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

the supercapacitors that, when fully charged, provide the power to start the engine. This reduces the maintenance costs associated with low-voltage conditions. The uSTART also stabilises the voltage throughout the 12 V electrical system, which improves the reliability and lengthens the service life of components such as starter motors, relays and powertrain control modules, says the company. “In EVs, the main application for ultracapacitors would be range extension through efficient brake energy regeneration, with peak power handled by the capacitors, allowing the battery to be sized and used for maintaining speed,” Hall says. Skeleton’s Dr Pohlmann points out that among the supercapacitor applications in passenger cars is Mazda’s iELOOP start/stop micro- hybrid system. Offered in the IC-engined Mazda cars, iELOOP continuously recovers kinetic energy as the vehicle decelerates, according to Mazda. It does this with a variable voltage alternator that charges a supercapacitor, which powers the vehicle’s 12 V electrical equipment and accessories, offloading the battery. The alternator varies its output voltage between 12 V and 25 V in response to the capacitor’s voltage, which is related to its state of charge. The system switches the alternator off when the driver presses the accelerator, leaving the supercapacitor to power the electrical system so that less engine power is needed to achieve the level of acceleration that the driver demands, reducing fuel consumption. Get the lead out EVs also have numerous electrical loads that run on automotive industry standard 12 V supplies, and many rely on lead-acid batteries rather than a DC-DC converter that takes power from the main high-voltage battery. Battery EVs also rely on a low-voltage supply to close the contactors to bring the main battery on line, so an independent 12 V supply is likely to remain important for the foreseeable future. Pollution from dangerous operations to recycle lead from vehicle batteries is attracting international attention and is expected to provoke new legislation, so replacing lead-acid batteries in these applications is firmly on the agenda, and supercapacitors/ultracapacitors look set to play an important role. “The advanced research team at our Maxwell Technologies subsidiary is working with industry partners to take an ultracapacitor, either in a module or in a bigger system, and combine it with a non-lead-acid battery technology,” says Gordon Schenk, CEO of UCAP Power. As far as other battery chemistries are concerned, particularly lithium-ion, supercapacitors look set to continue in their supporting role. “Battery- supercapacitor hybrid energy storage systems are the way of the future,” says Capacitech’s CEO Joe Sleppy. “The challenge is finding the physical space to add supercapacitors into a design.” Cable-format supercapacitors This is where the company’s cable- based capacitors (CBCs) come in, he adds. Where traditional capacitors use parallel plate electrodes (even if they are on films rolled into a cylinder), CBCs have two concentric electrodes. This long, thin and flexible form factor allows them to fit into vehicle wiring harnesses rather than battery casings or electronics enclosures. “Our CBCs offer engineers placement advantages over traditional supercapacitors, helping them to improve design and performance with fewer trade-offs,” Sleppy says. “The goal is to integrate supercapacitors into the wiring infrastructure of the vehicle to complement batteries. For smaller vehicles such as electric scooters, this placement advantage helps enable features such as regenerative braking systems.” In EVs and e-mobility in general, supercapacitors will be used in low- voltage applications, particularly in support of vehicle electronics on 12 V ‘board net’ subsystems, according to Dr Pohlmann. “They provide unique advantages such as low-temperature performance, very high power and very robust design, as required for redundancy when you have more autonomous and safety-critical systems such as braking and steering on the 12 V board net.” Hybrid option He adds that supercapacitors’ applications will widen into more propulsion-related areas as technology improves, with Skeleton’s contributions to this being its second-generation Curved Graphene supercapacitors and its SuperBattery hybrid energy storage system. While Skeleton’s Gen 2 supercapacitors, such as the SkelCap SCX5000 offer a specific energy of 11.1 Wh/kg, the SuperBattery offers 65 Wh/kg. Dr Pohlmann says SuperBattery technology offers new capabilities for high-voltage hybrids and fuel Cable-format supercapacitors are Åe_ible, allowing them to be bent into various shapes so that they can conform to wiring harness runs, for e_ample (Courtesy of Capacitech) 44 Summer 2022 | E-Mobility Engineering Deep insight | Supercapacitor applications