Hybrid battery pack including bi-directional charge regulator

1. A system for a rechargeable battery pack, comprising:

one or more lower voltage cells connectable to a charging circuit via a lower voltage terminal;

one or more higher voltage cells electrically coupled in series to the one or more lower voltage cells via a bi-directional charge regulator;

a higher voltage terminal electrically coupled to the one or more higher voltage cells; and

a common ground terminal coupled to the one or more lower voltage cells and to the one or more higher voltage cells.

2. The system of claim 1 , wherein the one or more lower voltage cells comprise a plurality of lower voltage cells coupled in parallel.

3. The system of claim 1 , wherein a quantity of lower voltage cells is greater than or equal to a quantity of higher voltage cells.

4. The system of claim 1 , further comprising a transistor selectively operable to electrically couple a negative terminal of the one or more lower voltage cells to the common ground terminal.

5. The system of claim 1 , wherein the bi-directional charge regulator is configured to provide current to the one or more higher voltage cells responsive to the one or more lower voltage cells being connected to the charging circuit.

6. The system of claim 5 , wherein the bi-directional charge regulator is further configured to:

responsive to the one or more lower voltage cells being connected to the charging circuit, monitor voltages of the one or more lower voltage cells and one or more higher voltage cells; and

regulate charge flow to the one or more higher voltage cells such that a state of charge increase at the one or more higher voltage cells is within a controller error margin of a state of charge increase at the one or more lower voltage cells.

7. The system of claim 1 , wherein the bi-directional charge regulator is configured to provide current to the one or more lower voltage cells from the one or more higher voltage cells responsive to a state of charge of the one or more lower voltage cells decreasing below a state of charge of the one or more higher voltage cells by a threshold.

8. The system of claim 7 , wherein the bi-directional charge regulator is further configured to cease providing current to the one or more lower voltage cells from the one or more higher voltage cells responsive to a state of charge of the one or more lower voltage cells increasing to within a threshold of the state of charge of the one or more higher voltage cells.

9. The system of claim 1 , wherein the bi-directional charge regulator is powered from the one or more higher voltage cells.

10. A system for an asymmetric rechargeable battery pack, comprising:

a first set of battery cells electrically coupled in parallel and connectable to a charging circuit;

a second set of battery cells electrically coupled in series to the first set of battery cells;

first and second output terminals;

a common ground terminal electrically coupled to both the first set of battery cells and to the second set of battery cells; and

a bi-directional charge regulator electrically coupled between the first set of battery cells and the second set of cells, the bi-directional charge regulator being configured to:

provide current to the second set of cells responsive to the first set of cells being connected to the charging circuit; and

provide current to the first set of cells responsive to a state of charge of the first set of cells decreasing below a state of charge of the second set of cells by a threshold.

11. The system of claim 10 , wherein the bi-directional charge regulator comprises:

an inductor;

a first transistor selectively operable to couple the inductor to the first set of cells; and

a second transistor selectively operable to couple the inductor to the second set of cells.

12. The system of claim 11 , wherein the bi-directional charge regulator is configured to provide current to the second set of cells responsive to the first set of cells being connected to the charging circuit by

generating charge buildup at the inductor by turning on the first transistor and not the second transistor; and

providing current to the second set of cells from the inductor by turning on the second transistor and turning off the first transistor.

13. The system of claim 11 , wherein the bi-directional charge regulator is configured to provide current to the first set of cells responsive to a state of charge of the first set of cells decreasing below a state of charge of the second set of cells by a threshold by

generating charge buildup at the inductor by turning on the second transistor and not the first transistor; and

providing current to the first set of cells from the inductor by turning on the first transistor and turning off the second transistor.

14. A rechargeable battery pack comprising:

a lower voltage portion including one or more lower voltage cells connectable to a charging circuit via a lower voltage output;

a higher voltage portion including one or more higher voltage cells coupled to a higher voltage output, the higher voltage cells electrically coupled in series to the one or more lower voltage cells;

a bi-directional charge regulator coupled between the lower voltage portion and the higher voltage portion, the bi-directional charge regulator comprising:

an inductor;

a first transistor selectively operable to couple the inductor to the lower voltage portion;

a second transistor selectively operable to couple the inductor to the higher voltage portion; and

a control circuit configured to selectively actuate the first and second transistor based on at least a mode control signal indicating whether the bi-directional charge regulator is to operate in a charging or discharging mode.

15. The rechargeable battery pack of claim 14 , where the control circuit is further configured to:

actuate one of the first transistor and second transistor responsive to receiving a periodic clock signal; and

switch which of the first transistor and the second transistor is actuated responsive to an inductor current reaching a threshold.

16. The rechargeable battery pack of claim 15 , where the control circuit is further configured to initiate actuation of the first and second transistors responsive to receiving signals indicating

an amount of charge stored on the lower voltage portion is below a threshold; and

a charge storage differential between the lower voltage portion and the higher voltage portion is above a threshold.

17. The rechargeable battery pack of claim 16 , wherein the control circuit is further configured to turn both the first and second transistors off responsive to receiving signals indicating

a state of charge on the lower voltage portion is within a threshold of the state of charge on the higher voltage portion.

18. The rechargeable battery pack of claim 15 , where the control circuit is further configured to initiate actuation of the first and second transistors responsive to receiving signals indicating

the lower voltage portion is coupled to a charging circuit;

a state of charge on the lower voltage portion is above a threshold; and

a state of charge differential between the lower voltage portion and the higher voltage portion is above a threshold.

19. The rechargeable battery pack of claim 18 , wherein the control circuit is further configured to turn both the first and second transistors off responsive to receiving signals indicating

the state of charge on the lower voltage portion is above a threshold; and

the state of charge on the higher voltage portion is above a threshold.

20. The rechargeable battery pack of claim 14 , wherein the mode control signal actuates one or more current amplifiers and one or more voltage amplifiers within the control circuit.