Battery Pack Full Charge Capacity Calculation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for calculating the full charge capacity of secondary batteries in battery packs are inaccurate due to offset errors in current sensors, which accumulate and increase the error in integrated current amounts during charging and discharging processes.
Innovation Solution
A battery pack configuration that includes a voltage detector, state of charge calculator, current detector, differential state of charge calculator, integrated current amount calculator, and charging-and-discharging control section, which restricts either charging or discharging based on the state of charge and required differential state of charge to accurately calculate the full charge capacity by minimizing offset errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional current sensor integration method is used to calculate full charge capacity, then the calculation can be performed continuously during charging and discharging, but the offset errors accumulate and increase the error in integrated current amounts
Solution Approach 1:
The patent implements periodic action by performing full charge capacity calculations only during specific periods when the battery is in a restricted state (either charging restricted or discharging restricted), rather than continuously. This periodic approach prevents offset error accumulation while maintaining calculation capability, as the integration period is limited to when only one direction of current flow occurs.
Solution Approach 2:
The patent applies preliminary action by setting the battery to a restricted state before performing the full charge capacity calculation. The charging-and-discharging control section restricts either charging or discharging in advance to create optimal conditions for accurate calculation, ensuring that the integration of current occurs during a controlled period with minimal error accumulation.
2Ease of operation
If the battery undergoes both charging and discharging during the integration period, then the calculation can be performed in normal operation, but the offset errors in the current sensor accumulate and reduce measurement accuracy
Solution Approach 1:
The patent extracts the problematic element (simultaneous charging and discharging) from the calculation period. By separating the charging and discharging operations and restricting one during the integration period, the patent eliminates the source of offset error accumulation while maintaining ease of operation through automated control.
Solution Approach 2:
The patent segments the battery operation into distinct periods: restricted periods (for accurate calculation) and normal operation periods. This segmentation allows the system to maintain normal operation compatibility while ensuring accurate measurements during designated calculation windows, effectively separating the conflicting requirements.
3Measurement precision
If the integration period is extended to capture more charge-discharge cycles, then the statistical accuracy improves, but the offset errors accumulate over a longer period
Solution Approach 1:
The patent changes the operational parameters during the integration period by restricting either charging or discharging. This parameter change allows for sufficient integration time to achieve statistical accuracy without the confounding factor of bidirectional current flow, effectively decoupling the relationship between integration duration and error accumulation.
Data Source
AI summary
A battery pack includes a secondary battery, a state of charge calculator, an integrated current amount calculator, a differential state of charge calculator, a full charge capacity calculator, and a charging-and-discharging control section. The differential state of charge calculator calculates a differential state of charge between a first state of charge at a first detection timing and a second state of charge at a second detection timing. The integrated current amount calculator calculates an integrated amount of a current flowing to the secondary battery in a subject period from the first detection timing to the second detection timing. The full charge capacity calculator calculates a full charge capacity of the secondary battery based on the differential state of charge and the integrated current amount. The charging-and-discharging control section is configured to restrict one of the charging and the discharging of the secondary battery during the subject period.