Battery Pack Relay Welding Detection via Alternating Terminal Voltage
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Solution Overview
Problem
Existing battery management systems inaccurately diagnose the welding of high-voltage relay switches in battery packs, leading to potential misdiagnosis and safety hazards due to misinterpretation of link capacitor voltages.
Innovation Solution
A battery pack design that includes insulated switches and resistors in series with battery terminals, controlled by a controller to alternately switch states, allowing for precise measurement of terminal voltage variations to determine switch welding by comparing voltage differences against a threshold, ensuring accurate diagnosis of switch malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a relay switch is used to control charging and discharging in a high-voltage battery pack, then the battery pack can operate at high voltage with reduced current, but the relay switch may be welded due to high voltage, leading to misdiagnosis of its welding state
Solution Approach 1:
The patent introduces insulated switches as intermediary components between the relay switch and the measurement circuit. These insulated switches allow the system to measure voltage differences across the relay switch terminals without directly exposing the measurement circuit to high voltage, thereby enabling accurate welding diagnosis while maintaining high-voltage operation capability
Solution Approach 2:
The patent replaces direct high-voltage electrical measurement with a controlled switching and voltage difference measurement approach. By using insulated switches to control circuit connectivity and measuring voltage differences rather than directly monitoring relay switch state, the system achieves accurate welding diagnosis without the risks associated with direct high-voltage measurement
2Difficulty of detecting and measuring
If the battery pack is configured to check relay switch welding by monitoring voltage, then welding detection is enabled, but the link capacitor voltage causes misdiagnosis even when the relay switch is not welded
Solution Approach 1:
The patent performs preliminary actions by controlling the insulated switches to specific states before measurement. The controller opens or closes the insulated switches in a predetermined sequence to isolate the link capacitor voltage from the measurement circuit, ensuring that only the voltage difference across the relay switch is measured when needed
Solution Approach 2:
The patent uses dynamic switching of the insulated switches to adapt the measurement circuit's connectivity. By dynamically changing the circuit configuration based on measurement needs, the system can selectively include or exclude the link capacitor from the measurement path, thereby achieving precise welding diagnosis without interference
Data Source
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AI summary
A battery pack includes first and second pack terminals, a battery between first and second battery terminals, a main switch between the first pack terminal and the first battery terminal, a first resistor and a first insulated switch in series between the first battery terminal and a ground, a second resistor and a second insulated switch in series between the second battery terminal and the ground, and a controller to control the first and second insulated switches to alternately repeat a first state, in which the first insulated switch is closed and the second insulated switch is opened, and a second state, in which the first insulated switch is opened and the second insulated switch is closed, detect a first terminal voltage, control the main switch, and determine whether the main switch malfunctions based on a difference between the first terminal voltage in the first and second states.