Battery SoC Estimation Using Electrode Ion-Concentration Profiles
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Solution Overview
Problem
Existing battery management systems (BMS) struggle to accurately estimate the state of charge (SoC) of lithium iron phosphate (LFP) batteries due to flat voltage profiles and unreliable methods, leading to inconsistent performance and increased computational load.
Innovation Solution
A method and apparatus that determine the equilibrium and transient ion-concentration profiles of battery electrode particles to calculate SoC by correlating initial ion-concentration values, particle size, and diffusivity, using a battery management system (BMS) to generate accurate SoC values during rest periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If typical BMS uses voltage mapping to estimate SoC, then the estimation process is simple, but the SoC estimation accuracy is low due to flat voltage profiles
Solution Approach 1:
The patent transforms the estimation approach by changing from voltage-based parameters to ion-concentration-based parameters. Instead of mapping voltage to SoC, the system calculates transient ion-concentration profiles within electrode particles and correlates these with equilibrium ion-concentration values to determine accurate SoC, especially effective for LFP batteries with flat voltage profiles
Solution Approach 2:
The patent replaces the simple voltage measurement system with a physics-based electrochemical model that calculates ion diffusion and concentration distributions. This substitution uses fundamental electrochemical principles (Fick's laws of diffusion) to model ion transport within electrode particles, providing accurate SoC estimation where voltage-based methods fail
2Reliability
If multiple SoC values map to the same voltage value, then the voltage table is compact, but the reliability of SoC estimation deteriorates
Solution Approach 1:
The patent applies local quality by examining ion-concentration distributions at different locations within electrode particles. Instead of relying on a single bulk voltage value that loses information, the system calculates and compares ion-concentration profiles at multiple radial positions within particles, preserving local concentration information that correlates uniquely with SoC
Solution Approach 2:
The patent adds a spatial dimension to the estimation problem by considering ion-concentration distributions across different radial positions within electrode particles. This transforms the problem from a single-value voltage measurement to a multi-point concentration profile analysis, creating a higher-dimensional state space where SoC can be uniquely determined
3Measurement precision
If LFP battery has long rest period, then the battery performance can be maintained, but the opportunity to accurately estimate SoC during operation is reduced
Solution Approach 1:
The patent performs preliminary action by calculating the transient ion-concentration profile during the rest period itself, rather than waiting for operation to begin. The system uses the rest period to establish the transient profile from the initial non-uniform concentration distribution, then correlates this with the equilibrium value to determine SoC before the battery is put into service
Solution Approach 2:
The patent ensures continuous useful action by making the SoC estimation process itself productive during the rest period. Instead of the rest period being idle time, the system continuously monitors and calculates ion-concentration evolution, transforming the rest period into an active estimation opportunity that improves overall system efficiency
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
Enhances SoC estimation accuracy and reduces computational burden by leveraging ion-concentration profiles, improving battery performance and reliability in devices like electric vehicles.
Implementation Method 1
determining an equilibrium ion-concentration value of a battery by correlating initial ion-concentration values, at a beginning of a rest period of the battery, over a plurality of surfaces of a battery electrode particle
Data Source
AI summary
A processor-implemented method including determining an equilibrium ion-concentration value of a battery by correlating initial ion-concentration values, at a beginning of a rest period of the battery, over a plurality of surfaces of a battery electrode particle of the battery, and a size of the battery electrode particle, generating, at an instance of interest, a transient ion-concentration profile over the plurality of surfaces, based on a configuration of the battery and the initial ion-concentration values, and determining a state of charge (SoC) of the battery at the instance of interest by correlating the equilibrium ion-concentration value and the transient ion-concentration profile.