Traction Battery SOC Correction for Low-Current Charging Accuracy

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Solution Overview

Problem

Existing methods for estimating the state of charge (SOC) of a traction battery in electric vehicles are less accurate at lower current flow rates due to signal noise, leading to potential overcharging or undercharging.

Innovation Solution

A method that retrieves SOC correction values from memory, accumulated using different SOC estimation algorithms, to correct the present SOC estimate and cease charging based on the corrected SOC, thereby improving accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If Coulomb counting is used to estimate SOC, then the method is simple and widely applicable, but the accuracy deteriorates at lower current flow rates due to signal noise

Engineering Contradiction:

Improvesimplicity of SOC estimation methodVSAvoidaccuracy of SOC estimation

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent combines multiple SOC estimation algorithms (Coulomb counting, OCV-based, and instantaneous operating conditions-based algorithms) into a unified system that selects and applies the most appropriate algorithm based on current operating conditions, thereby maintaining simplicity while improving accuracy across different scenarios

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The system dynamically selects among multiple SOC estimation algorithms based on real-time operating conditions such as current flow rate, battery state, and signal quality, transitioning between algorithms to maintain optimal accuracy without requiring a fixed, overly complex estimation approach

Inventive Principle:

Principle #15Dynamics

2Device complexity

If a single SOC estimation algorithm is used, then the system complexity is low, but the reliability of SOC estimation under varying operating conditions deteriorates

Engineering Contradiction:

Improvenumber of SOC estimation algorithmsVSAvoidaccuracy of SOC estimation under varying conditions

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements a multi-functional SOC estimation system where a single control mechanism can select and execute different estimation algorithms (Coulomb counting, OCV-based, instantaneous conditions-based) depending on the operating scenario, making the system universally applicable across diverse battery operating conditions without requiring separate dedicated systems for each condition

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If Coulomb counting is used for SOC estimation, then the implementation is straightforward, but the SOC accuracy deteriorates leading to overcharging or undercharging

Engineering Contradiction:

Improveease of SOC estimation implementationVSAvoidprecision of charging control

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The system continuously monitors actual battery parameters (voltage, current, temperature, terminal voltage) and uses this feedback to select and adjust the SOC estimation algorithm in real-time, correcting deviations from accurate SOC values and preventing overcharging or undercharging while maintaining straightforward implementation through automated control

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enhances the accuracy of SOC estimation during conditions where Coulomb counting is less reliable, compensates for vehicle and battery operating conditions, and ensures the traction battery is charged to a requested SOC level more accurately.

Implementation Method 1

an algorithm that is based on battery open circuit voltage (OCV)

Methodology Applied

Scientific EffectOpen circuit voltage: Ohm's Law

Data Source

PatentUS20250128630A1Charging a battery to a corrected state of charge

Publication Date: 2025.04.24 FORD GLOBAL TECH LLC

AI summary

Systems and methods for estimating a state of charge of a traction battery are described. In one example, a state of charge estimate may be corrected via one of three different state of charge estimates. The one of three different state of charge estimates may be selected based on state of charge correction values or traction battery operating conditions.