Battery Module Balancing Circuit with DC/DC Converter
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Solution Overview
Problem
Existing battery balancing techniques for high voltage battery packs in electric vehicles are either inefficient and time-consuming (passive balancing) or expensive due to the need for additional hardware (active balancing).
Innovation Solution
A battery unit with a balancing circuit and power electronics unit, including DC/DC converters and a switch matrix, that allows for flexible operation and efficient balancing by selectively connecting and disconnecting battery cells to extract energy from cells with higher state of charge and supply it to cells with lower state of charge, optimizing energy utilization and reducing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive balancing is used to balance battery cells, then the implementation cost is low, but the balancing time is long and efficiency is poor
Solution Approach 1:
The patent implements dynamic balancing by enabling the DC/DC converter to operate in different modes (power supply mode, energy extraction mode, bypass mode) based on real-time battery cell state assessments. The system dynamically adjusts the operating mode of each battery module's DC/DC converter to achieve efficient energy redistribution while maintaining cost-effectiveness through existing hardware infrastructure.
2Productivity
If active balancing is used to balance battery cells, then the balancing efficiency and speed are high, but the hardware cost is expensive
Solution Approach 1:
The patent makes the DC/DC converter multi-functional by enabling it to perform both power supply functions and energy extraction/balancing functions. The converter can operate in power supply mode to provide power to the battery module and in energy extraction mode to balance cells, eliminating the need for separate active balancing hardware and reducing overall system cost while maintaining high balancing efficiency.
Solution Approach 2:
The system enables the battery modules to balance themselves by having each module's DC/DC converter extract energy from higher state of charge cells and supply it to lower state of charge cells within the same module or other modules. This self-service mechanism eliminates the need for external active balancing hardware, reducing costs while maintaining efficient balancing performance.
3Use of energy by moving object
If battery energy is fully utilized without waste, then energy efficiency is optimized, but system complexity increases
Solution Approach 1:
The system performs preliminary assessment of battery cell states before initiating balancing operations. By continuously monitoring and assessing the state of charge of individual cells, the system can proactively identify which cells need energy extraction and which need energy supply, enabling efficient energy utilization without requiring complex real-time control mechanisms during the actual balancing process.
Solution Approach 2:
The system implements feedback control by continuously assessing battery cell states and using this information to control the operating modes of DC/DC converters. The feedback mechanism monitors energy transfer effectiveness and adjusts balancing operations accordingly, ensuring optimal energy utilization while maintaining manageable system complexity through intelligent control rather than hardware complexity.
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
Enables flexible and efficient balancing of battery cells during operation, optimizing energy use and reducing costs by fully utilizing battery energy without wasting it, while allowing for flexible voltage and state of charge management.
Implementation Method 1
a first DC/DC converter (16) with an input port with two input terminals (IN1, IN2) connected to the battery cells (4) of the battery module (2), an output port with two output terminals (OUT1, OUT2) on which an output voltage of the battery module (2) is provided
Implementation Method 2
the balancing circuit (15) is configured to extract energy from a selected battery cell or battery cells and to provide the energy at least partly as power supply to the first DC/DC converter (16) or the power electronics unit (14)
Implementation Method 3
the respective balancing circuit (15) comprises a switch matrix (18) and a second DC/DC converter (17), wherein the switch matrix (18) comprises multiple switches for selectively connecting and disconnecting the battery cells (4) in the battery module (2)
Data Source
AI summary
Various embodiments of the teachings herein include a battery unit comprising a string of battery modules in series. Each battery module includes a plurality of battery cells in series. Each battery module comprises a respective balancing circuit and a respective power electronics unit with a first DC/DC converter. The respective battery modules are connected in series via the respective power electronics unit. In each battery module, the first DC/DC converter comprises: an input port with two input terminals connected to the battery cells; an output port with two output terminals providing an output voltage; and a power supply port receiving power for the first DC/DC converter from the balancing circuit. The first DC/DC converter sets the output voltage of the battery module to a predetermined value. The balancing circuit extracts energy from a selected battery cells and provides it to the first DC/DC converter or the power electronics unit.