Battery pack manufacturers are under tremendous pressure from all angles like reducing weight, lowering costs, improving thermal performance, increasing energy density, and so on while maintaining reliability. And that is no easy task.

Electric vehicles, energy storage systems, and industrial battery applications continue to grow at an increasing rate. Manufacturers are reevaluating each and every component in the battery pack especially the busbar.

For decades copper has been the most commonly used material for battery interconnections. But with prismatic cell designs quickly becoming the norm, aluminum busbars have found themselves being positioned as a viable alternative to copper busbars.

The switch is not simply about saving costs. But about having the ability to create battery systems that are lighter, more efficient, and more easily produced at scale.

Now let us consider some of the reasons why aluminum busbars are emerging as the preferred material for today’s prismatic cell battery packs.

What Are Aluminum Busbars?

Aluminum busbars are conductive bars or strips that transfer electrical current from one battery cell to another and from the battery to the power electronics.

In a prismatic cell battery pack, bus bars provide low-resistance connections between the battery cells, battery management system (BMS), contactors, and external terminals.

Busbars have many advantages over traditional cable assemblies, such as:

• Reduced electrical losses

• Improved space utilization 

• Better capabilities to carry current

• Consistent electrical performance

Typically made out of high-conductivity aluminum alloy, the busbars can be customized to fit the design of the battery pack by adding insulation sleeves, surface treatments, bends, and mounting features.

What Is A Prismatic Cell Battery Pack?

Prismatic cell battery packs use rectangular-shaped battery cells encased in a rigid metal or polymer casing. The cells are stacked in compact modules and connected to deliver high energy density, energy-efficient packaging, and improved thermal performance.

 Prismatic cells are typically used in electric vehicles, energy storage systems, telecommunications back-up power systems, and industrial battery systems.

Prismatic Cells Are Boosting Busbar Development

The use of a prismatic cell enables many manufacturers to use the full space of a battery pack because of its flat surfaces and standardized measurements, resulting in more efficient large-scale manufacturing of battery packs made from prismatic cells.

However, this added benefit presents challenges. 

Here are some requirements for battery packs containing prismatic cells:

• Compact electrical interconnections.

• High current carrying capabilities.

• Minimal weight.

• Effective thermal dissipation.

• Design flexibility.

Conventional wiring techniques produce an excess of unnecessary size and complexity, whereas copper busbars partially solve some of these factors, yet they will also increase weight and cost of materials in the battery pack. This is why the use of aluminum has a significant positive benefit on busbar systems.

The Benefits of Using Aluminum Busbars in Battery Packs

Reduction In Weight

Weight is a consideration for all battery applications (such as for electric vehicles) as well as when replacing using copper busbars or other metal conductors with aluminum busbars.

Aluminum is about one-third the density of copper, so using aluminum busbars will allow for a reduction in the total battery pack weight without negatively affecting performance.

The use of lighter battery packs helps provide a number of benefits, such as:

• Longer Vehicle Range

• Better Energy Efficiency

• Easier To Handle During Assembly

• Lower Structural Requirements

For larger battery systems, where the weight of conductive busbars can have a significant impact on overall system performance, even small differences in weight can provide considerable performance improvements.

Lower Material Costs

Copper prices are subject to price fluctuations and have seen a number of price increases recently.

Aluminum offers a more cost-effective option while providing acceptable electrical performance in a variety of battery applications (compared to using copper).

For manufacturing battery packs in large quantities, much lower raw material prices will lead to a significant reduction in the total cost of ownership.

This is especially important for electric vehicle manufacturers, battery energy storage system providers, commercial fleet operators, and large-scale industrial battery manufacturing companies.

Improved Design Flexibility

Modern battery packs are often constructed out of multiple components with very complex geometric shapes and tight packaging specifications.

Aluminum is easy to stamp, form, bend, and machine compared to copper and allows manufacturers to produce the following:

• Multi-layer Busbar Assemblies

• Complex Geometric Shapes

• Integrated Mounting Features

• Custom insulated designs

As battery design and configuration continue to evolve, the use of flexible materials will only become more essential.

Thermal Management Improvements

The performance and life of the battery affect that battery’s thermal management.

While copper has higher electrical conductivity, aluminum is very thermally conductive and has a greater overall mass than a battery system therefore, it will be beneficial to use an aluminum busbar when you have both forms of materials.

Using aluminum busbars as they are designed to do allows for the following:

• Evenly distributing heat

• Minimizing localized hot spots

• Coordinating continued battery performance

When combined with an advanced cooling system for the busbars, this type of system may add thermal efficiency.

Sustainability Improvements

Sustainability has become an important factor for many of the battery supply chains.

Aluminum is a highly recyclable product and takes much less energy to recycle than to create new materials.

Using recycled aluminum allows manufacturers to:

• Minimize carbon dioxide emissions

• Increase sustainability within a supply chain

• Encourage closed-loop circulation for an additional period of time.

For companies that are concentrating on their goals for environmentally sustainable practices, aluminum offers a tangible advantage to the companies in their respective fields.

Top Benefits of Aluminum Busbars

Some of the benefits of aluminum busbars for prismatic cell batteries include:

• The weight of the battery system will decrease

• Less cost to manufacture

• More easily manufactured and shaped

• Greater efficiency of packaged product

• More environment-friendly product

Overall, when comparing aluminum busbars to copper busbars, the superiority of either one will ultimately rely upon the application in which it will be utilized.

Copper remains a top choice for applications with very high current densities and where space is limited for installation.

If weight, cost, and scalability are more important considerations, however, aluminum may provide a better balance.

For that reason, many EV and energy storage manufacturers are now shifting to aluminum-based designs.

