Battery Resistance Estimation via Polarization Correction
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Solution Overview
Problem
Existing methods for estimating battery resistance are inaccurate due to polarization of active materials during charging or discharging, leading to increased manufacturing costs with adaptive algorithms and errors in resistance measurement.
Innovation Solution
An apparatus and method that corrects measured battery resistance using a resistance increase/decrease rate based on the charge/discharge rate, determined by a processor that calculates resistance from voltage and current measurements, and adjusts the resistance when the battery's operation state meets specific SOC and temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the DC estimation method is used to calculate resistance from voltage change during charging or discharging, then the calculation is simple, but the measurement accuracy deteriorates due to polarization of active material
Solution Approach 1:
The patent applies preliminary action by measuring the open circuit voltage (OCV) before charging or discharging begins, and measuring the voltage immediately after charging or discharging stops. This allows calculation of voltage change without the distorting effects of polarization occurring during the charge/discharge process, thereby maintaining measurement accuracy while keeping the calculation simple.
2Measurement precision
If adaptive algorithms such as extended Kalman filter are used to estimate resistance, then the measurement accuracy improves, but the device complexity and manufacturing cost increase due to high-performance processor requirements
Solution Approach 1:
The patent extracts the polarization effect from the measurement process by avoiding voltage measurements during the charge/discharge process when polarization occurs. Instead, it uses voltage measurements taken before and after the process, thereby eliminating the need for complex adaptive algorithms to compensate for polarization while maintaining accurate resistance measurement.
3Speed
If voltage change is measured during charging or discharging to calculate resistance, then the resistance can be calculated in real-time, but the measurement accuracy deteriorates due to polarization
Solution Approach 1:
The patent performs voltage measurements at specific timing points (before charge/discharge and immediately after) to capture the voltage change without polarization interference. This timing strategy enables real-time resistance calculation while avoiding the polarization problem that would otherwise reduce accuracy.
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 reduces errors in battery resistance estimation by accurately accounting for charge/discharge rates, improving the accuracy of resistance measurement and reducing manufacturing costs by avoiding the need for high-performance processors.
Implementation Method 1
a voltage change amount is measured under the condition that the battery is charged or discharged by a constant current, then a resistance is calculated according to the Ohm's law (R = ΔV/I)
Implementation Method 2
a positive electrode, a negative electrode, a separator interposed between the electrodes, and an electrolyte that reacts electrochemically with active materials coated on the positive electrode and the negative electrode
Implementation Method 3
As the capacity of the battery decreases, the resistance increases and the electric energy dissipated by heat increases
Data Source
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AI summary
An apparatus for estimating a resistance of a battery includes: a sensing unit configured to measure voltage, current and temperature of a battery; and a processor operably coupled to the sensing unit, wherein the processor calculates a measured resistance of the battery by using the voltage and the current of the battery, determines whether an operation state of the battery corresponds to a resistance correcting condition, corrects the measured resistance by using a resistance increase/decrease rate of a beginning of life (BOL) resistance of the battery according to a charge/discharge rate when the operation state of the battery corresponds to the resistance correcting condition, and determines the corrected measured resistance as a resistance of the battery.