Building a Better Battery Module Interconnect

Consumers want their electric vehicles (EVs) to charge quickly and to drive for long distances on that charge. Both of those concerns focus squarely on the vehicle battery.

The battery represents 30 to 40 percent of the cost of an EV, and making the most of that investment means ensuring that electrical power gets into and out of the battery in the safest and most efficient way possible — and in a way that preserves battery life over the long term.

Battery module interconnects already play a key role in that effort, but there is a lot more that companies can do to prepare those interconnects for upcoming generations of battery technology.

Modularity

EV battery packs are composed of hundreds to thousands of cells. While some OEMs put those cells directly into the battery pack to keep the structure simple, many other OEMs aggregate those cells into modules before they are put into packs. EVs may contain as many as 24 modules, if not more.

This modular arrangement streamlines manufacturing. OEMs will often standardize on a specific module and then use a different number of modules in different vehicle models, to more easily scale capabilities up or down and facilitate manufacturing. They may even standardize on a specific battery pack size across vehicle models, filling each model with more or fewer modules to fit its requirements.

Modules also help enable servicing of the battery pack, by making it possible to swap out one module rather than replace an entire pack. OEMs can place the modules in series or in parallel to achieve the capacity required and to bring the total battery pack to the high-voltage levels — often 400V or 800V — used for fast charging.

Forming connections

The job of battery module interconnects is to join the modules to one another and ensure that they work together as one unit. Battery module interconnects are typically busbars — rigid metal bars capable of supporting high voltages and high currents. They are also often flat, a shape that naturally dissipates heat and works well in a flat battery pack, where vertical space is at a premium.

The limitation of busbars is that they are rigid, which can present challenges both when OEMs are allowing for tolerances during vehicle assembly, and when the vehicle generates heat that can lead to thermal expansion during operation.

To address these challenges, battery module interconnects can integrate flexible sections that absorb vibrations, thermal expansion or any micromovements. They can also incorporate technology to make assembly easier, through direct connectors that avoid screws and allow for position tolerance. Safety is always top of mind, and busbars that are intended to be used inside the battery pack are made from materials that can withstand up to 1,000° C for short periods, to protect the modules in the event of a failure.

Aptiv has been refining our busbar technology, leveraging our long history with connection systems to create innovative terminals for the next generation of high-voltage components. Our recent acquisition of Intercable Automotive Solutions allows us to couple those advances with next-level busbar manufacturing techniques that can help us meet every OEM requirement. Together, we are looking forward to ensuring that battery module interconnects continue to fulfill their critical role inside the EV battery pack.