1. A method of determining and predicting a state of a rechargeable battery device in real time, comprising: via respective measuring devices, measuring a current and a voltage of the rechargeable battery in real time; via a processor executing computer readable instructions and operatively coupled to a memory and to a non-transitory, tangible computer-readable medium, the processor performing steps including: determining that the battery is charging based on the current being positive, or that the battery is discharging based on the current being negative; determining a time derivative of the current and a time derivative of the voltage; estimating, based on results of an execution of a weighted recursive least squares regression of a linear solution of an equivalent circuit for the battery, for time intervals over a time duration, parameters including the voltage of the rechargeable battery, an open circuit voltage of the rechargeable battery, and a high-frequency resistance of the rechargeable battery; estimating, based on the results of the execution of the weighted recursive least squares regression of the linear solution of the equivalent circuit for the battery, for the time intervals over the time duration, if the battery is charging, the parameters further including a charge-transfer resistance, current and capacitance of the rechargeable battery for a charging state and excluding a charge-transfer resistance, current and capacitance of the rechargeable battery for a discharging state; estimating, based on the results of the execution of the weighted recursive least squares regression of the linear solution of the equivalent circuit for the battery, for the time intervals over the time duration, if the battery is discharging, the parameters further including the charge-transfer resistance, current and capacitance of the rechargeable battery for the discharging state; and excluding the charge-transfer resistance, current and capacitance of the rechargeable battery for the charging state; and estimating the state of the rechargeable battery for the time intervals over the time duration based on the parameters.