The electric vehicle battery pack does not function in a controlled environment. The battery parts are subjected to vibrations from driving conditions, heating-cooling cycles, electrical and mechanical loads.

The busbar is a small part, but it plays a key role. The busbar bridges the connection between the various cells or components of the battery and must meet specifications relating to the size and shape of the material, its thickness, curvature, and the surface area used for making the connection.

In the case of using the busbar for laser welding, the specifications are even stricter. The laser-welded busbar made of aluminum is supposed to have an appropriate shape, as well as a uniform welding surface, which would fit in perfectly with the battery assembly process.

This is the moment when the correct choice of design and manufacturing process of the busbar will make a real difference. Adinath Enterprises produces customized copper and aluminum busbars as per the client’s drawings and requirements, which includes laser-welding aluminum busbars for prismatic cell lithium batteries.

What are laser-welding-ready aluminum busbars?

A laser-welding-ready aluminum busbar is an engineered aluminum alloy conductive part that has the proper welding area for the external customer’s laser welding procedure. 

Unlike a normal flat strip, the busbar has additional peculiarities:

• Dimensions

• Grade of material

• Thickness

• Holes or slots

• Bending and forming

• Welding zones

• Dimensional tolerances

• Surface requirements

The exact design will depend on the pack cell type, battery architecture, current requirements, available space, and the customer’s welding method.

The busbar producer does not define the whole battery welding process. Instead, the busbar should be manufactured in accordance with the provided drawing and specifications put forward by the battery producer.

Why Vibration Matters in EV Battery Busbar Design

Electric vehicle (EV) battery packs are susceptible to constant mechanical motion. Vibration can be caused in the pack by different factors as the vehicle travels on the road, accelerates, brakes, and operates under other conditions.

Despite its small size, a busbar can be affected by mechanical stressing due to mobility because of some factors, including unsupported segments, sharp turns in its design, or if misalignment is caused while connecting it with other components.

This is why a good design should take into consideration that the busbar is a part of the entire battery assembly, while the busbar should not be treated as a separate piece of metal.

One should pay attention to:

• Unsupported busbar length: Longer unsupported spans could lead to more movements.

• Bending zones: Incorrect bending zones could cause undesirable stress concentrations.

• Weld zone: The welding needs to correspond to the assembling methods of the customer.

• Alignment of cells: Different sizes of cells and busbars could hinder the assembly process.

• Clearance: The busbar should fit within the constraints of the battery pack.

• Shape of the joints: The holes and slots should follow the need for assembly.

One should not think every EV busbar is complicated. In fact, in many situations, a simpler straight busbar design is more efficient as long as electrical and mechanical conditions are fulfilled.

How the Thermal Cycling Affects the Busbar Design

Another point to think about in relation to the EV battery systems is the temperature change.

During charging, discharging, as well as during operation, the battery will experience temperature changes.

The busbar has to be made of a material with a similar coefficient of thermal expansion as other materials of the battery.

This means one should take into consideration the interaction between the busbar and battery elements in the design.

A good busbar design needs to take account of

• Temperature range during operations

• Temperature variations in application

• Selection of materials

• Thickness of the busbar

• Electrical load rating

• Type of connection

• Available movement and expansion

• Support structure

• Location and type of welding

The aim of the design isn’t just to increase the thickness of the busbar. A larger cross-section can improve the current capacity of the busbar but will influence its weight, the amount of available space, shaping options, and thermal characteristics.

One needs to consider all these principles when designing busbars.

Simultaneous Design for Vibration and Temperature Cycling

It is important to recognize that vibration and temperature change may not always be considered independently. For example, it is possible for a busbar to operate through multiple temperature cycles while also experiencing vibration due to road conditions. Thermal expansion can cause small changes to dimensions while mechanical movements may occur simultaneously.

Therefore, it is essential for battery manufacturers to supply busbar manufacturers with complete application information.

The following application information may be useful:

• Battery cell model and sizes

• Dimensions and layout of the battery pack

• Busbar dimensions

• Material specifications

• Thickness

• Electric current rating

• Weld area

• Welding parameters

• Temperature range

• Tolerances

• Dimensions of holes and slots

• Surface quality requirements

• Quantity and production requirements

This allows manufacturers to assess the design’s manufacturability before production.

Essential Design Elements of a Dependable EV Battery Busbar

1. Suitable Aluminum Class

Aluminum grades like 1200, 1100, or 6061 may be taken into account depending on the intended use and customer preference.

Materials selection should be based upon the desired properties, i.e., mechanical, electronic, and forming capabilities.

2. Precisely Measured Thickness

The thickness of a busbar influences the amount of current carried, the mechanical strength, the weight, and how it is formed.

That is why the thickness of a busbar should be determined from the expected application.

3. Correct Area for Welding

The area for welding of a busbar that is to be welded using a laser should receive special attention.

The surface must be manufactured in line with the geometry and size provided by the customer. If the variation of dimensions of the surface exceeds the acceptable value, achieving successful assembly may be difficult.

4. Correct Bending and Shaping

Bending is not simply a decorative factor.

Its purposes may include:

• To provide some distance

• To be compatible with cell terminals

• To minimize interference

• To properly position a busbar

• To allow the arrangement of the battery pack

The radius of the bend, angle, and its placement and tolerance should be determined in accordance with the drawing.

