Battery Management System Leakage Resistance Detection Circuit
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Solution Overview
Problem
Existing battery management systems for electric vehicles face challenges in ensuring electrical isolation between high-voltage batteries and the chassis, requiring complex circuit configurations that limit flexibility and increase the risk of leakage currents due to the need for high-safety circuit components.
Innovation Solution
A battery management system with a simplified circuit structure that includes a first determination circuit with a voltage divider and a switch to change resistance, allowing for reduced resistance from the battery to the chassis, enabling the use of common solid-state relays and integrating the system on a single circuit board, thereby reducing space and production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex circuit configurations with multiple voltage dividers and switches are used to determine leakage path resistance, then measurement accuracy is improved, but device complexity increases and flexibility is reduced
Solution Approach 1:
The patent divides the leakage resistance measurement into two separate determination circuits: a first determination circuit for measuring leakage resistance from the positive battery terminal to chassis, and a second determination circuit for measuring leakage resistance from the negative battery terminal to chassis. Each circuit independently measures one polarity's leakage path, simplifying the overall measurement approach while maintaining accuracy.
Solution Approach 2:
The patent introduces a current-limiting resistor in series with the voltage divider in each determination circuit. This intermediary component limits the current flowing through the voltage divider, preventing excessive current that could damage components or create safety hazards, while still allowing accurate voltage measurements for leakage resistance calculation.
2Reliability
If high-safety circuit components are used to ensure electrical isolation, then reliability is improved, but circuit complexity and production costs increase
Solution Approach 1:
The current-limiting resistor serves as a safety intermediary that protects the voltage divider and other sensitive components from excessive current. This simple passive component provides an additional layer of safety without requiring complex active protection circuits, maintaining reliability while simplifying the overall design.
Solution Approach 2:
The patent incorporates protective resistors and carefully selected component ratings that can withstand potential overvoltage or overcurrent conditions before they occur. The current-limiting resistor and properly rated voltage divider resistors are designed to handle worst-case scenarios, providing built-in protection that simplifies safety certification and component selection.
3Measurement precision
If multiple circuit components are used for leakage resistance determination, then measurement accuracy is improved, but the risk of leakage currents increases
Solution Approach 1:
The current-limiting resistor acts as a protective intermediary that caps the maximum current that can flow through the measurement circuit regardless of component failures or unexpected conditions. This single component significantly reduces the risk of hazardous leakage currents while allowing the voltage divider to maintain its measurement function.
Solution Approach 2:
The patent carefully selects the resistance values of the voltage divider resistors and current-limiting resistors to optimize the measurement range while maintaining safety margins. By adjusting these resistance parameters, the system achieves accurate leakage resistance measurement across the required range while keeping measurement circuit currents well below hazardous levels.
4Device complexity
If simplified circuit structure is used, then device complexity and production costs are reduced, but flexibility in component selection is limited
Solution Approach 1:
The determination circuits are designed with universal components that can be selected from standard commercial parts. The voltage dividers use common resistor values, and the current-limiting resistors are standard power-rated components. This universality allows designers to select from a wide range of off-the-shelf components while maintaining the simplified circuit structure, thereby preserving flexibility without increasing complexity.
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 solution provides a safer, more flexible, and cost-effective battery management system that accurately determines leakage path resistance while minimizing the risk of leakage currents and enhancing the accuracy of isolation measurements.
Implementation Method 1
A voltage divider having at least two resistors (135, 140) is arranged in each case between the electrically conductive part and the two poles
Implementation Method 2
A switch unit is associated each with the two voltage dividers and is provided for alternately bypassing at least one of the resistors
Data Source
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AI summary
The present invention relates to a battery management system for an electric vehicle. The battery management system comprises a first terminal (105) for electrically connecting one terminal (505) of a battery (500) of the electric vehicle, a second terminal (110) for electrically connecting an electric load of the electric vehicle, and a third terminal (115) for electrically connecting a chassis (600) of the electric vehicle. Further the battery management system comprises a first determination circuit (130, 230) conductively coupled with a first node (120) between the first terminal (105) and the second terminal (110) and conductively coupled with a second node (125) to the third terminal (115), the first determination circuit (130, 230) comprising: a first voltage divider which comprises a first series circuit with at least a first resistor (135) and a second resistor (140), a first switch (145) which is conductively coupled to the first resistor (135), so that, when the first switch is ON, the first resistor (135) is short-circuited and that, when the first switch (145) is OFF, the first resistor (135) is not short-circuited, and a first measurement circuit (150) configured to measure a first voltage across the second resistor (140), when the first switch (145) is OFF, and to measure a second voltage across the second resistor (140), when the first switch (145) is ON. Further the battery management system comprises a processing circuit configured to determine a leakage path resistance between an other terminal (510) of the battery (500) and the chassis (600) of the electric vehicle based on the first voltage and the second voltage.