Smart Mid-Point Battery Disconnect for Multi-String Short-Circuit Isolation
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Solution Overview
Problem
Aircraft battery packs face challenges in high-voltage electrical protection due to stringent safety and criticality requirements, particularly in preventing short circuits and thermal runaway, with existing systems struggling to effectively manage high short-circuit currents and maintain safety without increasing weight or volume.
Innovation Solution
A modular, scalable battery pack protection system with a dissimilar/redundant distributed architecture, incorporating smart mid-point disconnects and a centralized battery management system, which includes redundant protection mechanisms, fail-safe disconnect capabilities, and immune-to-false-positives fault detection to isolate short circuits without arcing or stressing battery components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-voltage battery packs are used to provide sufficient power for aircraft propulsion, then power output is improved, but the risk of short circuits and thermal runaway increases
Solution Approach 1:
The battery pack is divided into multiple independent battery strings connected in parallel, with each string having its own protection circuitry and disconnect mechanism. This segmentation allows isolation of faulty strings while maintaining operation of healthy strings, thereby maintaining power output while improving safety through localized fault containment.
Solution Approach 2:
Smart mid-point disconnect circuits are introduced as intermediary protective devices between battery strings and the load. These disconnects include current sensors and control logic that detect short circuits and open the circuit before thermal runaway can occur, acting as a mediator that prevents harmful effects while allowing normal high-power operation.
2Reliability
If redundant protection mechanisms are implemented to meet stringent safety requirements, then reliability is improved, but device complexity increases
Solution Approach 1:
Multiple protection functions (overcurrent protection, short-circuit protection, thermal protection, and disconnect control) are merged into integrated smart mid-point disconnect units. Each disconnect unit combines current sensing, control logic, and switching elements in a single modular component, reducing overall system complexity while maintaining redundant protection layers.
Solution Approach 2:
The smart mid-point disconnect circuits are designed as universal protective devices that can handle multiple failure modes (short circuits, overcurrent, thermal events) through a single integrated system. This multi-functionality reduces the need for separate dedicated protection devices for each hazard, thereby reducing complexity while maintaining comprehensive safety.
3Reliability
If traditional high-voltage protection devices (fuses, vacuum-sealed contactors) are used, then short-circuit protection is improved, but weight and volume increase
Solution Approach 1:
Traditional mechanical protection devices (vacuum-sealed contactors, fuses) are replaced with solid-state smart disconnect circuits that use electronic current sensing and solid-state switching. This substitution eliminates heavy mechanical components while maintaining short-circuit protection capability, significantly reducing weight and volume of the protection system.
Solution Approach 2:
The protection system transitions from passive thermal-magnetic fuses and mechanical contactors to active solid-state devices with electronic control. This parameter change enables faster response times and more precise current threshold control, achieving equivalent or superior protection with lighter components that have no moving parts.
Data Source
AI summary
Methods and systems for protection/disconnect of airborne high-power/energy high-voltage modular multi-string battery packs (such as battery packs for airborne electric propulsion systems). The methods and systems are based on a dissimilar/redundant distributed battery pack protection architecture and use a smart mid-point battery disconnect in conjunction with centralized battery management system. The resulting battery disconnect/protection system is configured to detect bus faults, load faults and string faults and then take appropriate action to isolate the detected fault. For example, in response to a short circuit in one battery string, the faulty battery string may be disconnected from the positive and negative busbars while the remaining battery strings continue to provide power.