Researchers at the Fraunhofer Institute for Solar Energy Systems (ISE) took a detailed look at some of the wallboxes available on the market. By testing, they identified a number of differences between the various devices. The focus was on customised operation – both in terms of the supply of solar power from the building’s roof and in terms of variable electricity prices.
High solar power charging
Above all, the speed of control is important. How quickly do the wallboxes detect changes and how promptly are they able to react were the key questions that the researchers investigated. The main focus was on the wallboxes being able to react as quickly as possible to changes in the solar power supply to charge as much surplus energy as possible from the roof into the batteries.
They also analysed how fast the wallboxes switch from single-phase to three-phase operation. “A fast control speed with high control quality is crucial for solar-controlled charging,” explains Bernhard Wille-Haussmann, project manager of the wallbox inspection. ‘In practical operation, this means that the control by the wallbox follows the solar surplus as closely as possible.”
Delay of up to 90 seconds measured
The result: the wallboxes varied in their reaction time to changes in the solar power supply. While some of the devices adjusted their charging power immediately, other devices took up to 90 seconds. In their tests, the researchers also discovered that the energy management system of many wallboxes needs to be adjusted to achieve good regulating quality. That’s why they generally suggest users of the devices adjust them to the vehicle and their own needs. “This makes the devices work more precisely than with standard settings,” says Bernhard Wille-Haussmann. “To do so, the differences between the devices from the various manufacturers are less pronounced. The characteristics of the individual energy system play a major role.”
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Power consumption measured
The researchers also analysed the power consumption of the wallboxes. The devices are also very different in this respect. For example, just a few devices activate the so-called deep standby mode to save electricity.
Displaying differences in quality
The scientists at the Berlin University of Applied Sciences (HTW) used the results of the tests to develop a wallbox score. This indicates the differences in quality between the products using concrete figures. The basis for this are simulation calculations based on measurements in accordance with the test guidelines used by the researchers at Fraunhofer ISE.
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Set parameters correctly
The project partners also want to use the transparent and standardised measurement procedure and the measurement results to provide wallbox manufacturers with information on how they can optimise the quality and energy efficiency of their devices. The results will show end users and installers which parameter settings result in good solar energy utilisation. (su)