Resonant Cell Balancing via Inductive Energy Transfer
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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 and potential battery damage.
Innovation Solution
A resonant converter-based system with a transformer and MOSFET switches that redistributes energy from the entire stack to cells with lower charge, using a resonant tank circuit and transformer secondary windings to balance charge levels without dissipating energy, allowing for simple and efficient charge distribution across multiple cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistive balancing systems are used to equalize charge between battery cells, then charge imbalance is corrected, but energy is dissipated as heat
Solution Approach 1:
The patent introduces a resonant tank circuit as an intermediary energy transfer mechanism between battery cells. The tank circuit stores energy temporarily in its electromagnetic field and transfers it to cells needing charge, rather than dissipating energy through resistance. This mediator enables efficient energy redistribution while maintaining charge balance.
Solution Approach 2:
The patent replaces the resistive (thermal) balancing mechanism with an inductive/capacitive resonant system. By substituting the thermal conduction mechanism with electromagnetic resonance, energy is transferred through field coupling rather than heat generation, eliminating the energy loss inherent in resistive systems.
2Loss of energy
If inductive or capacitive energy transfer is used to reduce energy loss, then energy efficiency improves, but system complexity increases
Solution Approach 1:
The patent divides the battery system into discrete cell groups that can be independently charged through the resonant tank circuit. Each cell or group of cells can be addressed separately, allowing the complex resonant charging mechanism to be applied selectively rather than requiring simultaneous management of all cells, thereby reducing overall system complexity.
Solution Approach 2:
The resonant tank circuit serves multiple functions: it acts as an energy storage element, a transfer medium, and a control mechanism for selective cell charging. By making the tank circuit multi-functional, the patent reduces the need for separate components for each function, thereby managing complexity while maintaining energy efficiency.
3Quantity of substance
If charging is performed over multiple cells in series, then system capacity increases, but charge distribution becomes uneven
Solution Approach 1:
The patent employs dynamic switching control that monitors individual cell voltages and adjusts the charging distribution in real-time. The system dynamically redirects energy through the resonant tank circuit to cells that need charging, rather than applying static equal charging to all cells, thereby maintaining even charge distribution across the series-connected battery pack.
Solution Approach 2:
The patent incorporates voltage sensing and control logic that provides feedback on individual cell charge states. This feedback mechanism allows the system to detect charge imbalances and adjust the resonant tank circuit's energy transfer accordingly, ensuring that cells are charged evenly despite being connected in series, thus maintaining reliability while preserving system capacity.
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 balanced charging of battery cells across a stack without energy loss, ensuring all cells reach maximum charge voltage and extending battery life by automatically distributing charge without complex control mechanisms, while allowing for scalable configurations.
Implementation Method 1
a resonant circuit is connectable between the switching circuit and the common node of the batteries
Implementation Method 2
a resonant tank circuit consisting of an inductor and a capacitor
Implementation Method 3
A first transformer has a primary winding and a plurality of secondary windings
Data Source
Figure 1
Figure 2~3
Figure 4
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.