Battery Cell Charging with Variable Current
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Solution Overview
Problem
Existing methods for charging and discharging energy storage devices with serially connected battery cells are inefficient and time-consuming due to the need for active or passive balancing, which often leads to disproportionate aging and premature failure of cells with higher discharge depth, especially when cells have varying states of charge, capacity, internal resistance, or efficiency.
Innovation Solution
A method that charges all battery cells simultaneously until an individual cell reaches its final voltage, then reduces the charging current for that cell while continuing to charge others, ensuring all cells reach their final voltage nearly simultaneously, thereby eliminating the need for active or passive balancing and reducing the time required for the entire process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all battery cells are charged with the same charging current, then the charging process is simple, but cells with different internal resistances or efficiencies experience different power losses leading to different charge levels and requiring time-consuming balancing
Solution Approach 1:
The patent applies local quality by assigning different charging currents to different battery cells based on their individual characteristics (internal resistance, efficiency, charge level). Instead of uniform charging, each cell receives a customized current that compensates for its specific properties, ensuring all cells reach optimal charge levels simultaneously without requiring post-charging balancing
Solution Approach 2:
The patent dynamically adjusts charging parameters (current magnitude) based on real-time monitoring of cell voltage, temperature, and charge level. The charging current for each cell is modified according to its state, allowing the system to maintain both high charging speed and uniform charge distribution across all cells
2Reliability
If charge equalization is performed when a cell reaches final voltage, then all cells can reach similar charge levels, but the entire charging process becomes time-consuming and the cell block cannot be used during balancing
Solution Approach 1:
The patent performs preliminary action by continuously monitoring and adjusting charging currents during the charging process itself, rather than waiting until charging is complete to perform equalization. This prevents charge level disparities from developing in the first place, eliminating the need for time-consuming post-charging balancing operations
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that all battery cells are charged simultaneously throughout the process. By using different charging currents from the start, the system keeps all cells in a useful charging state at the same time, avoiding periods where some cells are being balanced while others are idle
3Reliability
If passive balancing is used to equalize charge levels, then cells with different charge levels can be balanced, but excess energy is converted to heat and lost, making the process inefficient
Solution Approach 1:
The patent applies self-service by having cells that are closer to full charge contribute their excess charging capacity to help charge cells that are further from full charge. The system automatically distributes charging current based on real-time cell states, allowing the battery pack to self-equalize without external balancing intervention or energy loss
4Loss of energy
If active balancing is used to equalize charge levels, then energy is transferred between cells rather than lost as heat, but charge balancing still only begins when at least one cell reaches final voltage, making the process time-consuming
Solution Approach 1:
The patent performs preliminary action by initiating differentiated charging currents from the very beginning of the charging process, before any cell reaches final voltage. This prevents charge level disparities from developing and eliminates the need for subsequent active balancing operations, achieving both energy efficiency and time savings
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 ensures all cells in the energy storage device have similar charge levels, reducing the risk of disproportionate aging and premature failure, allowing for rapid and efficient charging without the need for balancing, thus extending the service life of the cell block.
Implementation Method 1
An energy storage device comprises several galvanic cells connected in series and/or parallel, known as battery cells. When the battery cells are discharged, the stored chemical energy is converted into electrical energy.
Implementation Method 2
Since battery cells can have different internal resistances or efficiencies, the power losses of the individual battery cells vary during charging.
Implementation Method 3
With passive balancing, the excess energy of the battery cell that reaches its final charging voltage first is converted into heat via a resistor and is thus lost for the charging process.
Data Source
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AI summary
Proposed is a method for charging an energy store (1) with a charging current, wherein the energy store (1) has at least one cell block (2) having a number J of series-connected battery cells (3, 4, 5, 6, 7), of which at least some of the battery cells (3, 4, 5, 6, 7) may have different capacitances Cn, where 1 ≤ n ≤ J. Firstly, all J battery cells (3, 4, 5, 6, 7) are charged with a charging current Io until a battery cell i (3, 4, 5, 6, 7) reaches an end-of-charging voltage Ui,L that is specified for said battery cell i (3, 4, 5, 6, 7). Then, for all battery cells (3, 4, 5, 6, 7), the charging current is reduced to a value h. If the reduced charging current is less than a charging current threshold value, the charging current is shut off for all battery cells, and the battery cell m having the lowest cell voltage Umin and the battery cell I having the highest cell voltage Umax are determined. With the exception of the battery cell m, all battery cells are discharged across parallel-connected resistances until the cell voltage of the battery cell I corresponds to Umin. The process is repeated until the difference Umax - Umin is lower than a specified threshold value.