Asymmetric Battery Pack Tab Layout for C-Rate Balancing
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Solution Overview
Problem
Conventional battery packs with jelly rolls of differing capacities and/or designs connected in parallel experience imbalances in charging and discharging currents due to variations in impedance, leading to inefficient performance.
Innovation Solution
The battery pack utilizes C-Rate balancing by repositioning and/or increasing the number of cathode and anode tabs on higher capacity battery cells to reduce impedance, ensuring equal current distribution based on capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If jelly rolls with differing capacities are connected in parallel, then the battery pack can provide higher total capacity, but the charging and discharging current becomes imbalanced due to impedance differences
Solution Approach 1:
The patent applies local quality by positioning tabs at specific locations on the jelly roll electrodes rather than uniformly. The tab position is strategically selected to compensate for impedance differences between jelly rolls of varying capacities, creating localized electrical characteristics that balance the overall parallel connection.
Solution Approach 2:
The patent changes the parameter of tab position along the jelly roll length to adjust impedance characteristics. By varying the tab location parameter, the invention optimizes the electrical properties of each jelly roll to achieve balanced current distribution while maintaining different capacities.
2Adaptability or versatility
If jelly rolls with different battery cell designs are connected in parallel, then the battery pack can accommodate different form factors, but current imbalance occurs due to impedance differences
Solution Approach 1:
The patent uses local quality by adjusting tab positions specifically for each jelly roll design variant. This allows different jelly roll geometries and capacities to be integrated into the same parallel battery pack while maintaining current balance through localized electrical characteristic adjustments.
Solution Approach 2:
The patent applies asymmetry by allowing each jelly roll to have its tab positioned at a different location along its length, rather than using a symmetric or uniform tab position for all jelly rolls. This asymmetric approach enables customization for different capacities and designs.
3Ease of manufacture
If tabs are positioned at the end of cathode and anode layers, then the manufacturing process is simplified, but the impedance of higher capacity cells increases
Solution Approach 1:
The patent changes the tab position parameter from the conventional end-position to optimized intermediate positions along the jelly roll. This parameter adjustment increases impedance in a controlled manner to balance the parallel connection, while the manufacturing process remains relatively simple through automated positioning systems.
Data Source
AI summary
Battery packs having jelly roll battery cells of different capacities may have an imbalance in the charging and/or discharging current supplied to and provided by each jelly roll due to differences in capacity specific impedance between the battery cells of the battery pack. A C-rate (i.e., current relative to rated capacity) of a lower capacity first battery cell and a higher capacity second battery cell connected in parallel may be balanced by repositioning and/or increasing the number of cathode tabs and anode tabs of the second jelly roll battery cell to reduce an impedance of the second battery cell.