5. Right Positioning of Holes and Slots

Designs based on bolts or combinations of different connections may require holes and slots with certain dimensions and locations.

Even a slight transfer can cause problems with assembling.

Benefits of Correct Busbar Design

The busbar that is properly designed for laser welding will allow battery producers to obtain:

• Regular battery assembling

• Best compatibility with prismatic cells

• Correct welding geometry

• Optimal use of the space

• Accurate electric contact

• Consistently produced goods

• Limited corrections during assembling

• Accurate drawing and assembly process.

These advantages depend on the overall design of batteries and the process of manufacturing, so a busbar on its own does not guarantee good performance of battery packs.

Common Busbar Design Errors to Avoid

Some issues arise before the first batch of the production is made.

Selecting a standard busbar in place of custom design

Normally battery packs require a relevant space. Generic busbars may not meet specifications regarding the length or place of holes and welding area.

Disregarding tolerances

Designs may show the nominal dimension, but the actual production needs certain tolerances for dimensions.

Repeatability matters in case of mass production.

Choosing material based only on the conductivity

Conductivity is a significant feature, but not the only one.

All other aspects, like formability, mechanical requirements, thickness, temperature of application, manufacturing process, and customer request, should be defined.

Designing busbars without considering the configuration of the cells

Busbars should be created based on the battery architecture.

The size of the cells, the place of the terminals, the insulation requirements, the casing, and the welding processes significantly affect the geometry of the final product.

Making busbars too complicated

The fact that the busbar has many bends does not always mean that the busbar design is successful.

If the geometry of the busbar is simple and performs all electrical and mechanical tasks, it will be a better choice.

How Adinath Enterprises Participates in Custom EV Battery Busbar Manufacturing

Adinath Enterprises manufactures customized copper and aluminum busbars according to customer specifications and technical requirements. Adinath Enterprises produces aluminum busbars that are ready for use with the customer’s laser welding technology for prismatic lithium battery applications.

The company follows the steps below during its manufacturing process:

• Analyzing the requirements and the drawing

• Choosing the right materials according to requirements

• Doing precision cutting

• Punching the brackets

• Bending and forming

• Drilling and tapping (if needed)

• Performing chamfering and deburring

• Finishing surfaces

• Inspecting dimensions

• Performing quality inspection

• Packaging for delivery

Adinath Enterprises does not conduct any laser welding of battery packs since the firm specializes solely in manufacturing busbars in the necessary shapes for the clients to use in their battery production process.

The difference is vital for battery companies. The busbar manufacturer must be aware of the clients’ technology and their requirements without posing as a battery pack producer or laser weld service provider.

Advice for Busbar Battery Buyers of Electric Vehicles

Before contacting suppliers, prepare necessary technical documentation.

At minimum, you should consider the following issues:

• Drawings: Provide dimensions, tolerances, bends, holes, slots, and welding areas.

• Material: Specify the required aluminum grade and thickness.

• Application: Specify cell type and battery application.

• Quantity: Separate prototype from production requests.

• Surface requirements: Indicate the surface treatment or finishing grade you need.

• Inspection: Indicate critical dimensions and quality requirements.

Having a proper drawing will make quotation and production discussions more straightforward.

Frequently Asked Questions

What is an aluminum busbar that is prepared to be used with laser welding?

An aluminum busbar that is designed both in shape and with a certain welding area for being part of the system for laser welding belonging to a particular customer.

Why is aluminum chosen for busbars used for EV batteries?

Aluminum provides adequate electrical conductivity and has low density. Therefore, it is suitable for cases where the weight and the efficiency of the electrical connection have to be balanced out.

Can vibrations affect busbars for electric battery systems?

Vibrations could introduce mechanical stress into the battery connections after going through numerous cycles. Therefore, the shape of the busbar, the method of supporting, and the connections should be looked at simultaneously.

What is the importance of thermal cycling for battery busbars?

Frequent temperature changes result in the expansion and contraction of materials and their parts. Therefore, the choice of materials should reflect that.

Is it possible to get custom aluminum busbars from Adinath Enterprises?

Yes. Adinath Enterprises custom-manufactures both aluminum and copper busbars based on the client’s drawings and specifications.

Does Adinath Enterprises perform laser welding?

No. Adinath Enterprises produces only aluminum busbars ready for the laser welding process. The welding of the busbar to the battery assembly is done during the customer’s battery assembly process.

What should be included in the order for a busbar?

Detailed technical drawings, material specifications and thickness, quantity, information on the cell, welding process, tolerances, surface requirements, and any inspection requirements should be provided.

Conclusion

Having accurate design details is the first step in achieving a reliable EV battery busbar.

Vibrations, thermal cycling conditions, movement of cells, electrical current flow, the welding process, dimensions, and space play an important role in finalizing busbar design. The aim should not be to make the busbar very complicated but to obtain the right configuration of a busbar to be used in the battery application.

In the case of battery manufacturers with prismatic lithium batteries, it is easier to manufacture aluminum busbars using a drawing method that allows for getting the busbars to be laser welding ready before putting them into production.

If you need a busbar matching your battery design or schematic, you can contact Adinath Enterprises, a professional busbar manufacturer located in India.