Hybrid Battery Cell Balancing Using Active and Passive Methods
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Solution Overview
Problem
Cell balancing in battery systems is essential to maintain homogeneous conditions and prevent premature failure, as imbalances due to internal resistance and charge/discharge cycles lead to underutilization and deterioration, especially in technologies like Li-Ion which are intolerant to overcharge or deep-discharge conditions.
Innovation Solution
A combination of active and passive cell balancing methods, where active balancing is used to raise the state of charge of undercharged cells and passive balancing is applied to reduce the charge of overcharged cells, utilizing a hybrid module balancing block with a microcontroller, switching array, and components like flyback DC/DC converters and MOSFETs to manage voltage and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive cell balancing is used to reduce charge of overcharged cells, then cell voltage balance is improved, but energy loss increases due to heat dissipation
Solution Approach 1:
The patent combines passive and active cell balancing methods into a hybrid system. Passive balancing is used when cells are overcharged (high voltage), while active balancing is used when cells are undercharged (low voltage). This merging allows the system to address different imbalance scenarios with the most appropriate method, reducing overall energy loss compared to using only passive balancing.
Solution Approach 2:
The system dynamically changes the balancing approach based on voltage parameters. When cell voltage exceeds a threshold (overcharged), passive balancing with resistors is activated. When cell voltage is below a threshold (undercharged), active balancing with DC-DC converters is activated. This parameter-based switching optimizes energy efficiency while maintaining cell voltage balance.
2Loss of energy
If active cell balancing is used to raise state of charge of undercharged cells, then energy efficiency is improved, but device complexity increases
Solution Approach 1:
The balancing system is segmented into different functional modules: passive balancing circuits with resistors for overcharged cells, active balancing circuits with DC-DC converters for undercharged cells, and a control unit that manages switching between them. This segmentation allows each module to perform its specific function efficiently while keeping the overall system manageable through modular design.
Solution Approach 2:
The control unit acts as an intermediary that monitors cell voltages and decides which balancing method to apply. It receives voltage information from the battery management system and activates the appropriate balancing circuit (passive or active) based on the current state of cells, thereby managing the complexity of coordinating multiple balancing methods.
3Device complexity
If cell balancing is not applied, then device complexity is reduced, but battery lifetime decreases due to underutilization and deterioration
Solution Approach 1:
The battery management system includes an integrated cell balancing function that automatically monitors and corrects cell imbalances without external intervention. The system uses the battery's own voltage information and control circuits to perform balancing, extending battery lifetime through self-service maintenance rather than requiring external balancing equipment.
4Duration of action of stationary object
If hybrid balancing system is implemented, then battery lifetime is extended, but manufacturing cost increases
Solution Approach 1:
The control unit serves multiple functions: it monitors cell voltages, determines which cells need balancing, selects the appropriate balancing method (passive or active), and controls the switching between different balancing circuits. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby controlling manufacturing costs while implementing a comprehensive hybrid balancing system.
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 extends the life span, increases efficiency, and improves safety of battery systems by maintaining optimal cell balance under various operating conditions, reducing energy storage capacity loss and preventing hazardous situations.
Implementation Method 1
an active cell balancing means configured to provide the active balancing under the control of the control signal
Implementation Method 2
a passive cell balancing means configured to provide the passive balancing under the control of the control signal
Data Source
AI summary
The invention relates to a system for battery cell balancing comprising a cell monitoring block (16) configured to monitor the voltage or a related quantity across individual cells (C.sub.1, C.sub.2, . . . C.sub.N) in a battery cell module; a microcontroller (18) configured for monitoring the positive terminal voltage (12) and the negative terminal voltage (13) of said battery cell module, and for monitoring (11) the output current I.sub.mod of said module, and monitored cell voltage of said individual cells (C.sub.1, C.sub.2, . . . C.sub.N), where the microcontroller (18) is configured to provide a control signal (20) based at least said positive terminal voltage (12), said negative terminal voltage (13), said output current I.sub.mod of said module, and said monitored cell voltage of said individual cells; and a hybrid module balancing block configured to provide either an active or a passive cell balancing or a combination of active and passive cell balancing of the cells (C.sub.1, C.sub.2, . . . C.sub.N) in the specific module under the control of the control signal provided by the microcontroller. The invention further relates to a method for battery cell balancing in a battery comprising one or more modules each comprising one or more cells.