State of charge

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State of charge (SOC) is the equivalent of a fuel gauge for the battery pack in a battery electric vehicle (BEV), hybrid vehicle (HEV), or plug-in hybrid electric vehicle (PHEV). SOC is sometimes difficult to determine as it cannot usually be determined by simple voltage measurements. Electrolyte pH levels are a good SOC indication, but many modern chemistries don't offer easy access to that part of the battery. Most SOC methods take into account voltage and current as well as temperature and other aspects of the discharge and charge process to in essence count up or down within a pre-defined capacity of a pack. E-Meters take into account Peukert's law which is a function of charge/discharge rate or ampere.