Capacity independent fast charging of batteries

1. A battery charging monitor comprising:

a first sensor and a second sensor electrically connected to at least one battery cell of at least one battery, wherein the first sensor is configured to measure an internal temperature of the at least one battery cell and the second sensor is configured to measure a cell voltage of the at least one battery cell; and

a microcontroller configured to:

determine a rate of change of the internal temperature of the at least one battery cell based on the internal temperature of the at least one battery cell;

determine a state of charge of the at least one battery cell based on the rate of change of the internal temperature;

cause a charging rate to be applied, by a battery charger, to the at least one battery cell based on the determined state of charge;

compare the cell voltage to a voltage threshold; and

cause the charging rate to be reduced in an instance in which the cell voltage exceeds the voltage threshold.

2. The battery charging monitor of claim 1 , wherein the determined state of charge comprises a determined state transition.

3. The battery charging monitor of claim 1 , wherein the internal temperature of the at least one battery cell comprises at least an anode temperature of the at least one battery cell.

4. The battery charging monitor of claim 1 , wherein measuring the internal temperature of the at least one battery cell comprises:

applying a current across the at least one battery cell at a first alternating current (AC) frequency,

measuring a resultant AC voltage across the battery cell,

measuring a first phase shift between the applied AC current and the resultant AC voltage across the at least one battery cell, and

determining the temperature of an anode of the at least one battery cell based on the first phase shift.

5. The battery charging monitor of claim 1 , wherein measuring the internal temperature of the at least one battery comprises:

applying a voltage across the at least one battery cell at a second (AC) frequency,

measuring a resultant AC current across the battery cell,

measuring a second phase shift between the applied AC voltage and the resultant AC current across the at least one battery cell, and

determining the temperature of a cathode of the at least one battery cell based on the second phase shift.

6. The battery charging monitor of claim 1 further comprising:

a multiplexor,

wherein the at least one battery cell comprises a plurality of battery cells electrically connected to the first sensor by the multiplexor, and

wherein the first sensor is configured to measure an internal temperature of each battery cell of the plurality of battery cells.

7. The battery charging monitor of claim 1 , wherein the electrical connection to the at least one battery cell comprises a connection to each terminal of the at least one battery, and no portion of the first sensor is within the at least one battery cell.

8. The battery charging monitor of claim 1 , wherein the microcontroller is further configured to:

compare the internal temperature of the at least one battery cell to a temperature threshold; and

cause the charging rate to be reduced in an instance in which the internal temperature exceeds the temperature threshold.

9. The battery charging monitor of claim 1 , wherein causing the charging rate to be applied to the at least one battery cell based on the determined state of charge comprises:

applying a first charging rate in an instance in which the state of charge is below a first state of charge threshold, and

applying a second charging rate in an instance in which the state of charge is equal to or above the state of charge threshold.

10. The battery charging monitor of claim 9 , wherein the state of charging threshold is about 60 percent.

11. The battery charging monitor of claim 9 , wherein the first charging rate is less than or about 0.7 of a capacity of the at least one battery.

12. The battery charging monitor of claim 9 , wherein the second charging rate is greater than about 0.7 of a charging capacity of the at least one battery.

13. The battery charging monitor of claim 1 , wherein the at least one battery comprises a lithium ion battery.

14. A battery charging monitor comprising:

a sensor electrically connected to at least one battery cell of at least one battery, wherein the sensor is configured to measure an internal temperature of the at least one battery cell; and

a microcontroller configured to:

compare the internal temperature of the at least one battery cell to one or more charging temperature thresholds; and

cause a charging rate to be applied, by a battery charger, to the at least one battery cell based on the comparison of the internal temperature to the one or more charging temperature thresholds, wherein causing the charging rate to be applied comprises:

applying a first charging rate in an instance in which the state of charge is below a first charging temperature threshold,

reducing the charging rate, and

applying a second charging rate in an instance in which the first charging temperature threshold has been met.

15. The battery charging monitor of claim 14 , wherein the internal temperature of the at least one battery cell comprises at least an anode temperature of the battery.

16. The battery charging monitor of claim 14 , further comprising a second sensor configured to measure a cell voltage of the at least one battery cell, and

wherein the microcontroller is further configured to:

compare the cell voltage to a charging voltage threshold, and

apply a constant voltage charging rate in an instance in which the cell voltage satisfies the charging voltage threshold.

17. The battery charging monitor of claim 14 , wherein measuring the internal temperature of the at least one battery cell comprises:

applying a current across the at least one battery cell at a first alternating current (AC) frequency,

measuring a resultant AC voltage across the battery cell,

measuring a first phase shift between the applied AC current and the resultant AC voltage across the at least one battery cell, and

determining the temperature of an anode of the at least one battery cell based on the first phase shift.

18. The battery charging monitor of claim 17 , wherein measuring the internal temperature of the at least one battery comprises:

applying a voltage across the at least one battery cell at a second (AC) frequency,

measuring a resultant AC current across the battery cell,

measuring a second phase shift between the applied AC voltage and the resultant AC current across the at least one battery cell, and

determining the temperature of a cathode of the at least one battery cell based on the second phase shift.

19. A battery charging monitor comprising:

a sensor electrically connected to at least one battery cell of at least one battery, wherein the sensor is configured to measure an internal temperature of the at least one battery cell; and

a microcontroller configured to:

determine a rate of change of the internal temperature of the at least one battery cell based on the internal temperature of the at least one battery cell;

determine a state of charge of the at least one battery cell based on the rate of change of the internal temperature; and

cause a charging rate to be applied, by a battery charger, to the at least one battery cell based on the determined state of charge, wherein causing the charging rate to be applied to the at least one battery cell comprises:

applying a first charging rate in an instance in which the state of charge is below a first state of charge threshold, and

applying a second charging rate in an instance in which the state of charge is equal to or above the state of charge threshold.