With a focus on developing and manufacturing construction equipment for urban environments, it shouldn’t come as a surprise that Mecalac plans to begin production of an all-electric compact wheeled excavator—for quieter, cleaner operation on tight building sites—in the second half of 2019. The French manufacturer not only displayed its prototype electric machine at the Intermat exhibition in Paris, it also proved the operability of the e12 in the dirt at its outside stand.

Serving as machine operator for the demo was Jean-Baptiste Rousseau, program manager for the e12. “This project had a very quick development process. We started about one year ago,” Rousseau told Truck & Off-Highway Engineering following the demonstration. The team began selecting the components in May 2017 and started to order the parts to build the machine in October.

The main technical engineers from Mecalac have been involved in the project for the past many months, he said, core competences being in electric system design, electro-hydraulic management, software development and mechanical integration.

The excavator is currently undergoing intensive testing to validate the components and final-tune the complete electric and hydraulic system. Alexandre Marchetta, managing director of the Mecalac Group, left little doubt about the future of the e12: “This machine will be produced.”

Bye-bye diesel, hello 1.5 m³ of batteries
The e12 electric excavator, which was honored with an Intermat Innovation Award, winning the Energy Transition category, is based on the conventionally-powered 12MTX excavator loader. The e12 replaces the diesel engine with lithium iron phosphate (LiFePO4) batteries, which have the highest energy density available on the market, said Patrick Brehmer, head of design and product management. LiFePO4 offers three times longer service life than traditional batteries, the company claims, and can be recharged in 6-7 hours.

The e12 is about 1 ton heavier than the conventional 12MTX, mainly due to the batteries, Rousseau said. “On this kind of product, it is not a problem to have more weight. We even get more stability with the machine—the center of gravity of the batteries is very low.”

This is not the first time Mecalac used Intermat to reveal an advanced machine concept; at the 2009 exhibition the company showed a 12MTX Hybrid concept that also received an Innovation Award. But, because of the economic downturn and the market not quite being ready for such a machine, the project was abandoned. The e12 is completely different from that concept, and the 12MTX platform has been entirely redesigned since then.

The 12MTX architecture with its articulated chassis was a logical choice for this latest project, Brehmer told TOHE at the product reveal: “The only machine in the world where you can put 1.5 cubic meters of batteries without changing the compactness is this one…Our customers said, ‘I want direct visibility and I don’t want you to add one centimeter [to the height].’ So we kept the external shape but inside we have changed everything.”

What’s inside
Early in the planning process the team evaluated multiple alternative-drive technologies. “We wanted to find the right solution,” Brehmer said. “It wasn’t just about electric—it could have been hydrogen, [for example]. What is the best solution for not just a prototype, but for the future?”

Once the team settled on electric drive, the target was to achieve autonomy for a full day. Range, along with performance and compactness, are three key criteria for electric drive systems, according to Brehmer. “The challenge was really about battery volume, this was a big question, because electric motors are small,” he explained. “The key to our machine’s range and performance is in its very architecture. The power source, which is separate from the upper structure, means we can install a capacity of 146 kW·h, which results in an unrivaled range of 8 hours.”

Autonomy drives acceptance of the product, Brehmer stressed. Mini and midi excavators or loaders work only 30% of the time (they are in idle mode 70% of the working time), he noted, while a versatile machine like the e12 works for over 70% of the time. “That was the challenge.”

Two electric motors are employed—one driving a hydraulic pump, located at the rear of the machine to operate the boom, and one affixed directly to the rear axle to drive the wheels. They allow simultaneous and independent control of excavating and driving functions.

Mecalac collaborated with Dana to develop this particular e-axle, “which does not exist yet on the market,” said Brehmer. While the axle (Spicer 112) and hydrostatic transmission (Spicer 367) are available on the market, additional customized components were needed to adapt them for the Mecalac machine. The unit delivers “unmatched” traction at startup and provides energy recovery when braking.

“We had to adapt the driveline because the electric motors don’t have the same performance points as the hydraulic modules,” Rousseau explained. “We have more speed but less torque, which means we need to adapt the complete transmission and introduce a gearbox between the e-motor and the axles to achieve the necessary tractive effort and drive speed, without compromising the drive performances…Working hydraulics have been optimized as well, in order to save more energy. We switched the complete control distribution from a hydraulic system to electro-hydraulic, to have precise hydraulic power delivery matching perfectly the driver’s requests.”

The e12 prototype also features Mecalac’s new Connect Energy Link coupler that allows automatic connection of the machine’s hydraulic lines and electric cables to the hydraulic attachment—operators no longer need to leave the cab to connect attachments by hand.

RFID (radio-frequency identification) is the enabling technology. The patented unit combines a sensor fitted to the end of the excavator’s articulated arm with an electronic chip built into the hydraulic tool, and the coupler’s central system takes direct control of adjusting flows/pressure.

U.S.-bound
In 2017, Mecalac acquired the Terex division in Coventry, England, to expand its global distribution network, and established a holding company, Mecalac North America LLC, in Walpole, Mass., to help fulfill its goal of entering the North American market. The company is now working to add distributors to the West Coast of the U.S., as well as in Canada.

Mecalac plans to bring many of its machines, including the e12, to North America. As Brehmer quipped, “That’s the beautiful thing about electric, there’s no Stage IV, no Stage V—it is zero emission. If you have electricity in North America, you can have this machine.”

Concern about pricing of the e12 is fully understandable, said Marchetta, adding that the company would “come to market with a clear financing offer” for the machine. He expects that the total cost of ownership (purchase + fuel + maintenance) of the e12 will be between 0 and +20% compared to the conventional 12MTX.

“This is clearly a direction where the company wishes to go,” said Marchetta, in response to a question on whether other electric machines from Mecalac will follow the e12. “There will be for sure [more] coming in this direction in the future.” Continue reading »