State of charge estimation using battery voltage

1 . A device comprising:

a battery having a maximum charging capacity, wherein a first state of charge of the battery is 100% when charged to the maximum charging capacity;

a first sensor configured to measure voltage of the battery;

a second sensor configured to measure temperature of the battery;

memory configured to store computer-executable instructions; and

at least one computer processor configured to access the memory and execute the computer-executable instructions to:

determine, by the device, a first voltage of the battery during a first time interval;

determine, by the device and using the first voltage, a first open circuit voltage of the battery during the first time interval;

determine, by the device, a first temperature of the battery during a first time interval;

determine, by the device, a first resistance value of the battery based at least in part on the first open circuit voltage and the first temperature;

determine, by the device, a first estimated current of the battery using the first voltage, the first open circuit voltage, and the first resistance value;

determine, by the device, a first adjustment to a first estimated amount of charge in the battery during the first time interval by multiplying the first estimated current by a length of the first time interval;

determine, by the device, a second estimated amount of charge in the battery at an end of the first time interval using the first adjustment and the first estimated amount of charge; and

determine, by the device, a second state of charge of the battery at the end of the first time interval using the second estimated amount of charge.

2 . The device of claim 1 , wherein the at least one processor is further configured to access the memory and execute the computer-executable instructions to:

determine a second open circuit voltage at the end of the first time interval based at least in part on the second estimated amount of charge; and

determine an updated state of charge using the second open circuit voltage during a second time interval.

3 . The device of claim 1 , wherein the at least one processor is configured to determine the first estimated current of the battery by executing the computer-executable instructions to:

determine a difference between the first voltage and the first open circuit voltage; and

determine the first estimated current by dividing the difference by the first resistance value.

4 . A device comprising:

a battery;

memory configured to store computer-executable instructions; and

at least one computer processor configured to access the memory and execute the computer-executable instructions to:

determine, by the device, a first value indicative of a battery voltage during a first time interval;

determine, by the device, a second value indicative of an open circuit voltage of the battery during the first time interval;

determine, by the device, a third value indicative of a battery temperature during the first time interval;

determine, by the device and using the second value and the third value, a fourth value indicative of battery resistance during the first time interval;

determine, by the device and using the first value, the second value, and the fourth value, a first estimated current associated with the battery; and

determine, by the device, a first estimated state of charge value of the battery using the first estimated current.

5 . The device of claim 4 , wherein the at least one processor is further configured to access the memory and execute the computer-executable instructions to:

determine, at an end of the first time interval, a first estimated amount of charge in the battery;

determine a first adjustment to the first estimated amount of charge in the battery by multiplying the first estimated current by a length of the first time interval; and

determine a second estimated amount of charge in the battery using the first adjustment and the first estimated amount of charge.

6 . The device of claim 5 , wherein the at least one processor is further configured to access the memory and execute the computer-executable instructions to:

determine, using the second estimated amount of charge, a fifth value indicative of an open circuit voltage of the battery during a second time interval.

7 . The device of claim 6 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

determine, using the second estimated amount of charge, a sixth value indicative of an open circuit voltage of the battery during a third time interval.

8 . The device of claim 4 , wherein the at least one processor is configured to determine the first estimated current of the battery by executing the computer-executable instructions to:

determine a difference between the first value and the second value; and

determine the first estimated current by dividing the difference by the fourth value.

9 . The device of claim 4 , wherein the at least one processor is further configured to access the memory and execute the computer-executable instructions to:

determine that the device is rebooted;

determine the first estimated state of charge value after the device is rebooted;

determine a fifth value indicative of an open circuit voltage of the battery during a second time interval;

determine that a difference between the fifth value and the second value is less than a threshold; and

determine that a state of charge of the battery is the first estimated state of charge value.

10 . The device of claim 4 , wherein the at least one processor is further configured to access the memory and execute the computer-executable instructions to:

determine that the device is rebooted;

determine the first estimated state of charge value after the device is rebooted;

determine a fifth value indicative of an open circuit voltage of the battery during a second time interval;

determine that a difference between the fifth value and the second value is greater than a threshold; and

determine a second estimated state of charge based at least in part on the fifth value.

11 . The device of claim 4 , wherein the at least one processor is further configured to access the memory and execute the computer-executable instructions to:

determine that the first estimated state of charge value is greater than a first threshold;

determine that a difference between the first estimated state of charge value and a second estimated state of charge value is greater than a second threshold; and

cause the second estimated state of charge value to be deleted from the memory.

12 . The device of claim 4 , wherein the at least one processor is configured to determine the fourth value by executing the computer-executable instructions to:

determine, using the second value, the third value, and a direct current cell resistance lookup table, the fourth value indicative of battery resistance during the first time interval.

13 . The device of claim 4 , wherein the device is devoid of a battery current sensor.

14 . A method comprising:

determining, by a device comprising a battery, a first value indicative of a battery voltage during a first time interval;

determining, by the device, a second value indicative of an open circuit voltage of the battery during the first time interval;

determining, by the device, a third value indicative of a battery temperature during the first time interval;

determining, by the device and using the second value and the third value, a fourth value indicative of battery resistance during the first time interval;

determining, by the device and using the first value, the second value, and the fourth value, a first estimated current associated with the battery; and

determining, by the device, a first estimated state of charge value of the battery using the first estimated current.

15 . The method of claim 14 , further comprising:

determining, at an end of the first time interval, a first estimated amount of charge in the battery;

determining a first adjustment to the first estimated amount of charge in the battery by multiplying the first estimated current by a length of the first time interval; and

determining a second estimated amount of charge in the battery at an end of the first time interval using the first adjustment and the first estimated amount of charge.

16 . The method of claim 15 , further comprising:

determining a fifth value indicative of an open circuit voltage of the battery during a second time interval using an open circuit voltage lookup table and the second estimated amount of charge.

17 . The method of claim 14 , further comprising:

determining that the device is rebooted;

determining the first estimated state of charge value after the device is rebooted;

determining a fifth value indicative of an open circuit voltage of the battery during a second time interval;

determining that a difference between the fifth value and the second value is less than a threshold; and

determining that a state of charge of the battery is the first estimated state of charge value.

18 . The method of claim 14 , further comprising:

determining that the first estimated state of charge value is greater than a first threshold;

determining that a difference between the first estimated state of charge value and a second estimated state of charge value is greater than a second threshold; and

causing the second estimated state of charge value to be deleted from the memory.

19 . The method of claim 14 , further comprising:

determining, using the second value, the third value, and a direct current cell resistance lookup table, the fourth value indicative of battery resistance during the first time interval.