Battery Capacity Estimation Using Dynamic SOC Charge Limits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The precision of estimating the full charge capacity of power storage devices is reduced when the devices are not charged to the fully charged state, as the state of charge (SOC) increase (ΔSOC) becomes smaller, leading to potential degradation of the devices.
Innovation Solution
An estimation system that includes a power storage device, a charge device, and one or more processors. The processors execute a restricted charge process to limit the SOC of the power storage device to an upper limit set below the full charge state, and an estimation process to calculate the full charge capacity by dividing the amount of charge by ΔSOC. When a predetermined condition is met, the upper limit SOC is raised, increasing ΔSOC and improving estimation precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the power storage device is charged to the fully charged state to increase ΔSOC and improve estimation precision, then the precision in estimating full charge capacity is improved, but the power storage device degradation is promoted
Solution Approach 1:
The upper limit SOC is made dynamic rather than fixed. The control device adjusts the upper limit SOC based on charge cycle history: it sets the upper limit SOC to a first value (lower than full charge) during normal operation to suppress degradation, and raises it to a second value (higher, potentially full charge) when a predetermined condition is met to improve estimation precision. This dynamic adjustment resolves the contradiction by adapting the charge limit to operational needs.
Solution Approach 2:
The invention changes the parameter of upper limit SOC based on charge cycle accumulation. When the number of charge cycles reaches or exceeds a predetermined threshold, the upper limit SOC is increased from the first value to the second value, enabling larger ΔSOC for improved estimation precision. This parameter change strategy allows the system to optimize estimation accuracy at specific intervals while maintaining protective charging limits during normal operation.
2Reliability
If the upper limit SOC is kept low to suppress power storage device degradation, then the device reliability is improved, but the ΔSOC becomes small and estimation precision deteriorates
Solution Approach 1:
The upper limit SOC transitions from a static protective value to a dynamic value that responds to charge cycle accumulation. The control device monitors the number of charge cycles and automatically adjusts the upper limit SOC from the first protective value to the second higher value when the predetermined condition is met, thereby improving estimation precision without requiring continuous low-level charging that would limit ΔSOC.
Solution Approach 2:
The system performs preliminary protective charging with a lower upper limit SOC during normal operation to suppress degradation. This preliminary action prepares the device for subsequent estimation operations, where the upper limit SOC can be raised to enable larger ΔSOC and improved precision. The predetermined condition acts as a trigger that switches from protective mode to estimation-optimized mode.
Data Source
AI summary
An estimation system includes a power storage device and one or more processors. The one or more processors are configured to execute a charge process of controlling a charge device so as to charge the power storage device, and an estimation process of estimating a full charge capacity of the power storage device. The one or more processors are configured to execute the charge process with an upper limit state of charge of the power storage device set to a value that is more than a first upper limit state of charge when a predetermined condition is met, the first upper limit state of charge being the upper limit state of charge at the time when the predetermined condition is not met.