Vehicle Battery Relay Switching for Low-Loss DC Charging
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Solution Overview
Problem
Charging efficiency of electric storage devices in vehicles is decreased due to high energization currents resulting from heat generation by energized components during DC charging, especially when the batteries are connected in parallel, leading to increased losses.
Innovation Solution
A charging apparatus with a control device that switches batteries between series and parallel connections, using a changeover relay and main relay to optimize charging efficiency by reducing energization current and heat generation, especially in a READY-OFF state where batteries are connected in series.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the batteries are connected in parallel to increase charging current capability, then the charging power can be increased, but the energization current becomes large causing heat generation and reduced charging efficiency
Solution Approach 1:
The patent applies dynamics by making the battery connection configuration changeable between series and parallel states based on operating conditions. The control device dynamically switches between series connection (for normal charging) and parallel connection (for high-power charging when main relay is closed), allowing the system to adapt to different charging scenarios and minimize energy loss while maintaining high charging power capability when needed.
Solution Approach 2:
The patent changes the electrical parameters of the battery system by switching between series and parallel connections. In series connection, the voltage is doubled while current remains the same; in parallel connection, the current capability is doubled while voltage remains the same. This parameter change allows the system to optimize charging efficiency by using series connection for normal operations and parallel connection only when high power is required and the main relay is closed.
2Power
If the charging voltage is decreased to accommodate parallel battery configuration, then the charging power can be maintained, but the energization current increases causing heat generation
Solution Approach 1:
The system dynamically adjusts the battery connection configuration based on the main relay state. When the main relay is open, series connection is used to maintain high voltage and low current. When the main relay is closed, parallel connection is permitted to allow higher current at lower voltage without excessive heat generation, as the main relay being closed indicates the vehicle is in READY state and can handle the additional thermal load.
Solution Approach 2:
The patent changes the voltage and current parameters by switching battery configuration. Series connection maintains high voltage (reducing current for same power), while parallel connection allows lower voltage with higher current capability. The control device selects the appropriate parameter set based on main relay state to minimize heat generation during charging.
3Ease of operation
If the main relay is kept closed to allow power supply to electric load, then the vehicle can operate, but the batteries cannot be charged efficiently due to high energization current
Solution Approach 1:
The patent creates a dynamic charging system where the battery connection configuration automatically adapts to the main relay state. When main relay is closed (vehicle in READY state), the system permits parallel connection for charging, accepting some energy loss in exchange for operational flexibility. When main relay is open (READY-OFF state), series connection is enforced to maximize charging efficiency. This dynamic adaptation resolves the contradiction between vehicle operation and charging efficiency.
Solution Approach 2:
The system changes the battery electrical parameters based on operational state. When main relay is closed, parallel connection parameters (lower voltage, higher current capability) are used, accepting reduced efficiency for operational convenience. When main relay is open, series connection parameters (higher voltage, lower current) are enforced to maximize charging efficiency. This parameter adaptation allows the system to balance operational needs with energy efficiency.
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
Enhances charging efficiency by decreasing energization current and heat generation, thereby reducing losses in the charging process.
Implementation Method 1
a changeover relay that is switchable between a first state in which the plurality of batteries are connected in series to one another and a second state in which the plurality of batteries are connected in parallel to one another
Implementation Method 2
a main relay that is provided between the electric storage device and an electric load of the vehicle
Implementation Method 3
the loss resulting from heat generation by cables, components and the like through which the charging current flows at the time of charging
Data Source
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AI summary
A charging apparatus includes a plurality of batteries (11, 12), a changeover relay (Rl, R2, R3) that can be changed over between a first state where the plurality of the batteries (11, 12) are connected in series to one another and a second state where the plurality of the batteries (11, 12) are connected in parallel to one another, an electric storage device (10), a main relay (21, 22) that is provided between the electric storage device (10) and an electric load of a vehicle, and a control device (100) that controls the opening/closing of the changeover relay (Rl, R2, R3). The control device (100) renders the changeover relay (R1, R2, R3) in the first state when the main relay (21, 22) is in an open state.