Open Circuit Voltage Estimation Using Active Material Amount
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Solution Overview
Problem
Existing methods for accurately estimating open circuit voltage in secondary cells require specific charge/discharge cycles and alternating current application, which is not typical in normal usage, making it difficult to grasp the relationship between charged capacity and open circuit voltage over time.
Innovation Solution
A cell state calculation apparatus that includes a voltage detector, current detector, database, active material amount calculation unit, and open circuit voltage calculation unit, which estimates active material amounts and calculates the relationship between open circuit voltage and charged capacity using current/voltage curves, allowing for accurate estimation without specific charge/discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alternating current is applied and impedance measurement is carried out to accurately estimate open circuit voltage, then measurement precision is improved, but device complexity and operation difficulty increase
Solution Approach 1:
The patent extracts the essential information needed for open circuit voltage estimation from normal charge/discharge voltage and current data, removing the need for separate impedance measurement systems. By utilizing voltage and current curves obtained during regular operation, the method eliminates complex impedance measurement apparatus while maintaining estimation accuracy through calculation based on extracted charge/discharge characteristics
Solution Approach 2:
The system uses the voltage and current data already generated during normal cell operation to estimate open circuit voltage, without requiring external alternating current signals or separate measurement equipment. The normal charge/discharge process itself provides the necessary data, making the system self-sufficient and avoiding additional device complexity
2Measurement precision
If specific charge/discharge cycles are performed to grasp the relationship between charged capacity and open circuit voltage, then measurement precision is improved, but productivity and ease of operation deteriorate
Solution Approach 1:
The patent enables continuous estimation of open circuit voltage and charged capacity relationship during normal cell operation without interrupting service for specific test cycles. By processing voltage and current data in real-time during regular charge/discharge use, the system maintains continuous monitoring capability while the cell remains in productive service, eliminating downtime associated with dedicated measurement cycles
Solution Approach 2:
The method uses partial information from normal operation (voltage and current curves during regular charge/discharge) sufficient for accurate estimation, without requiring complete or excessive test procedures. This partial action approach achieves the necessary measurement precision using only the data naturally generated during normal cell usage, avoiding the need for exhaustive specific charge/discharge cycles
3Measurement precision
If impedance measurement is carried out to obtain accurate cell state data, then measurement precision is improved, but ease of operation worsens
Solution Approach 1:
The system automatically processes voltage and current data during normal operation to estimate open circuit voltage and charged capacity without requiring user-initiated impedance measurement procedures. The cell state monitoring is self-executing using data from regular use, eliminating the need for users to perform complex impedance measurement operations
Solution Approach 2:
The patent extracts cell state information directly from normal operational data, removing the need for users to perform separate impedance measurement operations. By calculating open circuit voltage from voltage and current curves obtained during regular use, the system eliminates the operational complexity of impedance measurements while maintaining measurement precision
Data Source
AI summary
According to an embodiment, a cell state calculation apparatus includes the following elements. The database stores a function indicating a relationship between a voltage and a charged capacity of an active material. The active material amount calculation unit calculates an amount of an active material of the secondary cell by referring to the database and by using the voltage detected by the voltage detector and the current detected by the current detector while the secondary cell is charged or discharged. The open circuit voltage calculation unit calculates a function indicating a relationship between an open circuit voltage and a charged capacity of the secondary cell by referring to the database and by using the calculated amount of the active material.