Major trends in the continuing evolution of electric vehicles involve the creation of larger batteries to provide longer driving range, along with using advanced integration methods to incorporate batteries more efficiently within the overall vehicle design. Architectural approaches such as Cell-to-Pack (CTP) and Cell-to-Chassis (CTC) are examples of this evolution.
This article provides an exploration of how these overall trends are influencing the requirements for new busbar designs that often need to be longer and have more complex shapes than in the past. It also delves into how new advanced high-voltage extruded busbar technology can provide an important new alternative for meeting these changing busbar requirements.
The Ongoing Evolution of EV Batteries
EV batteries have been evolving along two major tracks over recent years:
- Voltage levels have been increasing to accommodate more advanced powertrains.
- The size of battery modules is increasing and how they are integrated is changing.
Cell-to-Pack (sometimes referred to as C2P or CTP) is a battery design approach that eliminates the intermediate modules and connects the battery cells directly to the pack. This reduces the weight, size, and cost of the battery and increases its energy density and efficiency. Another related approach called Cell-to-Chassis (CTC) integrates the battery cells directly into the EV chassis.
Both CTP and CTC are driven by benefits from eliminating the material and cabling needed to protect and connect separate modules within the overall battery pack. While modules have been steadily getting larger to support higher power requirements, CTP and CTC take a leap forward by eliminating the modules completely.
To accommodate these architectural changes, automotive OEMs and Tier 1 battery suppliers need access to reliable, configurable, high-voltage busbar technologies. The following sections provide more information on various busbar design approaches and detail on how high-voltage extruded busbars fit into the mix.
Overview of Busbar Design Approaches
Over the years, several different busbar design approaches have been used for EV batteries with various advantages and drawbacks.
- Bare busbars were the early default, providing high conductivity, but issues with lack of insulation and reliability over extended lifespans led to the development of other alternatives.
- Overmolded busbars address the need for insulation along with high conductivity and reliability but lack cost effectiveness and thermal performance.
- Laminated busbars excel in insulation effectiveness but lack cost effectiveness and are difficult to customize shapes for new CTP and CTC applications. The most common use of laminated busbars is in the current collector assemblies to connect the battery cells.
- Powder coated busbars, PVC dipped busbars and Busbars with Heat Shrinking also don’t deliver the highest conductivity and lack cost effectiveness due to the need for secondary manufacturing operations.
- Extruded Busbars can provide a useful blend of high conductivity, insulation, thermal performance, and reliability, along with moderate cost effectiveness and the ability to be shaped for custom applications.
Capability rating:
✔✔✔ = Excellent | ✔✔ = Good | ✔ = Poor
Specifics of HV Extruded Busbar Technology
With over six decades of experience delivering all types of busbars, ENNOVI is already well established as the industry leader in busbar technologies for use in EV batteries.
However, we also believe that true leadership means constantly improving on the status quo by extending existing technologies to meet changing market requirements.
Building on this leadership, over recent years our engineering teams have invested significantly in fundamental research, design, testing and new manufacturing capabilities to extend and enhance the capabilities of extruded busbars.
Basically, an extruded busbar is an electrical conductor made by forcing heated metal through a die to form a specific shape. This process allows for creating complex shapes that are difficult to produce using other methods, such as bending or stamping.
Starting with these inherent characteristics, the ENNOVI engineering team set out to create extruded busbar capabilities with these goals:
- High conductivity.
- Compact design: optimize space.
- Good heat dissipation.
- Excellent mechanical strength.
- Cost-effectiveness (no scrap).
- Design flexibility to create complex shapes.
The resultant processes enable forming busbars with either copper (Cu) or Aluminum (Al) conductor materials, plating options with Tin (Sn) or Nickel (Ni) and Nylon PA12 insulation.
As shown below, the continuous processing sequences are designed to consistently deliver custom-formed HV busbars, with minimal scrap, high-volume production output, and maximal consistency for high reliability.
Not only does this new approach provide OEMs and battery manufacturers with an attractive cost-effective option for next-generation EV batteries, Cell-to-Pack, and Cell-to-Chassis applications; it also has applicability for other EV applications such as power distribution units, inverters, powertrains, etc.
Summary
As customer requirements for busbar functionality become more complex and specialized, ENNOVI’s single-step, continuous production, extruded busbar technology can deliver optimized solutions for the most demanding custom specifications while enhancing volume production and keeping costs low.
By partnering with ENNOVI, customers can benefit from our industry-leading expertise in high-precision mechanical engineering, molding, and volume production. Our global footprint and local facilities also offer the best blend of scale, logistics efficiency, and responsiveness.
