Post-Charging Leakage Current Balancing for Lithium-Ion Cells
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Solution Overview
Problem
Existing methods for balancing lithium-ion or lithium-polymer battery cells during charging are inefficient, leading to energy waste, overheating, and accelerated battery aging, as they discharge cells during charging and require multiple cycles to achieve balance.
Innovation Solution
A method that introduces a leakage current across all cells except the least charged one after charging is complete, allowing for slow and gentle discharge to reduce state-of-charge differences, thereby avoiding energy wastage and overheating, and extending battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If cells are balanced during charging by connecting balancing resistors in parallel to reduce charging current, then cell charge differences are reduced, but energy is wasted and charging time is prolonged
Solution Approach 1:
The patent applies preliminary action by completing the charging process to 100% capacity first, then initiating the balancing operation afterward. This sequence allows the battery to reach full charge state before any energy dissipation occurs during balancing, thereby avoiding the energy waste that would result from reducing charging current during the charging phase itself.
Solution Approach 2:
The patent implements periodic action by alternating between charging phases and balancing phases. The battery management system monitors cell voltages and periodically switches between charging all cells uniformly and applying individual balancing resistance to specific cells, creating a cyclic operation that achieves both full charging and charge balance while minimizing energy waste.
2Productivity
If high intensity charging currents are applied to achieve 100% charge of all cells, then charging speed is improved, but temperature rises and battery aging accelerates
Solution Approach 1:
The patent applies partial action by using high intensity charging currents only for the necessary duration to reach 100% charge, then immediately transitioning to a balancing phase with reduced current. This controlled application of excessive charging power achieves fast charging goals while limiting the cumulative thermal and aging effects through subsequent low-current balancing operations.
Solution Approach 2:
The patent uses preliminary action by first achieving full charge with high current, then preparing and applying balancing current in a controlled manner afterward. This sequential approach allows the battery to benefit from fast charging initially, then undergoes a gentler balancing phase that corrects charge differences without subjecting the battery to prolonged high-stress conditions.
3Stability of the object's composition
If multiple charging cycles are performed to balance cells, then charge balance is achieved, but time is wasted and productivity decreases
Solution Approach 1:
The patent applies preliminary action by completing the charging process to 100% capacity before initiating any balancing operations. This ensures that the battery reaches its full charge state in a single charging cycle, and subsequent balancing is performed as a separate, efficient post-charging step rather than requiring multiple interrupted and resumed charging cycles.
Solution Approach 2:
The patent implements periodic action by establishing a systematic alternation between uniform charging phases and targeted balancing phases. The battery management system periodically monitors cell voltages and switches between charging all cells simultaneously and applying individual balancing resistance, creating an efficient cyclic process that achieves charge balance without requiring multiple complete charging cycles.
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 reduces energy wastage and overheating, prolongs battery life by balancing cells post-charging, and maintains the battery in a stable state without unnecessary cycling, ensuring efficient and prolonged battery operation.
Implementation Method 1
creation across the terminals of at least one cell of a leakage current, so as to reduce the charge difference between cells
Data Source
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AI summary
The method involves establishing leakage current across cells (40) of a battery (4) so as to reduce the difference in charge between the cells when an end of charge of the battery is detected, where the end of charge of the battery is detected if a value of load current of the battery is lower than a threshold value i.e. 400 milli amperes. The leakage current is established during balancing time so as to reduce the difference in the charge state of the cells by a percentage ranging between 40 percent and 70 percent. Independent claims are also included for the following: (1) a power supply system for supplying direct current to a motor (2) an electronic module for balancing cells of a lithium-ion battery or a lithium-polymer battery.