EV Battery SOC Control for High-Rate Deterioration
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Solution Overview
Problem
High-rate deterioration in secondary batteries of electric vehicles due to non-uniform salt concentration leads to increased internal resistance, reducing EV traveling distance and potentially making EV traveling impossible.
Innovation Solution
A control method that switches between EV and HV modes based on the state of charge (SOC) and evaluates the degree of deterioration, inhibiting high-rate deterioration by adjusting the SOC control target when in HV mode and allowing recovery during EV mode, ensuring EV traveling distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target SOC is made higher than the target SOC at normal time when high-rate deterioration occurs, then the battery output and travelling distance can be ensured, but the EV travelling distance becomes shorter unnecessarily or EV travelling becomes impossible
Solution Approach 1:
The patent applies dynamics by making the target SOC adjustable rather than fixed. The control target of SOC is dynamically changed based on the operating mode (EV mode vs. HV mode) and the deterioration state of the secondary battery. This allows the system to adapt the target SOC to different situations, resolving the contradiction between ensuring battery output and maintaining EV travelling distance.
2Power
If the target SOC is made higher than the target SOC at normal time when high-rate deterioration occurs, then constant battery output can be ensured, but the EV travelling becomes impossible
Solution Approach 1:
The system dynamically adjusts the target SOC based on the current operating mode and deterioration state. When in EV mode, the target SOC remains at the lower limit to preserve EV travelling availability. When in HV mode and high-rate deterioration is detected, the target SOC is raised to ensure constant battery output. This dynamic adjustment resolves the contradiction between power output and EV travelling availability.
Solution Approach 2:
The patent changes the parameter of target SOC based on different conditions. By monitoring the deterioration state and operating mode, the system changes the target SOC parameter appropriately - keeping it at the lower limit during EV mode to maintain EV travelling capability, and raising it during HV mode to ensure battery output, thus resolving the contradiction.
3Length of moving object
If the SOC is controlled to the lower limit during HV mode, then the EV travelling distance can be maximized, but high-rate deterioration accelerates due to non-uniform salt concentration
Solution Approach 1:
The system dynamically adjusts the target SOC based on the deterioration state. When high-rate deterioration is detected during HV mode, the target SOC is raised above the lower limit, which slows down the progression of deterioration by reducing salt concentration non-uniformity. This dynamic adjustment resolves the contradiction between maximizing EV travelling distance and maintaining battery durability.
Solution Approach 2:
The patent changes the target SOC parameter in response to deterioration state. By raising the target SOC when high-rate deterioration is detected, the system reduces the stress on the battery that causes non-uniform salt concentration, thereby improving battery durability while still allowing EV travelling to occur, thus resolving the contradiction between EV travelling distance and battery durability.
Data Source
AI summary
An ECU switches a control mode to an HV mode when an SOC decreases to a lower limit during an EV mode. The ECU calculates an evaluation value ΣD of high-rate deterioration indicating a deterioration component of a secondary battery due to non-uniformity in salt concentration in a battery. The ECU executes high-rate deterioration inhibiting control when the HV mode is currently selected and when the battery is evaluated as deteriorating based on the evaluation value ΣD, the high-rate deterioration inhibiting control being control for increasing the SOC by making a control target of the SOC higher than the lower limit of the SOC. On the other hand, the ECU does not execute the high-rate deterioration inhibiting control when the EV mode is currently selected.