Lead-Acid Battery State Judgment via Voltage Drop Analysis
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Solution Overview
Problem
Existing methods for judging the state of lead-acid batteries, such as open-circuit voltage measurement and internal resistance measurement using alternating current, face challenges like discrepancies in measurement, requirement of large and complex apparatus, and difficulty in accurately associating resistance values with battery states, especially in distinguishing between charged state lowering and deterioration.
Innovation Solution
A method and apparatus that calculate the DC internal resistance of a lead-acid battery by measuring open-circuit voltage and lowest voltage at engine starting time, allowing for state judgment without measuring currents, using equations to determine the load imposed at engine starting and comparing it with a known non-deteriorated state resistance to assess battery health.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If open-circuit voltage measurement is used to judge battery state, then the measurement process is simple, but large discrepancies appear in measurement and it is difficult to distinguish between charged state lowering and deterioration
Solution Approach 1:
The patent changes the measurement parameter from open-circuit voltage alone to the combination of open-circuit voltage and lowest voltage during engine starting. By measuring the voltage drop characteristics during actual engine starting, the system obtains more informative parameters that enable accurate calculation of DC internal resistance and distinction between charged state lowering and battery deterioration.
2Measurement precision
If internal resistance measurement using alternating current is used, then resistance value can be measured, but a large-scale and complicated measuring apparatus is required and it is difficult to accurately associate measured resistance value with battery state
Solution Approach 1:
The patent replaces the complex alternating current measurement system with a voltage-based measurement approach. Instead of using AC signals and complex impedance measurement apparatus, the system measures open-circuit voltage and lowest voltage during engine starting, then calculates DC internal resistance through mathematical computation. This substitution of measurement methodology dramatically simplifies the apparatus while maintaining measurement capability.
3Measurement precision
If charging current and discharging current measurement is used, then accuracy of measurements is increased, but a large current sensor is required which increases sensor size and cost, and retrofitting to ordinary vehicle is difficult
Solution Approach 1:
The patent extracts the essential measurement information (voltage drop during engine starting) from the complex current measurement system. By measuring only the voltage at open circuit and the lowest voltage during engine starting, the system obtains sufficient data to calculate DC internal resistance without requiring current sensors. This extraction of key measurement parameters eliminates the need for intrusive current sensing while maintaining measurement accuracy.
4Device complexity
If voltage measurement only is used, then current sensors and complex apparatus are eliminated, but accurate calculation of DC internal resistance requires proper load determination
Solution Approach 1:
The patent performs preliminary measurement of open-circuit voltage before engine starting and lowest voltage during engine starting. By capturing these voltage values in advance and using them to calculate DC internal resistance through established equations, the system determines the load characteristics without requiring direct current measurement. This preliminary voltage measurement approach provides the necessary data for accurate resistance calculation while maintaining apparatus simplicity.
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
Enables accurate judgment of lead-acid battery state by measuring voltages only, eliminating the need for current sensors and complex apparatus, providing a reliable and cost-effective means to assess battery health and determine when replacement is needed.
Implementation Method 1
calculating a DC internal resistance r of the lead-acid battery, using a following Equation (2), from an open-circuit voltage OCV and a lowest voltage Vst at an engine starting time, both measured when the lead-acid battery is in a deteriorated or insufficiently-charged state, and the calculated load R imposed at the engine starting time; r=R×(OCV−Vst)/Vst
Data Source
AI summary
A battery state judging method is provided capable of properly judging a state of a lead-acid battery by measuring voltages without measuring currents. A state of the battery is judged by obtaining, in advance, a DC internal resistance r0 of a same type battery in a new and fully-charged state; calculating, in advance, a load R [R=r0×Vst0/(OCV0−Vst0)] at an engine starting time (S112) from an open-circuit voltage OCV0 (S104) and a lowest voltage Vst0 (S108) at the engine starting time, both measured when the loaded battery is in a new and fully-charged state, and the DC internal resistance r0; calculating a DC internal resistance r [(r=R/(OCV−Vst)/Vst)] of the loaded battery from an open-circuit voltage OCV (S104) and a lowest voltage Vst (S108), both measured when the loaded battery is in a deteriorated/insufficiently-charged state, and the load R; and comparing r and r0.