Lithium Battery Pack Management Circuit for Self-Discharge Reduction
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Solution Overview
Problem
Existing lithium battery technologies face challenges in maintaining long battery life due to high self-discharge currents, especially in high power density applications, and struggle with accurate end-of-life predictions, particularly at temperature extremes and under varying current loads.
Innovation Solution
A method and system that dynamically manage the voltage of a battery pack by adding or removing fractions of lithium oxyhalide cells, using a management circuit to monitor output voltage and control the connection of additional fractions, thereby reducing self-discharge and maintaining continuous power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high power density is achieved by providing a large electrode surface area using spirally wound or jelly roll cell designs, then current sourcing capability is improved, but self-discharge current increases proportionally to surface area
Solution Approach 1:
The battery pack is divided into multiple independent battery cells, each with its own management circuit. This segmentation allows individual monitoring and control of each cell's voltage and current characteristics, enabling precise management of self-discharge while maintaining overall high power capability through the combined array of cells.
Solution Approach 2:
The battery management system dynamically adjusts operating parameters based on real-time monitoring of voltage, current, and temperature. The system can dynamically switch between different cell configurations, adjust discharge rates, and modify operational modes to optimize the balance between power delivery and self-discharge minimization under varying load conditions.
2Duration of action of moving object
If lithium primary battery technology is used to achieve long battery life and high energy density, then battery duration is improved, but accurate prediction of end-of-life becomes difficult due to sharp voltage roll-off near depletion
Solution Approach 1:
The battery management system implements continuous feedback monitoring of multiple parameters including voltage, current, temperature, and charge-discharge cycles. This multi-parameter feedback approach enables accurate tracking of battery state of charge and health, providing early warning signals for end-of-life conditions before the sharp voltage roll-off occurs, thereby improving prediction accuracy.
Solution Approach 2:
The system performs preliminary assessments of battery health and state of charge using multiple sensing parameters before the battery reaches critical depletion levels. By continuously monitoring trends in voltage, current, and temperature, the system can predict remaining capacity and anticipate end-of-life conditions in advance, avoiding the inaccuracies associated with waiting for sharp voltage drops.
3Reliability
If unscheduled battery failures are avoided by predicting end-of-life, then reliability is improved, but disposal of partially discharged batteries results in costly waste of residual capacity
Solution Approach 1:
The continuous feedback monitoring of battery state of charge, health, and operational parameters enables precise tracking of remaining capacity. This allows the system to schedule maintenance and battery replacement at the optimal moment—just before actual depletion—thereby ensuring reliable operation while maximizing utilization of the battery's full capacity and minimizing waste of residual energy.
Solution Approach 2:
The system replaces conservative, schedule-based battery replacement policies with intelligent, condition-based management. By using electronic monitoring and analysis of actual battery performance data, the system substitutes mechanical timing mechanisms with sophisticated algorithms that predict true end-of-life, enabling just-in-time replacement that eliminates both premature disposal and unscheduled failures.
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 self-discharge currents, extends battery life, and allows for accurate battery life predictions and high current sourcing capabilities at extreme temperatures, making spirally wound lithium primary battery packs superior to composite batteries for certain applications.
Implementation Method 1
A key limiting factor in the battery life of primary lithium batteries is the self-discharge current. When a lithium primary cell is first manufactured, the self-discharge current is relatively high.
Implementation Method 2
The flow of a self-discharge current inside the cell creates a protective film, called passivation, on the surface of the lithium reactant inside the cell. As the passivation layer increases, the self-discharge current required to complete its formation and eventually maintain it, reduces.
Implementation Method 3
Lithium battery technology systems include, for example, lithium/thionyl chloride (Li/SOCl2) and lithium/sulfuryl chloride (Li/SO2Cl2), both collectively known as Li/oxyhalide cells.
Data Source
AI summary
A method for supplying power from a battery pack includes monitoring an output voltage of a battery pack, where the battery pack comprises a number of fractions and determining whether the output voltage is below a predetermined threshold. The method further includes adding at least one fraction of the number of fractions to the output voltage, when the output voltage is below the predetermined threshold and removing the at least one fraction, if previously added, when the output voltage is no longer below the predetermined threshold.