Methods and apparatus for determining a resistance value of a resistor in a battery system

1. An apparatus adapted to connect to a battery, comprising:

a resistor connected to the battery and having a nominal resistance value;

a first computation circuit connected to the battery and configured to compute a plurality of voltage-based capacity values;

a first counter connected to the first computation circuit and configured to accumulate the plurality of voltage-based capacity values and generate a first accumulated value;

a second computation circuit connected to the battery and configured to compute a plurality of current-based capacity values;

a second counter connected to the second computation circuit and configured to accumulate the plurality of current-based capacity values and generate a second accumulated value; and

a logic circuit configured to receive the first and second accumulated values and compute an actual resistance of the resistor according to the first and second accumulated values and the nominal resistance value.

2. The apparatus according to claim 1 , further comprising: a temperature sensor to measure a temperature of the battery and generate temperature data.

3. The apparatus according to claim 2 , wherein the first and second computation circuits are configured to receive the temperature data and selectively operate according to the temperature data.

4. The apparatus according to claim 1 , further comprising: a cycle counter configured to count a total number of charge cycles of the battery according to the current-based capacity values and the voltage-based capacity values.

5. The apparatus according to claim 1 , wherein the actual resistance value is equal to: the multiple of the nominal resistance value by the second accumulated value divided by the first accumulated value.

6. The apparatus according to claim 1 , wherein the logic circuit is further configured to compute a battery current according to the actual resistance value and transmit the computed battery current to an external adapter, the adapter comprising a charger control circuit.

7. The apparatus according to claim 1 , wherein the resistor is connected between a negative terminal of the battery and the second computation circuit.

8. A method for determining an actual resistance value of a resistor in a battery system, comprising:

computing a plurality of first capacity values according to a voltage of a battery;

accumulating the plurality of first capacity values and generating a first accumulated value;

computing a plurality of second capacity values according to a current through the resistor;

accumulating the plurality of second capacity values and generating a second accumulated value; and

computing the actual resistance of the resistor according to the first and second accumulated values and a nominal resistance value of the resistor.

9. The method according to claim 8 , wherein computing the actual resistance comprises dividing the second accumulated value by the first accumulated value and multiplying by the nominal resistance value.

10. The method according to claim 8 , further comprising: measuring a temperature of the battery and selectively computing the plurality of first and second capacity values according to the measured temperature.

11. The method according to claim 8 , further comprising: counting a total number of charge cycles of the battery.

12. The method according to claim 11 , wherein the actual resistance value is computed when the total number of charge cycles reaches a predetermined number.

13. The method according to claim 8 , wherein:

computing a first capacity value of the plurality of first capacity values comprises: computing a first relative state of charge value; and

computing a second capacity value of the plurality of second capacity values comprises: computing a second relative state of charge value.

14. A battery system, comprising:

a battery;

a sense resistor, having a nominal resistance value, connected to the battery; and

a fuel gauge circuit connected to the battery and the sense resistor, the fuel gauge circuit comprising:

a first computation circuit configured to compute a plurality of first capacity values;

a first counter connected to the first computation circuit and configured to accumulate the plurality of first capacity values and generate a first accumulated value;

a second computation circuit configured to compute a plurality of second capacity values;

a second counter connected to the first computation circuit and configured to accumulate the plurality of second capacity values and generate a second accumulated value; and

a logic circuit connected to the first and second counters and configured to:

receive the first and second accumulated values; and

compute an actual resistance value of the resistor according to:

the first and second accumulated values; and

the nominal resistance.

15. The battery system according to claim 14 , further comprising an adapter connected to the battery and configured to:

directly charge the battery; and

receive battery current data from the fuel gauge circuit.

16. The battery system according to claim 14 , wherein the actual resistance value is equal to: the multiple of the nominal value by the second accumulated value divided by the first accumulated value.

17. The battery system according to claim 14 , further comprising a cycle counter connected to the first and second counters and configured to count a total number of charge cycles of the battery according to the plurality of first and second capacity values.

18. The battery system according to claim 14 , further comprising a temperature sensor configured to measure a temperature of the battery and generate temperature data.

19. The battery system according to claim 18 , wherein the first and second computation circuits are configured to receive the temperature data and selectively operate according to the temperature data.

20. The battery system according to claim 14 , wherein the sense resistor is connected between a negative terminal of the battery and the second computation circuit.