Shunt Resistor Over-Current Diagnosis in Battery Management Circuits
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Solution Overview
Problem
Current lithium-ion battery management systems lack an effective over-current detection function, which can lead to increased internal battery temperatures and potential fires, particularly in vehicles, necessitating a reliable method to diagnose and prevent over-current conditions.
Innovation Solution
A battery management apparatus incorporating a shunt resistor and voltage generator to differentiate between charging and discharging over-currents, utilizing a circuitry with amplifiers, comparators, and controllers to determine and control over-current flows, including switches and resistors to accurately detect and manage over-currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If over-current detection function is implemented in battery management system, then safety against fire is improved, but device complexity increases due to additional circuitry components
Solution Approach 1:
The shunt resistor serves multiple functions: it is used during normal operation for current measurement and during diagnosis mode for over-current detection function testing. The voltage generator can operate in both normal voltage generation mode and diagnosis mode where it generates specific test voltages to simulate over-current conditions, eliminating the need for separate dedicated test equipment.
Solution Approach 2:
The battery management apparatus performs self-diagnosis of its over-current detection function using its own internal components. The controller activates the voltage generator to produce test voltages, measures the resulting currents through the shunt resistor, and automatically determines whether the detection function operates normally, without requiring external testing equipment or manual intervention.
2Reliability
If diagnosis function for over-current detection is added, then operational integrity is improved, but manufacturing complexity increases due to additional components
Solution Approach 1:
Existing components are designed to serve dual purposes: the shunt resistor functions as both a current sensing element during normal operation and a test load during diagnosis. The voltage generator serves both normal voltage generation and diagnosis mode operations. This multi-functionality reduces the need for additional dedicated components that would complicate manufacturing.
Solution Approach 2:
The diagnosis function is merged with the existing battery management apparatus structure. The voltage generator, shunt resistor, and controller work together in an integrated manner for both normal operation and self-diagnosis, combining multiple functions into a unified system rather than adding separate independent subsystems.
3Measurement precision
If voltage generator generates output values corresponding to over-current conditions, then detection accuracy is improved, but energy consumption increases during diagnosis operations
Solution Approach 1:
The voltage generator operates periodically: it generates normal output voltages during standard battery management operations, and switches to generating specific test output voltages (first and second output values) only during diagnosis mode. This periodic operation ensures high detection accuracy when needed while minimizing energy consumption during normal operation when diagnosis is not required.
Solution Approach 2:
The voltage generator pre-calculates and generates specific output values (first output value corresponding to charging over-current, second output value corresponding to discharging over-current) that are designed to produce measurable voltage drops across the shunt resistor. This preliminary preparation of test voltages enables accurate detection without requiring excessive energy, as the voltages are precisely tailored to the diagnostic needs.
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
The apparatus effectively diagnoses the operation of the over-current detection function, preventing potential fires by accurately determining and managing over-currents, thereby enhancing safety integrity levels in battery management systems.
Implementation Method 1
a voltage generator configured to generate a first output value and a second output value, in which a difference between the first output value and the second output value corresponds to a magnitude of the voltage applied to the shunt resistor when charging over-current or discharging over-current flows in the shunt resistor
Implementation Method 2
the circuitry may include an amplifier configured to receive and amplify the first output value and the second output value
Data Source
AI summary
A battery management apparatus includes a shunt resistor connected to a battery and a voltage generation unit configured to generate a first output value and a second output value which have a difference therebetween corresponding to a magnitude of a voltage applied to the shunt resistor, in which the difference between the first output value and the second output value corresponds to the magnitude of the voltage applied to the shunt resistor when charging over-current or discharging over-current flows in the shunt resistor.