables, this difference can become substantial. Yet the price per metre alone does not provide a useful business case.

Include at least the following items in the comparison:

• cable price per fully dimensioned route;
• additional cross-section and any additional parallel cables;
• cable ducts, conduits and trench dimensions;
• glands, cable lugs and transition connections;
• installation and crimping time;
• larger or modified distribution boards;
• inspection and thermographic surveys;
• spare parts and repairability in the event of failures;
• consequences for warranty and system responsibility.

On a route of tens of meters, the material savings can far outweigh additional connection costs. On a short route with several bends and tight connections, the financial advantage can almost completely disappear.

What should be recorded in a design or procurement specification?

If aluminum is allowed, a quotation must include more than just a cable type and cross-section. Otherwise, important design choices are postponed to implementation.

• material and alloy of the conductor;
• calculated current, simultaneity and load duration;
• permitted voltage drop per cable route;
• thermal calculation including installation method and bundling;
• short-circuit withstand capability and protection concept;
• maximum cable length and number of parallel conductors;
• actual bending radius and cable diameter;
• type of cable lugs, clamps and any bimetallic transition;
• written confirmation that the charging equipment supports the selected conductor material;
• assembly instructions with crimping tools and tightening torques;
• delivery inspection and baseline measurement for thermography;
• maintenance instructions and division of responsibilities during operation.

This makes the choice between copper and aluminum controllable. A supplier must then not only demonstrate that the cable is electrically compliant, but also that the entire route remains feasible, inspectable and maintainable.

Standards framework: pay attention to the system boundary

NEN 1010:2020+C1:2024 is an important starting point for fixed low-voltage installations in the Netherlands. IEC 60364-5-52 is relevant for selection and installation of cable systems. IEC 60364-7-722 covers electrical installations for the supply of electric vehicles and ends at the connection point.

IEC 61851-23:2023 is relevant for the DC charging equipment itself. IEC 62477-1:2022 covers safety aspects of power electronic converters up to 1,000 V AC and 1,500 V DC. NEN 3140 and NEN-EN 50110-1 are relevant for safe operation and maintenance.

IEC 62196 is particularly relevant for the vehicle connector and the interface with the vehicle. That standard does not independently determine whether a fixed power or distribution cable must be made of copper or aluminum.

The standard alone therefore does not provide a choice of materials. The design must also comply with the connection conditions, installation instructions and product limits of the charging equipment and components used.

When is aluminum logical and when is copper?

Situation	Most logical starting point	Why
Long fixed cable route with plenty of space	Examine aluminum	Material savings can be significant and a larger cross-section can be accommodated spatially.
Transformer or distributor to power cabinet	Compare aluminum and copper	Often sufficient space and economically interesting at high powers.
Cramped box with small bending radii	Copper as a starting point	More compact conductor and easier installation.
Power cabinet to compact satellite	Often copper	Multiple DC cables, limited space and mechanical stress.
Integrated charger	Follow manufacturer specification	Terminal and warranty limit determine which conductor is permitted.
Very long heavy power cables	Calculate aluminum explicitly	Here the difference in material and construction costs can become substantial.

Need a cable calculation or independent cable advice?

A useful cable calculation looks beyond current and nominal cross-section. Green Fellows assesses cable dimensioning, voltage drop, thermal load, short-circuit withstand capability, installation method, bundling, connection technology and the available space in cabinets and cable routes. We can draw up a design or independently test a supplier’s calculation.

• Specific technical question: submit this via the Green Fellows Helpdesk. This gives you access to independent specialist knowledge without immediately starting a full advisory process.
• Cable calculation required: Green Fellows can perform a cable calculation or independently review an existing calculation. We not only look at current and cross-section, but also at installation method, thermal load and practical feasibility.

For cable-related questions, Paul Borghouts is an important technical point of contact within our expert team. His expertise lies in electrical cable issues, dimensioning and the practical translation of calculations into a practicable design.

Sources and standard documents

• NEN 1010:2020+C1:2024, Low voltage electrical installations.
• IEC 60364-5-52:2009 and Amendment 1:2024, selection and erection of wiring systems.
• IEC 60364-7-722:2018, supply of electric vehicles.
• IEC 61851-23:2023, requirements for DC charging equipment.
• IEC 62477-1:2022, safety of power electronic converter systems and equipment.

Standards provide the framework, but not automatically the correct choice of material or cross-section. The calculation must always be linked to the actual load profile, installation method and data from cable and component manufacturers.

Conclusion

Aluminum can be a technically viable alternative to copper within DC charging infrastructure for heavy vehicles, but only if the entire cable route is designed accordingly. The larger cross-section affects space, bending radius, cabinet layout and connection technology.

On long, fixed routes to distribution systems and power cabinets, aluminum is often an obvious choice to calculate. In compact parts of the system, especially towards satellites, copper remains more practical in many projects.

The economically best solution therefore does not follow from the price per meter of cable. Compare the total installation: conductor, cable route, connections, mounting, cabinet size, inspection, maintenance and risk during operation.