Battery Cell Detection Line Disconnection via Sequential Discharge

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Solution Overview

Problem

Conventional disconnection detection devices in battery packs often erroneously determine that a voltage detection line has been disconnected when the cell voltage significantly decreases, leading to incorrect disconnection assessments.

Innovation Solution

A disconnection detection device with CR filters and discharge circuits for each battery cell, where the detection unit successively discharges adjacent cells and monitors the voltage differences across detection lines after a predetermined time to accurately determine disconnection based on voltage differences, independent of cell voltage fluctuations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the cell voltage is monitored using a voltage detection line, then the cell voltage can be monitored to balance battery voltages, but when the cell voltage greatly decreases, erroneous disconnection determination occurs

Engineering Contradiction:

Improvevoltage detection accuracyVSAvoiddisconnection detection reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The voltage detection function is segmented into two independent detection paths: one for normal voltage monitoring and another for disconnection detection. The disconnection detection path uses a separate voltage detection line that is electrically isolated from the main voltage detection line, allowing it to detect disconnection conditions without being affected by normal voltage variations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A separate voltage detection line acts as an intermediary to detect disconnection conditions. This dedicated detection line is connected in parallel to the battery cell and provides a reference voltage that remains stable even when the main voltage detection line experiences large voltage drops, enabling reliable disconnection detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Difficulty of detecting and measuring

If a voltage threshold is used to detect disconnection, then disconnection can be detected when voltage decreases, but erroneous determination occurs when cell voltage greatly decreases

Engineering Contradiction:

Improvedisconnection detection capabilityVSAvoiddisconnection detection accuracy

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The system prepares for potential disconnection detection by establishing a separate voltage detection path that is immune to normal voltage fluctuations. This pre-configured detection path ensures that when disconnection occurs, the detection can be performed accurately without being cushioned or masked by the magnitude of voltage changes in the main circuit.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

Instead of detecting disconnection by monitoring voltage drops in the main voltage detection line (which leads to erroneous determination), the invention inverts the approach by using a separate detection line that maintains a stable reference voltage. The disconnection is detected by comparing the stability of this reference voltage rather than by detecting voltage drops.

Inventive Principle:

Principle #13The other way round (Inversion)

3Productivity

If the voltage detection line voltage is monitored continuously, then disconnection can be detected when voltage decreases to threshold, but the system cannot distinguish between actual disconnection and voltage fluctuations

Engineering Contradiction:

Improvedetection speedVSAvoiddetection accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The separate voltage detection line is pre-configured and continuously maintains a reference voltage level before any disconnection event occurs. This preliminary setup allows the system to immediately compare the reference voltage with expected values upon detecting a potential disconnection, enabling fast and accurate detection without waiting for voltage fluctuations to subside or for complex analysis.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11909233B2Disconnection detection device and disconnection detection method

Publication Date: 2024.02.20 DENSO TEN LTD

AI summary

A disconnection detection device includes CR filters, discharge circuits, and a detection unit. The CR filters are provided for respective battery cells of a battery pack in which the battery cells are connected in series. Each of the discharge circuits is connected between the battery cell and the CR filter and discharging the battery cell when cell voltages of the battery cells are made balanced. The detection unit successively discharges two of the battery cells connected in series, successively detects voltages of detection lines detecting contact voltages of the two battery cells after a predetermined time has passed from finish of discharge of each of the battery cells, and detects disconnection of each of the detection lines on the basis of a difference between the two detected voltages.