In-Vehicle Battery State Estimation via Polarization Segmentation
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Solution Overview
Problem
Conventional methods for detecting the internal electric state of in-vehicle secondary batteries are inaccurate due to irregularities in the polarization state and neglect the influence of charge efficiency, leading to low accuracy in estimating charge capacity and time during constant-voltage charging.
Innovation Solution
An apparatus and method that detect and regulate the charge current of in-vehicle secondary batteries using a current detector, sampling means, and calculation means to estimate the internal electric state by calculating a polarization-relevant quantity and correcting the charge current function, allowing for accurate estimation of the charge current and state of charge (SOC) without being affected by polarization irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional charge current approximation function is used for estimation, then the estimation process is simple, but the accuracy of charge capacity and time estimation becomes low due to polarization irregularities
Solution Approach 1:
The patent divides the charge current estimation into two segments: an initial period where polarization effects are significant and a subsequent period where steady-state characteristics dominate. By separating these periods and applying different estimation approaches, the method achieves higher accuracy without excessive complexity.
Solution Approach 2:
The patent performs preliminary calculation of polarization-relevant quantities during the initial charge period before using the charge current approximation function. This preliminary action removes polarization irregularities from subsequent estimations, improving accuracy while maintaining computational efficiency.
2Device complexity
If conventional charge current approximation function is used, then the estimation method is straightforward, but the accuracy in end period of charge action is reduced due to neglecting charge efficiency differences
Solution Approach 1:
The patent introduces charge efficiency as a variable parameter that changes during the charge process. By incorporating charge efficiency differences into the estimation model, the method accurately captures end-period characteristics while maintaining overall method simplicity through systematic parameter management.
3Device complexity
If charge current approximation function is deviated from actual waveform due to polarization, then calculation is simpler, but the timing estimation becomes inaccurate
Solution Approach 1:
The patent uses feedback from measured charge current data to calculate polarization-relevant quantities and adjust the approximation function. This feedback mechanism corrects deviations between the approximation function and actual waveform, improving timing estimation accuracy while keeping calculations manageable through iterative refinement.
Data Source
AI summary
In a proposed apparatus and method, constant-voltage charge is performed with an in-vehicle secondary battery immediately after start of a vehicle or during running of the vehicle. A quantity relevant to polarization caused in the battery immediately after start of the constant-voltage charge is calculated using data of the charge current. It is determined whether or not a change rate of the calculated polarization-relevant quantity is less than a given threshold. When the change rate is less than the given threshold, a plurality of data of the charge current sampled and held during a predetermined period of time are acquired. A value of the charge current to be accumulated until the charge current reaches a given final value is calculated using the plurality of data of the charge current. The internal electric state of the battery is estimated based on the accumulated value of the charge current.