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VDV 261: Redefining the Charging Ecosystem for European Electric Buses
In the future, electric public transport fleets in Europe will enter the era of intelligence sooner rather than later, involving the interaction of innovative technologies across numerous fields. When charging, a smart EV connects to a smart grid—via a smart charger to a smart charging station. With Plug & Charge (PnC), the charging process is greatly simplified and starts automatically, with the vehicle automatically selecting the most economical tariff. Authorization is completed based on certificates from the vehicle, platform, and operator.
Such a "smart" EV charging ecosystem must consider the personalized needs of station users, vehicle user profiles, charging time windows, and grid load conditions. Charging infrastructure and grid resources will undergo multimodal analysis based on current energy availability (including pricing structures) to determine the optimal start time. The BPT (Bi-directional Power Transfer) function of ISO 15118 even allows battery energy to be fed back into the grid or serve as emergency power for other EVs or homes.
What Does This Mean for EV "Preconditioning"?
If you work in public transport in Europe, you may have heard of the VDV 261 standard. You might also be familiar with the need for "preconditioning" electric vehicles (EVs) before they go into operation. So, what exactly is VDV 261? How does it work? And what problems does it solve? In this article, we dive deep into these questions.
Figure 1: Electric buses utilizing overnight charging for preconditioning at the depotWhat is VDV 261?
VDV 261 is a data communication standard between the charging station and the vehicle that allows electric buses to be preconditioned via the charging station's software. Simply put, it helps operators pre-heat or cool down electric buses before they leave the depot.
This means not only is the interior temperature comfortable for drivers and passengers right from the start of service, but the bus also begins its route with the maximum possible range. There is no need to dispatch staff to manually start preconditioning for every bus—everything can be scheduled and automated.
What Does VDV 261 Mean for Public Transport Operators?
VDV 261 meets a major need for operators running electric buses by providing a standardized method for fleet preconditioning. It allows operators to warm up buses on colder days or cool them down on hot summer days before the vehicles actually leave the depot.
In some countries, it is even legally required for buses to provide a specific interior temperature range for drivers and passengers when service begins.
In short, by incorporating VDV 261 into the overnight charging process, operators can ensure their vehicles leave the depot with the necessary, comfortable internal temperature, while ensuring the vehicle battery is not depleted and has a sufficient State of Charge (SOC) to run its route.
How Does VDV 261 Manage EV Preconditioning?
VDV 261 is built on top of other communication protocols like ISO 15118 and OCPP. It leverages existing charging infrastructure and communication protocols to enable preconditioning. It is exciting to see how industry standards continue to build upon and inform each other, accelerating progress.
Figure 2: VDV 261 Data Interaction ArchitectureTo charge at the depot, any electric bus needs to connect to a charging station. The associated telematics platform sees and identifies the bus, and subsequently, the following information is sent to the vehicle:
- Departure Time: Or the time by which the vehicle must finish preconditioning;
- Type of Preconditioning: Such as cooling, heating, or ventilation;
- External Temperature: In case the bus is parked indoors while the outdoor temperature differs significantly from the indoor temperature.
⚡️ Tech Implementation Tip: The Role of Charge Bridge
To achieve seamless transmission of the data above, the underlying ISO 15118 communication link is critical. The Charge Bridge Hardware Module acts as a vital communication bridge in this process, accurately parsing and transparently transmitting the various parameter instructions required by VDV 261, ensuring accurate dialogue between the vehicle and backend systems.
Given these parameters, the vehicle knows whether it needs preconditioning, exactly what to do (heat or cool), and when it must be ready (departure time). Based on this information, the vehicle can use its climate system to prepare to roll out at the perfect temperature.
The electric bus and the charging station communicate using the charger as a "proxy." They communicate multiple times throughout the night to ensure software systems are updated with the latest information and to guarantee the bus has finished preconditioning by the start of service.
During this process, the electric bus remains connected to the charging station. While preconditioning, the vehicle charges to compensate for the energy consumed by temperature control. When the desired temperature is reached, the bus stops preconditioning and is ready to start its day.
What are the Key Benefits of VDV 261 for Public Transport Stakeholders?
As public transport becomes increasingly electrified, operators have noticed some nuances in managing electric buses. For example, if you heat an EV without charging it, you will lose range.
In winter, heating a bus from an outdoor temperature of -10°C to a comfortable 15-18°C inside consumes a significant amount of energy before the bus even leaves the depot. This negatively impacts range. In the worst-case scenario, the bus might not be able to complete its full route or might even need to be towed.
VDV 261 helps operators optimize their processes and planning, and mitigate risks. Furthermore, the standard reduces range anxiety, increases comfort for passengers and drivers, and ensures planning accuracy and reliability.
What are the Requirements for Preconditioning?
To successfully perform preconditioning, both the charging station software and the vehicle must be VDV 261 compliant.
I like to compare standards to a "language" and chargers and vehicles to "people." They might speak the same language but with different "regional accents," which can lead to misunderstandings without practice.
We face the same situation with VDV 261. All parties may have read the standard, but interpretations can vary slightly. Therefore, it is always necessary to test communication between the bus, the charging station, and the software to ensure they exchange the correct information, allowing the bus to start its route with the correct interior temperature.
Eliminating the "Accent" Barrier
To avoid misunderstandings caused by these "accents," choosing components that have passed rigorous conformance testing is crucial. The Charge Bridge Module is developed strictly following standard protocol stacks, acting like a standard "interpreter." It smooths out comprehension differences between various devices, ensuring VDV 261 commands are accurately executed on any compatible equipment.
To get the most value from VDV 261, we also recommend that operators comply with the VDV 463 standard. This additional VDV standard defines interoperability between charging station software and Depot Management Systems.
Compliance with VDV 463 will help achieve full automation of the preconditioning process. The charging station will communicate with the depot management system to exchange relevant information, ensuring a smooth process for getting vehicles ready. For operators who do not yet have a depot management system, we can also obtain the necessary information through alternative means to enable a successful preconditioning flow.
Standards like VDV 261 are essential to the success of fleet electrification. We are proud to be dedicated to defining, implementing, and testing these standards to help fleets go electric.
