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Customer application 27 August 2021

E-Bus Charging Station: Breathing New Life into Second-Life Batteries

An e-bus charging station whose energy is supplied from sources including the braking energy of trolleys – implemented by the Dortmund engineering firm Ingenieurbüro Fehringer for the energy supplier RheinEnergie AG and the Cologne transport authority, Kölner Verkehrs-Betriebe (KVB AG). The linchpin: a sophisticated battery and energy management system for decommissioned car batteries – perfectly balanced and extensively interconnected, thanks to WAGO automation technology.

Since the end of December 2020, the Bocklemünd district of Cologne has had a ready-made e-bus charging station with a charging capacity of up to 500 kW; final commissioning was completed in April 2021. This was the practical result of a research project funded by the German Federal Ministry of Transport and Digital Infrastructure (BMVI) and Projektträger Jülich (PTJ). Externally, the e-bus charging station resembles a huge concrete block, but its interior shows off the results engineering know-how and a good dose of innovative spirit. The goal is to electrify local public transport bus networks – and do so sustainably. First of all, the required electricity is generated from the braking energy released by trolleys, which would otherwise be wasted. Secondly, the energy storage system in the e-bus charging station is made out of second-life batteries.

Energy and Battery Management Systems – with WAGO Automation Technology as the Data Hub:

  • Established, modular programmable logic controllers (PLCs) with simple, open Linux® programming

  • A large number of adaptable interfaces for visualization, analysis and processing of data flows.

  • Decentralized, user-friendly visualization on the WAGO controller, in HTML5 or Grafana for example

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From Hazardous Waste to Temporary Storage

The second-life batteries used are decommissioned e-car batteries from Ford Werke GmbH. On its own, each battery is now too weak to serve as a drive battery for an e-car. However, when combined, these batteries are still powerful enough to be used for temporary storage. “We breathe new life into these batteries,” says Nicolaj Fehringer, managing director of Ingenieurbüro Fehringer. “Otherwise, these batteries would have ended up as environmentally hazardous waste, even though they still have up to 80 percent of their original capacity.”

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In April 2021, the e-bus charging station, with a charging capacity of up to 500 kW, was put into operation in the Bocklemünd district of Cologne.

Photo: Holger Jacoby/vor-ort-foto.de

288 Second-Life Batteries Become an Energy Storage System

The crux of the matter is that each individual battery has its “own history, its own character.” This makes it difficult to combine second-life batteries in series to form a stable energy storage system for an e-bus charging station. The solution: “The battery management system we developed gets these batteries to a common voltage level. For this purpose, each individual battery’s voltage is measured and balanced,” explains Nicolaj Fehringer. That sounds simpler than it is – behind this technology, a separate battery management system had to be developed and specially tailored to the concept based on second-life batteries. The higher-level energy management system, which was also newly developed for this purpose, handles the functional interaction among all the technical components.

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The 288 second-life batteries used in total are decommissioned e-car batteries from Ford Werke GmbH, which are combined for use as temporary storage.

Photo: Holger Jacoby/vor-ort-foto.de
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Simple, Open Linux® Programming

Balancing energy sources is a key component. The algorithms this requires were programmed by an eight-member team from Ingenieurbüro Fehringer over a year and a half of laborious development work – on Linux®-programmable PLCs from WAGO. “This simple, open Linux® programming is exactly what tipped the scales in favor of using WAGO technology for communication and control,” says Nicolaj Fehringer. This was important “in order to connect our Linux®-based database system to the energy storage system.”

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The WAGO PFC200 is used to direct the energy data flows of the e-bus charging station’s energy storage system.

Photo: Holger Jacoby/vor-ort-foto.de