Battery Module Switching Control for Parallel Cross-Current Limits
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Solution Overview
Problem
The parallel connection of battery packs in electric vehicles can lead to a decrease in the upper limit value of current or power allowed to be discharged or charged, causing adverse effects such as decreased acceleration performance and increased charging time due to cross currents.
Innovation Solution
A management device that estimates the upper limit values of current or power based on the state of charge (SOC) characteristics of each power storage module, preventing switches from turning on if these limits are not met, thereby managing the parallel connection to prevent cross currents and maintain efficient charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If battery packs being separated are connected in parallel at the time of discharge, then the upper limit value of current or power allowed to be discharged from the entire parallel system usually increases, but due to cross current generated by the parallel connection, the upper limit value of current or power allowed to be discharged decreases to be lower than that before the parallel connection
Solution Approach 1:
The management device performs preliminary estimation of the upper limit value of current or power after parallel connection before actually connecting the battery packs. Based on this preliminary assessment, the system determines whether to permit the parallel connection, thereby preventing cross-current losses from occurring in the first place.
Solution Approach 2:
The management device continuously monitors the actual current or power of the parallel system and compares it with the estimated upper limit value. When the actual value approaches the limit, the system provides feedback to prevent further increase, thereby avoiding excessive cross-current generation and energy loss.
2Power
If battery packs being separated are connected in parallel at the time of charge, then the upper limit value of current or power allowed to be charged to the entire parallel system usually increases, but due to cross current generated by the parallel connection, the upper limit value of current or power allowed to be charged decreases to be lower than that before the parallel connection
Solution Approach 1:
The management device performs preliminary estimation of the upper limit value of current or power after parallel connection before actually connecting the battery packs. Based on this preliminary assessment, the system determines whether to permit the parallel connection, thereby preventing cross-current losses from occurring in the first place.
Solution Approach 2:
The management device continuously monitors the actual current or power of the parallel system and compares it with the estimated upper limit value. When the actual value approaches the limit, the system provides feedback to prevent further increase, thereby avoiding excessive cross-current generation and energy loss.
3Device complexity
If the management device permits parallel connection without estimation, then the system complexity is reduced, but current shortages occur and charging efficiency decreases
Solution Approach 1:
The patent replaces complex real-time dynamic monitoring and adjustment mechanisms with a simplified estimation-based decision system. By using predetermined SOC-discharge upper limit characteristics and SOC-charge upper limit characteristics, the system achieves efficient management without requiring complex continuous monitoring infrastructure.
Data Source
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AI summary
Provided is management device (30) that manages a plurality of power storage modules (M1) connected in parallel to load (60) with respective switches (RY1). Management device (30) has a first state where some of switches (RY1) connected to some of the plurality of power storage modules (M1) are turned on and other of switches (RY1) connected to remaining power storage modules (M1) are turned off, and includes determination unit (313) that does not permit turning on at least one of the other of switches (RY1) connected to other power storage modules (M1) and turned off in the first state when an upper limit value of current or power that is allowed to be discharged to load (60) from the entire plurality of power storage modules (M1) is lower than a first threshold based on a maximum value of current or power required by load (60) in a state where the at least one of the other of switches (RY1) is turned on.