Battery charge determination

1. A method for determining a current state of charge of a battery having an internal resistance, comprising:

during a charge or discharge phase, iteratively estimating, in a CPU, the current state of charge (SOC new ) of the battery at a current time as a function of a previous state of charge (SOC old ) of the battery at a previous time, a battery voltage (V t ) of the battery during a time interval (t) between the previous time and the current time, and a value (R i ) of the internal resistance of the battery wherein at each iteration, the most recently estimated SOC new is used as the SOC old for the next estimation; and

during an idle phase, stopping the iterative estimation and determining a current idle state of charge SOC idle — new ) of the battery as a value associated to a current voltage value (V idle ) of the battery using a predetermined relation between an open-circuit voltage (OCV) and a state of charge (SOC) of the battery.

2. The method of claim 1 , wherein estimating the current state of charge (SOC new ) comprises estimating a charge provided by or to the battery during the time interval (t) as a function of the battery voltage (V t ) and the value (R i ) of the internal resistance.

3. The method of claim 2 , wherein estimating the charge provided by or to the battery during the time interval (t) comprises determining a value representative of the difference (V diff ) between the battery voltage (V t ) and an open-circuit voltage value (OCV t ) of the battery during the time interval (t).

4. The method of claim 3 , wherein determining the value representative of the difference (V diff ) comprises determining the open-circuit voltage (OCV t ) of the battery during the time interval (t) as a value associated to the previous state of charge (SOC old ) in a predetermined relation between the open-circuit voltage (OCV) and the state of charge (SOC) of the battery.

5. The method of claim 1 , wherein estimating the current state of charge (SOC new ) comprises

making a plurality of measures of the voltage of the battery over the time interval (t); and

determining the battery voltage (V t ) of the battery during the time interval (t) as an average of the plurality of measures.

6. The method of claim 1 , further comprising detecting the idle state of the battery by detecting that an electric current provided by or to the battery has dropped below a predefined threshold.

7. The method of claim 1 , further comprising determining an improved internal resistance value as a function of: the current idle state of charge (SOC idle — new ), and a previous idle state of charge (SOC idle — old ) of the battery at a beginning of the charge phase or the discharge phase.

8. The method of claim 7 , wherein determining the improved internal resistance value comprises determining an average electric current (I Avg ) provided by or to the battery during the charge phase or the discharge phase by comparing the current idle state of charge (SOC idle — new ) to the previous idle state of charge (SOC idle — old ), and dividing a value representative of the difference between the battery voltage (V) and the open-circuit voltage (OCV) during the charge phase or the discharge phase by the average electric current (I Avg ).

9. The method of claim 7 , wherein the internal resistance value (R i ) used for estimating the state of charge during a next charge phase or a next discharge phase is the improved resistance value or an average of values including the improved internal resistance value and at least one previously used resistance value.

10. A non-transitory computer readable medium having recorded thereon program steps operative to cause a CPU to determine a current state of charge of a battery having an internal resistance by performing the steps of

during a charge or discharge phase, iteratively estimating the current state of charge (SOC new ) of the battery at a current time as a function of a previous state of charge (SOC old ) of the battery at a previous time, a battery voltage (V i ) of the battery during a time interval (t) between the previous time and the current time, and a value (R i ) of the internal resistance of the battery wherein at each iteration, the most recently estimated SOC new is used as the SOC old for the next estimation; and

during an idle phase, stopping the iterative estimation and determining a current idle state of charge (SOC idle — new ) of the battery as a value associated to a current voltage value (V idle ) of the battery using a predetermined relation between an open-circuit voltage (OCV) and a state of charge (SOC) of the battery.

11. An electronic device, comprising:

a battery having an internal resistance;

memory; and

a CPU operatively connected to the memory, the CPU operative to,

during a charge or discharge phase, iteratively estimating the current state of charge (SOC new ) of the battery at a current time as a function of a previous state of charge (SOC old ) of the battery at a previous time, a battery voltage (V t ) of the battery during a time interval (t) between the previous time and the current time, and a value (R i ) of the internal resistance of the battery wherein at each iteration, the most recently estimated SOC new is used as the SOC old for the next estimation; and

during an idle phase, stopping the iterative estimation and determining a current idle state of charge SOC idle — new ) of the battery as a value associated to a current voltage value (V idle ) of the battery using a predetermined relation between an open-circuit voltage (OCV) and a state of charge (SOC) of the battery.

12. The device of claim 11 , wherein the device is a mobile communication device, and further comprising:

a transceiver operative to effect wireless communications with a wireless communication network.