Systems and methods for supplying power in a hybrid vehicle using capacitors, a battery and one or more DC/DC converters

1. A system for controlling connections between a battery of a hybrid vehicle and at least one of a capacitor of the vehicle and electrical loads of the vehicle, the electrical loads including essential loads and nonessential loads, the system comprising:

a battery monitoring circuit configured to determine a state of charge of the battery; and

a battery protection circuit configured to:

monitor the state of charge of the battery when the vehicle is off; and

disconnect the nonessential loads from the battery while maintaining a connection between the essential loads and the battery when the state of charge of the battery is less than a first state of charge threshold, wherein the battery protection circuit is configured to reconnect the nonessential loads to the battery when an engine start is likely to occur within a first predetermined period.

2. The system of claim 1 further comprising a power management circuit configured to:

supply a first amount of power from the battery to at least one of a starter of the vehicle and a generator of the vehicle during cranking of an engine of the vehicle; and

supply a second amount of power from the capacitor to the at least one of the starter and the generator during cranking of the engine, wherein the second amount of power is greater than the first amount of power.

3. The system of claim 1 wherein the battery protection circuit is configured to determine that an engine start is likely to occur when at least one of (i) a key FOB is within a predetermined vicinity of the vehicle, and (ii) doors of the vehicle are opened.

4. The system of claim 1 further comprising a capacitor charge/discharge circuit configured to:

determine whether a state of charge of the capacitor of the vehicle is less than a capacitor state of charge threshold; and

charge the capacitor using power from the battery when an engine start is likely to occur and the state of charge of the capacitor is less than the capacitor state of charge threshold.

5. The system of claim 1 wherein the battery protection circuit is configured to disconnect the nonessential loads from the battery for a second time when the engine start does not occur within a second predetermined period after the nonessential loads are reconnected to the battery.

6. The system of claim 1 wherein the essential loads are associated with at least one of vehicle power management, vehicle access, and vehicle starting.

7. The system of claim 1 further comprising a diode configured to allow current flow in a first direction from the battery to the essential loads and to prevent current flow in a second direction that is opposite of the first direction.

8. A system for controlling connections between a battery of a hybrid vehicle and at least one of a capacitor of the vehicle and electrical loads of the vehicle, the electrical loads including essential loads and nonessential loads, the system comprising:

a battery monitoring circuit configured to determine a state of charge of the battery; and

a battery protection circuit configured to:

monitor the state of charge of the battery when the vehicle is off;

disconnect the nonessential loads from the battery while maintaining a connection between the essential loads and the battery when the state of charge of the battery is less than a first state of charge threshold;

determine whether the state of charge of the battery is less than a second state of charge threshold, wherein the second state of charge threshold is less than the first state of charge threshold; and

send a message to an owner of the vehicle to request an engine start when the state of charge of the battery is less than the second state of charge threshold.

9. A system for controlling connections between a battery of a hybrid vehicle and at least one of a capacitor of the vehicle and electrical loads of the vehicle, the electrical loads including essential loads and nonessential loads, the system comprising:

a battery monitoring circuit configured to determine a state of charge of the battery;

a battery protection circuit configured to:

monitor the state of charge of the battery when the vehicle is off; and

disconnect the nonessential loads from the battery while maintaining a connection between the essential loads and the battery when the state of charge of the battery is less than a first state of charge threshold;

a DC/DC converter configured to control flow of current between the battery, the capacitor, and at least one of a starter of the vehicle and a generator of the vehicle; and

a disconnect circuit configured to disconnect the nonessential loads and the DC/DC converter from the battery based on a signal sent by the battery protection circuit.

10. The system of claim 9 wherein the disconnect circuit includes a bi-stable relay.

11. The system of claim 9 wherein the disconnect circuit includes P-channel MOSFETs and N-channel MOSFETs that are connected in series.

12. A method for controlling connections between a battery of a hybrid vehicle and at least one of a capacitor of the vehicle and electrical loads of the vehicle, the electrical loads including essential loads and nonessential loads, the method comprising:

monitoring a state of charge of the battery when the vehicle is off;

determining whether the state of charge of the battery is less than a first state of charge threshold;

disconnecting the nonessential loads from the battery while maintaining a connection between the essential loads and the battery when the state of charge of the battery is less than the first state of charge threshold;

determining whether an engine start is likely to occur; and

reconnecting the nonessential loads to the battery when an engine start is likely to occur within a first predetermined period.

13. The method of claim 12 further comprising:

supplying a first amount of power from the battery to at least one of a starter of the vehicle and a generator of the vehicle during cranking of an engine of the vehicle; and

supplying a second amount of power from the capacitor to the at least one of the starter and the generator during cranking of the engine, wherein the second amount of power is greater than the first amount of power.

14. The method of claim 12 further comprising determining that an engine start is likely to occur when at least one of (i) a key FOB is within a predetermined vicinity of the vehicle, and (ii) doors of the vehicle are opened.

15. The method of claim 12 further comprising:

determining whether a state of charge of the capacitor of the vehicle is less than a capacitor state of charge threshold; and

charging the capacitor using power from the battery when an engine start is likely to occur and the state of charge of the capacitor is less than the capacitor state of charge threshold.

16. The method of claim 12 further comprising disconnecting the nonessential loads from the battery for a second time when the engine start does not occur within a second predetermined period after the nonessential loads are reconnected to the battery.

17. The method of claim 12 wherein the essential loads are associated with at least one of vehicle power management, vehicle access, and vehicle starting.

18. A method for controlling connections between a battery of a hybrid vehicle and at least one of a capacitor of the vehicle and electrical loads of the vehicle, the electrical loads including essential loads and nonessential loads, the method comprising:

monitoring a state of charge of the battery when the vehicle is off;

determining whether the state of charge of the battery is less than a first state of charge threshold;

disconnecting the nonessential loads from the battery while maintaining a connection between the essential loads and the battery when the state of charge of the battery is less than the first state of charge threshold;

determining whether the state of charge of the battery is less than a second state of charge threshold, wherein the second state of charge threshold is less than the first state of charge threshold; and

sending a message to an owner of the vehicle to request an engine start when the state of charge of the battery is less than the second state of charge threshold.