Master and Slave BMS Over-Charging Prevention via Signal Feedback
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Solution Overview
Problem
In high voltage battery systems of plug-in hybrid electric vehicles, the master battery management system (BMS) cannot prevent continuous over-charging of the master battery, as it cannot control the charging relay, leading to potential safety hazards like vehicle fires or explosions.
Innovation Solution
Implementing a communication mechanism between the master BMS and slave BMS to transmit over-charging signals, allowing either BMS to turn off the main or charging relays when an over-charged condition is detected, ensuring both relays are disconnected to prevent over-charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the master BMS and slave BMS are independently operated, then each BMS can control its own battery, but the master BMS cannot prevent continuous over-charging of the master battery when it is over-charged during charging
Solution Approach 1:
The patent implements a feedback mechanism where the master BMS and slave BMS exchange over-charging signals. When the master BMS detects over-charging of the master battery, it transmits an over-charging signal to the slave BMS, which then turns off the charging relay. This feedback loop ensures that over-charging prevention is achieved across both batteries while maintaining independent operation of each BMS.
Solution Approach 2:
The patent introduces a communication mechanism as an intermediary between the master BMS and slave BMS. This intermediary enables the transmission of over-charging signals, allowing the slave BMS to act on behalf of the master BMS when needed, thus resolving the contradiction between independent operation and comprehensive over-charging prevention.
2Reliability
If the master BMS turns off the main relay to prevent over-current, then motor protection is achieved, but the master BMS cannot control the charging relay to stop continuous over-charging
Solution Approach 1:
The communication mechanism acts as an intermediary that bridges the control authority gap. When the master BMS detects over-charging, it sends a signal through this intermediary to the slave BMS, which then controls the charging relay. This allows motor protection to be maintained while extending control capability to the charging relay without increasing device complexity.
Solution Approach 2:
The over-charging signal transmission mechanism provides multi-functionality: it enables the master BMS to indirectly control the charging relay, ensures both batteries are protected, and maintains the independent operational structure. This universal solution addresses multiple control scenarios without requiring additional hardware complexity.
3Reliability
If both main relay and charging relay are turned off when over-charging is detected, then over-charging prevention is improved, but communication mechanism between BMS is required
Solution Approach 1:
The communication mechanism implements a simple feedback system where over-charging detection by one BMS triggers a signal to the other BMS, which then executes the relay disconnection. This feedback-based approach achieves comprehensive over-charging prevention (both relays turned off) while keeping the communication mechanism minimal and straightforward, avoiding excessive complexity.
Data Source
AI summary
The present invention relates to an apparatus for preventing a battery including a master battery and a slave battery from being over-charged, the apparatus including: a master battery management system (BMS) which determines whether the master battery is over-charged, and turns off a main relay which connects or disconnects between the battery and a motor of a vehicle when the master battery is over-charged as a result of the determination; and a slave BMS which determines whether the slave battery is over-charged, and turns off a charging relay which connects or disconnects between the battery and a charger provided outside the vehicle when the slave battery is over-charged as a result of the determination.