Battery Block SOC Reset via Constant Current Discharge
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Solution Overview
Problem
Existing electrically powered vehicles face challenges in accurately estimating the state of charge (SOC) of their power storage systems due to variations in battery characteristics over time, especially under varying environmental conditions, leading to insufficient estimation accuracy.
Innovation Solution
The implementation of a charge/discharge control device that discharges the power storage system with a constant current and estimates the SOC of each unit, resetting the states of charge to reference values based on voltage and temperature changes, thereby accounting for variations between units and improving estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the battery assembly is used as the power storage system with multiple battery blocks connected in series, then the electric power supply capacity is improved, but the variations in SOC between battery blocks occur due to battery characteristic deterioration, leading to reduced estimation accuracy
Solution Approach 1:
The patent divides the power storage system into multiple independently monitored battery blocks, each with its own SOC estimation. By segmenting the monitoring and estimation process for each battery block individually, the system can detect and correct SOC variations between blocks, thereby maintaining overall estimation accuracy while preserving the high power capacity benefits of multiple blocks connected in series.
Solution Approach 2:
The patent implements a feedback mechanism where the SOC estimation results of individual battery blocks are continuously monitored and compared. When variations beyond a predetermined threshold are detected, the system provides feedback to adjust the estimation, ensuring that SOC accuracy is maintained across all battery blocks despite characteristic deterioration over time.
2Reliability
If deep charge and discharge are executed multiple times to erase the memory effect, then the memory effect is removed, but the time required for SOC estimation and reset processing increases
Solution Approach 1:
The patent performs preliminary SOC estimation and comparison for all battery blocks before initiating any reset operations. By pre-identifying which battery blocks require reset based on SOC variations exceeding the threshold, the system avoids unnecessary deep charge/discharge cycles for blocks that don't need resetting, thereby reducing the overall time required while still effectively eliminating memory effects where present.
Data Source
AI summary
A first power storage unit is a battery assembly, and is divided into battery blocks of n (n is a natural number) in number each formed of several electric cells connected together in series. When a state allowing charging with an external power supply is attained, the ECU executes an operation of resetting an SOC of a first power storage unit. The ECU controls a corresponding converter to discharge the first power storage unit with a constant current, and sets reset values for battery blocks of n in number based on battery voltages and battery temperatures exhibited when any one of the battery voltages of the n battery blocks becomes lower than a reset voltage. The ECU resets the SOCs of the battery blocks of the first power storage unit to the respective reset values thus set.