Common Applications of Aluminum Busbars

Aluminum busbars are found being used in many diverse industries.

Electric Vehicle Applications:

• Passenger EV battery packs

• Commercial electric vehicles (CEVs)

• Two-wheeled / three-wheeled electric vehicles

• Electric buses

Energy Storage Applications:

• Grid-scale energy storage batteries

• Renewable energy integrations

• Solar energy storage systems

Industrial Applications:

• Material handling equipment

• Back up power systems

• Telecommunication infrastructure

• Automated guided vehicle systems (AGV)

Charging Infrastructure Applications:

• Fast charge stations

• Power distribution systems

• Electric vehicle (EV) charging equipment

Design considerations for aluminum busbars

While aluminum busbars provide considerable benefits to the installer, they do not offer a solution for every application. Manufacturers of aluminum busbars should take into account and design for the following considerations. 

Cross-Sectional Area

Aluminum’s electrical conductivity is lower than copper, meaning larger cross-sectional areas may be necessary to produce equivalent results. This is a consideration for design reviews in the initial design phase.

Oxidation of Aluminum

Aluminum’s natural oxidation when exposed to the atmosphere is an issue for manufacturers. Improperly treated surfaces can also lead to increased contact resistance due to the formation of aluminum oxide. There are several ways to treat aluminum to minimize contact resistance, including:

• Tin plating

• Nickel plating

• Coatings

Joining Techniques

Specialized expertise is necessary when joining and welding aluminum. Some popular methods include laser welding, ultrasonic welding, and friction stir welding to provide reliable connections. Selecting a method is also critical for long-term reliability of the connection.

Common Mistakes When Selecting Battery Busbars

Many manufacturers focus only on conductivity and overlook other important factors. 

Avoid these common mistakes:

• Focusing on conductivity of materials only

• Using a cheap material without regard for its thermal expansion characteristics

• Not considering the insulation requirements

• Using generic designs for complex battery layouts

• Not providing max corrosion protection

• Not confirming the current rating of the busbars

All of the above design considerations are important for creating a well-designed busbar by blending electrical, mechanical, thermal, and manufacturing specifications.

Tips for Selecting a High-Quality Manufacturer of Aluminum Busbars

Many busbar manufacturers lack experience with battery applications.

When assessing a manufacturer, take the following elements into account:

Engineering Support

Find a busbar supplier that offers engineering support by providing design assistance, simulation capabilities, and prototype support.

Expertise in Materials

Select a supplier who understands aluminum alloys, surface treatments, and insulation systems.

Customization Options

Each battery pack will differ in design.

The busbar supplier must have the ability to supply:

• Customized geometries

• Isolated busbars

• Production lots of differing quantities

• Finishes specific to the application

Quality Standards

Confirm that the manufacturer adheres to recognized quality management systems and testing standards.

Scalability

Suppliers must have a high level of capability to grow with the customer as production volumes increase and will not compromise quality when manufacturing high volumes.

Do Not Just Look at Conductivity of Copper vs. Aluminium.

Many engineers dismiss aluminum because it is less conductive than copper.

While this is true, there are additional parameters to consider.

The two materials also need to be compared based on the following:

• Weight / conductivity ratio

• Cost / ampere

• Thermal performance

• Manufacturing efficiency

• Total system costs

When looking at the battery pack as a whole, aluminum generally offers better overall value as compared to copper when viewed at the battery pack level rather than the materials level.

Frequently Asked Question

Are aluminum busbars rated for high-current battery applications?

Yes as long as you properly design the aluminum busbar, they can handle high-current applications. It is important to select proper dimensions, alloy, and surface treatment.

Why are prismatic cells almost always paired with aluminum busbars?

Prismatic cells are designed for compactness and light weight, which means high-performance and overall lower manufacturing costs, both of which are supported by aluminum busbars.

Do aluminum busbars need a special coating?

In most battery applications, a protective coating or plating is recommended to reduce oxidation and increase the reliability of connections.

Are aluminum busbars less expensive than copper busbars?

Yes, aluminum provides a less expensive material cost and less weight, which can result in lower total system costs.

Can aluminum busbars be customized?

Yes, manufacturers can create customized shapes, options for insulation, mounting options, and surface finishes to suit the specific battery pack design.

What are the top industries using aluminum busbars?

Electric vehicles, battery energy storage systems, telecommunication infrastructure, industrial automation, and electric vehicle charging infrastructure are some of the fastest-growing sectors.

Conclusion

The development of battery technology has been rapidly growing, with continuous improvements made to all of the parts of a battery pack. The components within the pack are being upgraded for improved performance and reduced costs.

Because aluminum busbars can reduce the weight, increase manufacturing efficiencies, and fully support the ability to scale the manufacture of modern prismatic cell batteries, they are well suited for use in battery packs.

While copper will still play an important role in some very high-performance applications, most battery makers are finding that aluminum provides the most advantageous combination of performance, efficiency, and cost.

For next-generation battery systems, consider evaluating your options for the use of aluminum busbars at the beginning of the design process. By doing so, you will gain significant value throughout the entire lifecycle of your design.

Looking for Customized Battery Busbar Solutions?

When selecting a busbar design, the choice of material is not the only consideration behind the quality of the busbar. The following factors also have an impact on the overall long-term durability of the busbar: the amount of current flowing through the busbar, thermal properties of the busbar, insulative properties of the busbar, and how the busbars will be manufactured.

If you are considering customized aluminum busbars for use in prismatic cell battery packs, you would get benefit from working with an experienced aluminum busbar manufacturer who has experience in the manufacture of products for the battery industry and can assist you with both prototype and mass production quantities.