Bias Compensated Battery Capacity Estimation
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Solution Overview
Problem
Existing methods for estimating battery capacity are inaccurate due to uncertainties in measured voltage and current, leading to potential secondary failures and premature battery degradation.
Innovation Solution
A bias compensated capacity estimator is introduced, which subtracts bias terms from the expected value of the capacity estimator to improve accuracy, allowing for the use of less complex and costly sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common capacity estimator based on measured voltage and current is used, then the estimation process is simple, but the measurement precision deteriorates due to uncertainties in voltage and current measurements
Solution Approach 1:
The patent transforms the capacity estimation approach by changing from direct measurement-based estimation to a differential-based estimation. Instead of using absolute voltage and current measurements directly, the system uses changes in voltage and current over time, which reduces the impact of measurement biases and uncertainties. This parameter transformation allows maintaining estimation simplicity while improving accuracy.
Solution Approach 2:
The patent introduces differential changes as an intermediary between the raw measurements and the capacity estimation. By using the rate of change of voltage and current as intermediate parameters, the system indirectly estimates capacity while filtering out measurement uncertainties. This intermediary approach decouples the estimation from direct dependency on absolute measurement accuracy.
2Measurement precision
If high-precision voltage and current sensors are used to improve capacity estimation accuracy, then the measurement precision improves, but the device complexity and cost increase
Solution Approach 1:
The patent enables the use of lower-cost, less precise sensors by compensating for their limitations through algorithmic processing. Instead of relying on expensive high-precision sensors, the system uses computationally intensive differential calculations to achieve accurate capacity estimation. This trades hardware cost for processing complexity, allowing the use of simpler, cheaper sensor components.
Solution Approach 2:
The patent replaces the need for high-precision mechanical/electrical sensing hardware with a computational/mathematical approach. By substituting hardware precision requirements with algorithmic processing of differential changes, the system achieves accurate measurements without requiring expensive precision sensors, effectively replacing a hardware solution with a software/mathematical solution.
Data Source
AI summary
A method for estimating a capacity of an electrical energy storage device with higher accuracy than what is provided in the prior art. The uncertainties in measured electrical current or voltage used in the estimation of the capacity of the electrical energy storage device are at least partly compensated for by using a bias compensated capacity estimator instead of the often-used prior art capacity estimator. The accuracy of the voltage and/or electric current sensor becomes of less importance which leads to that less complicated and less costly sensors may be used and to improve accuracy of the estimated energy storage capacity. The above advantages are obtained by providing a bias compensated capacity estimator that includes at least one bias term which is related to a deviation of an expected value of an original capacity estimator from a true capacity value.