Battery State of Charge Estimation Using Voltage and Current Correction

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Solution Overview

Problem

Existing battery life measurement techniques face inaccuracies due to errors in estimating open circuit voltage and current integration, leading to unreliable state of charge calculations, which can result in over-discharge and reduced battery lifespan, especially in critical applications like electric vehicles.

Innovation Solution

A device comprising a first estimator for open circuit voltage-based state of charge estimation, a second estimator for current-based estimation, and a correction unit that adjusts the reliability of these estimates using a graph-based correspondence to minimize errors, ensuring accurate battery life measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If open circuit voltage estimation is used to determine state of charge, then measurement simplicity is improved, but estimation accuracy deteriorates due to errors in open circuit voltage measurement

Engineering Contradiction:

Improvemeasurement simplicityVSAvoidstate of charge estimation accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary correction mechanism that mediates between the simple open circuit voltage estimation and the actual state of charge. A correction value is calculated based on the difference between open circuit voltage estimation and current integration estimation, then applied to correct the state of charge determination, thereby improving accuracy while maintaining operational simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct reliance on open circuit voltage measurement with a corrected estimation approach. Instead of using open circuit voltage directly, the system substitutes it with a corrected state of charge value that compensates for measurement errors, thereby improving precision without significantly increasing operational complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If current integration method is used to estimate state of charge, then short-term accuracy is improved, but long-term reliability deteriorates due to cumulative errors

Engineering Contradiction:

Improveshort-term state of charge accuracyVSAvoidlong-term state of charge reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the open circuit voltage estimation serves as a reference to correct cumulative errors in current integration. The correction value is generated by comparing the current integration result with the open circuit voltage-based estimation, and this correction is fed back to adjust the state of charge determination, thereby maintaining long-term reliability

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies beforehand cushioning by pre-calculating correction values based on open circuit voltage characteristics before cumulative errors significantly impact long-term reliability. The correction mechanism is prepared in advance to compensate for expected drift in current integration over time

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Device complexity

If single estimation method is used, then device complexity is reduced, but measurement accuracy deteriorates

Engineering Contradiction:

Improveestimation system complexityVSAvoidbattery life measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent merges two estimation methods (open circuit voltage estimation and current integration estimation) into a unified corrected estimation approach. By combining the simplicity of voltage-based estimation with the accuracy of current integration, and applying a correction mechanism, the system achieves high measurement accuracy without proportionally increasing device complexity

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS9551757B2Measuring devices of remaining battery life and measuring methods thereof

Publication Date: 2017.01.24 SAMSUNG ELECTRONICS CO LTD

AI summary

A remaining battery life measuring device may include a first estimator configured to estimate a state of charging of a battery using an open circuit voltage of the battery; a second estimator configured to estimate the state of charging of the battery using charge, discharge, or charge and discharge currents of the battery; a correction unit configured to generate a correction value on the state of charging estimated by the second estimator, based on the state of charging estimated by the first estimator or an output state of charging; and/or a state of charging (SOC) processing unit configured to calculate the output state of charging using the state of charging estimated by the second estimator and an accumulated correction value. The accumulated correction value may be generated based on the correction value.