PWM Battery Balancing Current Control for Cell Voltage Equalization
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Solution Overview
Problem
Existing battery balancing technologies, particularly passive balancing systems, are inadequate in compensating for significant variations in cell characteristics, leading to premature degradation and reduced lifespan of rechargeable batteries.
Innovation Solution
The implementation of a switch mode divider (SMD) system connectable in parallel to battery cells, which modulates to equalize voltages between cells and limits balancing current to prevent damage, using a controller to manage the SMDs and sensors to monitor current and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive balancing systems are used to compensate for cell variations, then minor variations can be corrected, but significant variations in cell characteristics cannot be compensated leading to premature degradation
Solution Approach 1:
The patent implements dynamic balancing by switching between passive balancing mode (for minor variations) and active balancing mode (for significant variations). The system dynamically adjusts the balancing current based on real-time cell voltage differences and impedance characteristics, enabling adaptation to both minor and major cell variations while extending battery lifespan.
2Productivity
If balancing current is increased to equalize cell voltages faster, then balancing efficiency improves, but cell damage may occur
Solution Approach 1:
The system continuously monitors cell voltage differences and impedance values, using this feedback to dynamically adjust the balancing current. When cell voltage differences are large, the system increases balancing current to speed up equalization; when cells approach equilibrium or impedance indicates vulnerability, the current is reduced to prevent damage. This closed-loop control enables both fast and safe balancing.
Solution Approach 2:
The patent changes the balancing current parameter dynamically based on real-time cell conditions. The system adjusts current magnitude according to voltage differences between cells and their impedance characteristics, transforming the static balancing current into a dynamic parameter that adapts to cell state, thereby achieving both high productivity and safety.
3Productivity
If switch mode dividers are used to equalize voltages between cells, then balancing efficiency improves, but device complexity increases
Solution Approach 1:
The switch mode dividers are designed to perform multiple functions: voltage equalization between cells, impedance measurement for cell characterization, and dynamic current regulation. By making the balancing circuit multi-functional, the patent reduces the need for separate measurement and control circuits, thereby improving balancing efficiency while limiting the increase in overall system complexity.
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 solution enables efficient and effective balancing of battery cells, prolonging battery life by up to 100% in tier-2 batteries and maintaining performance similar to tier-1 batteries, while also allowing for real-time measurement of cell impedance.
Implementation Method 1
an output voltage Vo that is a function of a duty cycle of a drive waveform and high and low rail voltages
Data Source
AI summary
A battery cell balancing system contains a switch mode circuit employing voltage sensors across the cells and current sensors on the balancing legs to enable reliable and efficient cell balancing during battery charge.