Battery Charge Acceptance Determination via Compartment Model
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Solution Overview
Problem
Existing methods for determining charge acceptance in rechargeable batteries, particularly in motor vehicles, are inadequate as they do not accurately account for various parameters associated with prior charging and discharging phases, leading to inefficient energy recovery during braking and charging operations.
Innovation Solution
A computational model divides the battery into compartments with prescribed charge capacitances and resistances, allowing for the estimation of instantaneous and average charge acceptance, which is improved by considering the state of charge, health, voltage, and temperature, and different resistance values for charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a simple time integration method is used to determine state of charge, then the calculation is computationally simple, but the determination of charge acceptance is inaccurate because it does not account for prior charging and discharging phases
Solution Approach 1:
The battery is divided into multiple compartments (typically 3-5), each representing a portion of the total charge capacity. Each compartment has its own state of charge and resistance characteristics. This segmentation allows the model to capture different charging/discharging phases at different depths within the battery, improving charge acceptance accuracy without requiring an overly complex full-physics model.
Solution Approach 2:
The model uses dynamic parameter changes by adjusting the state of charge and resistance values of each compartment based on prior charging and discharging phases. The resistance of each compartment varies depending on its charge level and history, allowing the model to adapt to different operating conditions and accurately determine charge acceptance without complex computational overhead.
2Measurement precision
If multiple compartments are used to improve charge acceptance accuracy, then the measurement precision improves, but the computational complexity increases
Solution Approach 1:
The model uses a limited number of compartments (typically 3-5) rather than dividing the battery into every possible segment. This partial action provides sufficient accuracy for determining charge acceptance during braking energy recovery, while avoiding the excessive computational complexity that would result from using too many compartments. The model strikes an optimal balance between accuracy and computational efficiency.
Solution Approach 2:
The compartment model dynamically adjusts the state of charge and resistance of each compartment based on real-time operating conditions. During brief braking events, the model quickly computes charge acceptance by considering only the relevant compartments affected by the recent discharge, rather than recalculating the entire battery state, thus maintaining computational efficiency while improving accuracy.
3Reliability
If the battery is divided into many compartments to capture all charging phases, then the charge acceptance determination becomes accurate, but the device complexity and computational burden increase significantly
Solution Approach 1:
The battery is divided into a moderate number of compartments (3-5) that represent different depth-of-charge regions. Each compartment tracks its own state of charge and resistance, allowing the model to capture the effects of prior charging and discharging phases. This segmentation provides reliable charge acceptance estimation without creating an overly complex model structure that would be difficult to implement in real-time control systems.
Data Source
AI summary
In the case of a method for determining a charge acceptance ICA of a rechargeable battery, the battery is computationally split up into a predetermined number n of compartments i having a respective maximum charge capacitance Ci, which are connected in parallel via resistances Ri, and the charge acceptance ICA of the battery is determined on the basis of the charge capacitance C1 and the resistance R1 of the compartment adjacent to the battery terminals. The invention also relates to a method for charging a rechargeable battery.