Bidirectional On-Board Charger Testing

The On-Board Charger is now bidirectional!

In the world of electric vehicles (EVs), the On-Board Charger (OBC) plays a crucial role in the battery charging process. This device is responsible for converting alternating current (AC) from a charging station to the direct current (DC) that the vehicle’s battery needs to charge. In this article, we will take a closer look at the functionality of the OBC, its importance for EVs, and why the implementation of a BOBC (Bidirectional On-Board Charger) will improve the future of electric driving.

What is an OBC?

An On-Board Charger (OBC) is a component integrated into the electric vehicle that is responsible for converting AC power (alternating current) from a charging station into DC power (direct current) that powers the vehicle’s battery. The OBC is part of the vehicle’s electrical charging network and ensures that the battery can be charged efficiently and safely without the need for external equipment.

Functionality of an OBC

The OBC has a number of important functions that are essential for the charging process and the operation of an electric vehicle:

Conversion from AC to DC: The primary task of an OBC is to convert the AC power from the charging station to the DC power required by the battery. This process is essential because electric vehicles use batteries that operate on DC, while charging stations often only offer AC power.

Charge management: The OBC regulates the charging process by ensuring that the correct voltage and current are sent to the battery. Most OBCs have a built-in charge controller that carefully monitors the charging process to ensure that the battery does not become overloaded or overheated. This helps to extend the battery’s service life and prevents potential damage.

Communication with the Battery Management System (BMS): The OBC works closely with the vehicle’s Battery Management System (BMS). The BMS monitors the health of the battery, and the OBC ensures that the charging process is in line with the BMS’s recommendations. For example, when the battery is almost fully charged, the OBC reduces the charging speed to prevent damage from overheating or overloading.

Safety: The OBC also ensures safety during the charging process. It monitors the voltage and current and can stop charging if a problem is detected, such as a short circuit, overvoltage or excessive battery temperature.

Charging conditions Optimisation: Modern OBCs are equipped with technologies that optimise the charging process, such as adjusting the charging strategy based on environmental factors (such as temperature) or the condition of the battery.

Why a BOBC (Bidirectional On-Board Charger)?

In the near future, BOBC will revolutionise the way we use and manage energy, through the ability to feed energy back into the grid or for Vehicle-to-Home applications. This makes BOBC important not only for charging the battery, but also for the broader role of electric vehicles in smarter, more sustainable energy management of the grid. By integrating bi-directional charging systems into the vehicle, we can reduce energy costs, improve grid balance, and contribute to a greener future for mobility and energy.

Advantages of a BOBC:

Returning energy to the grid, or Vehicle to Grid (V2G): With a BOBC, EVs can return energy to the electricity grid when necessary. This can be useful during periods of high energy consumption (peak load), when the EV can be used to support the grid. Conversely, when there is a surplus of energy (sunny hours with strong winds), the EV can be used to its full potential to charge the battery. In this way, the electric vehicle becomes not only a means of transport, but also a storage medium for energy. Vehicle to Grid (V2G): With a BOBC, EVs can return energy to the electricity grid when necessary. This can be useful during periods of high energy consumption (peak load), when the EV can be used to support the grid. Conversely, when there is a surplus of energy (sunny hours with strong winds), the EV can be used to its full potential to charge the battery. In this way, the electric vehicle becomes not only a means of transport, but also a storage medium for energy.

Vehicle-to-Home (V2H): In addition to feeding energy back into the grid, vehicles can also supply energy to household appliances in the event of a power outage. This allows users to power their homes using their electric vehicles, thereby increasing their energy independence.

Optimisation of Energy Costs: A BOBC offers the possibility to store energy at cheaper times (when the electricity price is low) and to use it or feed it back into the grid at times of high demand. This can result in cost savings for EV owners, especially in areas with variable electricity prices.

Extending the Lifespan of the OBC: The bidirectional function of the BOBC enables the OBC to better handle dynamic energy flows, which increases the efficiency of the charging system and may extend the lifespan of both the OBC and the battery through a more balanced energy distribution.

Bidirectional test setup BOBC

Testing a Bidirectional On-Board Charger (BOBC) requires advanced test equipment to effectively simulate both the charging function and the return of energy to the grid (e.g., for Vehicle-to-Grid (V2G) applications). Two key test components in this scenario are a regenerative grid emulator and a bidirectional DC source. These devices enable the AC/DC conversion and bidirectional energy transfer to be tested under realistic conditions. Here, we take a closer look at how these systems work, how they test the operation of the BOBC, and which measurement results are important for the validation of the BOBC.

A regenerative grid emulator simulates the power grid that normally supplies energy to an electric vehicle (EV). In a traditional charging setup, the charging station would supply AC power to the vehicle. However, a regenerative grid emulator goes beyond simply supplying energy; it also has the capacity to supply energy back to the on-board charger (OBC), which is essential for testing the bi-directional charging and discharging functions of an OBC.

A bidirectional DC source is a powerful device that can not only supply DC energy, but also store energy. The difference with traditional DC sources is its bidirectional nature, which is essential for simulating all possible situations and characteristics specific to an EV battery pack.

For a comprehensive overview of regenerative grid emulators from Itech and Cinergia, please refer to the overview page. And for an overview of bi-directional power supplies/battery simulators from H&H, NF Corp, Itech, and Cinergia, please refer to our bi-directional power supplies.