Vital interconnect technology for European EV Gigafactory supply chain

The report identifies major automotive OEMs such as Volkswagen, Renault and Daimler as among the main drivers for these projects, and it goes on to forecast that by 2025, Europe's battery manufacturing capacity will hit 479GWh, representing an eight-fold increase since 2020.

Whilst comprehensive in its analysis of cell types and chemistries, key producers, sustainability and community, the report misses one important consideration: the technology required to connect all these cells into usable batteries.

The big concern for users of EVs, according to most research, is the driving range of these vehicles. The major influencing factor on EV range is energy density of the battery – how much power a battery of a certain size can produce. In discussions on this subject, the headlines tend to be grabbed by cell makers discussing various improvements they have made to the chemistry of their products.

However, they often miss a critical element: the cells themselves are only one part of the solution.

The interconnect technology that enables high-power-density batteries to be manufactured and used is just as vital as the cells themselves, and having a local European Gigafactory manufacturing cells will not help European EV makers if they do not also have a local partner capable of providing the required interconnect products to connect each of these cells and form cell-to-pack batteries.

Cell-to-pack technology enables EV makers to increase battery pack power density. Battery packs are built using cells rather than by combining modules which has been the traditional approach. Every EV maker is adopting some form of this technology, and some are taking it even further.

According to an article in electrive.com, Chinese battery cell manufacturer CATL is working on a new approach, 'cell-to-chassis', where the battery cells will be integrated directly into the chassis of electric cars, dispensing not only with the modules but also the packs, making the bulky housings that are usually built into the underbody of cars today superfluous.

According to a Reuters report, CATL intends to bring cell-to-chassis technology to market before 2030.

How far along this road an EV maker choses to go will vary on particular requirements and applications. However, the need for a means of connecting the cells remains. Of course this interconnect must take up as little space as possible, must be lightweight, rugged and reliable, and should also facilitate quick and simple installation.

Finally, of course, EV makers need a European manufacturing partner for this interconnect technology, if they are to keep supply lines as short as possible and reap any taxation and regulatory benefits of European manufacture.

Enter flexible printed circuits (FPC).

FPC is a mature technology, proven in many designs ranging from consumer to industrial, and is now also used for hi-rel applications. A typical FPC comprises a polymer carrier and a conductor layer, which is usually etched copper. The most basic FPC combines one layer of each type and can have a thickness of 25µm or less. A cover layer may be added to protect the conductor. Successive copper and dielectric layers can be added to create multilayer interconnects. Plated-through holes may be used to connect conductors in different layers, if needed, and terminations can be applied on one or both sides. Components can be mounted on one or both sides of the FPC, combining the functions of both interconnect and PCB in a single part, termed FPC Assembly (FPCA).

FPCs offer many advantages over conventional wired looms. They are much lighter – up to 75% less – and take up a lot less space. Manufacture can be automated, resulting in cost-savings and improved quality. Perhaps best of all, they are simple to install, removing production steps and eliminating connection errors. All of these benefits suit FPC technology to widespread adoption in cell-to-pack or cell-to-vehicle applications, which is why several tier one automotive companies have adopted the technology in their new EVs.

Why do companies build Gigafactories in the UK or in Europe? It's not because they have a great source of materials or because they have access to low-cost manufacturing. Rather it is because batteries are heavy and therefore costly to ship around the world.

There may also be concerns surrounding possible risks of fire or explosions during transportation. Yet if the interconnect is not also available locally, then the point of having an enormous plant to manufacture the cells falls down.

Which is why Trackwise, a UK company based in Tewkesbury which specialises in manufacturing FPCs, has just opened a massive new facility in the UK to service this market.

Trackwise is highly experienced in FCP manufacture for EV applications, having been working on cell-to-pack designs for as long as the concept has existed. The company offers multilayer IHT (Improved Harness Technology) FCPs of unlimited length – the longest the company has produced to date is 72m.

This capability is only possible because of the company's patented reel-to-reel processing. Most other FCP producers use a static, labour-intensive process which is limited to lengths of 600mm – in a few cases lengths of up to 5m may be possible. Although currently, most EVs still retain the shape of a traditional internal combustion engine, new designs are being proposed based on a 'skateboard' platform to fully take advantage of the benefits of electrification. Such vehicles could require long FCP interconnects, especially for buses and trams.

But Trackwise's dynamic process, developed to produce very long lengths for the communications and, subsequently, aircraft industries, means that the company is agnostic about the length of interconnect that an EV company may require for a cell-to-pack or cell-to vehicle application. You can have any length you like. And because the process is highly automated, the interconnect can be made reliably, repeatably and cost-effectively.

Trackwise's new £2.8 million facility will have the capability of producing over 400,000m2 of FCP/year. It is also able to make FPC Assemblies (FPCA) with components for monitoring and controlling on either side of the FPC, to any required length.

The company has already won a £60 million contract to supply one major EV maker with cell-to-pack interconnect products and is busy fulfilling RFI (Request for Information) documentation for several other brand-leading names. Electric aircraft makers are also evaluating Trackwise's capabilities.