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

Dossier | InoBat Auto 0no)at (uto has de]eloped a Åe_ible approach to its cell technologies, working on multiple formats, chemistries and phased product de]elopment has a different focus because of the nature of the operation,” he says. “Continued safe flight, for example, is an EASA requirement stipulating that an aircraft must not be sensitive to a fault to the point where it can’t continue its journey and land safely. That’s different from the safety case for automotive, where maybe the powertrain can be powered down substantially or completely if the battery suffers a fault, as the vehicle will be able to get to the side of the road safely. In aviation there is no side of the road. “We need to help aviation businesses design robust, rugged systems that can react to any potential fault and to remain safe in flight. We carry out cycle testing to make sure the cells operate in normal conditions as well as under abusive conditions and with faults, which we simulate to make sure the system can provide the necessary power, even if part of it has been taken offline.” The rules stipulate that if the aircraft develops a fault during the approach to landing, for example, it must be able to complete a go-around or an aborted landing and be able to divert, he adds. As with conventional aviation, the power system is designed with enough margin so that it can deliver the power needed to achieve the required performance, even with a fault or under abusive conditions. “So you have an extra 20%, or whatever the number has to be, and the system’s ability to deliver it comes from the design of the cell all the way through to the complete installation.” BMS involvement While InoBat Auto’s core business is the development and manufacture of cells, which are only part of a battery’s architecture, the company works with battery OEMs to help ensure that their battery management systems (BMSs) are defined robustly enough to operate the battery safely. Wight emphasises the importance of focusing on cell development and avoiding competition with integrators and battery pack designers, and how InoBat Auto will help them develop modules if asked, principally by providing advice on the best approach for their applications. MacAndrew adds that InoBat Auto defines the operating regimes for the cells, and then provides those characterisations to the BMS developers. In some instances, the parameters are relatively simple, such as temperature limits, but the nature of the characterisation goes much deeper and involves the creation of look-up tables (‘maps’) for the BMS. “We also provide specific conditions of operation for specific states of charge at specific temperatures,” MacAndrew says. “There is a map that the BMS uses to understand what the allowable charge and discharge rates are at all states of charge at those temperatures. That map table allows the BMS to maintain safe and secure use of that chemistry. “Similarly, we also provide a voltage operating window where the maximum and minimum voltages are set out, and another look-up table that the BMS uses to assess what the maximum charge and discharge voltages are at different temperatures. “Each of those tables are a part of what we provide to the integrator to allow them to create a BMS that will make informed decisions about how hard the battery can be operated and how quickly it can be charged.” Ideally, each cell would maintain as near as possible the same state of charge as all the others under all conditions, so that their performance is uniform. That is not always possible when the cells are integrated into a pack, MacAndrew explains, as some cells will be in locations that will be hotter or cooler than others, so 26 Summer 2022 | E-Mobility Engineering