Battery Pack Inrush Current Limiting Circuit
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Solution Overview
Problem
Conventional series-parallel and parallel-series battery structures face safety issues due to inrush currents during cell shorting events, with series-parallel structures being safer but requiring more complex and costly battery management units, while parallel-series structures are more economical but riskier.
Innovation Solution
A matrix of series-parallel connected battery cells with intra-row isolation and an inrush current limiting circuit, utilizing variable buffer resistors and current regulating elements to manage and limit current during cell shorts, including positive temperature coefficient devices and fuses to prevent damage to other cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If series-parallel battery structure is used, then safety against internal short is improved, but device complexity and cost increase
Solution Approach 1:
The battery pack is divided into multiple independent modules, each containing a series string of cells with its own current limiting device. This segmentation isolates faults to individual modules, preventing system-wide failures while maintaining overall safety without requiring complex centralized management systems.
Solution Approach 2:
Current limiting devices are introduced as intermediary components between battery cells in series strings. These devices act as mediators that automatically limit inrush current during internal shorts, providing safety functionality without requiring complex active management systems.
2Device complexity
If parallel-series battery structure is used, then device complexity is reduced, but safety against internal short deteriorates
Solution Approach 1:
Current limiting devices are pre-installed in each series string before any fault occurs. These devices remain dormant during normal operation but automatically activate when an internal short is detected, providing immediate protection without requiring complex real-time management system intervention.
Solution Approach 2:
Each series string within parallel banks is equipped with its own current limiting device, enabling the system to protect itself automatically during internal shorts. This self-service mechanism eliminates the need for complex external management systems while maintaining safety.
3Reliability
If series-parallel battery structure is used, then safety against internal short is improved, but manufacturing cost increases
Solution Approach 1:
Simple, inexpensive current limiting devices are installed in each series string as a cost-effective safety measure. These passive components are much cheaper than complex active management systems, providing reliable safety functionality at minimal manufacturing cost.
4Ease of manufacture
If parallel-series battery structure is used, then manufacturing cost is reduced, but safety against internal short deteriorates
Solution Approach 1:
Current limiting devices are applied selectively to specific series strings within parallel banks rather than requiring complex system-wide management. This localized approach provides targeted safety where needed while maintaining manufacturing simplicity and cost-effectiveness.
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 reduces inrush current risks, enhances safety by preventing overheating, and optimizes battery management by synchronously varying resistor values to balance voltage and current, thereby achieving a safer and more economical battery pack configuration.
Implementation Method 1
each of the buffer resistors is a variable resistor that will increase resistance when one or more battery cell or string of cells short
Data Source
Figure 1~2b
Figure 3~4
Figure 5~6
AI summary
A battery pack (100) has series-parallel connected battery cells (B11, B12,..., B33, B34). An inrush current limiting circuit has current limiting devices (R11, R12,..., R32, R33) and a current limiting tracking means (HS) limiting inrush current from shorted battery cells (B11, B12,..., B33, B34). Each current limiting tracking means (HS) is coupled to the current limiting devices (R11, R12,..., R32, R33) such that they limit an inrush current from parallel neighbor battery cells (B11, B12,..., B33, B34) when one battery cell on the column shorts. The current limiting devices (R11, R12,..., R32, R33) are variable buffer resistors (R11, R12,..., R32, R33) with a positive temperature coefficient. The current limiting tracking means (HS) are heat sinks (HS) that thermally couples the buffer resistors (R11, R12,..., R32, R33) together such that the buffer resistors (R11, R12,..., R32, R33) increase in resistance with a temperature increase caused by current flowing through the buffer resistor associated with the shorted battery cell. Current regulating elements (CR1, CR2, CR3) are in series with columns of the battery cells (B11, B12,..., B33, B34) for preventing the inrush current to the columns of the battery cells (B11, B12,..., B33, B34).