Supplementary Wallbox Charging Circuit for Efficient EV Discharging
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Solution Overview
Problem
Existing charging systems for electric vehicles suffer from low efficiency during discharging operations, as the AC/DC converters are designed for nominal charging power, leading to inefficient use of vehicle battery storage as a mobile home storage system, and require additional components like photovoltaic systems for DC power conversion.
Innovation Solution
A supplementary charging device with two anti-parallel current paths, one for charging and one for discharging, allowing for optimal efficiency in both modes by dimensioning each path differently based on nominal power requirements, and incorporating a monodirectional DC/AC converter for cost-effective and efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bidirectional charging capability is added, then versatility is improved, but device complexity increases
Solution Approach 1:
Instead of using a single complex bidirectional converter, the patent segments the system into two separate unidirectional converters. This approach achieves bidirectional functionality through simpler components, reducing overall system complexity while maintaining versatility
Solution Approach 2:
The wallbox system achieves multi-functionality (both charging and discharging capabilities) through the combination of two specialized converters. Each converter performs its dedicated function efficiently, and together they provide universal bidirectional energy transfer capability without requiring a single complex bidirectional device
2Reliability
If cooling measures are implemented, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent converts the potential harm of heat generation into a benefit by designing the system such that the discharging converter operates at low power levels where heat generation is minimal. This eliminates the need for active cooling measures while maintaining reliability, as the low power operation naturally keeps temperatures within acceptable ranges
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Achieves high efficiency in both charging and discharging operations, reducing power loss and eliminating the need for cooling measures, while allowing the vehicle's battery to be used as a temporary storage device in an environmentally friendly and resource-saving manner.
Implementation Method 1
incorporating a monodirectional DC/AC converter for cost-effective and efficient operation
Data Source
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AI summary
The invention relates to an auxiliary charging device (74) for an AC wallbox (82) comprising: - a housing (92); - a control device (76) arranged in the housing (92); - a first connection (40) that can be connected to a charging plug (54a) of an AC-DC charging cable (46), wherein the first connection (40) comprises an AC connection (44) and a DC connection (42); - a second connection (78) for connecting to an AC output (80) of the AC wallbox (82) via an AC charging cable (84), wherein the control device (76) is designed to connect the second connection (78) to the AC connection (44) of the first connection (40);- a DC/AC converter (52) designed to be at least unidirectional, wherein the control device (76) is designed to couple its AC terminal with the second terminal (78) in a first operating mode and to couple its DC terminal with the DC terminal (42) of the first terminal (40), so that power coupled in via the DC terminal of the DC/AC converter (52) can be made available at the second terminal (78). The invention further relates to an AC-DC wallbox (94) comprising such a supplementary charging device (74).