Hybrid Construction Machine Battery Charging for Deterioration Control
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Solution Overview
Problem
Existing hybrid construction machines, such as hybrid shovels, face challenges in accurately detecting battery deterioration and performing precise charging control, as the degree of deterioration is not consistently reflected by indicators like accumulated operating time and battery voltage, leading to inefficient battery usage or overvoltage states.
Innovation Solution
A hybrid construction machine equipped with a control unit that includes a difference voltage calculating unit, storage unit, updating unit, correcting unit, and charging/discharging control unit, which calculates and updates the difference voltage between the set and detected battery voltage, corrects the upper-limit working SOC, and adjusts the charging rate accordingly to prevent overvoltage and optimize battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper-limit working charging rate is set to a low value by taking a margin corresponding to deterioration into account, then the battery voltage does not exceed the upper-limit working voltage even when regeneration energy is absorbed, but the remaining capacity of the battery is not used sufficiently and the upper-limit working charging rate is lower than the original setting
Solution Approach 1:
The upper-limit working charging rate is changed from a static fixed value to a dynamic value that automatically adjusts based on the detected degree of battery deterioration. The control unit detects the actual battery voltage during charging and calculates the degree of deterioration, then updates the upper-limit working charging rate accordingly, allowing it to vary with operating conditions and battery state.
Solution Approach 2:
The system implements a feedback mechanism where the control unit continuously monitors the battery voltage during charging, detects the actual degree of deterioration based on voltage deviation from expected values, and uses this information to adjust the upper-limit working charging rate. This closed-loop feedback ensures the charging rate is optimized based on real-time battery condition rather than relying on fixed conservative estimates.
2Productivity
If the upper-limit working charging rate is set to a high value without considering deterioration margin, then the battery performance is maximized, but an overvoltage state occurs when the battery deteriorates and regeneration energy is absorbed
Solution Approach 1:
The upper-limit working charging rate transitions from a static high value to a dynamic value that automatically decreases as battery deterioration is detected. The control unit continuously updates the charging rate limit based on the detected degree of deterioration, ensuring the rate remains appropriate for the current battery condition rather than maintaining an overly optimistic fixed value.
Solution Approach 2:
The system uses feedback from actual battery voltage measurements during charging to detect deterioration and adjust the upper-limit working charging rate. When the battery voltage deviates from expected values indicating deterioration, the control unit reduces the charging rate limit to prevent overvoltage, creating a self-correcting mechanism that responds to actual battery condition.
3Measurement precision
If accumulated operating time or battery voltage is used as indicators of deterioration, then the degree of deterioration can be estimated, but these indicators do not always indicate the degree of deterioration directly and precise charging control cannot be performed
Solution Approach 1:
The system replaces indirect mechanical/time-based indicators (accumulated operating time) with direct electrical measurements (actual battery voltage during charging). By measuring the actual voltage deviation from expected values during a charging process, the system directly detects the degree of deterioration rather than inferring it from time-based estimates, enabling more accurate and direct measurement of battery condition.
Data Source
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AI summary
A hybrid construction machine detects the voltage of each cell that forms a battery, calculates a difference voltage between the detected voltage and a predetermined upper-limit working voltage, selects the lower one of the calculated difference voltage and a stored difference voltage, corrects an upper-limit working charging rate to decrease as the selected difference voltage decreases, and controls charging of the battery, based on the corrected upper-limit working charging rate.