Battery Usable Charge Capacity Estimation with Dynamic Error Reserves
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Solution Overview
Problem
Current methods fail to accurately predict and estimate the usable charge capacity of electrical energy stores in vehicles, leading to safety and reliability concerns due to uncertainties in state-of-health, state-of-charge, and power supply capability, especially in aged or degraded batteries.
Innovation Solution
A method that determines nominal and maximum estimation errors for new and degraded energy stores, using interpolation techniques such as linear, sectional linear, regression curves, and neural networks to estimate usable charge capacity with dynamic estimation reserves, ensuring accurate and adaptable range estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer margin or estimation reserve is required for safety and reliability, then the reliability is improved, but the loss of information about actual state-of-charge increases
Solution Approach 1:
The estimation reserve is made dynamic rather than static. The method adapts the size of the estimation reserve based on the determined maximum estimation error and degradation state of the energy store. For new energy stores with lower estimation errors, a smaller reserve is applied, while for degraded stores with higher estimation errors, a larger reserve is applied. This dynamic adjustment resolves the contradiction by optimizing the balance between reliability and information loss in different operational contexts.
Solution Approach 2:
The method changes the parameter of estimation reserve size based on degradation state and estimation error characteristics. By determining maximum estimation errors for new and degraded energy stores and using these to dynamically set appropriate reserve levels, the system optimizes the trade-off between safety margins and accurate range information presentation to the user.
2Productivity
If the maximum achievable state-of-charge of a degraded energy store is used, then the range exploitation is improved, but the measurement precision of usable charge capacity deteriorates
Solution Approach 1:
The method applies different quality standards and estimation approaches for different degradation states. For new energy stores, more aggressive range exploitation is permitted with smaller estimation reserves, while for degraded stores, larger reserves are applied to maintain precision. This local differentiation resolves the contradiction by optimizing range exploitation according to the specific condition of the energy store.
Solution Approach 2:
The estimation reserve is dynamically adjusted based on the degradation state rather than applying a fixed conservative margin. By determining maximum estimation errors specific to new and degraded stores and adapting the reserve accordingly, the system enables maximum achievable range exploitation while maintaining appropriate measurement precision for each degradation level.
Data Source
AI summary
A method for estimating the usable charge capacity of an electrical energy store includes determining a nominal initial charge capacity and a maximum initial estimation error of a new or slightly degraded energy store; determining one or more nominal charge capacities and one or more maximum estimation errors for the degraded energy store; interpolating a graph for the nominal charge capacity and for the maximum lower and upper estimation errors between the interpolation points of the nominal charge capacity and the interpolation points of the maximum estimation errors; and estimating a nominal charge state, a current usable charge capacity with a lower estimation reserve, and a current usable charge capacity with an upper estimation reserve for a current degradation state of the electrical energy store.