Laser welding cold-resistant batteries for electric snowmobiles
The eSled emits no CO2 and makes less noise when travelling through the Arctic landscape. (Image: Aurora Powertrains)
Finnish startup Aurora Powertrains has developed an electric snowmobile with cold-resistant batteries, which it will present at this year’s Laser World of Photonics trade fair in Munich.
The startup, which hails from Lapland, designed the snowmobile to encourage sustainable mobility in cold climates. It emits no CO2 and makes less noise when travelling through the Arctic landscape.
Known as the eSled, the snowmobile is powered by cold-resistant batteries with high energy density, which Aurora Powertrains manufactured using customised joining technology provided by the Fraunhofer Institute for Laser Technology (ILT).
The battery can power the snowmobile – which weighs around 270kg – for up to 100 kilometres on a single charge. At more than 190Wh/kg, the energy density of the battery is strikingly high, according to Fraunhofer ILT.
Aurora Powertrains used lithium-ion NMC pouch cells with 0.2mm thin copper and aluminium electrical contacts to produce the battery. Since there was not enough space to efficiently use ultrasonic welding equipment to join the battery's components, the company opted to have a customised laser welding process developed at the Fraunhofer ILT.
“We evaluated the idea, manufactured the first samples and supported the Finnish startup in its further development,” said Dr Alexander Olowinsky, head of the Joining and Cutting department at Fraunhofer ILT. “Now we are helping them implement the technology for large-scale production.”
Aurora Powertrains had a customised laser welding system developed at Fraunhofer ILT for its modular, scalable snowmobile battery. (Image: Aurora Powertrains)
The Finnish engineers welded using a 1kW single-mode fibre laser with a wavelength of 1,070nm and a 30µm beam width. The laser's control electronics locally modulated the power, causing the laser beam to follow lines with superimposed circles on the component rather than a straight line.
“What speaks in favour of power modulation is that we achieve significantly wider weld seams at the same laser power and thus increase electrical conductivity,” explained Sören Hollatz, research associate at Fraunhofer ILT.
The infrared laser was used to join an aluminium cell tab to a copper tab.
“Because aluminium is on top, the absorption at green or blue laser wavelengths is not as advantageous as it is with copper. For this reason, we prefer to use an infrared laser with a small beam diameter,” says Sören Hollatz. “The beam quality is currently even worse with green or blue laser systems. The single-mode infrared laser is, therefore, the more elegant, faster and significantly more cost-effective solution.”
The battery is also suitable for work machines, energy storage systems, and larger vehicles, according to the startup.
“Since the batteries can be scaled, we can even manufacture them for electrically powered trucks and do so without significantly higher costs for the additional technical effort compared to conventional battery modules,” explains Matti Autioniemi, CEO and co-founder of Aurora Powertrains. “Currently we are developing concepts for a Finnish electric boat company and an off-road vehicle whose battery is designed for 120kWh. In April we started a new project to develop a concept for special electric watercraft.”
Both the eSled and cold-resistant battery will be presented at booth 441 in hall A3 at Laser World of Photonics in June.