New Drive for Old Locomotives

SUNCAR AG is contributing its high-voltage system to the electrification of the diesel-hydraulic rack locomotives of the Brienz Rothorn Railway from 1975 and 1987. The new drive must do justice to a historic locomotive that not only transports passengers but also clears snow. Locomotive No. 11 is making the start, with its conversion having begun at the end of October 2026. It is expected to resume operation for the 2028 season. If the remotorization is successful, the other two locomotives will also be converted. The effect: each locomotive is expected to save around 30,000 liters of diesel and approximately 80 tons of CO₂ annually. If the project succeeds, the BRB will be among the first rack railways worldwide to convert existing diesel locomotives for battery-electric operation.

The chassis, wheelset gears, and braking systems will be retained. The diesel engine, transfer case, and hydrostatic drive will be replaced by a lithium iron phosphate (LFP) battery with an expected capacity of around 300 kWh, two frequency converters for the two electric motors on the axles, and a new vehicle control system. The complete high-voltage distribution and DC charging interface are manufactured in-house by SUNCAR. The company also participates in the system development of the powertrain and develops the complete control software. The electrical system utilizes the topography of the route: on the descent, the motors become generators during braking and feed up to 50 percent of the braking energy back into the accumulators. These are recharged during downtimes in Brienz in about 20 to 25 minutes, whenever possible with electricity from the BRB’s photovoltaic systems. During operation, not only are diesel emissions eliminated, but noise and odor are also significantly reduced, especially in tunnels. “A battery-electric propulsion formula fits very well with rack railways. The energy the locomotive needs uphill is largely recovered downhill thanks to recuperation. Based on the existing route and infrastructure, the storage capacity can also be optimally designed for the application area and lifespan,” says Stefan Schneider, CEO of SUNCAR AG.

For the conversion of locomotive No. 11, the BRB has allocated 5.89 million Swiss francs, financed from its own funds and provisions. According to a preliminary study, converting all three locomotives costs significantly less than purchasing new ones. The vehicles are thus expected to remain in service for 20 to 30 years longer. SUNCAR has been designing such conversions in Swiss rail transport since 2020, previously mainly for shunting locomotives and special rail vehicles. Now, the electrical system is increasingly to be used in mountainous terrain. “Many mountain railways operate with diesel locomotives whose mechanics will last for decades. The transformation of the Rothorn locomotive aims to demonstrate that electrification is worthwhile – among other things, because otherwise common investments in overhead or catenary lines are eliminated,” Stefan Schneider is convinced.

In the BRB project, various gears interlock operationally: while SUNCAR contributes its innovative high-voltage components as well as expertise in system and software development, Zaugg AG (Eggiwil BE) acts as the general contractor for the conversion and thus bears the manufacturer’s responsibility for the new locomotive. Ferdinand Steck Maschinenfabrik AG (Bowil BE) contributes its vehicle know-how and prepares the locomotives. PROSE AG, in turn, is responsible for engineering, approval, and client representation, and Solar21 AG for the energy concept.

Josua Haas
Member of the Executive Board
Tel. +41 44 542 05 00
press@suncar-ag.com

An additional fact sheet and the presentation from the first media conference can be downloaded below.

You may use the image material freely with the respective credit: “© Brienz Rothorn Bahn AG” for the locomotive images and “© SUNCAR AG” for the SUNCAR images.

SUNCAR AG, based in Oberbüren (SG), is a Swiss technology and development company for the electrification of commercial, municipal, off-highway, and rail vehicles. The company originated from an ETH focus project and was founded in 2015 as a subsidiary of Huppenkothen Baumaschinen AG. SUNCAR has its own research and development center and a production facility in Schlieren (ZH). SUNCAR is credited with the world’s first battery-powered electric excavator in 2014. To this day, the company works on innovations that drive decarbonization and accelerate the energy transition. For this purpose, the company employs 50 people in electronics, software, and mechanical development, as well as in its own product division. The portfolio includes high-voltage distribution systems, DC fast-charging interfaces, and assistance and monitoring systems. As a contract developer, SUNCAR has also developed numerous commercial and municipal vehicles for its customers.