44 November/December 2023 | E-Mobility Engineering Peter Donaldson gives his round-up of the products on display at this show, where the focus was on tackling thermal issues Heat seekers This year’s Battery Show North America and Electric & Hybrid Vehicle Technology Expo, held in Novi in Michigan, had if anything an even greater emphasis on battery safety than usual, with many innovations aimed at stopping a thermal runaway in its tracks, as well as on thermal management. Packaging and Crating Technologies (PACT) showcased its proprietary ThermoShield, which absorbs heat and prevents thermal runaway from spreading beyond the original failing cell and its immediate surroundings, according to Rodger Mort. The Exhibitors answer attendees’ questions in the halls at a lively and well-attended Battery Show North America and Electric & Hybrid Vehicle Technology Expo (Courtesy of Informa Markets) company has developed and tested the material, which it now offers alongside a similar material used to wrap complete battery packs for transport. He explained that four layers of special ink are applied to a single layer of paper. This material is used to wrap each individual cell in a module or pack. When the material reaches 200 oC, he said, it undergoes a chemical reaction that absorbs much of the heat and releases moisture with a temperature of 60 oC. “So the paper basically creates a nontoxic moisture vapour cloud, and when the cell starts its thermal runaway and vents gas, the moisture turns it to char and doesn’t allow oxygen or other gases back in,” Mort explained. “The chemistry in the cell creates enough oxygen to keep it burning, but it can’t explode. By keeping the internal temperature below 780 oC you don’t hit the 820 oC point where lethal and explosive chlorine carbides and acids form.” Mort said the company has put ThermoShield through a range of tests at an internationally recognised facility run by Transport Canada and passed all of them. “We put a hundred 18560 cells charged to 35% in a box and set one off. Nothing propagated and it shut off,” he said. “We then tested 91 cells charged at 35%, put a heat stick in one of them, but then put nine cells charged at 100% in the centre of the pack and lit the first cell. Nothing happened after 20 minutes, so we let the second one go off at 100%, and even that didn’t propagate through the box. Then we worked up to batteries of 1200 Wh with big pouch cells and prismatics, and the paper passed every test.”
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