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

“So now they were being cycled hundreds of times per day, and hence they were failing far earlier than usual. So we quickly devised technologies for diagnosing when fuses were close to failure, and worked to educate the automotive industry about the importance of simulating for the lifetime of fuses in EV applications before determining fuse sizings.” At the time, Eaton had also grown its capabilities in HV DC-DC converters and industrial controls. These, combined with its inverter and fuse box capabilities, were crystallised as the Eaton eMobility business, for which Fisher was named manager of new product introductions across HV power distribution and production systems in 2018, when Eaton formally launched the eMobility business, and then engineering product line manager for such solutions in 2021. Although Fisher started alone in the role, he has since grown his team to 53 engineers, and leads them in r&d for commercial EVs and electric production passenger cars. “Our automotive products typically fall into two categories: HV auxiliary fuse boxes, and what a lot of OEMs might call a ‘battery junction box’ or ‘battery electrical centre’ – essentially the main distribution and protection point out of the battery pack,” he explains. “Also, we leverage technologies being developed in other parts of the business, which has contributed hugely to our newest and perhaps most successful product, the Breaktor.” The Breaktor is an HV circuit- breaker developed specifically for automotive use, and is designed as a replacement for traditional contactor- and-fuse junctions in EVs. While fuses must be replaced after shorting, the Breaktor’s mechanical contactor linkages can close or open to connect or disconnect (respectively) HV power to or from the drivetrain, based on the turn of the driver’s ignition key. Most critically, it can open within 4 ms of a short- circuit or over-current to break an HV connection, and then be closed later to reconnect the HV network, without needing fuses. Fisher also mentions an isolation measurement system, now available for reporting the resistance between HV battery packs and the chassis, and hence detecting when isolation systems are starting to break down and when shutting off the HV power delivery might become safety-critical. “The early years of EVs were fraught with fears over their safety, not only from passengers but from first responders, technicians who had to work on them, and others, so we’re constantly focusing on designing our power management and safety systems really well,” he says. “We’ve taken lessons from Eaton’s existing HV distribution technologies across the aerospace, industrial and residential sectors, and worked to apply them in the automotive space, changing our simulation and validation approaches where necessary to produce something that will ensure OEMs can make vehicles that are fully protected.” Future plans Although the Breaktor is rapidly becoming Eaton eMobility’s star product, Fisher and his colleagues maintain an eye towards the future, and what HV safety systems for EVs might look like in the next 5-10 years. “Everything in EVs is moving towards more solid-state solutions, so instead of mechanical switching devices, I think in the future we’re going to see distribution systems built around IGBTs and FETs made from advanced semiconductor materials,” he says. “The Breaktor is an order of magnitude faster than fuses, and IGBTs are an order of magnitude faster than the Breaktor. They’re too expensive to use in HV distribution and protection right now, but volume production will drive the prices down. “We already have LV systems in that regard that are solid-state, designed around FETs. The level of control you gain, and the amount of packaging volume you reduce, are too beneficial to ignore as HV technologies advance, and new microcontrollers and diagnostics algorithms mean that connected, software-defined EVs can become safer as they get smarter. “And as battery cells gain more energy capacity, that’s naturally going to drive higher requirements in safety systems. I think that’s going to be a healthy progression that will make EVs more usable and accessible for everybody.” Brandon Fisher Brandon Fisher was born and raised in Oregon, attending Oregon City High School before starting a Bachelor’s Degree in Mechanical Engineering at the California Polytechnic State University that lasted 5 years. In the inal year of his degree programme he began an engineering internship with US sportscar company Saleen, which was irst extended and then transitioned into a full-time role as a chassis systems engineer. In December 2006 he became a project engineer at MillenWorks (known as Rod Millen Motorsports until 2005 and acquired by Textron in 2011), a position he held until February 2009. After a year of independent engineering consultancy, Fisher moved to work as a project design engineer for Cooper-Bussman, which was acquired by Eaton. In the years following the acquisition, he moved up Eaton’s engineering management ladder until he became engineering product line manager for power distribution and protection systems for Eaton’s eMobility business in January 2021. Summer 2022 | E-Mobility Engineering 19 InConversation | Brandon Fisher