D.he middle one is the boss. David Gruber, 36, trained concert musician at the Salzburg Mozarteum, operates as CEO of the family business, his brothers Christian, 38, and Simon, 31, handle those areas of responsibility that David cannot “manage”. His siblings, no less involved in the development and sale of electric vehicles, do not come from electrical engineering or the automotive industry: Christian was a freelance business psychologist in his first professional life, Simon is currently ending his musical career. Despite successful careers, three out of four Gruber brothers from Bad Dürrnberg near Hallein near Salzburg have turned to electromobility: They deal in cars and also developed a battery-powered bus that can cope with the Grossglockner High Alpine Road, which goes up to an altitude of 2504 meters. The Grubers recently provided the proof.
Silenth is what the brothers call their nascent brand; phonetically it becomes unmistakably clear that their buses – soon to be available in three sizes for regular and travel services – are vehicles with almost silent drives. Anyone who gets into the Erstling at the Großglockner toll station in Ferleiten actually hears primarily the smacking of the tires on the wet asphalt. The drive noises of the 476 hp (350 kW) engine are barely noticeable. At 30 to 40 km / h the Silenth moves up the inclines from 1145 meters above sea level to the first stop at the Fuscher Törl viewpoint, 1283 meters higher. With the exception of the serpentines, there is almost always full throttle. “No problem,” says David Gruber on the way. “All components, including the motor and battery as well as the control technology, are generously dimensioned so that they do not overheat and can always provide full performance.”
The Gruber brothers not only have a pioneering spirit, but also immense trust in their development. Because apart from the transfer tour from the seaport in Bremerhaven to Salzburg a few weeks earlier, the bus has not yet made a long journey. A high mountain tour certainly not at all. The Glockner excursion is both a rehearsal and a premiere. To anticipate the result: It actually went better than expected. “If things continue like this, we will arrive back in Salzburg with 35 percent remaining capacity,” said David Gruber happily at the stop on the way home at Fuscher Törl. The battery then signaled a level of 42 percent. But on arrival in Salzburg-Wals, where the Grubers are working on the Silenth project in a rented hall, there was not 35, but 41 percent battery capacity left. Thanks to the apparently excellent recuperation. In view of the six recuperation levels, there was no need to brake once downhill.
Although the body of the bus is a Chinese production model (“Unfortunately, nobody in Europe delivers this to us”), European components represent the technical heart of the Silenth bus Installation sent to China, ”says David Gruber, describing the processes. For the battery made for the pre-production bus in China, he decided on cells made of lithium iron phosphate: “Their disadvantages – higher weight and lower energy density – are more than outweighed by the advantages,” says Gruber. “They charge better, are more cycle-resistant and many times more difficult to burn.”
The batteries were installed in a completely different location than on the Chinese production bus: “We have placed around 60 percent of the 2.5-ton batteries in the rear and 40 percent in the roof area”. The low-floor concept of the bus does not allow for a more favorable installation. The series batteries are to be produced in Germany from next year. “Then the added value changes – so far 50 percent China, 35 percent Europe, 15 percent Austria – in favor of the EU,” says Gruber. The Austrian services mainly concern charging control and other software. A Norwegian company is helping with the cooperation with China and will probably soon take a 30 percent stake in Gruber.