Battery Management System Voltage Error Compensation
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Solution Overview
Problem
Battery management systems (BMS) face measurement errors due to ohmic losses from cable impedances, which affect voltage measurements in electric vehicle batteries, leading to inaccuracies and safety hazards.
Innovation Solution
A method is introduced to compensate for measurement errors by performing a calibration cycle to calculate correction factors based on discharge switch states, applying these factors to raw voltage measurements to generate accurate compensated voltage readings, and scaling them to account for filter response errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If specialized hardware is used to sense cell voltages in a battery management system, then voltage measurement capability is enabled, but ohmic losses are introduced resulting in voltage measurement error
Solution Approach 1:
The patent performs a calibration cycle before normal operation to determine correction factors. During calibration, the system measures voltages with discharge switches in different states (enabled/disabled) and calculates the ohmic loss characteristics in advance. These pre-determined correction factors are then applied during runtime to compensate for the ohmic losses, resolving the measurement accuracy issue without changing the hardware.
Solution Approach 2:
The system continuously monitors voltage measurements and uses the pre-determined correction factors to compensate for ohmic losses. By comparing measured voltages with expected values and applying corrections based on the calibration data, the system creates a feedback loop that maintains accurate voltage readings despite the presence of ohmic losses in the measurement hardware.
2Measurement precision
If calibration cycles are performed to calculate correction factors, then measurement accuracy is improved, but system operation time is consumed
Solution Approach 1:
The calibration cycle is performed during system initialization or maintenance periods before normal operation begins. By completing the time-consuming calibration process in advance, the system establishes correction factors that can be quickly applied during runtime without impacting operational time. This separates the time-intensive accuracy improvement from the operational phase.
Solution Approach 2:
The calibration cycle can be performed periodically or at scheduled intervals rather than continuously. This allows the system to maintain measurement accuracy by updating correction factors only when necessary, minimizing the impact on operational time while ensuring accuracy is maintained over the system's operational lifecycle.
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 effectively reduces measurement errors, ensuring accurate voltage monitoring and maintaining battery health, thereby enhancing the reliability and safety of electric vehicle battery management systems.
Implementation Method 1
the hardware used by the BMS can introduce ohmic losses, resulting in voltage measurement error
Data Source
AI summary
Voltage measurement techniques for battery cells in a battery management system (BMS) are described. Raw voltage measurements may include errors caused by ohmic losses due to cable impedances and other elements in the BMS. The techniques include performing a calibration cycle to generate correction values based on measured response with discharge switches in different states. The techniques also include scaling the correction values during runtime to correct for filter response errors in the voltage measurement.