As the push toward electrification gains momentum globally, attention to battery performance, safety, and efficiency is more critical than ever. While battery chemistry and BMS design often take center stage, busbar engineering plays a pivotal—though often overlooked—role in enabling high-current operation, safe energy flow, and reliable long-term performance.
When dealing with cylindrical cells such as 18650, 21700, or 4680 formats, busbar design becomes a key structural and electrical element in the pack. These interconnects must carry substantial currents across hundreds of individual cells, with high precision, minimal losses, and excellent thermal behavior—all within tightly constrained volumes. The position of busbars, orientations of final positive and negative terminals are the key aspect when it comes to packaging of battery pack into EV system as we need to consider the placement of all elements around the energy source. Many pack and EV manufacturers - including XLEX - have designed numerous designs suitable for different welding methods, application and orientation to meet all types of requirements and figuring out these patterns is a work of art!
The Evolving Role of Busbars in Cylindrical Cell Packs
In modern battery packs, busbars are more than just passive conductors. They must be optimized for:
- Current-carrying capacity
- Thermal performance
- Manufacturability
- Voltage sensing and diagnostics
- Mechanical durability
An ill-considered busbar design can result in uneven current distribution, voltage imbalance, excessive heating, or difficulty in assembly. As systems scale up, these issues compound, affecting not just performance but safety and service life.
Shift to Same-Sided Busbar Connection: Efficiency Meets Elegance
A significant advancement in cylindrical cell pack design is the move toward same-sided busbar architecture—where both positive and negative terminals of each cell row are accessed and connected from the same side (typically the top). This change delivers multiple benefits:
- Freeing up the bottom of the pack for thermal management solutions like cooling plates, immersion cooling interfaces, or structure-integrated heat spreaders.
- Improved serviceability and diagnostics, as all critical connections and sense points are accessible from a single side.
- Greater design flexibility in packaging—allowing for thinner or more geometrically optimized enclosures.
However, this topology brings its own set of challenges. Designing top-side-only interconnects that can cleanly and efficiently route both polarities without crossing over or compromising current paths is a technical and aesthetic challenge. The resulting conductor patterns are often complex, resembling electrical artwork, with carefully tuned routing paths, thicknesses, and bends. Precision laser cutting, 3D contouring, and FEM-guided topology optimization are all part of achieving this level of integration.
Key Design Considerations
1. Material Selection : Copper remains the dominant choice due to its superior conductivity, though aluminum is used in weight-sensitive applications. Coating strategies (e.g., tin, nickel) are often applied to improve weldability and prevent corrosion.
2. Welding Techniques : In high-density packs, wire bond welding, laser welding, or ultrasonic welding are employed with high repeatability and low thermal damage. Same-side designs often demand highly precise welding jigs and robotic alignment to avoid cell terminal stress.
3. Thermal and Electrical Balance : Busbar width and thickness must be tuned not just for ampacity but also for equal current sharing among parallel cells. Poorly balanced designs can lead to thermal hotspots or degraded cells, even within a single string.
4. Voltage Sensing and Safety Integration : Voltage taps and current sensors are routed along the busbar edges. Isolation, creepage, and EMI shielding become more critical in high-voltage configurations, especially as same-side topologies reduce spatial separation between polarities.
Looking Ahead: Toward Integrated and Intelligent Busbars
With battery packs evolving to support higher C-rates, solid-state cell architectures, and smart diagnostics, the future of busbar technology is also progressing rapidly:
- Multi-layer laminated busbars for reduced inductance and improved switching behavior
- Flexible PCB-integrated interconnects that combine structural, electrical, and sensing functions
- 3D-printed conductors and topology-optimized copper routes using generative design
- Embedded sensing for real-time current, voltage, and temperature monitoring
XLEX Batteries: Engineering Art Into Busbar Design
At XLEX Batteries Pvt Ltd, we’ve embraced the challenge of crafting top-side-only busbar architectures for our cylindrical cell packs. Our in-house design team leverages precise and modular fixture concepts to build elegant yet functional interconnects. There are as many patterns to connect these cells as we can imagine.
These same-sided busbars not only unlock valuable space for bottom-side cooling integration, but also allow us to push the boundaries of energy density and thermal performance. The geometry and patterns of these designs are the result of countless iterations—where every curve, junction, and pad reflects both engineering intent and visual finesse.
We're actively accepting custom design projects and supporting partners who want to elevate their battery pack architecture—whether for high-discharge performance, thermal optimization, or modular pack development.
Conclusion
Busbars in cylindrical cell battery packs are no longer a secondary consideration—they are a cornerstone of intelligent energy system design. From same-side connection strategies that unlock new packaging efficiencies, to precision-crafted interconnects that blend function with form, modern busbar design demands deep cross-functional expertise.
As the industry moves toward denser, safer, and more thermally optimized packs, busbar innovation will continue to shape how next-generation batteries are built, integrated, and scaled. If your application requires robust, aesthetic, and thermally balanced Battery Pack — get in touch with us. We’re always up for building something exceptional.