Parallel Cell Current Limiting for Battery Thermal Runaway Isolation
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Solution Overview
Problem
Battery modules face challenges in preventing thermal runaway propagation due to short circuit events, which can lead to heat transfer, flame impingement, and electrical heating, compromising module performance and safety.
Innovation Solution
Incorporating current limiting elements, either passive fuses or active semiconductor switches, into the parallel paths between cells to mitigate short circuit currents without affecting normal charge/discharge currents, thereby preventing thermal runaway propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current limiting elements are placed in the series path to limit short circuit current, then thermal runaway propagation is prevented, but resistance and voltage drop increase during normal operation
Solution Approach 1:
The patent divides the battery system into parallel groups of cells, with current limiting elements placed only in the parallel paths between groups, not in the series path. This segmentation allows normal series current to flow without restriction while isolating parallel short circuit currents to specific groups, preventing thermal runaway propagation without adding resistance to the main current path.
Solution Approach 2:
The patent introduces parallel path current limiting elements as intermediary components between parallel cell groups. These elements act as mediators that specifically intercept and limit short circuit currents in parallel paths while leaving the series charge/discharge current path unaffected, thus preventing thermal runaway without increasing voltage drop during normal operation.
2Reliability
If current limiting elements are added to protect against thermal runaway, then safety is improved, but device complexity increases
Solution Approach 1:
Instead of placing current limiting elements throughout the entire battery system, the patent segments their placement to only the parallel paths between cell groups. This reduces the total number of current limiting elements needed compared to a comprehensive series path protection approach, while still providing effective thermal runaway prevention.
Solution Approach 2:
The patent applies current limiting elements locally only where needed - in the parallel paths between cell groups - rather than uniformly throughout the entire battery system. This localized approach provides safety where thermal runaway propagation risk exists while minimizing overall device complexity and component count.
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
Effectively isolates affected cells to prevent thermal runaway spread, maintaining module performance and safety by limiting short circuit currents without increasing resistance or voltage drop in the series path.
Implementation Method 1
The cells in parallel with the shorted cell discharge through the short, producing ohmic heating and sometimes arcing.
Implementation Method 2
a passive current limiting element in a parallel path between parallelly connected cells. The passive current limiting element may be a fuse
Implementation Method 3
The active current limiting element may be a semiconductor switch
Data Source
AI summary
A battery system, battery packs and battery modules are disclosed. The battery module comprises a plurality of cells mounted within a housing. The housing has a plurality of openings respectively for a corresponding cell. The module has a plurality of groups of cells. Each group comprises a plurality of parallel connected cells from among the plurality of cells. The plurality of groups is connected in series. The module has a plurality of current limiting elements. Each current limiting element are electrically connected in a parallel path to one or both terminals of cells which are parallelly connected. The current limiting elements may be passive or active elements. The current limiting elements may be integrated in or separate from busbars which are connected to terminals of the cells.