Battery Management System Cell Balancing via FET Switching
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Solution Overview
Problem
Conventional battery management systems for vehicles require extensive time and increased circuit complexity to maintain cell balance, especially as the number of battery cells increases, leading to reduced cycle life and output power due to inefficient cell balancing methods.
Innovation Solution
A battery management system that includes a sensing unit, cell balancing determiner, and controller to detect and balance cell voltages by discharging over-charged cells and transferring energy to over-discharged cells based on the vehicle's operational state, using a combination of switches, relays, and drivers to efficiently manage cell balancing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cell balancing method using discharge path with resistance is used, then cell voltage balance can be maintained, but a lot of time is required for determining cell balancing and determining whether cells are balanced
Solution Approach 1:
The patent replaces the conventional mechanical/electrical resistance-based discharge path with a field-effect transistor (FET) based switchable discharge mechanism. The FETs act as electronic switches controlled by gate voltages to selectively discharge specific cells, replacing the passive resistance-based system with an active field-controlled system that enables faster and more precise cell balancing determination.
Solution Approach 2:
The patent changes the operational parameters by using variable resistance values in the discharge paths of different cells. By adjusting the resistance values differently for each cell, the system can control the discharge rate selectively, enabling faster determination of cell balancing status while maintaining reliable voltage balance across all cells.
2Power
If the number of cells forming the battery is increased to enhance output power, then battery output power is improved, but constituent elements of circuit for cell balancing are increased and additional wiring is required
Solution Approach 1:
The patent segments the battery management system into modular units where each cell has its own switchable discharge path with FETs and associated control circuitry. This segmentation allows the system to scale to any number of cells without requiring a completely different architecture, as each cell can be managed independently through its own FET switch and control logic.
Solution Approach 2:
The patent creates a universal cell balancing circuit design that can handle any number of cells using the same basic components (FETs, resistors, control logic). The switchable discharge mechanism with FETs serves multiple functions: it can discharge individual cells, groups of cells, or all cells simultaneously, providing multi-functionality that reduces overall system complexity despite the increased number of cells.
3Power
If the number of cells is increased, then battery output power is enhanced, but another main controller is required for information exchange between controller and cells
Solution Approach 1:
The patent merges the control functions for multiple cells into a single main controller by using shared control lines and a common control logic unit. The FETs for multiple cells can be controlled through shared gate control signals, and the discharge path resistances can be adjusted by a single controller, eliminating the need for separate controllers for each cell or group of cells.
Solution Approach 2:
The patent introduces FETs as intermediary elements between the main controller and the battery cells. The FETs act as controlled switches that translate control signals from the main controller into actual discharge actions on specific cells. This intermediary layer allows a single controller to efficiently manage a large number of cells without requiring direct complex communication with each cell.
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 reduces the time required for cell balancing, maintains cell balance efficiently across multiple cells, and eliminates the need for additional controllers or wiring, enhancing battery cycle life and output power while simplifying system design.
Implementation Method 1
a sensing unit for measuring a voltage of each of the plurality of cells
Implementation Method 2
performs a cell balancing operation on the at least one first cell by using different methods depending upon an operational state of the vehicle
Data Source
AI summary
A battery management system is provided for managing a battery that supplies power to a vehicle. The battery includes a plurality of cells. The battery management system includes a sensing unit for measuring a voltage of each of the plurality of cells. The battery management system detects at least one first cell among the plurality of cells that needs to be balanced according to the measured voltage of each of the plurality of cells. In addition, the battery management system performs a cell balancing operation on said at least one first cell by using different methods according to a driving state of the vehicle.