Parallel Battery Cell Protection via Electronic Switch Pairs
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Solution Overview
Problem
Existing solutions for protecting parallel-coupled battery cells from short circuit and over-temperature conditions, such as thermal cutoffs, are limited by their inability to provide comprehensive protection against over current, voltage, and under voltage, and are mechanically fragile and costly to implement.
Innovation Solution
A battery pack design incorporating pairs of electronic switches, such as FETs and BJTs, controlled by a fault control circuit that provides serial protection between battery cells and a common node, eliminating the need for thermal cutoffs and offering adjustable over current protection, as well as over voltage and temperature protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal cutoffs are used to protect parallel-coupled battery cells, then protection against short circuit and over-temperature conditions is provided, but the solution is mechanically fragile, costly, and cannot provide comprehensive protection against over current, voltage, and under voltage
Solution Approach 1:
The patent replaces mechanical thermal cutoff devices with electronic switch elements (such as FETs or BJTs) controlled by a control circuit. This substitution eliminates the mechanical fragility of thermal cutoffs while providing comprehensive electrical protection against short circuits, over-current, over-voltage, and under-voltage conditions through electronic control mechanisms.
Solution Approach 2:
The control circuit with switch elements provides multiple protection functions simultaneously - short circuit protection, over-current protection, over-temperature protection, over-voltage protection, and under-voltage protection. This multi-functional approach replaces the single-function thermal cutoff with a universal protection system that addresses all identified vulnerabilities.
2Reliability
If thermal cutoffs are used for protection, then short circuit protection is provided, but power consumption is higher and the device is less compact
Solution Approach 1:
The electronic switch elements and control circuit consume significantly less power than thermal cutoff devices. The electronic system uses active control to prevent fault conditions rather than relying on thermal mass and phase change mechanisms, resulting in reduced overall power consumption while maintaining protective functionality.
3Reliability
If thermal cutoffs are used, then protection is provided, but the solution lacks adjustability for over current protection
Solution Approach 1:
The control circuit enables dynamic adjustment of protection thresholds and parameters. The electronic switch elements can be controlled to provide adjustable over-current protection levels, allowing the system to adapt to different operating conditions and battery configurations, unlike fixed-threshold thermal cutoffs.
Data Source
AI summary
In general, techniques are disclosed for providing short circuit protection to a battery pack having a number of battery cells, at least some of which are connected in parallel. Short circuit protection is provided by using pairs of electronic switches (e.g., integrated circuits consisting of a pair of transistors designed as battery charge/discharge switches) serially connected between one terminal of a battery cell and a battery pack's common node—a position which is upstream of conventional battery pack fault controllers. The state of all such switches may be controlled by a control unit that is also upstream of a conventional fault controller. The combination of switch pairs and control unit can provide a battery pack with over current (short circuit) protection without the use of thermal cutoff devises. The described devices and systems can also provide over voltage, under voltage and over temperature protection.