Battery Cell Micro-Short Circuit Detection via Charging Current

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Solution Overview

Problem

Existing methods for detecting micro-short circuits in secondary batteries, such as lithium ion batteries, face challenges in accurately determining the presence of high-resistance micro-short circuits due to minute voltage reductions, leading to potential shipment of defective cells with foreign matter, and require lengthy suspension periods for detection.

Innovation Solution

An inspection device and method that involves constant current and constant voltage charging of battery cells, utilizing the peak current generated during a switch from constant current to constant voltage charging to determine the presence of micro-short circuits with high accuracy in a short period.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If voltage reduction during suspension period is used to detect micro-short circuit, then detection capability is provided, but detection accuracy deteriorates for high-resistance cases and inspection time increases

Engineering Contradiction:

Improvemicro-short circuit detection capabilityVSAvoiddetection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the detection parameter from voltage reduction during suspension period to charging current characteristics during constant current charging. By monitoring the charging current and its rate of change (dI/dt), the system can detect micro-short circuits with high resistance values without requiring long suspension periods, thereby improving both detection accuracy and inspection speed

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the time-based detection method (suspension period) with an electrical characteristic-based method (charging current analysis). By substituting the mechanical/waiting approach with electrical measurement, the system achieves faster and more accurate detection of micro-short circuits

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If suspension period is extended to detect micro-short circuit, then detection capability improves, but inspection time increases

Engineering Contradiction:

Improvemicro-short circuit detection capabilityVSAvoidinspection time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent skips the lengthy suspension period by directly analyzing charging current characteristics during the constant current charging phase. This allows the system to detect micro-short circuits during the charging process itself, dramatically reducing inspection time while maintaining detection capability

Inventive Principle:

Principle #21Skipping (Rushing through)

Solution Approach 2:

The patent replaces the time-consuming suspension period with real-time electrical measurement during charging. By substituting the waiting approach with active electrical characterization, the system achieves fast detection without sacrificing reliability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If conventional voltage or current methods are used for micro-short circuit detection, then simple detection is provided, but detection accuracy deteriorates when micro-short circuit resistance is several hundred ohms

Engineering Contradiction:

Improvedetection method simplicityVSAvoiddetection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent changes the detection parameter from absolute voltage or current values to the rate of change of current (dI/dt) during constant current charging. This differential measurement approach enhances sensitivity to micro-short circuits with high resistance values while maintaining relatively simple detection methodology

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies a more sensitive measurement approach (monitoring dI/dt) than simple voltage or current threshold detection. By using the rate of change rather than absolute values, the system achieves higher precision for high-resistance micro-short circuits without excessive complexity

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11275125B2Inspection device, inspection method, inspection program, management device, and power storage system

Publication Date: 2022.03.15 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An input and output device of an inspection device is configured to instruct charging devices capable of charging respective cells to perform constant current charging or constant voltage charging, and acquire a voltage value and a current value of each of the cells from corresponding one of the charging devices. A controller of the inspection device is configured to instruct the charging devices to perform constant current charging of the respective cells, and perform constant voltage charging of the respective cells when a voltage value of each of the cells acquired from corresponding one of the charging devices reaches a preset value. The controller of the inspection device is configured to determine presence or absence of a micro-short circuit in each of the cells with reference to a peak current value of corresponding one of the cells generated in switching from the constant current charging to the constant voltage charging.