Battery Module Switching Control for Cross-Current-Limited Charging
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Solution Overview
Problem
The parallel connection of battery packs during charging leads to cross currents, reducing the maximum charging current and power, resulting in longer charging times and lower regenerative brake force, which decreases charging efficiency.
Innovation Solution
A management device that controls the parallel connection of power storage modules by using a determination unit to assess the maximum current or power allowed before and after connecting additional modules, preventing the switch from turning on if the resulting value is lower than a threshold, thus maintaining efficient charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If battery packs are parallel-connected during charging, then the maximum charging current and power should increase, but cross currents cause the maximum charging current and power to decrease
Solution Approach 1:
The determination unit calculates the maximum charging current and power before allowing parallel connection, and predicts the values after connection. This preliminary assessment prevents cross current issues by identifying unsuitable connection candidates before they are connected, thereby maintaining charging efficiency.
Solution Approach 2:
The control unit receives information from the determination unit about whether parallel connection is suitable, and adjusts the switching element accordingly. This feedback mechanism ensures that only battery packs that will maintain or improve charging efficiency are connected in parallel, preventing energy loss from cross currents.
2Quantity of substance
If battery packs are parallel-connected, then charging capacity increases, but charging time increases due to reduced maximum charging current
Solution Approach 1:
Before parallel connection is executed, the determination unit performs preliminary calculations to predict the impact on maximum charging current and charging time. This allows the system to select connection candidates that increase capacity without significantly extending charging time.
Solution Approach 2:
The system dynamically adjusts the parallel connection configuration based on real-time calculations of charging current and time requirements. The control unit can add or remove battery packs from parallel connection to optimize the balance between charging capacity and charging time.
3Power
If battery packs are parallel-connected, then system power increases, but regenerative brake force decreases due to cross current effects
Solution Approach 1:
The determination unit calculates the expected regenerative brake force after parallel connection by predicting the maximum charging power. This preliminary assessment prevents connections that would reduce regenerative brake force, ensuring that system power increases do not come at the expense of braking performance.
Solution Approach 2:
The control unit uses feedback from the determination unit to decide whether to permit parallel connection based on the predicted impact on regenerative brake force. This ensures that the system maintains adequate braking capability while utilizing parallel connection for power enhancement.
Data Source
AI summary
Management device manages storage modules each parallel-connected to power supply through switch. Determination unit of management device, in a state where switches connected to some of power storage modules the power storage modules are on; and switches connected to the remaining power storage modules are off, when at least one of the off-state switches are turned on, determination unit does not permit the switch to be turned on when a maximum value of current or power allowed to charge all of the power storage modules is lower than a threshold based on the maximum before the switches are is turned on.