Methods and system for a battery

1. A battery system, comprising:

a fuel gauge circuit coupled to a battery and adapted to:

measure a current of the battery;

store the measured current of the battery;

store a previously-computed RSOC value of the battery;

store a predetermined design capacity of the battery;

compute a first RSOC value based on at least one of: the measured current, the previously-computed RSOC value, and a terminal current;

compute a second RSOC value based on the design capacity; and

selectively output one of the first RSOC value and the second RSOC value to maintain continuity among consecutively-output RSOC values.

2. The battery system of claim 1 , wherein the fuel gauge circuit comprises:

a first RSOC calculation circuit that computes the first RSOC value to maintain a linear relationship between the first RSOC value and the current of the battery during the constant voltage charge mode; and

a second RSOC calculation circuit to compute the second RSOC value.

3. The battery system of claim 2 , wherein the fuel gauge circuit further comprises:

a first register connected to an input terminal of the first RSOC calculation circuit and adapted to store a new battery current;

a second register connected to an input terminal of the first RSOC calculation circuit and adapted to store a previously-measured battery current; and

a third register connected to an input terminal of the first RSOC calculation circuit and adapted to store the previously-computed RSOC.

4. The battery system of claim 3 , wherein the fuel gauge circuit further comprises a multiplexer adapted to:

receive the first RSOC value from the first RSOC calculation circuit;

receive the second RSOC value from the second RSOC calculation circuit; and

selectively output one of the first RSOC value and the second RSOC value based on a charge mode of the battery.

5. The battery system of claim 4 , further comprising a battery charger adapted to transmit a signal to the multiplexer, wherein the signal corresponds to the charge mode of the battery.

6. The battery system of claim 4 , further comprising a display unit to display the selected output RSOC value.

7. The battery system of claim 1 , wherein the fuel gauge circuit comprises a second RSOC calculation circuit to compute the second RSOC value according to a coulomb counting method.

8. The battery system of claim 1 , wherein the previously-computed RSOC value comprises one of:

an RSOC value computed during a constant current charge mode; and

an RSOC value computed during a constant voltage charge mode.

9. The battery system of claim 1 , wherein the fuel gauge circuit selectively outputs one of the first RSOC value and the second RSOC value based on a charge mode of the battery, wherein the charge mode comprises a constant current charge mode and a constant voltage charge mode.

10. The battery system of claim 9 , wherein the fuel gauge circuit outputs:

the first RSOC value if the battery is in the constant voltage charge mode; and

the second RSOC value if the battery is in the constant current charge mode.

11. A method for reporting an RSOC of a battery, comprising:

determining a charge mode of the battery, wherein the charge mode is one of a constant voltage charge mode and a constant current charge mode;

computing a plurality of first RSOC values according to a linear function based on at least one of: a terminal current of the battery, a measured current of the battery, and a previously-computed RSOC value, to provide linearly decreasing consecutively-computed first RSOC values;

computing a second RSOC value according to a coulomb counting method; and

selectively outputting one of the first and second RSOC values to a display unit based on the charge mode, comprising:

outputting the plurality of first RSOC values if as long as the battery is in the constant voltage charge mode; and

outputting the second RSOC value if as long as the battery is in the constant current charge mode.

12. The method of claim 11 , wherein, during a change in the charge mode from the constant current charge mode to the constant voltage charge mode, the outputted first and second RSOC values form a smooth line.

13. The method of claim 11 , wherein:

the second RSOC value is computed based on a predetermined design capacity of the battery; and

the terminal current comprises a predetermined value and corresponds to a 100% RSOC value.

14. The method of claim 11 , wherein the plurality of computed first RSOC values form a line with a linear slope ending at the terminal current.

15. A battery system, comprising:

a current sensor coupled to a battery and adapted to measure a current of the battery;

a battery charger coupled to the battery and adapted to generate a charge mode signal according to a charge mode of the battery; and

a fuel gauge circuit coupled to the battery charger, and comprising:

a memory adapted to store the measured current of the battery;

a first RSOC calculation circuit coupled to the memory and adapted to compute a first RSOC value according to the measured current of the battery;

a second RSOC calculation circuit coupled to the memory and adapted to compute a second RSOC value according to the measured current of the battery; and

a multiplexer connected to:

an output terminal of the first RSOC calculation circuit;

an output terminal of the second RSOC calculation circuit, and an output terminal of the battery charger;

wherein the multiplexer selectively outputs one of the first RSOC value and the second RSOC value according to the charge mode signal.

16. The battery system of claim 15 , wherein the charge mode is one of a constant voltage charge mode and a constant current charge mode.

17. The battery system of claim 16 , wherein the first RSOC calculation circuit computes the first RSOC value to maintain a linear relationship between the first RSOC value and the battery current during the constant voltage charge mode.

18. The battery system of claim 16 , wherein the multiplexer outputs:

the first RSOC value if the battery is in the constant voltage charge mode; and

the second RSOC value if the battery is in the constant current charge mode.

19. The system of claim 16 , wherein, during a change in the charge mode from the constant current charge mode to the constant voltage charge mode, the outputted first and second RSOC values form a smooth line.

20. The battery system of claim 15 , wherein the memory comprises:

a first register connected to an input terminal of the first RSOC calculation circuit and adapted to store a new battery current;

a second register connected to an input terminal of the first RSOC calculation circuit and adapted to store a previously-measured battery current; and

a third register connected to an input terminal of the first RSOC calculation circuit and adapted to store a previously-computed RSOC.