Energy Storage Cell Balancing via Impedance Characterization
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Solution Overview
Problem
Conventional balancing methods for energy storage modules with series-connected lithium-ion cells do not optimize voltage situations across cells, leading to suboptimal energy storage due to variations in cell impedance and chemistry, resulting in incomplete charging and reduced maximum usable energy.
Innovation Solution
A device and method that communicate with monitoring electronics to determine relative charge and impedance variations across energy storage cells, allowing for dynamic balancing by discharging cells to achieve an energy-optimized state where all cells reach the upper voltage threshold, thereby maximizing stored energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional balancing methods are used to equalize states of charge, then cell voltage uniformity is improved, but maximum usable energy is reduced due to incomplete charging
Solution Approach 1:
The patent changes the balancing parameter from equalizing state of charge (voltage) to equalizing impedance characteristics. By measuring impedance during charging/discharging cycles and balancing cells based on impedance rather than voltage, the system allows cells with different impedance to be charged to higher states of charge without causing overvoltage, thereby increasing maximum usable energy while maintaining safety.
2Reliability
If charging is limited by the cell with highest voltage, then overvoltage damage is prevented, but overall energy storage is reduced
Solution Approach 1:
The patent performs preliminary impedance measurement and characterization of each cell before charging. By knowing the impedance characteristics in advance, the charging current can be individually optimized for each cell, allowing all cells to be charged closer to their maximum capacity without risking overvoltage, thus increasing overall energy storage while maintaining protection.
3Device complexity
If impedance variations between cells are not considered, then balancing complexity is reduced, but charging optimization is lost
Solution Approach 1:
The patent replaces complex voltage-based balancing mechanisms with simpler impedance-based measurement and control. By using impedance measurements during normal charging/discharging cycles rather than complex relaxation and voltage equalization procedures, the system achieves charging optimization without significantly increasing device 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
The solution enables higher energy storage by ensuring all cells in the energy storage module reach the upper voltage threshold, allowing for greater energy extraction during discharging and optimizing energy storage efficiency without requiring relaxation phases or prior knowledge of cell states.
Implementation Method 1
discharging individual energy storage cells by way of a respective resistor that is connected in parallel with a respective energy storage cell
Data Source
AI summary
A device balances an energy storage module having multiple energy storage cells connected in series. The device includes: an interface for communication with a monitoring electronics system of the energy storage module; a charge determining device for determining a relative electrical charge quantity based on respective cell voltages and a respective resting voltage characteristic curve for each energy storage cell; a balancing requirement calculation unit for determining a respective relative balancing requirement by forming a difference between the relative electrical charge quantity of a respective energy storage cell and the relative electrical charge quantity of the energy storage cell for which the lowest relative electrical charge quantity was determined, for every energy storage cell with the exception of the energy storage cell for which the lowest relative electrical charge quantity was determined, and for determining an absolute balancing requirement for each energy storage cell; a discharging circuit which is configured to be connected to the energy storage module in such a way that a respective energy storage cell can be separately discharged by the discharging circuit; and a control device that can control the discharging circuit in such a way that the respective determined absolute balancing requirement can be removed from the respective energy storage cells.