Resonant Converter Cell Balancing Using Series Inductor Capacitor
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Solution Overview
Problem
Existing cell balancing and charging systems for series-connected battery cells face inefficiencies due to energy dissipation in resistive systems and complexity in inductive or capacitive energy transfer, especially when charging over multiple cells, leading to uneven state of charge distribution and potential battery damage.
Innovation Solution
A system utilizing a resonant converter with a series-connected inductor and capacitor, coupled with a transformer, allows for efficient energy redistribution across battery cells by transferring energy from the entire stack to cells with lower charge, balancing voltages without dissipating energy through resistors and simplifying the charging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistive balancing systems are used to charge battery cells, then cell balancing can be achieved, but energy is dissipated as heat leading to energy loss
Solution Approach 1:
The patent replaces the resistive (electrical dissipation) system with an inductive energy transfer system using transformers. Instead of dissipating excess energy as heat through resistors, the system uses magnetic coupling to transfer energy from higher-voltage cells to lower-voltage cells through transformer windings, thereby achieving cell balancing without energy loss.
Solution Approach 2:
The patent changes the operating parameters by using variable switching ratios in the transformer windings. By adjusting the number of active secondary windings connected to different cells, the system can dynamically control energy distribution to achieve balanced charging across all cells while maintaining high efficiency.
2Loss of energy
If inductive or capacitive energy transfer systems are used for cell balancing, then energy dissipation is reduced, but system complexity increases
Solution Approach 1:
The patent creates a universal transformer-based platform that can balance any number of series-connected battery cells using the same basic circuit topology. The system uses a single primary winding that can couple to multiple secondary windings, allowing the same hardware structure to serve multiple cells simultaneously, thereby reducing overall system complexity compared to individual balancing circuits for each cell.
Solution Approach 2:
The patent merges multiple cell balancing functions into a single transformer core structure. Multiple secondary windings are wound on the same transformer, allowing energy transfer to multiple cells from a single primary excitation source. This consolidation reduces the number of separate components and control circuits needed.
3Productivity
If traditional charging systems are used, then charging can be performed, but uneven state of charge distribution occurs leading to potential battery damage
Solution Approach 1:
The patent implements a feedback control mechanism where the controller monitors the voltage of each battery cell and dynamically adjusts the switching of secondary windings based on real-time cell state measurements. This feedback ensures that energy is transferred preferentially to lower-voltage cells, maintaining even state of charge distribution and preventing overcharging of any individual cell.
Solution Approach 2:
The patent uses dynamic switching of transformer windings to adapt the energy distribution in real-time. The system continuously monitors cell voltages and dynamically reconfigures which secondary windings are active, allowing the charging process to respond to changing battery conditions and maintain optimal charge balance throughout the charging cycle.
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 enables efficient and balanced charging of battery cells across a stack without energy loss, ensuring all cells reach maximum charge voltage, prolonging battery life and maximizing energy utilization with reduced complexity and cost.
Implementation Method 1
A system utilizing a resonant converter with a series-connected inductor and capacitor
Implementation Method 2
coupled with a transformer, allows for efficient energy redistribution across battery cells by transferring energy from the entire stack to cells with lower charge
Data Source
AI summary
An apparatus for charging a plurality of series connected battery cells, includes a first and second input terminals for providing a charging voltage to the plurality of series connected battery cell. A transformer includes a primary side associated with the charging voltage and a secondary side includes a plurality of portions. Each of the plurality of portions is connected across at least one of the plurality of series connected battery cell. A switch in series between each of the plurality of portions of the secondary side and the at least one of the plurality of series connected battery cells increases an impedance between the portion of the secondary side and the associated one of the plurality of series connected battery cells in a first state and decreases the impedance between the portion of the secondary side and the associated one of the plurality of series connected battery cells in a second state.