Battery Aging Estimation via Internal Resistance Extraction
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Solution Overview
Problem
Existing power management systems for battery-driven electronic devices face challenges in accurately estimating the remaining battery capacity and aging of secondary batteries, particularly due to increased calculation complexity and power consumption in precise resistance measurement methods, and the difficulty in calculating absolute capacity without full discharge state.
Innovation Solution
A power management system that includes a battery measurement unit, an initial resistance calculation unit, and an aging evaluation unit to estimate the aging degree of secondary batteries by calculating the internal resistance using a simple model and correcting battery capacity based on aging, while requiring minimal calculation and maintaining precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an equivalent circuit model with multiple impedance elements is used to detect internal resistance with high precision, then measurement precision is improved, but calculation complexity and power consumption increase
Solution Approach 1:
The patent extracts only the necessary resistance element from the equivalent circuit model, eliminating the capacitive and inductive impedance elements. This simplified model maintains sufficient measurement precision for aging detection while dramatically reducing calculation complexity and power consumption requirements.
Solution Approach 2:
The patent employs a simple resistive model that can be quickly calculated without requiring complex computational resources. This approach uses minimal calculation power and time, effectively treating the calculation as a lightweight operation that does not burden the battery-driven device.
2Ease of operation
If the voltage method is used to estimate remaining capacity, then ease of operation is improved, but measurement precision deteriorates because absolute capacity cannot be calculated
Solution Approach 1:
The patent introduces internal resistance as an intermediary parameter that bridges the voltage method and charge integration method. By measuring terminal voltage and calculating internal resistance, the system can derive absolute remaining capacity without requiring full discharge operations, thus maintaining ease of operation while improving measurement precision.
Solution Approach 2:
The patent replaces the mechanical process of full discharge testing with an electrical measurement approach using voltage and internal resistance. This substitution allows absolute capacity calculation without physically draining the battery, maintaining operational ease while achieving higher precision.
3Measurement precision
If charge integration method is used to calculate remaining capacity, then measurement precision is improved, but ease of operation deteriorates due to requirement of full discharge state
Solution Approach 1:
The patent uses internal resistance as an intermediary that enables absolute capacity calculation without requiring the battery to be in a full discharge state. The terminal voltage measurement combined with internal resistance provides the necessary information to calculate remaining capacity at any state, eliminating the operational constraint.
Solution Approach 2:
The patent performs preliminary measurement of terminal voltage and internal resistance at the current state of charge, rather than requiring the battery to be discharged to zero first. This preliminary action enables direct calculation of remaining capacity without waiting for or executing a full discharge cycle.
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
The system effectively evaluates battery aging and detects remaining capacity with high precision, reducing calculation complexity and power consumption, and correcting battery capacity estimates to account for aging, thus improving the accuracy and efficiency of battery management.
Implementation Method 1
an initial resistance calculation unit configured to calculate an initial value of the internal resistance of the secondary battery pack based on the battery voltage and the charge/discharge current
Data Source
AI summary
A battery monitoring unit monitors at least one from among: (i) the attachment state of secondary battery pack; (ii) the low state of a battery voltage VBAT; and (iii) the state of whether it is possible or impossible to use the secondary battery. A battery measurement unit measures the battery voltage VBAT, a charge/discharge current IBAT, and a temperature T of the secondary battery pack, and converts the measured values into digital data. A charging circuit is configured to charge the secondary battery pack using DC voltage from an external power supply based on the state information detected by the battery monitoring unit and the information measured by the battery measurement unit. A coulomb counter measures the charge/discharge current IBAT at predetermined time intervals, and integrates the measurement value, thereby calculating the sum total of the charged/discharged amount. The battery management circuit is monolithically integrated on a single semiconductor substrate.