E-Mobility Engineering 017 l ECE Doosan electric excavators dossier l In Conversation: Matt Faulks l Battery testing focus l Battery Show North America 2022 report l Ariel Hipercar digest l Cathode materials insight l Thermal management focus

Kayser Automotive gave us details of its Kayser Guard safety valve system for hermetically sealed battery housings. The system is designed to be able to accommodate moderate pressure differences that occur during normal operation using a low-rate equalisation mechanism, while providing a rapid means of safely relieving any pressure spike in an emergency. Low-rate pressure equalisation is handled by a semi-permeable PTFE membrane, while the emergency device is a spring-loaded safety valve. The development team said the system is flexible, in that the valve can be installed with or without the membrane, and that the company specialises in customised solutions for different battery pack designs. This tailoring extends, for example, to the size of the pores in the membrane, a team spokesperson said. “Kayser has different membranes to allow the right one to be chosen in terms of breathability and available space,” they explained. The valve is opened when the pressure inside a pack reaches a threshold level, which can be adjusted to a customer’s specification simply by changing the spring preload. In production, this pressure can be tested to 100% at the end of the line before delivery. Triggering is purely mechanical and does not depend on a signal from a sensor. “The pressure acts on the piston surface, and the piston is held by Briggs & Stratton showcased its new Vanguard 48 V, 10 kWh commercial lithium-ion battery pack designed for autonomous vehicles, utility vehicles, light duty zero-emissions construction equipment and outdoor power equipment. Its 10 kWh capacity represents the total energy measured using a C0.2 discharge according to the IEC 61960-3:2017 standard. The pack comes with an integrated BMS and charger, along with a steel roll cage for impact protection. The company said the Vanguard pack has been tested and validated to operate in any environment that the vehicles and equipment it powers are likely to encounter. Michael Marshall explained that the main development challenge was balancing power output with runtime. “Everyone wants high power and long runtime,” he said. “Our 10 kWh battery capitalises on the power output of our 5 kWh battery while providing twice the runtime. We decided not to pursue double the power output of this pack but instead focus on range extension while being more cost-effective. “The hardest part was proving to ourselves that this is what the industry was asking for,” he added. “We found that none of our current or prospective partners required sustained high-power output, but rather more runtime at a nominal rate.” The two 5 kWh batteries that form the 10 kWh pack are connected in parallel, and the company has applied for patents covering a ‘communication-less’ paralleling strategy. “That was developed for military-grade applications where compromised comms environments will still allow battery packs to be paralleled and power a machine. For safety, however, we always require comms for charging, but not for discharging.” The battery is based on Briggs & Stratton’s cell module assembly (CMA) design, which is focused on ease of manufacturing. It is based on cylindrical cells but is agnostic regarding cell chemistry. Marshall explained that CMA enables the company to switch seamlessly between cells optimised for energy density, power density or for a good compromise between them, and it can also use cells from different manufacturers. He also pointed out that the battery pack is designed to be serviceable. “Unlike foam-filled automotive batteries, each battery module is 100% replaceable,” he said. The new 10 kWh pack is also designed to withstand a wide range of temperatures during both charge and discharge, enabled by a function in the BMS called PowerMap. “It’s obvious that lithium-ion doesn’t like being too warm or too cold, and we can’t fight physics,” Marshall said. “What we capitalise on is the fact that our BMS performs real-time calculations to provide applications with knowledge of how current can be delivered and accepted at any time. “That allows applications to ‘deplete the tank’ or discharge to empty without overheating. Similarly, we can charge without faulting, even in high ambient temperatures.” The company chose a combination of convective and conductive cooling as the basis of its thermal management approach to the pack. “Our packs are used in applications where Briggs & Stratton doesn’t control the end product, so we rely on free and forced-air convection for heat transfer,” Marshall said. “Our die-cast packs use higher levels of conductive thermal management.” Briggs & Stratton’s Vanguard pack is assembled from two 5 V packs connected in parallel using an innovative ‘communication- less’ paralleling strategy The Kayser Guard relief valve is purely mechanical and protects hermetically sealed packs from overpressure conditions January/February 2023 | E-Mobility Engineering 49 ShowReport | Battery Show North America 2022