Battery Cell Equalization Using Pulse Closed-Circuit Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing battery equalization methods using open circuit voltage are imprecise due to small differences in voltage between cells, leading to unsatisfactory equalization and interference from internal resistance, making it difficult to accurately determine the state of charge (SOC) and inequality between cells.
Innovation Solution
A method and device that utilize pulse charge and pulse discharge closed circuit voltages to determine the relationship of SOC values between cells, allowing for accurate identification of high and low SOC cells without precise SOC calculation, and perform charge equalization based on these relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If open circuit voltage detection is used to estimate SOC, then the measurement process is simple, but the measurement precision is insufficient due to small voltage differences between cells
Solution Approach 1:
The patent applies periodic pulse charging and discharging actions to the battery cells. By periodically applying current pulses and measuring the resulting voltage responses, the system transforms the static voltage measurement into a dynamic measurement process. This periodic action amplifies the voltage differences between cells with different SOC levels, thereby improving measurement precision while maintaining operational simplicity.
Solution Approach 2:
The patent changes the measurement parameters by introducing current pulses rather than relying solely on open circuit voltage. By measuring closed circuit voltage during pulsed charging and discharging, the system exploits the relationship between current, voltage, and internal resistance to enhance SOC differentiation. This parameter change transforms the measurement from a static voltage reading to a dynamic electrochemical response measurement.
2Measurement precision
If closed circuit voltage is measured during current flow, then the voltage difference between cells is more significant, but internal resistance interference makes accurate SOC determination difficult
Solution Approach 1:
The patent employs feedback by measuring both the applied current and the resulting closed circuit voltage, then using this feedback information to calculate and compensate for internal resistance effects. The system uses the voltage response during pulse charging and discharging to infer SOC while accounting for internal resistance variations, thereby eliminating the harmful interference and achieving accurate SOC determination.
Solution Approach 2:
The patent introduces pulse current as an intermediary element that mediates between the battery cells and the measurement system. By applying controlled current pulses and measuring the voltage responses, the system uses this intermediary action to amplify SOC differences while the known current waveform serves as a reference for compensating internal resistance effects.
3Measurement precision
If precise SOC values and SOC difference percentages are calculated, then accurate equalization can be achieved, but the computational load increases
Solution Approach 1:
The patent applies partial action by determining only the relative SOC relationships between cells rather than calculating precise absolute SOC values for each cell. By focusing on identifying which cells have higher or lower SOC levels relative to others, the system achieves sufficient accuracy for equalization control without the computational burden of precise SOC calculation, thereby reducing device complexity while maintaining effective equalization.
Data Source
AI summary
This application describes a battery equalization method and device, and a battery management system. The battery equalization method includes: obtaining a first closed circuit voltage of N cells in a duration of a pulse charge current and a second closed circuit voltage of the N cells in a duration of a pulse discharge current, where the N cells constitute a battery, and N is a positive integer; determining a relationship of SOC values between the N cells based on the first closed circuit voltage and the second closed circuit voltage; and performing charge equalization on target cells, where the target cells are determined from the N cells based on the relationship of SOC values.