METHODS AND APPARATUS FOR MEASURING THE REMAINING CAPACITY OF A BATTERY

1 . A circuit for determining a remaining capacity of a battery, comprising:

a memory device for storing a plurality of aging curves, each aging curve indicating a relationship between an internal resistance of the battery and a temperature of the battery; and

a logic circuit having access to the memory device, wherein the logic circuit is configured to:

select one aging curve from the plurality of aging curves according to a first measured temperature and an initial internal resistance value;

utilize the selected aging curve to determine an updated internal resistance value according to a second measured temperature; and

compute the remaining capacity based on the updated internal resistance value.

2 . The circuit according to claim 1 , wherein the memory device further stores remaining capacity data indicating a relationship between output voltage data of the battery, remaining capacity data of the battery, and battery current data.

3 . The circuit according to claim 1 , wherein the logic circuit is further configured to compute an adjusted output voltage according to the updated internal resistance value.

4 . The circuit according to claim 1 , further comprising a sensing circuit connected to the battery, wherein the sensing circuit detects a current.

5 . The circuit of according to claim 4 , further comprising a first switch and a second switch connected to the battery and selectively operable to facilitate a charge operation and a discharge operation.

6 . The circuit according to claim 5 , wherein both the charge operation and the discharge operation of the battery are disabled prior to and during detection of the current.

7 . The circuit according to claim 1 , further comprising a voltage sensor responsive to an actual output voltage of the battery, wherein the logic circuit utilizes the actual output voltage to compute the initial internal resistance value.

8 . A method for monitoring a remaining capacity of a battery, comprising:

measuring a first temperature of the battery;

calculating an internal resistance of the battery;

selecting one aging curve from a plurality of aging curves according to the measured first temperature and the calculated internal resistance;

measuring a second temperature of the battery;

utilizing the selected aging curve and the measured second temperature to determine an expected internal resistance; and

determining the remaining capacity based on the expected internal resistance.

9 . The method of claim 8 , further comprising measuring a battery current and measuring an actual output voltage of the battery.

10 . The method of claim 8 , wherein calculating the internal resistance comprises utilizing the measuring battery current and the measured output voltage.

11 . The method of claim 8 , wherein determining the remaining capacity comprises utilizing a predetermined look-up table containing output voltage data of the battery, remaining capacity data of the battery, and battery current data.

12 . The method of claim 8 , further comprising:

detecting a current through a sense circuit, wherein the sense circuit is connected to the battery; and

disabling both a charge operation and a discharge operation of the battery during detection of the current through the sense circuit.

13 . The method of claim 8 , further comprising computing an adjusted output voltage according to the expected internal resistance.

14 . A system for monitoring a remaining capacity of a battery, comprising:

a temperature sensor configured to measure a temperature of the battery and generate actual temperature data according to the measured temperature;

a memory, wherein the memory stores a plurality of aging curves and each aging curve from the plurality of aging curves indicates a relationship between predicted internal resistance values of the battery and predicted temperature values; and

a logic circuit configured to:

receive a first actual temperature data;

compute an internal resistance of the battery;

access the memory;

select one of the aging curves from the plurality of aging curves according to the computed internal resistance and the first actual temperature data;

receive a second actual temperature data;

determine an expected internal resistance value according to the selected aging curve and the second actual temperature data; and

compute the remaining capacity of the battery according to the expected internal resistance value.

15 . The system of claim 14 , wherein the memory device further stores remaining capacity data indicating a relationship between output voltage data of the battery, remaining capacity data of the battery, and battery current data.

16 . The system of claim 14 , further comprising a sensing circuit connected to the battery, wherein the sensing circuit is selectively operable to detect a current.

17 . The system according to claim 16 , wherein, both a charge operation and a discharge operation of the battery are disabled prior to and during detection of the current.

18 . The system according to claim 14 , further comprising a voltage sensor responsive to an actual output voltage of the battery, wherein the logic circuit utilizes the actual output voltage to compute the initial internal resistance value.

19 . The system according to claim 14 , further comprising a first switch and a second switch connected to the battery and selectively operable to facilitate a charge operation and a discharge operation.

20 . The system according to claim 14 , wherein the logic circuit is further configured to compute an adjusted output voltage according to the expected internal resistance value.