Estimating the state of charge of a lithium based on voltage measurements from the battery is rather challenging. This is due to not only the state of chacrge but also the condition of the battery, current drawn, ambient temperature, etc all having a significant impact on the voltage measured. The best way for SoC estimation would be a columb counter which wasn’t available for my project. For my project the current drawn is rather constant around 200ma and the temperature is relatively stable around 20-25C. Thus a much better estimate should be possible with polynomials than the simple linear SoC estimations. For the polynomial regeressions and to find the polynomial coefficients r was used.

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