Better battery monitoring systems through graphene-based sensors Graphene-based sensors improve battery monitoring systems Startup company Paragraf, a Cambridge University spin-off and expert in graphene-based electronics, promises much higher dynamic range and linearity for current measurements. With its latest product, a Hall Effect sensor, the company targets battery monitoring systems for electric vehicles. Paragraf claims to have mastered the technological challenges of mass-manufactured and contamination-free graphene-based electronic components at the wafer scale. This enables designing electronic devices with unseen properties with regard to noise freedom, linearity and exactness – and the scalable mass production of such components, said Paragraf CEO Simon Thomas.
A promising field of application is automotive battery management systems. In electric vehicles, high-voltage traction batteries are made of cell stacks with a rather high number of cells. To achieve reliable performance, these cell stacks need to be thoroughly evaluated and characterized before they can be designed into the actual vehicles. This is where Paragraf’s new graphene GHS01AT Hall Effect sensor steps in.
The device is optimised for use in relatively low field environments. Bringing the magnetic field measurement resolution towards that of more complex magnetic sensors, yet with the small size and ease of use of a Hall sensor, it can address monitoring tasks that conventional technologies simply cannot provide an effective solution for.
Owing to the performance parameters that the GHS01AT delivers, detailed real-time current density mapping can be carried out - 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.<p>
Moreover, the sensors can 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 utilising a graphene monolayer (just 0.34nm thick), the device at hand 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.
For design engineers planning to work with the new sensor category, the company also offers a starter kit. This compact board enables simultaneous measurements to be taken from up to eight GHS01AT sensors. Each sensor is attached to a probe with a 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. With this product, Paragraf is addressing companies in the automotive value chain who are responsible for the selection of traction batteries and the design of complete battery systems. Currently used in quality control applications in the first place, the product will be further developed for use in the car itself, Thomas said.
More information: www.paragraf.com