Secondary Battery State Detection via Current Inflection Analysis
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Solution Overview
Problem
Existing methods for determining the starting capability of an engine based on secondary battery state are inadequate, as they fail to consider critical factors such as engine type and environmental conditions, leading to incorrect judgments about engine startability.
Innovation Solution
A secondary battery state detecting device and method that includes a current detecting unit, extreme value detecting unit, inflection point detecting unit, and calculation unit to determine the starting current and voltage, internal resistance, and voltage before starting, allowing for accurate assessment of engine startability by distinguishing between inrush and cranking currents and their variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the art in Patent Document 1 is used to judge engine startability, then the judgment can be made based on voltage at specific timings, but the judgment becomes incorrect when the piston reaches top dead center in compression stroke at region Px due to engine type and environmental conditions
Solution Approach 1:
The invention changes the parameter used for judgment from fixed voltage thresholds at specific timings to dynamic detection of current characteristics (extreme values and inflection points) that adapt to different engine types and environmental conditions. This allows the system to accurately identify the maximum current point regardless of whether it occurs at P2, P3, or Px, thereby maintaining both ease of operation and precision of judgment.
2Device complexity
If only points P2 and P3 are emphasized for judgment, then the judgment process is simplified, but the engine cannot be started when maximum current is required at point P4 or region Px
Solution Approach 1:
The invention enables the system to automatically identify the critical current point (whether P2, P3, P4, or Px) through self-detection of extreme values and inflection points in the current waveform. This self-service approach eliminates the need for pre-programmed judgment based on fixed points, allowing the system to adapt to any engine condition and maintain reliable starting capability without increasing operational complexity.
3Measurement precision
If the current waveform is analyzed to detect extreme values and inflection points, then the accuracy of starting current detection is improved, but the detection complexity increases
Solution Approach 1:
The invention replaces complex mechanical analysis of engine operation with electrical signal analysis of the current waveform. By detecting extreme values and inflection points in the current signal, the system achieves precise starting current detection without requiring complex mechanical sensors or analysis of engine physical state, thereby improving measurement precision while keeping the detection system relatively simple.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A current detecting unit (current sensor 12) detecting a current value of a current flowing in a secondary battery 14; an extreme value detecting unit (CPU 10a) detecting a first extreme value of a current after an inrush current flows from the secondary battery to a starter motor after electricity to the starter motor is turned on based on the current value; an inflection point detecting unit (CPU 10a) detecting a first inflection point of the current after the inrush current flows based on a variation of the current value per a predetermined time; and a calculation unit (CPU 10a) selecting the inflection point when timings when the extreme value and the inflection point are detected are separated for a predetermined time or more, and selecting either one of the extreme value or the inflection point in the other cases to set as a starting current, and calculating a starting voltage from the starting current, an internal resistance of the secondary battery, and a voltage before starting being a voltage of the secondary battery before the electricity to the starter motor is turned on, are included.