Battery Internal Resistance Estimation for Cold Start Reliability
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Solution Overview
Problem
Secondary batteries used in vehicles face challenges in accurately measuring internal resistance and predicting temperature changes, especially under low temperatures, leading to unreliable start-up and inefficient energy use due to decreased cell output.
Innovation Solution
A battery measuring device that includes a temperature measuring unit, resistance measuring unit, and estimating unit to calculate the electric resistance and reaction resistance of a secondary battery, allowing for the estimation of internal resistance and maximum output power, and a battery control system that determines deterioration conditions and alerts for necessary power output, with the option to warm up the battery for reliable activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the battery is used under low temperature conditions, then the cell output decreases, but the vehicle start-up reliability deteriorates
Solution Approach 1:
The system performs preliminary warming-up of the battery before vehicle start-up when low temperature is detected. The control unit activates the warming-up function to raise the battery temperature to an appropriate range, ensuring reliable start-up performance before the actual engine starting operation occurs.
Solution Approach 2:
The battery warming-up system utilizes the battery itself to generate heat for warming up through controlled charging currents. The control unit regulates the charging process to generate thermal energy within the battery, eliminating the need for external heating devices and using the battery's own electrochemical properties for temperature management.
2Measurement precision
If the internal resistance is measured to predict cell deterioration, then the measurement precision improves, but the measurement complexity increases under varying temperature conditions
Solution Approach 1:
The control unit acts as an intermediary that coordinates between temperature sensing and resistance measurement operations. It first detects the battery temperature, determines the appropriate measurement timing, and then triggers the resistance measurement at optimal moments, simplifying the overall measurement system architecture while maintaining precision.
Solution Approach 2:
The system changes the measurement parameters (timing and conditions) based on temperature variations. By adjusting when and how resistance measurements are taken according to the detected temperature state, the system achieves accurate measurements across different temperature conditions without requiring complex temperature-independent measurement hardware.
3Reliability
If the battery warming-up function is activated, then the start-up reliability improves, but the energy consumption increases
Solution Approach 1:
The warming-up function operates dynamically based on real-time temperature conditions and battery state assessments. The control unit continuously monitors temperature and adjusts or terminates the warming-up process as needed, rather than operating continuously, thereby optimizing energy usage while maintaining start-up reliability when necessary.
Solution Approach 2:
The system implements feedback control by continuously monitoring battery temperature and performance parameters during the warming-up process. The control unit uses this feedback information to determine when the battery has reached an appropriate temperature for start-up, allowing the warming-up function to be deactivated timely and avoid unnecessary energy consumption.
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
Accurately predicts the usability of secondary batteries under cold conditions, prevents unnecessary energy consumption, and ensures reliable vehicle start-up by estimating internal resistance and output power, enabling stable operation of vehicles powered by secondary batteries.
Implementation Method 1
a temperature measuring unit which measures temperature T1 of a secondary battery
Implementation Method 2
a resistance measuring unit which measures an AC resistance value and a DC pulse resistance value of a first discharging period of the secondary battery
Data Source
AI summary
A battery measuring device includes a temperature measuring unit which measures temperature T1 of a secondary battery, a resistance measuring unit which measures an AC resistance value and a DC pulse resistance value of a first discharging period of the secondary battery at the temperature T1, and an estimating unit in which an electric resistance Re1 and a reaction resistance Rc1 of the secondary battery at the temperature T1 are considered as,Re1=AC resistance valueRc1=DC pulse resistance value of the first discharging period−AC resistance value, and which estimates at least an internal resistance of the secondary battery using the temperature T1, electric resistance Re1 and reaction resistance Rc1.