Electric Charger Voltage Drop Compensation for State of Charge
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Solution Overview
Problem
The accurate determination of the state of charge of an electric storage device is hindered by voltage drops in charging cables due to resistance and impedance, leading to erroneous charging control.
Innovation Solution
An electric charging system that includes reference setting units for supplied and received voltage data, a data synchronization unit, a voltage difference calculation unit, a resistance calculation unit, and a charging determination unit, which updates the determination voltage based on the voltage drop to accurately assess the state of charge, independent of the charging cable's effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage measurement is performed at the electric charger side, then charging control can be implemented, but the state of charge determination becomes inaccurate due to voltage drop in the charging cable
Solution Approach 1:
The system measures the actual received voltage at the electric vehicle side and feeds this information back to the electric charger. The charger then uses this feedback to calculate the voltage drop and compensate for it when determining the state of charge, thereby improving measurement accuracy despite the voltage drop in the charging cable.
Solution Approach 2:
The patent introduces an intermediary measurement mechanism where the electric vehicle measures the received voltage and communicates it back to the charger. This intermediary approach allows the charger to indirectly obtain accurate voltage information at the battery terminals without directly measuring at the battery side, resolving the accuracy issue caused by cable voltage drop.
2Measurement precision
If charging cable resistance is considered, then accurate state of charge determination is achieved, but system complexity increases due to additional measurements and calculations
Solution Approach 1:
The electric vehicle performs the additional measurement of received voltage and the calculation of voltage drop using its own resources. The vehicle's control unit measures the voltage at its input terminals and communicates this information to the charger, thereby eliminating the need for the charger to perform additional hardware measurements or complex calculations, thus reducing overall system complexity while maintaining accuracy.
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
This solution allows for precise determination of the state of charge, preventing erroneous charging and ensuring accurate charging control by accounting for voltage drops in the charging cable, thus enhancing the reliability of electric vehicle charging systems.
Implementation Method 1
since the charging cable has an electric resistance and an impedance, a voltage drop occurs in the charging cable during charging
Data Source
AI summary
There is provided an electric charging system in which an electric charger and an electric vehicle are connected by a charging cable. The electric charger calculates a voltage drop amount in the charging cable on the basis of a supplied current at the electric charger side and an electric resistance of the charging cable. The electric charger also compares a determination voltage with a supplied voltage at the electric charger side and determines that a battery has been charged to a fully charged state when the supplied voltage reaches the determination voltage. The determination voltage used for such full charge determination is updated by adding the voltage drop amount to a basic determination voltage that is set in advance.