Passive Battery Charging Control for Sealed Sodium-Metal Chloride Cells
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Solution Overview
Problem
Existing methods for preventing overcharging in sodium/metal chloride batteries rely on active circuit elements, which increase costs and reduce reliability, and are not suitable for sealed batteries with variable fluid level anode compartments.
Innovation Solution
A passive battery charging control system that uses anode current collectors and a passive control element, such as a high temperature resistor, to limit charging when the anode fluid reaches a maximum level, eliminating the need for active electrical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active circuit elements are used to prevent overcharging, then charging control is achieved, but cost increases and reliability decreases
Solution Approach 1:
The patent extracts the active electrical control elements from the charging control system and replaces them with a passive mechanical/chemical control mechanism. The anode compartment itself becomes the control element through its variable fluid level, eliminating the need for external active circuitry and thereby improving reliability while reducing device complexity.
Solution Approach 2:
The battery system performs its own charging control through the natural relationship between anode fluid level and charging state. When the anode compartment reaches full charge, the sodium metal accumulates to a level that automatically makes electrical contact with the second current collector, which is connected to the passive control element, thereby self-regulating the charging process without external intervention.
2Reliability
If active circuit elements are used for charging control, then charging limitation is achieved, but cost increases
Solution Approach 1:
The patent replaces expensive active circuit elements with inexpensive passive components, specifically a high-temperature resistor or similar passive element. This passive control element has no moving parts, no active electronics, and can be manufactured at very low cost while providing reliable overcharge prevention through the battery's own operating characteristics.
3Volume of moving object
If the anode volume is reduced to accommodate less Na, then battery size decreases, but pressure increases causing failure
Solution Approach 1:
The patent designs the anode compartment with a predetermined volume that is exactly sufficient to accommodate the sodium metal produced during complete charging of the cathode. The volume is calculated in advance based on the cathode capacity and expected sodium accumulation, ensuring that the compartment is large enough to prevent pressure buildup while minimizing excess volume. This preliminary sizing prevents both over-pressurization and unnecessary battery size.
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 solution effectively prevents overcharging in sodium/metal chloride batteries while being cost-effective and reliable, applicable to any sealed battery with a variable fluid level anode compartment, thereby enhancing the safety and performance of the charging process.
Implementation Method 1
a passive control element configured to limit the charging state of the battery when the second anode current collector makes physical contact with the anode fluid
Implementation Method 2
The Na ions are transported out of the cathode through a solid ion-conducting electrolyte into the anode compartment. The corresponding anode volume must be large enough to accommodate complete charging of the cathode.
Data Source
AI summary
A passive battery charging control system for charging a battery is devoid of active electrical components. The passive battery charging control system includes one or more passive electrical control elements configured to limit the charging state of the battery.