Bi-directional Module Balancing Circuit for Battery Systems
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Solution Overview
Problem
Battery systems face challenges in balancing voltages across cells and modules due to deviations in capacity and impedance, leading to over-charging or over-discharging, which existing technologies fail to address effectively.
Innovation Solution
A battery system with a cell balancing circuit and a module balancing circuit that measures voltages and controls switches to balance selected cells and modules by transferring energy between them, using bi-directional switches and a multi-winding transformer for efficient energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cells are connected in series to obtain high voltage and large capacity, then the battery system achieves higher voltage and capacity, but voltage deviations between cells increase due to capacity and impedance differences
Solution Approach 1:
The battery system is divided into multiple modules, each containing a subset of cells. This segmentation allows independent balancing control for each module, enabling precise management of voltage deviations while maintaining overall high capacity. Each module can be balanced separately based on its specific voltage characteristics.
Solution Approach 2:
A module balancing circuit is introduced as an intermediary component between modules to transfer energy and balance voltages. This intermediary circuit measures voltage deviations and actively transfers energy from modules with higher voltage to those with lower voltage, resolving the voltage imbalance caused by series connections.
2Reliability
If cell balancing is performed to prevent over-charging and over-discharging, then cell safety is improved, but energy loss increases due to conventional balancing methods
Solution Approach 1:
The balancing function is merged with the normal charge/discharge operation. Instead of separate balancing circuits that dissipate energy, the system uses the existing power flow to transfer energy between modules during regular operation, achieving balancing without additional energy loss.
Solution Approach 2:
The battery system performs self-balancing by transferring energy internally between modules during normal charge/discharge cycles. The module balancing circuit automatically identifies voltage deviations and redistributes energy without external intervention or additional energy consumption, allowing the system to balance itself.
3Measurement precision
If multiple balancing circuits are implemented for both cells and modules, then balancing precision is improved, but device complexity increases
Solution Approach 1:
The balancing system is segmented into two hierarchical levels: cell-level balancing within each module and module-level balancing across the entire battery system. This segmentation allows each balancing circuit to focus on a specific scope, reducing the complexity of individual circuits while maintaining overall precision through coordinated operation.
Solution Approach 2:
The module balancing circuit is designed to perform multiple functions: it balances voltages between modules, monitors overall system voltage distribution, and coordinates with cell-level balancing circuits. This multi-functionality reduces the need for separate dedicated circuits for each function, simplifying the overall system architecture.
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
The solution ensures balanced voltages across cells and modules, reducing energy loss and improving efficiency by directly transferring energy between cells and modules, while minimizing conduction losses and preventing over-voltage.
Implementation Method 1
a multi-winding transformer. The bi-directional switches may be configured to bi-directionally control a flow of an electric current. The multi-winding transformer may be configured to transfer energy between the selected modules
Implementation Method 2
The cell balancing circuit is configured to measure voltages of the plurality of cells. The cell balancing circuit is configured to select a first number of the plurality of cells for cell balancing based on the voltages of the plurality of cells
Data Source
AI summary
According to an example embodiment, a battery system includes: a plurality of modules, each including a plurality of cells connected to each other in series and a cell balancing circuit performing a balancing operation between the plurality of the cells based on voltages of the plurality of the cells; and a module balancing circuit performing a balancing operation between the modules based on voltages of the modules.