New Interconnect Designs for Evolving EV Battery Management Systems

As EV sales surge, advancements in interconnect technology are helping EV manufacturers save time and space.

TTI has submitted this post. Written by: Gijs Werner, Director of Distribution & Marketing FCI Basics BU, Amphenol Communications Solutions.

(Image courtesy of TTI.)

(Image courtesy of TTI.)

While total new vehicle sales fell eight percent in the U.S. in 2022, Americans bought more electric vehicles (EVs) than ever before—an annual increase of 65 percent. Globally, sales of EVs increased by around 60 percent, surpassing 10 million for the first time. That’s one in every seven cars, compared to one in every 70 in 2017. EVs are becoming the new norm on the road.

As more EVs are manufactured and their capabilities expand, the effective use of a battery management system (BMS) is critical to prioritizing and powering all of the vehicle’s systems. The BMS, which intelligently controls the battery charge to protect it from operations beyond safe limits, must keep pace with the increased speed and demands of today’s EV technology. And the interconnects within the BMS, which dictate operational accuracy, performance and reliability, must prioritize space savings and meet a variety of design requirements while withstanding rugged environments.

The result is longer battery life for increased range and efficiency, enhanced safety from overcharging or over-discharging, and added convenience and automation, such as equalizing charges and balance cells that save valuable time and hassles.

The BMS: The brains of the vehicle

The typical BMS includes a battery monitoring unit that acquires data and manages safety, a system that manages the battery temperature, and has the ability to communicate with all systems throughout the vehicle. In essence, it should be viewed as a whole subsystem set, not just one system.

(Image courtesy of TTI.)

(Image courtesy of TTI.)

As an integral part of the vehicle, the BMS provides power to safety systems, uses logic to balance which systems to manage and ensures that critical systems are properly powered at all times. As additional capabilities are added to vehicles, the BMS must assess which systems need constant power while managing temperature, electricity output and other safety components. Of course, all these intelligent systems working together within the BMS must be connected.    

For EV applications, battery systems are organized into three main stages and the individual battery cells are formulated into modules, which are organized into packs. The interconnects between those groupings and from the three stages to the other systems are essential to the success of the BMS and must meet certain safety criteria in the form of standards. The United States Council for Automotive Research (USCAR) performance standard and its European counterpart, LV214, require these components to undergo rigorous testing to ensure they are suitable for use in EVs and more rugged commercial applications. Testing involves many factors, including temperature, retention-based robustness and shock and vibration.  

Once interconnects meet USCAR or LV214 requirements, vehicle designers can be assured that the connectors will work for the BMS. If designers use the same interconnect family throughout the vehicle, they only need to qualify the connectors once to meet approvals, saving valuable time. 

Considerations in system design

Since not every car is the same and their systems are designed in a way that is conducive to their manufacture, not every manufacturer has the same component requirements. And though all BMS have the same functions, the way they are connected and the various signal and power requirements can vary widely. To customize a vehicle’s BMS, manufacturers often work with interconnect suppliers for a specific solution.   

Meeting safety standards will ensure that interconnects are compatible with the BMS. Once that is accomplished, there are a lot of variables depending on the use: different attachment methods, whether discrete wires or semirigid flex wires are being used on the battery modules themselves, power and signal requirements, and the size of the connector in terms of contact pitch and pin count. 

To get smaller and lighter, interconnect suppliers are moving away from the industry standard 1.8mm pitch and offering more compact, smaller pitch size and automotive-grade connector solutions while maintaining the required current capability requirements. Advances in interconnect technology and design have led to the recent introduction of the more compact 1.27mm pitch size interconnect, which saves space while offering the same current capability—typically 4A/contact with all contacts powered. 

New industry trends

Advancements in electric vehicles are driving more product customization. Beyond following industry standards for vibration, shock and robustness, many component manufacturers, like Amphenol with its Communications Solutions division, are developing a wider range of high-speed, high-performance interconnects in a smaller form factor for space and weight savings as more components and features are added to the vehicle.  

Suppliers are constantly identifying new trends to extend and improve battery life and performance through new attachment methods or current requirements. While emerging design requirements can be hard to predict, suppliers that have strong relationships with BMS designers and engineers can anticipate emerging design trends and prepare for the next evolution of interconnect technology. 

Suppliers are also seeing more requests for waterproof components to ensure reliability even in rugged environments. And as space and weight savings become more important, some manufacturers are moving away from wires and towards lighter-weight flex connectors that save space and make assembly easier.  

Interconnect suppliers must be able to produce new reliable systems in very limited timeframes since the rate at which electric vehicles are being developed and designed is constantly increasing. By partnering with distributors, like TTI, that offer a deep and wide inventory of high-quality, ready-to-ship Amphenol interconnects that meet the highest automotive performance and safety standards, designers and engineers can work together to build on that existing technology to speed up time to market.