Battery Sensor Self-Calibration Using Reference Current
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Solution Overview
Problem
Existing battery sensor designs face challenges in cost-effectiveness and complexity due to the high cost of precise resistors for measuring load current and state-of-charge calculations, particularly in recalibrating shunt resistors under varying conditions in motor vehicles.
Innovation Solution
A method and battery sensor design utilizing two measuring resistance elements connected in series with a reference resistor circuit, allowing for precise determination of electrical resistance using a reference current and correction factors, reducing the need for multiple analog/digital converters and simplifying the calibration process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-precision resistors are used for measuring load current, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The system performs self-calibration by using the known reference resistor value and measured voltage drops to automatically calculate and store correction factors in the microcontroller's memory, eliminating the need for manual calibration procedures and external calibration equipment
Solution Approach 2:
The system continuously monitors voltage drops across both resistors and uses the reference resistor's known characteristics to generate feedback signals that enable the microcontroller to calculate and apply correction factors, ensuring ongoing measurement accuracy without external intervention
2Measurement precision
If shunt resistor recalibration is performed repeatedly over battery sensor lifetime, then measurement precision is maintained, but device complexity increases
Solution Approach 1:
The system performs self-calibration by using the known reference resistor value and measured voltage drops to automatically calculate and store correction factors in the microcontroller's memory, eliminating the need for manual calibration procedures and external calibration equipment
Solution Approach 2:
The calibration current is applied periodically or at specific intervals (e.g., during vehicle startup or when the vehicle is stationary) to update correction factors, maintaining measurement accuracy without requiring continuous complex calibration systems
3Measurement precision
If reference current is applied continuously for calibration, then measurement precision is maintained, but power consumption increases
Solution Approach 1:
The calibration current is applied periodically or at specific intervals (e.g., during vehicle startup or when the vehicle is stationary) to update correction factors, maintaining measurement accuracy without requiring continuous complex calibration systems
Solution Approach 2:
Once correction factors are calculated and stored in memory, the system continuously uses these factors to compensate for resistor drift without requiring continuous application of calibration current, maintaining accuracy while minimizing power consumption during normal operation
4Measurement precision
If multiple analog/digital converters are used for precise measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The microcontroller's single analog/digital converter is used for multiple functions: measuring voltage drops across both resistors, reading temperature sensor data, and performing calibration calculations, eliminating the need for separate dedicated converters for each measurement function
Solution Approach 2:
The system combines voltage measurement, current measurement, temperature monitoring, and calibration functions into a single integrated microcontroller unit that processes all signals through one analog/digital converter, reducing component count and system complexity
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 approach enables accurate and cost-effective determination of load current and battery state with reduced hardware requirements, allowing for uninterrupted current measurement and battery status monitoring using only three analog/digital converters.
Implementation Method 1
detecting the respective resulting voltage drops across the first and second measuring resistance elements
Implementation Method 2
determining the reference current from the quotient of the battery voltage and the electrical resistance of the reference resistance
Data Source
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AI summary
The invention relates to a method for operating a battery sensor and to a battery sensor, comprising at least one first battery sensor connection (Vat+) and a second battery sensor connection (Vba-), in particular for connecting to a battery and a load current connection, a current measuring device for detecting the load current (Iload), comprising a first measuring resistor element (R1) and a second measuring resistor element (R2), wherein the first and the second measuring resistor element (R1, R2) are connected in series between the load current connection and the second battery sensor connection (Vbat-), and a reference current circuit with at least one reference resistor (Rref, Rref1, Rref2), said reference resistor (Rref, Rref1, Rref2) being in contact with the first battery sensor connection (Vbat+) and a contact point provided between the measuring resistor elements (R1, R2). The electric resistance of the first resistor element (R1) is determined by connecting the reference current (Iref) and detecting the voltage drops (U1, U2) over the first and second measuring resistor element (R1, R2) and the battery voltage (Vbat), determining the reference current (Iref) from the quotient of the battery voltage (Vbat) and the electric resistance of the reference resistor element (Rref), and determining the electric resistance of the first resistor element (R1) from the detected voltage drops (U1, U2), the reference current (Iref), and at least one correction factor (α, β) which characterizes the relationship between the electric resistance of the first resistor element (R1) and the electric resistance of the second resistor element (R2).