Battery Heat Flow Sensing for Accurate SOC and SOH Estimation
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Solution Overview
Problem
Existing methods for estimating the state of charge (SOC) or state of health (SOH) of battery cells, particularly those with small voltage changes relative to capacity variations, suffer from reduced accuracy.
Innovation Solution
A battery unit design that incorporates battery heat flow detectors and reference heat flow detectors, with the latter positioned in areas of minimal temperature fluctuation and high heat capacity, allowing for accurate estimation of SOC and SOH by subtracting reference heat flows from detected heat flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage-based estimation is used for battery cells with small voltage changes (e.g., graphite negative electrode), then the estimation accuracy of SOC/SOH deteriorates
Solution Approach 1:
The patent changes the measurement parameter from voltage to heat flow. By detecting heat flow during phase transitions in the active material, the system can accurately estimate SOC/SOH even in battery cells where voltage changes are minimal, thus resolving the contradiction between measurement precision and adaptability to different battery types.
Solution Approach 2:
The patent replaces the electrical measurement system (voltage detection) with a thermal measurement system (heat flow detection). This substitution enables accurate state estimation through thermal phenomena during phase transitions, making the system adaptable to battery types where electrical voltage measurement is ineffective.
2Measurement precision
If heat flow detection is used to estimate battery cell state, then estimation accuracy improves, but noise from other heat flows in the battery unit reduces measurement precision
Solution Approach 1:
The patent segments the heat flow measurement into two components: battery cell heat flow (detected by battery heat flow detector) and unit-level ambient heat flow (detected by reference heat flow detector). By separating these measurements and subtracting the reference from the battery measurement, the system isolates the target signal from noise, improving measurement precision.
Solution Approach 2:
The reference heat flow detector acts as an intermediary that measures the ambient thermal environment. This intermediary measurement allows the system to compensate for external thermal influences by subtracting the reference heat flow from the battery heat flow measurement, thereby eliminating noise effects.
3Measurement precision
If reference heat flow detector is placed near battery cells for accurate measurement, then heat flow detection precision improves, but temperature fluctuation and low heat capacity increase measurement error
Solution Approach 1:
The patent applies different quality requirements to different measurement locations. The battery heat flow detector is placed near the battery cell to capture local heat flow, while the reference heat flow detector is placed in a thermally stable location with large heat capacity to measure ambient conditions. This differentiated placement optimizes each detector's performance for its specific function.
Solution Approach 2:
The reference heat flow detector serves as a thermal intermediary that captures the ambient thermal environment. By placing it in a location with large heat capacity and stable temperature, it provides a stable reference measurement that can be subtracted from the battery measurement, isolating the battery's heat flow signal from environmental noise.
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 and SOH estimation by isolating the heat flow from noise effects, maintaining precision even in battery cells with minimal voltage changes.
Implementation Method 1
a change in voltage is small with respect to a change in capacity, such as a lithium-ion battery (secondary battery) including graphite as a material forming the negative electrode. In the case of a battery unit including battery cells of this type, if a state of the battery cells (e.g., the SOC or the SOH) is estimated based on a voltage of the battery cells, the accuracy of the estimation is expected to be reduced.
Implementation Method 2
The present inventor(s) has found that there is a correlation between a state of a battery cell (e.g., the SOC or the SOH) and a heat flow of the battery cell that is generated when a phase transition occurs in an active material contained in an electrode material.
Implementation Method 3
The at least one reference heat flow detector is disposed in the battery unit at a location where temperature fluctuation is small and heat capacity is large.
Implementation Method 4
a battery state estimator that estimates a state of the at least one battery cell, based on a heat flow of the at least one battery cell given by subtracting the reference heat flow detected by the at least one reference heat flow detector from the heat flow detected by the at least one battery heat flow detector
Data Source
AI summary
A battery unit includes at least one battery module that includes at least one battery cell, at least one battery heat flow detector that detects a heat flow of the at least one battery cell and the battery unit, at least one reference heat flow detector that detects a heat flow of the battery unit as a reference heat flow, and a battery state estimator that estimates a state of the at least one battery cell, based on a heat flow of the at least one battery cell given by subtracting the reference heat flow detected by the at least one reference heat flow detector from the heat flow detected by the at least one battery heat flow detector. The at least one reference heat flow detector is disposed in the battery unit at a location where temperature fluctuation is small and heat capacity is large.