Bidirectional Energy-Transmission Apparatus for Battery Cell Equalization
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Solution Overview
Problem
Existing charge equalization methods for series-connected lithium-ion battery cells are inefficient due to energy losses, high costs, and limited scalability, as they either convert excess energy to heat or require expensive transmitters, leading to suboptimal utilization of battery capacity and reduced battery life.
Innovation Solution
A circuit with bidirectional energy-transmission apparatuses, each connected to multiple battery cells, allows for efficient energy exchange between cells through nodes and inductors, enabling isochronous charging and discharging of individual cells, thereby balancing the stack quickly and effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive balancing with resistors is used to discharge overcharged cells, then charge equalization is achieved, but excess energy is converted to heat causing energy losses
Solution Approach 1:
The patent introduces an intermediary energy storage element (capacitor or battery cell) that mediates the energy transfer between overcharged and undercharged cells. Instead of directly dissipating energy through resistors, the excess energy is temporarily stored in the intermediary element and then transferred to cells that need charging, achieving equalization without energy loss.
Solution Approach 2:
The patent recovers the excess energy from overcharged cells that would otherwise be discarded as heat. By capturing this energy in an intermediary storage element and redistributing it to undercharged cells, the system recovers and reuse the energy, eliminating the waste inherent in passive balancing.
2Adaptability or versatility
If expensive transmitters are used for charge equalization, then energy can be transferred between non-adjacent cells, but device complexity and cost increase
Solution Approach 1:
The patent uses a simple intermediary energy storage element (capacitor or battery cell) connected to all cells through a common bus, enabling energy transfer between any cells in the series string. This intermediary approach provides versatile energy redistribution capability without requiring complex transmitters at each cell location.
Solution Approach 2:
The intermediary energy storage element serves multiple functions: it stores excess energy from overcharged cells, supplies energy to undercharged cells, and enables equalization between any pair of cells regardless of their position in the series string. This single universal element replaces the need for multiple specialized transmitters.
3Power
If cells are connected in series to achieve high total voltage, then battery pack voltage is increased, but the weakest cell limits the total energy capacity
Solution Approach 1:
The patent implements a feedback mechanism through the common bus and intermediary energy storage element that continuously monitors and compensates for cell imbalances. During charging, if one cell reaches full charge before others, the feedback system automatically redirects excess energy to other cells through the intermediary element, ensuring all cells reach their maximum capacity while maintaining the series connection for high voltage.
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 allows for high charging or discharging currents during charging or discharging cycles, ensuring each cell is fully charged, increasing battery range or enabling the use of cheaper battery types, while minimizing energy dissipation and reducing the number of required structural elements.
Implementation Method 1
A circuit with bidirectional energy-transmission apparatuses, each connected to multiple battery cells, allows for efficient energy exchange between cells through nodes and inductors
Data Source
AI summary
In one embodiment, a method includes receiving a first input current from a battery through a first connection and a second connection and generating a first output current through a third connection to a first node and a fourth connection to a second node. The first and second nodes are configured to output the first output current to an energy store configured to store a charge. The method includes receiving a second input current through the third connection from the first node and the fourth connection from the second nodes and generating a second output current through the first and second connections to charge the battery.