Battery Capacity Estimation Using Rest Period Validation

Solution Overview

Problem

Existing algorithms for estimating battery capacity in electric vehicles are less effective due to difficulties in validating inputs and accurately determining battery state-of-charge, especially as battery cells degrade differently over time.

Innovation Solution

A method that estimates battery capacity by using the change in battery state-of-charge and integrated current amp-hours after the battery has rested for a predetermined period based on temperature, involving data collection, validation of battery data, and calculation of capacity through specific logic operations and look-up tables.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If battery capacity is estimated using conventional algorithms, then capacity calculation is performed, but the estimation reliability is low due to invalid inputs and inability to detect battery equilibrium

Engineering Contradiction:

Improvebattery capacity estimation reliabilityVSAvoidbattery capacity measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The system performs preliminary validation of battery inputs (voltage, current, temperature) before capacity calculation to ensure data quality. It also determines whether the battery has reached equilibrium state before proceeding with estimation, preventing inaccurate calculations from invalid or unstable measurements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors battery parameters and uses feedback loops to validate inputs and assess battery equilibrium status. This feedback mechanism ensures that capacity estimation is only performed when reliable conditions are met, improving both reliability and precision of the measurement.

Inventive Principle:

Principle #23Feedback

2Productivity

If battery capacity estimation is performed without validating inputs, then calculation speed is maintained, but the accuracy of state-of-charge tracking deteriorates

Engineering Contradiction:

Improvecapacity calculation speedVSAvoidstate-of-charge tracking accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system performs preliminary validation of battery inputs (voltage, current, temperature) before capacity calculation to ensure data quality. This upfront checking prevents inaccurate calculations while maintaining efficient processing of valid data.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors battery parameters and uses feedback loops to validate inputs and assess battery equilibrium status. This feedback mechanism ensures that capacity estimation is only performed when reliable conditions are met, improving both reliability and precision of the measurement.

Inventive Principle:

Principle #23Feedback

3Device complexity

If battery capacity is estimated without considering battery rest time and temperature, then calculation complexity is reduced, but the reliability of end-of-life assessment deteriorates

Engineering Contradiction:

Improvecalculation algorithm complexityVSAvoidend-of-life assessment reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The system performs preliminary validation of battery inputs (voltage, current, temperature) before capacity calculation to ensure data quality. This upfront checking prevents inaccurate calculations while maintaining efficient processing of valid data.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors battery parameters and uses feedback loops to validate inputs and assess battery equilibrium status. This feedback mechanism ensures that capacity estimation is only performed when reliable conditions are met, improving both reliability and precision of the measurement.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8525519B2Algorithm for determining the capacity of a battery while in service

Publication Date: 2013.09.03 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method for estimating the capacity of a vehicle battery while in service. The method includes providing a previous battery state-of-charge, battery temperature and integrated battery current amp-hours, and determining that battery contactors have been closed after they have been opened and disconnected from a load. The method determines if the battery has been at rest for a long enough period of time while the contactors were open, where the battery rest time is based on battery temperature, and determines an initial battery voltage from a last time step when the battery contactors were closed prior to the contactors being open during the battery rest time. The method determines a present battery state-of-charge from the initial battery voltage and the battery temperature and calculates the battery capacity based on the battery integrated current amp-hours divided by the difference between the present battery state-of-charge and the previous battery state-of-charge.