Saturday, June 24, 2017

Alta Says Its Electric Motorcycle Battery Has Highest Energy Density

The Alta Redshift MX electric motorcycle is designed to compete successfully against the best off-road bikes in the world. To do that, it needs a great battery that is both powerful and light in weight. Even though it begins with the same 18650 lithium ion battery cells as Tesla uses in its Model S and Model X cars, it packages them in a way that is unique to Alta. The result is an electric motorcylcle battery with higher energy density than virtually any other battery in a production vehicle.

Alta electric motorcycle battery
“We’re right around 180 Wh/kg, which is about 20-30% higher than the current Tesla Model S. We believe the Model 3 will probably be on par with where we are today, although they haven’t announced numbers yet, so we can’t calculate it,” says Rob Sweney, Alta’s director of advanced powertrains.

The Secret Sauce

Battery cells are battery cells. It’s how you put them together that makes the difference. Alta builds its own electric motorcycle battery pack and thermal management system with help from two companies you have probably never heard of. Kevin Kim, Alta’s head mechanical engineer, explains. “Unfortunately we can’t disclose too many details about the interconnect system because it’s proprietary. I will say that the system allows us to very effectively cool the battery using passive (air-cooled) methods, with no need for liquid cooling. We describe it as being passively air-cooled, and it helps keep the weight down significantly.
“Passive cooling means that the thermal conductivity of the materials that surround the cells is very important. After some testing, we found that a two-part polyurethane from Wevo-Chemie (a German company that specializes in casting, bonding, and sealing resin solutions) had the highest thermal performance, so it became a critical component in our system as an adhesive.”
The bonding agent has to be strong, light, and provide a high degree of electrical insulation. “For any battery pack, you have to balance the need to take away heat from the system while dealing with the high voltage electrical challenge,” says Kim. “Usually things that are good at conducting heat are also good at conducting electricity.
“Optimizing for those two goals is a fundamental challenge of any battery pack design, so this implementation with the Wevo-Chemie material is part of our solution to improve that tradeoff, because it conducts heat extremely well and at the same time has a high dielectric strength – so it’s also electrically insulating.” It helps that the bonding agent also has a bit of give to it. That helps the pack stay together under the rigors of off-road riding.

Getting The Sauce Where It’s Needed

Once Alta found the bonding agent it wanted, the problem became how to use it in its electric motorcycle manufacturing process. For that, the company turned to Scheugenpflug, another German specialist. The Wevo-Chemie material has to be mixed precisely with a catalyst just at the time of use. The main ingredient is about the same consistency as peanut butter. The catalyst is thin like water. Scheugenpflug was the only company that had ever built a machine that could mix the two together successfully on a production line.
Christian Geier, general manager at Scheugenpflug USA explains. “When an adhesive contains a lot of filler material, in this case inorganic fillers, it can increase the complexity of the production equipment. For instance, the inorganic fillers can be incredibly abrasive and quickly wear out dispensing machine components. Depending on the material, each system is designed based on the needed application.”

It Ain’t Rocket Science

Advances in battery technology are happening everywhere around the world. Recently, the Fraunhofer Institute for Ceramic Technologies and Systems in Dresden announced a new system for packing more battery cells into less space. The result is a battery that fits in the same space as a conventional battery but can double the effective range of an electric car. Building a battery with high energy density isn’t rocket science, but it’s close.

Other Applications

According to Business Insider, Alta CEO Marc Fenigstein has plans to use its proprietary battery technology to build batteries for other companies. “The technology, the architecture, and the capabilities that we built as a company in introducing the Redshift have very, very broad applicability across lightweight vehicles,” Fenigstein said. “Really nobody in the market can build a drivetrain for a small vehicle that is as compact, robust, or economical as ours is for a given range and power.”
Source: Charged EVs

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