Lead-Acid Battery State of Charge Estimation via Predictive Modeling

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Solution Overview

Problem

Current methods for managing lead-acid batteries in standby mode are energetically expensive and reduce battery life, and accurately determining the state of charge is challenging, especially for sealed batteries where internal components are inaccessible.

Innovation Solution

A predictive model governed by differential equations estimates the state of charge of lead-acid batteries by determining the evolution of electric potential and density of the electrolyte, allowing for maintenance charging only when necessary and optimizing temperature regulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the battery is maintained in a fully charged state through continuous voltage-controlled overcharge, then the battery remains ready for power outages, but energy consumption increases and battery life is reduced

Engineering Contradiction:

Improvebattery readinessVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by using predictive modeling to forecast the battery's state of charge at future time points, allowing maintenance charging to be scheduled only when necessary based on predicted depletion, rather than continuously charging to maintain readiness

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by continuously monitoring actual battery parameters (voltage, temperature, density) and using this information to validate and refine the predictive model, enabling dynamic adjustment of charging schedules based on actual battery behavior

Inventive Principle:

Principle #23Feedback

2Reliability

If the battery is maintained in a fully charged state through continuous voltage-controlled overcharge, then the battery remains ready for power outages, but battery life is reduced

Engineering Contradiction:

Improvebattery readinessVSAvoidbattery life

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent transitions from continuous charging to periodic charging by calculating optimal charging intervals based on the predictive model's forecast of when the battery will deplete to critical levels, charging only at these predicted moments rather than continuously

Inventive Principle:

Principle #19Periodic action

3Ease of operation

If simple voltage measurement between battery terminals is used, then the measurement is easy to perform, but the state of charge cannot be accurately determined

Engineering Contradiction:

Improvemeasurement simplicityVSAvoidstate of charge determination

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary predictive model that processes multiple battery parameters (voltage, temperature, density) and time information to calculate the state of charge, serving as a mediator between simple measurements and accurate state determination

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct mechanical/electrical measurement of electrode potentials with a computational model that uses easily measurable parameters (terminal voltage, temperature, density) and mathematical relationships to infer the state of charge

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The method accurately estimates the state of charge, reducing unnecessary maintenance charging and extending battery life, while enabling better temperature control and anticipation of recharging needs.

Implementation Method 1

determining the evolution of the electric potential of each electrode, and optionally the density of the electrolyte

Methodology Applied

Scientific EffectElectrochemical potential evolution:

Implementation Method 2

Self-discharge can be expressed by the following reaction at the negative electrode and the following reaction at the positive electrode

Methodology Applied

Scientific EffectElectrochemical reactions:

Implementation Method 3

self-discharge, which is the cause of battery wear

Methodology Applied

Scientific EffectSelf-discharge:

Implementation Method 4

the self-discharge of a battery is accelerated by thermal agitation

Methodology Applied

Scientific EffectThermal agitation:

Data Source

PatentEP4198535A1Method for estimating the state of charge of a lead-acid battery in a self-discharge situation

Publication Date: 2023.06.21 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

Figure 1a~1b
Figure 2~3a
Figure 3b~4

AI summary

Method for estimating the state of charge of a lead-acid battery in a self-discharge situation. Method for estimating the state of charge of an electrically rechargeable lead-acid battery at rest, the battery comprising at least one electrochemical cell comprising an acid electrolyte, at least one negative lead electrode and at least one positive lead dioxide electrode immersed in the electrolyte, the method comprising the implementation of a predictive model governed by at least several differential equations to estimate the state of charge.