Marine power supply system and method for power control in marine propulsion system

1. A marine power supply system for supplying power to a marine propulsion unit including a propulsion generator, an engine that drives the propulsion generator, and an electric motor that drives the propulsion generator, the marine power supply system comprising:

a battery unit including a first battery to supply power to a starter to start the engine, and a second battery to supply power to the electric motor; and

a power distributor connected to the first battery and the second battery; wherein

the power distributor outputs a demand power amount of power required by the first battery to the first battery, and outputs at least a portion of surplus power to the second battery when a total demand power amount required by the battery unit includes the surplus power.

2. The marine power supply system according to claim 1 , wherein at least a portion of the surplus power is obtained by subtracting at least the demand power amount required by the first battery from the total demand power amount.

3. The marine power supply system according to claim 1 , wherein

the battery unit further includes a third battery to supply power to at least one of a plurality of devices in a marine vessel excluding the electric motor and the starter; and

the power distributor outputs the demand power amount of the power required by the first battery to the first battery, and outputs at least a portion of the surplus power to the third battery when the total demand power amount includes the surplus power.

4. The marine power supply system according to claim 3 , wherein the power distributor outputs to the second battery a power amount of power obtained by subtracting a demand power amount required by the third battery from the surplus power.

5. The marine power supply system according to claim 1 , wherein

the battery unit further includes a third battery to supply power to at least one of a plurality of devices in a marine vessel excluding the electric motor and the starter; and

the power distributor performs a control to limit a power supply to the third battery or to stop the power supply to the third battery when the surplus power is less than a surplus power threshold.

6. The marine power supply system according to claim 1 , further comprising:

an electric motor controller configured or programmed to limit driving of the electric motor based on a charge amount of the second battery.

7. The marine power supply system according to claim 6 , wherein

the battery unit further includes a third battery to supply power to at least one of a plurality of devices in a marine vessel excluding the electric motor and the starter; and

the power distributor performs a control to limit a power supply to the third battery or to stop the power supply to the third battery when the charge amount of the second battery is equal to or less than a charge amount threshold.

8. The marine power supply system according to claim 7 , wherein

the marine propulsion unit includes a clutch provided between the engine and the propulsion generator to switch between a state in which a rotational force is transmitted from the engine to the propulsion generator and a state in which a rotational force is not transmitted from the engine to the propulsion generator; and

the electric motor controller is configured or programmed to control the electric motor to assist driving of the clutch when the clutch performs a switching operation even when the charge amount of the second battery is equal to or less than the charge amount threshold.

9. The marine power supply system according to claim 6 , further comprising:

a charge amount acquirer to acquire the charge amount of the second battery based on a current value of a current that flows from the power distributor to the second battery and a current value of a current that flows from the second battery to the electric motor controller.

10. The marine power supply system according to claim 1 , wherein the power distributor includes a current value detector to detect a current value of a current that flows between the power distributor and the first battery, and acquires the demand power amount required by the first battery based on the current value.

11. The marine power supply system according to claim 10 , wherein the power distributor acquires, as the demand power amount required by the first battery, an amount obtained by subtracting an amount of power in the first battery being consumed based on a current value of a current that flows from the first battery to the power distributor from an amount of power being stored in the first battery based on a current value of a current that flows from the power distributor to the first battery.

12. The marine power supply system according to claim 1 , wherein the power distributor includes a converter to boost a voltage of at least a portion of the surplus power and output boosted power to the second battery.

13. The marine power supply system according to claim 1 , wherein the power distributor inputs power from the second battery to the power distributor when there is not the surplus power.

14. The marine power supply system according to claim 1 , further comprising:

a generator to generate power and input generated power to the power distributor.

15. The marine power supply system according to claim 1 , wherein the power distributor outputs the demand power amount of the power required by the first battery to the first battery, and outputs at least a portion of the surplus power to the second battery when the total demand power amount obtained by subtracting an output power amount output from the battery unit from an input power amount input to the battery unit includes the surplus power.

16. A marine power supply system for supplying power to a marine propulsion unit including a propulsion generator, an engine that drives the propulsion generator, and an electric motor that drives the propulsion generator, the marine power supply system comprising:

a battery unit including a first battery to supply power to a starter to start the engine, and a second battery to supply power to the electric motor; and

a power distributor connected to the first battery and the second battery to output power to the first battery in preference to the second battery.

17. A method for power control in a marine propulsion system including a propulsion generator, an engine that drives the propulsion generator, and an electric motor that drives the propulsion generator, the method comprising:

outputting, to a first battery that supplies power to a starter that starts the engine, a demand power amount of power required by the first battery; and

outputting at least a portion of surplus power to a second battery that supplies power to the electric motor when a total demand power amount required by a battery unit including the first battery and the second battery includes the surplus power.

18. The method for power control according to claim 17 , wherein

the outputting of at least the portion of the surplus power to the second battery includes outputting to the second battery at least a portion of the surplus power obtained by subtracting at least the demand power amount required by the first battery from the total demand power amount.

19. The method for power control according to claim 17 , wherein

the battery unit further includes a third battery to supply power to at least one of a plurality of devices in a marine vessel excluding the electric motor and the starter; and

the method further comprises outputting at least a portion of the surplus power to the third battery when the total demand power amount includes the surplus power.

20. The method for power control according to claim 19 , wherein the outputting of at least the portion of the surplus power to the second battery includes outputting to the second battery a power amount of power obtained by subtracting a demand power amount required by the third battery from the surplus power.