Battery Pack Voltage Calibration via Differential and Common-Mode Parameters
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Solution Overview
Problem
Conventional methods for calibrating battery pack voltage require high voltage operational amplifiers and complex resistor matching, leading to increased costs and inconvenience due to high common-mode gain and offset voltage errors, and the need for precise resistor adjustments.
Innovation Solution
A method and system that calculates differential-mode and common-mode calibration parameters through a two-point calibration process, allowing for accurate cell voltage calibration without precise resistor matching, and enabling random connection of battery cells to a battery management system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high voltage operational amplifier is used to accommodate large potential difference, then the voltage detection range is improved, but common-mode gain and offset voltage errors increase
Solution Approach 1:
The patent segments the voltage detection function into two independent paths: a differential-mode path for measuring voltage differences with high precision, and a common-mode path for measuring common-mode voltages separately. This segmentation allows each path to be optimized independently, avoiding the need for a single high-voltage operational amplifier that suffers from both range limitations and error accumulation.
Solution Approach 2:
The patent introduces an intermediary computational process that combines measurements from separate differential-mode and common-mode detection paths. By calculating the final voltage as the sum of differential voltage (measured with high precision) and common-mode voltage (measured separately), the system achieves high voltage range capability without suffering from the compounded errors of a single high-voltage amplifier.
2Measurement precision
If complex calibration process with fine adjustments to resistors is performed, then voltage translation accuracy is improved, but device complexity and calibration time increase
Solution Approach 1:
The patent extracts the calibration requirements into two separate, simplified calibration processes: one for the differential-mode path and one for the common-mode path. Each calibration process only requires adjusting a single resistor value rather than performing complex multi-resistor matching, significantly reducing calibration complexity while maintaining accuracy.
Solution Approach 2:
The patent changes the calibration approach by separating the calibration of differential-mode parameters and common-mode parameters into independent steps. This parameter separation allows each mode to be calibrated independently with simpler adjustments, avoiding the need for complex simultaneous adjustment of multiple resistors that would be required in a unified calibration approach.
3Measurement precision
If all four resistor values are balanced through complex calibration, then voltage translation error is reduced, but calibration time and manufacturing complexity increase
Solution Approach 1:
The patent segments the resistor balancing requirement into two independent sets: differential-mode resistors and common-mode resistors. Each set only requires single-resistor adjustment rather than coordinated adjustment of all four resistors, reducing calibration time while achieving the same error reduction effect.
Solution Approach 2:
The patent performs preliminary separation of the calibration tasks before actual calibration begins. By pre-defining which resistors belong to which mode (differential or common-mode), the system enables independent, simplified calibration of each mode without requiring iterative adjustment of all resistors simultaneously, thus reducing calibration time.
4Measurement precision
If precise resistor matching is required, then voltage measurement accuracy is improved, but manufacturing cost and difficulty increase
Solution Approach 1:
The patent segments the resistor matching requirement into two independent groups: differential-mode resistors and common-mode resistors. Each group only requires matching of a single resistor value rather than precise matching of all four resistors, significantly easing manufacturing requirements while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the manufacturing requirement by separating the resistor matching parameters into independent differential-mode and common-mode parameters. This allows each mode to be manufactured and calibrated independently with relaxed tolerances, avoiding the need for tight matching of all four resistors that would increase manufacturing difficulty and cost.
Data Source
AI summary
Method, system, and programs for calibrating battery pack voltage are disclosed. A negative terminal voltage of a cell is changed from a first to a second negative terminal voltage so that a cell voltage is changed from a first to a second output voltage. A positive terminal voltage of the cell is maintained at a substantially constant level. A differential-mode calibration parameter is calculated based on a difference between the first and second output voltages and a difference between the first and second negative terminal voltages. The negative terminal voltage of the cell is then changed from the first to second negative terminal voltage so that the positive terminal voltage of the cell is changed from a first to a second positive terminal voltage and the output voltage is changed from a third to a fourth output voltage. The cell voltage is maintained at a substantially constant value. A common-mode calibration parameter is calculated based on the differential-mode calibration parameter and a difference between the third and fourth output voltages and a difference between the first and second positive terminal voltages.