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

Each individual battery has its own history, its own character. This makes it difficult to combine them to form a stable energy storage system.

Nicolaj Fehringer, Managing Director of Ingenieurbüro Fehringer

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.”

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.

Simple, open Linux^® programming was the deciding factor in using WAGO technology for communication and control.

Nicolaj Fehringer, Managing Director of Ingenieurbüro Fehringer

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.”

WAGO PFC200: The Flexible Controller for Complex Automation Tasks

WAGO’s PFC200 programmable logic controller (PLC) was designed to be “open and easy” – it can be used not only to implement complex algorithms and interfaces in classic IEC 61131 programming, but also to work with open programming languages such as C++, Python, or NodeRed, or to implement functions simply via Docker^®, for example. The WAGO PFC200 is used to direct the energy data flows of the e-bus charging station’s energy storage system. “We can use it to adapt a large number of interfaces and visualize, analyze and process the resulting data flows.” This creates a data hub that links complex systems with an industrial hardware platform that has been proven in practice for over twenty years. The final part of the whole system is the option of decentralized, user-friendly visualization of these processes, for example in HTML5 or Grafana, on the PFC controller. “The data collected and processed in this way is exactly what we need to further optimize the charging of the buses via the 10 kV grid or the battery and energy management system – depending on the requirements and availability.”

This multimodal e-bus charging station is a testament to a strong spirit of innovation.

Jeff Witting, RheinEnergie AG.

A Lighthouse Project for Greater Sustainability

In this complex system, the electricity must be converted twice: from the direct current (DC) of the braking energy to the alternating current (AC) of the battery storage units, in order to then provide direct current (DC) again at the charging point so the e-buses can use it to recharge. “Nevertheless, the efficiency of electromobility remains greater than that of gasoline-powered vehicles,” says Nicolaj Fehringer with conviction. In addition, the use of braking energy harnesses a previously wasted energy source and gives decommissioned e-car batteries a second life. Therefore, with its innovative battery and energy management system, this e-bus charging station serves as a “lighthouse project” that reduces the negative aspects of e-mobility and improves the energy balance toward greater sustainability. Jeff Witting of RheinEnergie AG, the principal client, agrees: “We are thrilled. This multimodal e-bus charging station is a testament to a strong spirit of innovation. The concept is unique in Germany and shows off research, innovation, technical know-how and exactly the kind of sustainability that the energy industry is under so much pressure to achieve.”

The E-Bus Charging Station Concept in Pictures

The e-bus charging station is a lighthouse project that reduces the negative aspects of e-mobility and improves the energy balance toward greater sustainability.