SoC is an indicator of the charge remaining in a battery or it may be explained as an indicator of the difference in charge between a fully charged battery and when that battery is in operation. It is specified as a ratio of the remaining charge in a battery to the maximum charge that can be obtained from the battery. The upper and lower limits of the voltages of a battery are found to be depending on the chemistry of the battery. Sometimes it is higher or lower but in general, it is the span of about 1V from full charge to almost an empty condition of the battery.