Switched-Capacitor Cell Balancing With Simultaneous SOC/SOH Characterization
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Solution Overview
Problem
Conventional battery cell balancing techniques, such as passive and active balancing, face inefficiencies and limitations, particularly in power efficiency and the need for external stimuli that can cause electromagnetic interference, while also lacking simultaneous characterization capabilities for accurate SOC and SOH estimation.
Innovation Solution
A switched-capacitor system that uses true random or pseudo-random control signals to simultaneously balance and characterize stacked battery cells, allowing for accurate estimation of State-of-Charge (SOC) and State-of-Health (SOH) without causing electromagnetic interference, by moving charge between cells and generating characterization signals through the same capacitive and switching topology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If passive balancing is used to balance battery cells, then the voltage between cells is aligned, but the power efficiency is 0% and battery lifetime is reduced
Solution Approach 1:
The patent merges the balancing function with the characterization function into a single switched-capacitor system. The same switches and capacitors used for balancing also generate characterization signals, eliminating the need for separate external stimulus sources and achieving both voltage alignment and cell characterization simultaneously.
Solution Approach 2:
The switched-capacitor system performs multiple functions: it balances the battery cells by transferring charge between them, generates characterization signals for measuring AC impedance, and enables SOC/SOH estimation. This multi-functionality resolves the contradiction by making the balancing process itself energy-efficient while providing additional characterization capabilities.
2Measurement precision
If external stimuli are injected for battery cell characterization, then AC characteristics can be measured, but electromagnetic interference is caused
Solution Approach 1:
The switched-capacitor circuit acts as an intermediary that generates internal characterization signals without requiring external stimulus injection. The random switching sequences of the capacitors create noise signals that can be correlated with the battery cell responses to extract AC impedance information, avoiding external EMI-prone signal sources.
Solution Approach 2:
The battery cell characterization is performed using signals generated within the balancing system itself. The switched-capacitor circuit self-generates the characterization signals through its random switching behavior, and the system correlates these self-generated signals with the cell responses to measure AC characteristics without external interference.
3Reliability
If separate units are used for active balancing and characterization, then each function can be optimized, but device complexity increases
Solution Approach 1:
The patent combines the active balancing circuit and the characterization signal generation into a single switched-capacitor system. The same capacitors and switches that transfer charge for balancing also generate the random signals needed for AC impedance measurement, reducing component count and system complexity while maintaining both functions.
Solution Approach 2:
The switched-capacitor system is designed to perform both balancing and characterization functions using the same hardware components. The multi-functionality eliminates the need for separate external stimulus generators and measurement equipment, reducing overall system complexity while achieving reliable characterization through the correlation of switching signals with cell responses.
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 enables efficient active balancing during operation, improves battery life, and provides accurate characterization of battery health and charge capacity, enhancing overall battery performance and longevity.
Implementation Method 1
at least one capacitor connectable to the plurality of stacked battery cells, wherein the at least one capacitor is adapted to move charge to and from the plurality of stacked battery cells
Implementation Method 2
by knowing the AC impedance of the battery cells during the balancing, more accurate balancing may be achieved
Data Source
AI summary
A switched-capacitor balancing and characterization system for balancing and characterization of a plurality of stacked battery cells includes at least one capacitor connectable to a plurality of battery cells via switches, configured to connect or disconnect the at least one capacitor to the battery cells and a processing unit configured to control the plurality of switches. The switched-capacitor balancing and characterization system is configured to perform simultaneous balancing and characterization of the battery cells. The disclosure further relates to a battery system comprising the switched-capacitor balancing and characterization system and the stack of battery cells and to a method for simultaneous balancing and characterization of a stack of battery cells, using a switched-capacitor balancing and characterization system and/or using a battery system.