Vehicle Power Source System Dynamic SOC Lower Limit Control
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Solution Overview
Problem
Existing vehicle power source systems unnecessarily restrict charging of low-voltage batteries from high-voltage batteries due to overly conservative setting of the lower limit state of charge, leading to increased frequency of low-voltage battery depletion.
Innovation Solution
A power source system with a controller that estimates the decrease in state of charge of the high-voltage battery over time and sets a lower limit based on this estimate, allowing charging of the low-voltage battery only when the state of charge is above this limit, thereby preventing overdischarge and reducing battery depletion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lower limit value of the SOC is set conservatively to account for SOC decrease during parking, then the high-voltage battery is protected from overdischarge, but the charging opportunity for the low-voltage battery is reduced
Solution Approach 1:
The system dynamically adjusts the lower limit SOC threshold based on parking time duration. For short parking periods, a conservative higher threshold maintains protection. For long parking periods, the threshold is lowered to enable charging operations. This dynamic adjustment resolves the contradiction by adapting the protection level to actual operational conditions rather than applying a uniformly conservative limit.
Solution Approach 2:
The control device calculates and determines the lower limit SOC value in advance based on the expected or actual parking time before charging begins. This preliminary determination allows the system to plan charging operations proactively, ensuring that charging occurs during appropriate time windows when it won't compromise high-voltage battery safety, thereby increasing charging frequency without risking overdischarge.
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
This approach ensures that the low-voltage battery is charged only when necessary, reducing the risk of depletion and maintaining vehicle functionality by setting a more dynamic and appropriate lower limit for charging, thus enhancing the reliability of power supply for auxiliary devices.
Implementation Method 1
The voltage converter is configured to perform voltage conversion of power output from the first power storage device and charge the second power storage device
Data Source
AI summary
A power source system for a vehicle includes a first power storage device, a second power storage device, a voltage converter, and a controller. The controller is configured to (a) execute a charging control in which the second power storage device is charged by the voltage converter when a parking time of the vehicle exceeds a predetermined period of time, (b) estimate a decrease amount in a state of charge of the first power storage device in a time period from after elapse of the predetermined period of time until a start of the vehicle, (c) set a lower limit of the state of charge based on the decrease amount, and (d) not execute the charging control when the state of charge is lower than the lower limit.