What Is an Onboard and Offboard Charger?
In a nutshell, an onboard charger converts AC power from the grid into DC power, which is then used to charge the battery. It's used whenever an electric car is plugged into an AC outlet. It's also used when an electric car is charging itself.
 | Power supply unit |
This invention consists of a power supply unit that provides onboard and offboard chargers with power that is appropriate for the vehicle's battery voltage. The unit has a dual level of programmability that allows it to accommodate the full range of stack voltages. It is composed of three basic components: a power supply unit, the flanged inlet, and a power cord.
Onboard chargers are smaller in size and have a low profile. They are designed to provide a slower charge than an offboard charger and may include EMI protection and small propagation delays. These chargers can also be used in PHEV and battery powered vehicles, and are compatible with charging stations.
| Measurement system |
In order to make sure that an onboard or offboard charger is efficient, the energy efficiency must be measured. The proposed measurement system should include a digital readout interface for analyzing the output energy and power factor. In addition, it should also include an extra power analyser on the AC input side to calculate the input energy and power factor. This is essential for energy metrology calibration.
The measurement system for offboard and onboard chargers consists of a high-speed AD converter that can perform multiple measurements simultaneously. In addition to this, the acquired data must be streamed into each iteration. This is a difficult problem for a DSP, so an FPGA is the preferred option.
| Control loops |
Control loops between onboard and offboard PEV chargers allow both devices to operate at a high level of efficiency. Unlike traditional inverters, which have a single control loop, PEV chargers can operate in multiple modes. For example, they can provide on-board power while off-board power is unavailable. Offboard chargers also have the advantage of incorporating a PV integration. They use a two-level, four-legged inverter topology to dynamically control real and reactive power flow and the PEV battery charging and discharging current. This ensures four-reactive quadrant operation, high-stability responses, and consistent performance. In addition, PV power generation is seamlessly integrated into the charging station and regulated for different environmental conditions.
An onboard charge system can improve vehicle safety and operating costs by reducing battery pack recharge times. Here, someone examines the technology used to implement onboard chargers in hybrid and electric vehicles. The viability of an electric vehicle (EV) depends on its ability to charge its battery packs quickly. Charge times are often as much of a bottleneck as range limits. The two primary types of charging architectures are offboard fast DC charging stations and onboard charging systems.
| Galvanic isolation |
Galvanic isolation is a critical safety measure in the charging process. Without this measure, a vehicle's electrical system could encounter dangerous ground loops, which can lead to noise and safety concerns. Furthermore, currents flowing through an electric vehicle's battery system can be potentially lethal for humans.
To meet these requirements, the onboard charger must be able to change the DC voltage output and the current level. It is also essential to protect these components from over-voltage and under-voltage, and a properly functioning system should ensure voltage monitoring.
| Cost |
In an electric vehicle, the cost of an onboard and offboard charger varies depending on the capacity and the quality of the onboard charger. Offboard chargers are more expensive but also require more power and may require special installation. Moreover, their cost per kW may vary widely. Hence, it is difficult to predict the optimal power rate.
To evaluate the cost-benefit ratios of onboard and offboard chargers, we used a single-objective optimization method. In this process, we determined the optimal power rating for an onboard charger and battery capacity. The optimization objective is to minimize the cost of charging over the life of a vehicle.
| Size |
There are a few key differences between onboard and offboard chargers. An onboard charger is smaller and converts current at a slower rate, whereas an offboard charger is bigger and can handle higher currents. The two types of chargers are made by most EV component manufacturers, but their conversion speeds vary significantly. An onboard charger is also heavier and takes up more space in the car.
