Battery Pack Thermistor Testing via Controlled Charge Thermal Stress
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Solution Overview
Problem
Existing methods for testing battery pack thermistors in hybrid electric vehicles (HEVs) and electric vehicles (EVs lack assurance of adequate contact pressure and contamination-free interface, making it difficult to verify proper temperature measurement, as variations in material-handling and assembly processes can affect thermistor performance.
Innovation Solution
A battery pack thermistor test method involving thermal stressing of cells by applying a controlled charge profile to generate heat, monitoring temperature rise, and calculating the thermistor slope using a least squares fit to ensure the thermistors are functioning correctly and within acceptable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a simple check of thermistor output with no thermal changes is performed, then the testing process is simple and quick, but it cannot ensure adequate contact pressure or detect contamination between the thermistor and battery cell
Solution Approach 1:
The patent applies preliminary action by performing a controlled charge cycle on the battery pack before testing the thermistor output. This pre-conditioning step generates predictable thermal changes in the battery cells, ensuring that the thermistors are properly contacted and free of contamination before the actual measurement is taken. The thermal stress from charging prepares the system in a known state that reveals interface quality issues.
Solution Approach 2:
The patent changes the thermal parameter of the battery cell by applying a controlled charge cycle that generates predictable temperature changes. Instead of testing at static temperature, the system dynamically changes the temperature parameter during the charge cycle, allowing the thermistor to demonstrate its thermal response characteristics and interface quality under actual operating conditions.
2Adaptability or versatility
If material-handling and assembly processes are varied, then manufacturing flexibility is improved, but contact pressure and contamination between thermistor and battery cell become unpredictable
Solution Approach 1:
The patent applies self-service by using the battery pack's own charging process to generate the thermal stress needed for testing. Rather than requiring external thermal testing equipment or complex fixtures to apply heat, the system uses the natural heat generated during a controlled charge cycle. This eliminates the need for additional testing hardware and allows the manufacturing process itself to provide the test conditions.
Solution Approach 2:
The patent implements feedback by monitoring the thermistor output during the charge cycle and comparing it against expected thermal response characteristics. The system measures the actual temperature changes detected by the thermistor and uses this feedback to determine whether the thermistor is properly installed and free of contamination, thereby closing the loop on quality verification.
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 ensures accurate thermistor performance by characterizing the thermal response and verifying that thermistors can detect temperature changes effectively, thereby ensuring safe operation and maximum performance of the battery pack.
Implementation Method 1
charging a battery pack, monitoring a rise in average temperature reported by at least one thermistor on the battery pack
Implementation Method 2
a thermistor must have adequate contact pressure with the battery pack cell and free of any contamination between the thermistor and the cell
Data Source
AI summary
A battery pack thermistor test method includes charging a battery pack, monitoring a rise in average temperature reported by at least one thermistor on the battery pack over a predetermined time period, preparing at least one thermistor slope by calculating a least square fit of time vs. temperature for the at least one thermistor and comparing the at least one thermistor slope to process-defined thermistor slope limits.