Paragraf’s Graphene Hall Effect Sensor Enables Accurate EV Battery Cell Mapping

Article By : Nitin Dahad

The new graphene Hall effect sensor from Paragraf directly measure magnetic field to better map EV battery cell.

The electric vehicle (EV) sector is seeking better batteries, but battery cell development is difficult because mapping current fields in battery cells is not straightforward. Battery companies who need to monitor performance often have to rely on temperature as a proxy for local current density and resistivity changes. In order to address this, Cambridge, UK-based Paragraf, which develops graphene-based electronics devices, said its new graphene Hall effect sensor provides a faster, more direct measurement of the magnetic field, with the resolution and range required for accurate battery cell mapping.
Paragraf GHS01AT_ Field and resolution chart
Field range and resolution of Paragraf graphene Hall Effect sensor compared to conventional sensors (Source: Paragraf)
Its new graphene GHS01AT Hall effect sensor is optimized for use in relatively low field environments and normal ambient temperatures. Paragraf said it can address monitoring tasks that conventional technologies simply cannot provide an effective solution for, since it provides a magnetic field measurement resolution towards that of more complex magnetic sensors, yet in a small size and simplicity of a Hall sensor. Speaking to EE Times, Simon Thomas, CEO of Paragraf, said, “One of the big challenges in batteries is uniform charge distribution and dissipation. With this sensor, we are offering true 2D magnetic field sensing, which is fundamental for batteries, and can accurately measure and map individual cells.” He added that graphene has major advantages over silicon-based sensors. “It enables much better resolution, and with graphene the dynamic field is better, which is good for detailed battery analysis.” The new magnetic sensors are particularly of value in battery cell analysis when investigating the validity of different battery cell chemistry derivatives and form factors under development. They enable a more detailed and localized (point-to-point) understanding of battery cell behavior. The performance parameters of the GHS01AT facilitate measurement of detailed real-time current density (local cell internal resistance) mapping – with any variations at different locations in the cell being detected during repeated charge/discharge cycles. If hotspots arise, the local mapping of internal cell resistance in these areas could provide insights into the physical processes occurring in the lead up to their formation. This might highlight early warning signs which could be monitored in service or scanned for during quality control. It may even provide the information required to help develop battery chemistries and design concepts that altogether safeguard against the risk of potential failure or thermal runaway. The sensors can also be used to measure the current flow into and out of cells. The method is an indirect means for measuring real-time magnetic field (current) data, so one of the advantages is that the battery cell itself and the tabs/busbars feeding into the cells are not disrupted during testing. By utilizing a graphene monolayer (just 0.34nm thick), the GHS01AT is not affected by the presence of in-plane stray electromagnetic fields that would severely impact the accuracy of alternative sensing mechanisms. The small footprint allows good spatial resolution. Thomas said, “Motivated by demands to safely extend EV range and accelerate charging times, battery manufacturers are under intense pressure to develop higher performance products. These need to be smaller and lighter, with heightened power densities and quicker charge responsiveness. To do this, they must have access to superior test data that they can analyze.”
Paragraf Hall sensor comparison table
Performance characteristics comparison with conventional magnetic sensors (Source: Paragraf)
“This new device easily outperforms what is currently available in terms of both magnetic field and spatial resolution. It means that, for the first time, battery manufacturers can compile comprehensive datasets relating to the internal structure of their products from a current density perspective. By implementing test rigs incorporating GHS01AT sensors, they will be able to ensure the long-term operation and safety of the battery packs they produce.” In addition to the sensor, Paragraf is also offering its GHS array starter kit. In a compact board, it enables simultaneous measurements to be taken from up to eight GHS01AT sensors. Each sensor is attached to a probe with a 1.5m serial interface cable and is accompanied by its own temperature sensor for simultaneous temperature monitoring and temperature correction of the magnetic measurement data. This plug-and-play hardware is simple to integrate into existing data acquisition systems. It will help manufacturers through the initial stages before they look to implement larger-scale test rigs featuring greater numbers of GHS01AT devices.
Simon Thomas
Simon Thomas
Thomas said that it is already working with automotive EV Tier 1 companies with this sensor, and expects volume sales later this year. Addressing the question of what’s next, he said, “The GHS01AT is just the first product in our range, and we intend to bring out new Hall Effect sensors in the family.” Beyond this, he said, “The nig goal is to bring graphene into other solid-state electronics, in other words enable graphene-based chips.” “Graphene has had quite a deep trough of disillusionment over the last 10 years, so we are working hard and deeper to prove it [the technology]. What we are doing is enabling contamination-free mass manufacture of graphene-based electronics, ensuring that it also plugs into the existing manufacturing infrastructure. We have our own manufacturing line and today we can make devices at scale.” According to market research analyst IDTechex, graphene has always been linked as a revolutionary material for the electronics industry. Principal analyst Richard Collins said, “Chemical vapor deposition (CVD) graphene is cited as the ideal solution in providing a perfect single layer produced in a low cost continuous R2R (reel-to-reel) process, but the manufacturing and commercial reality have proved very different. After a long period of research, and with players regularly exiting and entering the field, we are only now starting to see this technology mature and the dawn of the commercial reality.” In the research report, he said of the dream of low cost, pure, perfect single layer in R2R were to be achieved, it would be truly revolutionary to the electronics sector. “Many companies have spent a lot of money chasing this goal, including Samsung, Sony, and LG Electronics. However, there are multiple challenges in both the production and transfer of these films, mostly linked with metal contaminants and defects.” The report highlights Paragraf as a notable new player formed in 2017. “The company spun-out of the University of Cambridge and use MOCVD to directly grow high-quality graphene on a variety of substrates, avoiding challenges with copper (or similar) contamination. They have long term plans for semiconductor applications but have seen the technology validated and initially used in a magnetic sensor.” Thomas also told EE Times that the company is starting to look at its series B funding. “We are looking to raise in the range of $30-50 million, to help scale the business and growing our IP assets. We are also looking at licensing and strategic partnerships.” This article was originally published on EE Times. Nitin Dahad is a correspondent for EE Times, EE Times Europe and also Editor-in-Chief of embedded.com. With 35 years in the electronics industry, he's had many different roles: from engineer to journalist, and from entrepreneur to startup mentor and government advisor. He was part of the startup team that launched 32-bit microprocessor company ARC International in the US in the late 1990s and took it public, and co-founder of The Chilli, which influenced much of the tech startup scene in the early 2000s. He's also worked with many of the big names - including National Semiconductor, GEC Plessey Semiconductors, Dialog Semiconductor and Marconi Instruments.

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