E-Mobility Engineering 014 l InoBat Auto dossier l In Conversation: Brandon Fisher l Battery monitoring focus l Supercapacitor applications insight l Green-G ecarry digest l Lithium-sulphur batteries insight l Cell-to-pack batteries focus

oppositely charged particles, and the electrolyte contains an equal number of uniformly dispersed positive and negative ions. This is where the ‘double layer’ term comes from. The very large surface area of its electrodes, and the small distance between the ions’ charge and the surface charge gives EDLCs their very large capacitance values. Powertrains and beyond In automotive powertrains, the uses for supercapacitors include stabilising electrical system output in IC-engined and hybrid vehicles, engine downsizing and emissions reduction, energy capture from regenerative braking and in acceleration-boosting applications. They can also be found protecting batteries and even fuel cells from peak loads. Away from the powertrain, safety- critical electrical accessories such as power steering, braking and Advanced Driver Assist Systems and technologies need back-up power. Supercapacitors can provide vital seconds of power to enable the driver to guide the vehicle to a safe place to stop in case of a battery failure, for example. Another non-powertrain application in which supercapacitors have found a niche is in suspensions. “Our supercapacitors are used in active suspension systems, where they provide the power required and have the life cycles to last the lifetime of the vehicle,” says Dr Sebastian Pohlmann, vice-president of automotive and business development at Skeleton Technologies. “In this application, they provide a much better lifetime compared to batteries, a smaller form factor and, most important, the ability to work at -40 C.” The technology is also finding its way into IC-engined vehicles, including hybrids, in support of lead-acid batteries. Another supplier, Ioxus, provides starting modules based on supercapacitors that come packaged with power electronics for commercial trucks, off-road equipment, military vehicles and motorsport. “The main application is engine starting, increasing the reliability of start-up and enabling idle reduction efforts such as stop/start and engine-off allowance,” says Chad Hall, Ioxus’ senior VP, sales and operations. Skeleton provides a similar product, its SkelStart ultracapacitor module, for the same segments. Ioxus’ uSTART v5, for example, is a 24 Wh, 12 V supercapacitor bank that provides 700 Cold Cranking Amps, which as its name suggests is a rating used to define a battery’s ability to crank an engine in low temperatures. Fitting a truck with a uSTART module usually allows one or more 12 V batteries to be removed, although it is designed to work with at least one such battery connected in parallel. If the 12 V batteries are in a low state of charge, the uSTART goes into jump- start mode, initiating the sequence by pulling energy from the battery into Ordinary capacitors are rated in small fractions of a Farad, while supercapacitors are available in ratings of thousands of Farads. As with battery cells, supercapacitors come in a range of form factors, including cylindrical, prismatic and pouch types. The term ‘supercapacitor’ refers to the electric double-layer capacitor (EDLC). Other devices – including pseudocapacitors, which store energy electrochemically in a manner akin to that of batteries, and hybrids that store energy both electrochemically and electrostatically – are under development, but this article will focus on EDLCs. In an EDLC, the two electrodes are coated with porous activated carbon, separated by an insulating layer and immersed in a liquid electrolyte consisting of positive and negative ions in a solvent. The ions collect on each plate during charging, and two layers of charge form on each electrode. That is because supercapacitors also store energy in the electric field formed between two ‘Supercapacitor’ and ‘ultracapacitor’ refer to the electric double-layer capacitor, whose large-area electrodes and tiny distance between charges provides very large capacitances (Courtesy of Stanford University) Summer 2022 | E-Mobility Engineering 43 Deep insight | Supercapacitor applications