Battery Pack Switch Structure for Reusable Overcharge Blocking
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Solution Overview
Problem
Existing battery pack protection devices, such as PTC thermistors and thermal fuses, are not effective in preventing overcharging-induced overheating as they operate after temperature rise and are not reusable, making them unsuitable for high current environments like vehicle battery packs.
Innovation Solution
A battery pack with a current blocking member made of electroactive polymer (EAP) and metal layers that bends to disconnect the switch when a potential difference exceeds a reference value, blocking current before overheating occurs, using a switch and connecting rod configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal fuse is used to block overcurrent, then current blocking function is achieved, but the device becomes one-time use and cannot be reused
Solution Approach 1:
The patent changes the operating parameter from temperature-based (thermal fuse) to voltage-based (electroactive polymer). The EAP layer responds to voltage potential difference rather than temperature, enabling reversible deformation. When voltage is applied, the EAP bends to open the circuit; when voltage is removed, it returns to original position, allowing repeated use without degradation.
Solution Approach 2:
The patent replaces the thermal-mechanical system (heat-generated deformation in thermal fuse) with an electro-mechanical system (voltage-induced deformation in EAP). This substitution eliminates the one-time use limitation because the electroactive polymer can be repeatedly actuated by voltage without permanent damage, enabling the switch to be closed and opened multiple times.
2Reliability
If PTC thermistor or TCO is used to block overcurrent, then current blocking function is achieved, but the resistance increases as operation is repeated
Solution Approach 1:
The patent changes from resistance-based current blocking (PTC thermistor increases resistance with temperature) to voltage-based mechanical switching (EAP bends to physically disconnect the circuit). The EAP switch maintains low resistance when closed because it uses mechanical contact rather than resistive blocking, and this property is maintained across repeated operations without degradation.
3Reliability
If thermal-based devices are used to block overcurrent, then current blocking function is achieved, but the devices operate too early in high temperature environments
Solution Approach 1:
The patent changes the triggering parameter from temperature to voltage potential difference. The EAP layer is designed to bend at a specific voltage threshold rather than temperature threshold. This allows the switch to remain closed during normal high-temperature operation and only open when abnormal voltage (indicating overcharging or internal short) is detected, preventing premature operation.
Solution Approach 2:
The patent introduces the EAP layer as an intermediary that translates voltage potential difference into mechanical switching action. Instead of directly responding to temperature like thermal devices, the EAP responds to voltage, providing a more accurate indication of battery health status and enabling delayed operation until actual overcharging occurs.
4Reliability
If thermal-based devices operate after temperature rise, then current blocking is achieved, but the overcurrent cannot be blocked immediately when the cause occurs
Solution Approach 1:
The patent implements preliminary action by using the EAP to detect and respond to voltage abnormalities before temperature rise occurs. Since voltage potential difference increases immediately when overcharging or internal short happens, the EAP can trigger the switch to open instantly, preventing the subsequent temperature rise that would take time to develop in thermal-based systems.
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 solution effectively prevents overheating and potential explosions by detecting potential differences and blocking current before temperature rise, ensuring safety in high current environments like vehicle battery packs.
Implementation Method 1
a current blocking member (500) connected to one side of the switch (400) in a longitudinal direction and configured to turn off the switch (400) by causing a bending deformation
Data Source
AI summary
A battery pack includes a battery module assembly including a first battery module and a second battery module; a first connector connected to a first electrode of the first battery module; a second connector connected to a second electrode of the second battery module and spaced apart from the first connector; a switch configured to connect the first connector and the second connector; a current blocking member connected to one side of the switch in a longitudinal direction and configured to turn off the switch by causing a bending deformation when a potential difference formed between both electrodes of the battery module is equal to or greater than a reference value.