Battery String Disconnect Layout for Parasitic Fault Currents

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Solution Overview

Problem

Existing electrical energy stores in motor vehicles face issues with fault currents flowing through parasitic paths that cannot be detected or interrupted by conventional disconnecting elements, leading to localized overheating and potential thermal runaway.

Innovation Solution

The implementation of controllable disconnecting devices with current sensors and pyro fuses at string connectors to detect and interrupt fault currents by comparing string currents with total current, ensuring reliable disconnection of parasitic fault circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional disconnecting elements are used in electrical energy stores, then the structure remains simple, but fault currents flowing through parasitic paths cannot be detected or interrupted

Engineering Contradiction:

Improvefault current detection and interruption capabilityVSAvoiddisconnecting device structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The disconnecting device is segmented into multiple functional modules: current sensors are placed at string connectors to detect string currents, a control unit compares string currents to identify faults, and disconnecting units are positioned at specific locations to interrupt fault currents. This segmentation enables targeted detection and interruption of parasitic fault currents while maintaining overall system manageability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control unit serves as an intermediary that receives data from current sensors, processes the information by comparing string currents, and activates disconnecting units when faults are detected. This intermediary function enables intelligent decision-making for fault current interruption without requiring direct mechanical connection between sensors and disconnecting elements

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If passive disconnecting elements are used that trip on heat spreading, then the device complexity remains low, but fault currents with undefined resistance and lower than rated current cannot be reliably detected

Engineering Contradiction:

Improvefault current detection accuracyVSAvoidmonitoring system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The passive thermal trip mechanism is replaced with an active electrical monitoring system. Current sensors continuously measure string currents, and the control unit electronically compares these values to detect imbalances indicating parasitic fault currents. This substitution enables detection of low-magnitude faults that would not trigger thermal elements, while providing precise control over disconnection timing and location

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Volume of stationary object

If geometrically adjacent store strings are arranged to compact the energy store, then the volume efficiency improves, but parasitic fault current paths are created between adjacent strings

Engineering Contradiction:

Improveenergy store compactnessVSAvoidparasitic fault current paths

Core Design Contradiction:

Volume of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The harmful parasitic fault current paths are effectively extracted or removed from the system by placing disconnecting units at string connectors. When faults are detected between adjacent strings, the disconnecting units open the circuit, removing the fault path while maintaining the compact geometric arrangement of strings for volume efficiency

Inventive Principle:

Principle #2Taking out (Extraction)

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 prevents thermal events by reliably detecting and interrupting fault currents, thereby safeguarding the electrical energy store from thermal runaway.

Implementation Method 1

a current sensor for recording a string current flowing via the at least one string connector

Methodology Applied

Scientific EffectElectrical current measurement: Ohm's Law

Implementation Method 2

a controllable disconnecting unit for disconnecting the at least one string connector

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 3

pyro fuses at string connectors to detect and interrupt fault currents

Methodology Applied

Scientific EffectMelting: Melting

Data Source

PatentUS20250388096A1Electrical Energy Store With a Plurality of Storage Strands and Disconnecting Devices Between the Storage Strands

Publication Date: 2025.12.25 BAYERISCHE MOTOREN WERKE AG

AI summary

An electrical energy store for a motor vehicle includes at least two storage strands which extend geometrically adjacent to one another and each have a plurality of connected storage units which each have at least one storage cell; at least one strand connector for serially connecting the storage strands to a disconnecting device for detecting and interrupting a fault current circuit formed by an undesired electrical connection between two storage strands and by the at least one strand connector, where the disconnecting device has a controllable disconnecting unit for disconnecting the at least one strand connector and a current sensor for detecting a strand current flowing over the at least one strand connector; and a control device configured to detect at least one fault current circuit based on the detected strand current and to actuate the at least one disconnecting unit in order to interrupt the fault current circuit.