Electric Storage Device Internal Resistance Measurement
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Solution Overview
Problem
Conventional electric storage devices struggle to accurately determine the internal resistance of their electricity storing sections when the electric current varies greatly and unsteadily within a short time, which affects the reliability of the device in supplying power to loads such as motors in hybrid vehicles.
Innovation Solution
The electric storage device incorporates a current sensing section, a DC blocking capacitor, a resistor in series, an ON/OFF circuit, a peak voltage holding circuit, and a peak current holding circuit, allowing the ON/OFF circuit to control the peak voltage and current to accurately measure internal resistance based on peak values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional charging methods are used to charge the capacitor unit, then the charging process is simple, but the internal resistance value cannot be accurately determined when current varies greatly and unsteadily
Solution Approach 1:
The charging process is divided into multiple stages: a first charging period with first charging current, and a second charging period with second charging current. This segmentation allows separate measurement of voltage changes under different current conditions, enabling accurate internal resistance determination even when current varies greatly and unsteadily.
Solution Approach 2:
The charging circuit performs periodic charging operations with alternating current patterns. By repeatedly applying different charging currents in periodic intervals, the system accumulates sufficient voltage change data to calculate internal resistance accurately, while the periodic nature allows the system to handle unstable current conditions effectively.
2Measurement precision
If multiple charging currents are applied to accurately measure internal resistance, then measurement accuracy improves, but the charging control becomes more complex
Solution Approach 1:
The microprocessor continuously monitors voltage changes during charging and uses this feedback to determine when to switch between different charging currents. The system measures voltage change amounts during each charging period and automatically adjusts the charging current based on whether the measured value falls within expected ranges, simplifying the control process while maintaining high measurement accuracy.
Solution Approach 2:
The charging system automatically determines its own charging parameters based on real-time voltage measurements. The microprocessor autonomously decides when to apply first charging current versus second charging current by evaluating voltage change amounts, eliminating the need for complex external control and making the system self-regulating.
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 enables precise determination of internal resistance, enhancing the accuracy of degradation assessment and ensuring a highly reliable electric storage device capable of supplying instantaneous large currents to loads.
Implementation Method 1
a DC blocking capacitor (11) coupled to a positive electrode of the electricity storing section (1)
Implementation Method 2
a resistor (13) coupled in series with the DC blocking capacitor (11) and coupled to a negative electrode of the electricity storing section (1)
Data Source
AI summary
A DC blocking capacitor and a resistor are coupled in series, and coupled in parallel with an electricity storing section. An ON/OFF circuit and a peak voltage holding circuit are coupled in parallel with the resistor. A current sensing section is coupled in series with the storing section, with its output supplied to the peak current holding circuit. Current from a positive to a negative electrode of the storing section is referred to as a positive direction. The ON/OFF circuit is turned on when the current flows in a negative direction, and is turned off when the current flows in the positive direction. An internal resistor of the storing section is found based on a peak voltage and a peak current resulting from the control and held by the respective circuits. A degree of degradation of the electricity storing section is determined with this internal resistor.