Spring Fuse With Low Melting Solder For Battery Protection
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Solution Overview
Problem
Conventional fuses fail to function effectively across a range of short circuit loads, requiring expensive discharge FETs that generate significant heat, especially in battery cells without internal charge interrupt devices.
Innovation Solution
A spring fuse is integrated into the charge or discharge current path of devices like battery packs and power tools, featuring a low temperature solder connection that deteriorates at a specific temperature, causing the fuse to open and disconnect the current path, thereby protecting the device from excessive currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fuses are used in charge or discharge paths, then device protection from high current is provided, but the fuses do not function properly over the entire range of short circuit loads
Solution Approach 1:
The fuse incorporates a spring mechanism that dynamically adjusts the electrical contact pressure between the fuse element and terminals. The spring allows the fuse to adapt its mechanical properties in response to thermal expansion and contraction during different operating conditions, ensuring reliable operation across the entire range of short circuit loads rather than being fixed at a single operating point
2Reliability
If expensive discharge FETs are used to compensate for conventional fuse limitations, then protection across full load range is achieved, but significant heat is generated
Solution Approach 1:
The invention uses a simple, inexpensive fuse element designed to be replaced rather than repaired. This disposable fuse provides reliable protection across the full load range through its spring mechanism without the complexity and heat generation of electronic discharge FETs. The fuse sacrifices itself (opens the circuit) when needed, providing economical protection without ongoing thermal management requirements
3Reliability
If spring fuse with low temperature solder is used, then protection is provided without heat-generating components, but the solder deteriorates at specific temperature causing fuse to open
Solution Approach 1:
The invention deliberately uses low-melting-point solder as a protective mechanism. When abnormal temperature rises indicate dangerous conditions, the solder deteriorates and opens the circuit, converting the potentially harmful thermal event into a protective action. This transforms the weakness of low-temperature solder into a beneficial safety feature that prevents equipment damage
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
The spring fuse effectively protects devices from high currents by opening the current path without the need for expensive heat-generating components, providing reliable protection across varying load conditions.
Implementation Method 1
The power path connection is configured to be soldered to one or more leads using a low temperature solder. The solder of the power path connection to the at least one or more fuse pads secures the power path connection to the one or more fuse pads.
Implementation Method 2
The at least one extension spring is configured to connect the fixed base with the power path connection. The power path connection is configured to move toward the fixed base when the temperature of the one or more bonding joints exceeds a threshold value.
Data Source
AI summary
A device including a conductive path for passing electric current. The device including a terminal and a spring fuse. The spring fuse is connected in the conductive path and is electrically connected to the terminal. The spring fuse includes a fixed base, an extension spring connected to the fixed base at a first end, a power path connection connected to the extension spring at a second end, a plurality of fuse pads, and one or more solder joints configured to connect the power path connection to the plurality of fuse pads. The one or more solder joints are configured to melt when a temperature of the one or more solder joints exceeds a threshold value. The power path connection is configured to retract toward the fixed base when the temperature of the one or more solder joints exceeds a threshold value.