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Accurate voltage measurements can be made while a cell is resting (ensure that cell has been resting for a considerable amount of time)
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The relation between capacity and voltage is non-linear. A typical model is shown below
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PCB component accuracy
Ideally components with low drift/offset
Trace length may affect resistance
Instrumentation accuracy
ADC resolution
Sampling rate - Is the sampling fast enough to capture waveforms and integrate
Voltage drift (RESEARCH THIS MORE)
Noise immunity
Cell model accuracy
Capacity is susceptible to degradation upon repeat cycles, how does the model accurately capture this.
Hard and time consuming to extract adequate parameters using collected data, for resistances and OCV
Temperature
Impact parameters, especially resistance, and including max capacity, OCV, capacitance
Aging
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We want to predict the actual battery voltage curve
Start with OCV, then correct it using the internal resistance and current
Then correct it using the value of the low temperature, leaving us with the green curve which accurately resembles the actual battery voltage curve
CEDV Formula
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Impedance Track Fuel-Gauging
Includes advantages of both voltage lookup and coulomb counting
Allows for SOC updates, where initial SOC can be measured when voltage is relaxed, in addition to self-discharge
Impedance can be measured during discharge
Total capacity can be measure without full discharge or charge