“Most OEMs and start-ups developing BEVs are at least considering aluminum enclosures if not actively developing them,” he said.ĭespite lightweighting and recyclability benefits, aluminum enclosures fare less favorably when thermal runaway occurs or if a vehicle catches fire. Another trend he is seeing is OEMs increasingly bringing the development of battery enclosures in-house rather than outsourcing to tier suppliers. “We may see some load-bearing function in the solid-state battery cells themselves and therefore less structural demand on the enclosure,” Afseth said. If the industry shifts to solid-state batteries, the function of the enclosure likely will shift, too. “If the trend continues to eliminate the modules and then the enclosures and have cells directly integrated in the BiW, effective sealing and joining will grow in importance.” The concept of placing battery cells directly in the body-in-white (BiW) is “very interesting” and would remove the redundancy of having a “box within a box,” he said. “The outer reinforcement is designed to crumple in a very controlled way without fracturing so the maximum amount of energy is absorbed.” “The inner frame’s main function is to prevent intrusion into the cells even if it leads to fracture of the metal,” he said. The inner frame is made of strength-optimized 6000 from the HSA6 family, while the outer reinforcement is a ductile 6000 alloy of the HCA6 family. A dual-frame prototype illustrated by Constellium employs two different advanced extruded alloys. The battery enclosure has a critical role in crash energy management, both in terms of preventing intrusion into the battery cells as well as absorbing energy to protect the passengers. “At the moment, with the manufacturing processes needed, this benefit probably doesn’t cover the cost of using 7000,” Afseth said. 7000 could be considered for bottom plates where impact resistance is key, but a point of “diminishing returns” likely will hinder its use in this application. 7000-series alloys of Al-Zn-Mg-Cu are not yet widely used in automotive application, he noted. It is compatible with conventional cold forming and is cost-competitive, he said.Ī 7075 T6 alloy also in development offers 500-MPa yield stress and 70-GPa E-modulus.
#Aluminum battery box series
“You can think of this high-modulus 4000 series alloy as a ‘very excess’ silicon 6000 series alloy,” Afseth said, noting that gauges and widths will be similar to 6000. A 40% weight reduction is “technically feasible” with the developmental 4xxx alloy. The current state-of-the-art solution for bottom plates is high-strength 6111 alloy in peak aged temper, which reduces weight by 30% compared to the benchmark 5754 O-temper alloy.Ĭonstellium has a 4xxx alloy in development with 80-GPa E-modulus and 350-MPa yield stress. The most-used and best-suited alloys for battery enclosures are of the 6000-series Al-Si-Mg-Cu family, Afseth shared, noting that these alloys are “very well compatible” with end-of-life recycling. “There will continue to be a very high value of lightweighting, so I would expect aluminum to be the material of choice.”Īluminum battery enclosures or other platform parts typically provide a weight savings of 40% compared to an equivalent steel design. “ Electric trucks will require very large batteries, maximum payload and minimum energy consumption (operating costs),” he said. Growth is driven in part by the increasing market share of BEVs, including electric trucks and vans, which already employ a greater amount of aluminum than do conventional-powertrain models – more than 640 lb (290 kg) in BEV platforms compared to about 450 lb (205 kg) in non-BEVs. “Aluminum continues to be the fastest-growing material in automotive application,” Afseth said. Andreas Afseth, technical director for Constellium North America operations, said during a recent Center for Automotive Research (CAR) webinar. All currently available long-range BEVs – those that can travel beyond 250 miles (400 km) – use aluminum as the main material for the battery enclosure for that very reason, Dr. Soon, it may no longer be economically beneficial to use aluminum, especially for the small cars that have moderate range and target the lowest possible price point.”Īluminum is the dominant material for electric vehicle (EV) battery enclosures for one simple but significant factor: lightweighting capability.
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