Battery State of Charge Determination via Impedance Lookup
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Solution Overview
Problem
Existing battery monitoring systems are ineffective in accurately determining the state of charge (SOC) and impedance of batteries, which affects their ability to predict remaining battery run time and power delivery capacity.
Innovation Solution
A system comprising a power source and a controller that measures initial and subsequent open circuit voltages, calculates impedance based on charging current and time, and stores impedance-SOC relationships to predict SOC during discharge, allowing for accurate determination of battery state and remaining run time without continuous current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If battery impedance is monitored continuously to determine state of charge, then measurement precision is improved, but device complexity and energy consumption increase
Solution Approach 1:
The system performs preliminary impedance-SOC relationship characterization during manufacturing or initial setup, storing the correlation data for later use. This allows the monitoring system to determine SOC by simply looking up impedance values in a pre-established table, rather than continuously measuring and calculating SOC in real-time, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent introduces an impedance-SOC relationship table as an intermediary between impedance measurement and state of charge determination. This lookup table serves as a mediator that translates impedance measurements into SOC values without requiring complex real-time calculations, simplifying the monitoring system architecture while preserving accuracy
2Measurement precision
If continuous current measurement is performed to monitor battery state, then state of charge determination accuracy is improved, but energy consumption and device complexity increase
Solution Approach 1:
Instead of continuous current measurement, the system performs impedance measurements at periodic intervals or at specific charging/discharging stages. The impedance-SOC relationship is established once or occasionally updated, and then used repeatedly for SOC determination without requiring continuous active measurement, thereby significantly reducing energy consumption while maintaining determination accuracy
Solution Approach 2:
The system creates a copy of the impedance-SOC relationship in the form of a lookup table that can be referenced repeatedly without requiring ongoing measurements. This copied relationship data allows the system to determine SOC by simple table lookup rather than continuous measurement, reducing energy consumption while preserving accuracy
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 provides a reliable and accurate indication of battery state and remaining run time, enabling efficient power management and prolonging battery life by correlating impedance with SOC, thus improving battery utilization and monitoring accuracy.
Implementation Method 1
A battery is two or more electrochemical cells connected in series that store chemical energy and make it available as electrical energy
Implementation Method 2
There is a known relationship between a battery's capacity, e.g., its ability to deliver power to a load, and its internal resistance or impedance. Thus, battery impedance monitors can be employed to determine a remaining battery capacity
Data Source
AI summary
A system that includes a battery, a power source, and a controller. The power source is configured to provide a charging current to the battery initially, and the controller is configured to associate a first impedance associated with a first state of charge (SOC) of the battery. Subsequently, the controller is configured to determine a second impedance of the battery during a discharge state of the battery. The controller may then determine a second SOC of the battery during the discharge state based on the first SOC of the battery when the second impedance corresponds to the first impedance.