Battery Current Sensor Calibration for Temperature Drift Compensation
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Solution Overview
Problem
Current sensor calibration methods in electric vehicle battery systems are inadequate due to temperature and lifetime-related errors, leading to inaccuracies in current measurement, which affect range optimization, state of health determination, and rapid charging capabilities.
Innovation Solution
A method for calibrating multiple current sensors connected in series by determining temperature differences, calculating current regression areas, and deriving TCR regression curves to account for temperature-dependent errors, allowing for precise calibration and compensation of measurement inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current sensors are used in battery systems for monitoring supply current, then the electrical energy supply system can be monitored, but the current sensors and measurement electronics deviate over temperature and lifetime leading to measurement inaccuracies
Solution Approach 1:
The patent applies parameter changes by determining temperature differences between current sensors and using these temperature parameters to calculate correction factors. The measurement electronics adjust their measurement parameters based on the detected temperature variations, compensating for drift and maintaining precision across different operating conditions.
Solution Approach 2:
The patent implements feedback mechanisms where temperature sensors continuously monitor the temperature of current sensors, and this temperature information is fed back to the measurement electronics. The system uses this feedback to dynamically adjust calibration parameters and compensation factors, ensuring accurate current measurements despite temperature-induced drift over the sensors' lifetime.
2Ease of manufacture
If initial calibration is performed at factory or during production, then offset can be calibrated at 0A current flow, but the calibration does not account for temperature-dependent errors that occur during actual operation
Solution Approach 1:
The patent applies preliminary action by performing initial calibration at the factory under controlled conditions, establishing baseline parameters. Additionally, temperature compensation parameters are pre-determined and stored in the measurement electronics, ready for application during operation. This preliminary preparation enables rapid compensation without requiring complex real-time calibration procedures.
Solution Approach 2:
The patent addresses the limitation of fixed initial calibration by implementing dynamic parameter changes. The system stores multiple calibration parameters corresponding to different temperature ranges and selectively applies the appropriate parameters based on real-time temperature measurements, allowing the calibration to adapt to operating conditions without complicating the manufacturing process.
3Reliability
If multiple current sensors are connected in series to measure the same current, then redundancy and monitoring capability are improved, but temperature differences between sensors cause deviations in their error curves
Solution Approach 1:
The patent applies local quality by recognizing that each current sensor operates in its local thermal environment and may have different temperature characteristics. Instead of assuming uniform behavior, the system individually monitors the temperature of each sensor and applies sensor-specific compensation parameters, accounting for local thermal conditions and maintaining consistency across the sensor array.
Solution Approach 2:
The patent resolves the inconsistency issue by dynamically changing the measurement parameters for each sensor based on its individual temperature. The system calculates separate correction factors for each current sensor according to its temperature difference from a reference, ensuring that each sensor's measurements are adjusted to a common reference condition, thereby maintaining consistency across the redundant sensor network.
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 method provides accurate and precise current measurement across various temperatures and over the lifetime of the sensors, enhancing the usability and longevity of electric vehicle battery systems by minimizing measurement errors and ensuring reliable charging and discharging processes.
Implementation Method 1
a temperature sensor, such as an NTC (negative temperature coefficient) resistor or a PTC (positive temperature coefficient) resistor, is respectively provided for the current sensors
Implementation Method 2
current measuring resistors, also respectively referred to as a shunt
Implementation Method 3
contactless current sensors, such as Hall sensors
Data Source
AI summary
A method for calibrating a plurality of current sensors connected in series. The method include determining a temperature difference between the current sensors; sensing temperature values and current values of the respective current sensors at different temperatures and currents; calculating averaged current values of two current sensors based on the current measured values sensed by the respective current sensors; calculating a current regression area for the respective current sensors through measurement points that are dependent on the temperature of the respective current sensors and the deviation of the current values sensed by the respective current sensors relative to one another; and calculating a TCR regression curve or a TCR regression area for the respective current sensors based on a deviation and an intersection curve of the respective current regression areas relative to one another and/or relative to an averaged current regression area and a temperature difference between the current sensors.