Two-Stage Constant-Voltage Charging for Fast Battery Cells
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Solution Overview
Problem
Existing methods for charging electrochemical accumulator cells are inefficient, resulting in charging times that are several tens of minutes, which is not suitable for modern applications with increased energy density.
Innovation Solution
A method that involves applying a first voltage higher than the usual charging voltage to the cell until a predetermined charge capacity is reached, followed by switching to the usual charging voltage to complete the charging process, while maintaining the voltage constant at two successive predefined levels and gradually decreasing the charging current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a high charging current is applied to reduce charging time, then the charging speed increases, but the cell temperature increases and electrochemical degradation occurs
Solution Approach 1:
The charging process is divided into multiple stages with different current levels. The method applies high current only during specific voltage ranges (below 4.2V) where it is safe, and reduces current when voltage approaches the maximum threshold, thereby segmenting the charging process to avoid degradation while maintaining speed.
Solution Approach 2:
The charging current is dynamically adjusted based on the real-time voltage state of the cell. The controller continuously monitors voltage and modulates the current accordingly - maintaining high current when voltage is low and safely reducing it as voltage approaches 4.2V, creating a dynamic charging profile that optimizes both speed and safety.
2Loss of time
If the charging voltage is increased to accelerate charging, then the charging time decreases, but the cell undergoes electrochemical degradation
Solution Approach 1:
The method changes the voltage parameter dynamically during charging. Instead of applying a constantly high voltage that would cause degradation, the system maintains high voltage only when the cell voltage is below 4.2V and automatically reduces the voltage parameter as the cell approaches full charge, thereby reducing charging time without causing degradation.
Solution Approach 2:
The charging system incorporates voltage feedback control. The controller continuously monitors the cell voltage and uses this feedback to adjust the charging voltage in real-time, ensuring that the voltage remains high enough to enable fast charging but never exceeds the 4.2V threshold that would cause degradation.
3Productivity
If a constant high voltage is applied throughout the charging cycle, then the charging speed is maximized, but the internal resistance increases and cell safety is compromised
Solution Approach 1:
The charging voltage profile is segmented into different levels based on the cell's state of charge. The system applies high voltage (4.2V) only during the majority of the charging cycle when it is safe, and transitions to lower voltage near the end of charging, thereby maintaining high productivity while ensuring reliability through appropriate voltage segmentation.
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 method significantly reduces the charging time of electrochemical accumulator cells from 30 minutes with conventional methods to as little as 1 minute and 30 seconds, without causing electrochemical degradation.
Implementation Method 1
An electrochemical storage cell is the basic unit of a battery or electrochemical accumulator. It consists of two electrodes (an anode and a cathode) and an electrolyte that enables the chemical reactions that generate electrical energy.
Implementation Method 2
The charging speed of a cell depends on many factors, including cell capacity, cell technology, charging current, and safety features.
Data Source
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AI summary
The invention relates to a method for charging an electrochemical accumulator cell, in which the voltage across the terminals of the cell is kept constant at at least two successive predefined voltage levels, the charging current supplied to the cell gradually decreasing as the battery charges, the method comprising: E1) a first step of applying a first voltage (V1) across the terminals of the cell, the first voltage (V1) being greater than a usual charging voltage (Vbat), the usual charging voltage (Vbat) being defined as being a voltage such that it would not cause electrochemical degradation of the cell if it were applied over a complete charging cycle of the cell; E2) a second step of applying the usual charging voltage (Vbat).