Vehicle Battery SOC Control for Cruising Distance
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Solution Overview
Problem
Existing vehicle power storage devices deteriorate over time, reducing their capacity and affecting cruising distance, with existing control methods not effectively addressing battery deterioration during repeated use.
Innovation Solution
A vehicle system that includes a power storage device, an electric motor, a charging mechanism, and a controller with a state estimating unit and a setting unit to adjust the state of charge (SOC) upper limit value based on deterioration conditions, allowing for a longer usable period and detecting abnormalities to maintain or lower the SOC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the number of power storage devices or cells is increased to extend cruising distance, then the cruising distance is improved, but the volume, weight, and cost of the power storage device increase
Solution Approach 1:
The patent applies dynamics by making the SOC upper limit value adjustable rather than fixed. The control unit dynamically changes the SOC upper limit value based on the number of times the power storage device has been used, allowing the system to adapt to battery deterioration over time. This dynamic adjustment optimizes the balance between cruising distance and battery protection without requiring additional battery capacity
Solution Approach 2:
The patent changes the parameter of SOC upper limit value based on usage history. By modifying this control parameter according to the number of charge-discharge cycles, the system compensates for battery capacity degradation and maintains optimal cruising distance without increasing physical battery size or weight
2Duration of action of moving object
If the SOC upper limit value is increased to extend cruising distance, then the cruising distance is improved, but the power storage device deterioration accelerates
Solution Approach 1:
The system dynamically adjusts the SOC upper limit value based on the number of times the power storage device has been used. Initially, a higher SOC upper limit extends cruising distance, but as usage increases and battery deterioration occurs, the system automatically lowers the SOC upper limit to protect the battery, thereby extending the overall usable period while maintaining adequate cruising distance
Solution Approach 2:
The control unit preliminarily sets an appropriate SOC upper limit value before significant deterioration occurs, and proactively adjusts it based on usage history. This preliminary action prevents excessive deterioration by avoiding repeated high-SOC charging that would damage the battery, thereby extending the power storage device's usable period
3Reliability
If the SOC upper limit value is fixed to protect the power storage device, then the durability is improved, but the cruising distance becomes insufficient
Solution Approach 1:
Rather than using a fixed SOC upper limit, the system dynamically adjusts this parameter based on the number of usage cycles. In early stages with minimal deterioration, a higher SOC upper limit provides sufficient cruising distance. As usage increases and deterioration occurs, the SOC upper limit is automatically reduced to protect the battery, thereby maintaining both adequate cruising distance and durability throughout the battery's life
Data Source
AI summary
A vehicle is equipped with a battery, an electric motor configured so as to generate the driving force of the vehicle by use of the electric power stored in the battery, a charger configured so as to supply the electric power outputted from the power supply outside of the vehicle to the battery, and an ECU configured so as to control the state of charge of the battery when the battery is charged. The ECU calculates an index value indicating the state of charge of the battery, and sets the control range thereof. The ECU raises the upper limit of the index value so that the possible travel distance of the vehicle becomes not less than the target distance when predetermined conditions on degradation of the battery are satisfied.