Secondary Battery Step Charging with Polarization-Based Current Control
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Solution Overview
Problem
Conventional step charging methods for secondary batteries do not effectively adapt the charging current based on the state of charge (SOC) and polarization voltage, leading to inefficient charging times and potential lithium precipitation.
Innovation Solution
An apparatus and method that utilize a voltage, current, and temperature measuring unit, along with a charging control unit to estimate SOC and polarization voltage, adjust the charging current by applying a correction factor, and determine the optimal charging current based on predefined correlations, ensuring adaptive charging control before the charging process begins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the charging current is increased to shorten charging time, then the charging speed improves, but lithium precipitation may occur causing safety issues
Solution Approach 1:
The patent applies preliminary action by estimating the polarization voltage before charging begins and using this estimation to determine an appropriate charging current. The controller predicts the polarization state based on pre-stored voltage-time curves corresponding to different SOC regions, and adjusts the charging current in advance to prevent lithium precipitation while maximizing charging speed.
Solution Approach 2:
The patent changes the parameter of charging current based on the estimated polarization voltage and SOC region. By dynamically adjusting the charging current parameter according to the battery's polarization state and charge level, the system optimizes charging speed while preventing harmful lithium precipitation.
2Object-affected harmful factors
If the charging current is reduced to prevent lithium precipitation, then safety improves, but charging time increases
Solution Approach 1:
The patent dynamically changes the charging current parameter based on real-time estimation of polarization voltage and SOC region. This allows the system to maintain high charging current when safe (shortening charging time) while reducing current only when necessary to prevent lithium precipitation.
Solution Approach 2:
The system uses feedback by continuously monitoring the battery state, estimating polarization voltage based on pre-stored curves, and adjusting the charging current accordingly. This closed-loop control prevents lithium precipitation while minimizing charging time extension.
3Productivity
If conventional step charging is used without polarization voltage consideration, then the charging control is simple, but charging efficiency is reduced
Solution Approach 1:
The patent performs preliminary estimation of polarization voltage before charging begins and pre-divides the charging process into SOC regions with corresponding voltage-time curves. This preliminary preparation enables more efficient charging without significantly increasing control complexity during the actual charging process.
Solution Approach 2:
The patent introduces an intermediary estimation mechanism that uses pre-stored voltage-time curves as a mediator between the simple charging control and the complex battery chemistry. This intermediary layer provides accurate polarization voltage estimation without requiring complex real-time calculations.
Data Source
AI summary
Disclosed is an apparatus and method for controlling step charging of a secondary battery. A charging control unit determines a SOC, an OCV and a polarization voltage of the secondary battery, determines an OCV deviation corresponding to a difference between the OCV and a predefined minimum OCV value, determines a correction factor corresponding to the polarization voltage and the OCV deviation, determines a look-up SOC by correcting the SOC according to the correction factor, determines the magnitude of a charging current corresponding to the look-up SOC, and provides the determined charging current to a charging device.