Abstract:
A watercraft battery control system monitors a battery charge. The system informs the watercraft operator when the battery charge is below a predetermined value. Alternatively, the system automatically controls engine operation by starting the engine or by increasing the speed of the engine to allow a generator to replenish the battery charge when the battery charge has fallen below a predetermined value. By informing the user of an inadequate battery charge, the user can start the engine an recharge the battery. Alternatively, the system automatically maintains the battery at a predetermined charge level to ensure safe and enjoyable watercraft operation.

Description:
PRIORITY INFORMATION 
     This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2001-326814, filed on Oct. 24, 2001, the entire contents of which are hereby expressly incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a watercraft battery control system for monitoring a battery charge. The system informs the watercraft operator when the battery charge is below a predetermined value and automatically starts the engine to allow a generator to replenish the battery charge when the battery charge has fallen below a predetermined value. 
     2. Description of the Related Art 
     Watercraft (e.g., personal watercraft or boats) typically incorporate internal combustion engines along with propulsion units to provide power and propel the watercraft in a variety of popular applications. The internal combustion engines can operate according to the two-cycle (two-stroke) operating principle or the four-cycle (four-stroke) operating principle. Outboard motors are being manufactured in larger sizes to meet higher power demands from watercraft operators. The cranking torques required to start these large displacement engines, especially four-cycle engines, have become too large to allow such engines to be started by hand. Cold weather also increases engine-starting torque by affecting the viscosity of the lubricating oil. A high torque starter motor that receives electrical power from a battery is therefore necessary to start the watercraft engines. 
     A battery is essential for operating the watercraft, and since the amount of power consumed is larger for a starter than for the other electrical components, the remaining charge of the battery needs to be maintained at a relatively high level. If the remaining charge of the battery is low, the electrically operated starter cannot start the engine. 
     A typical watercraft is equipped with a number of power-consuming parts or devices that can be actuated even when the engine is stopped, for example, when the watercraft is anchored at sea. Therefore, it is possible that the remaining charge of the battery will be dissipated without the operator becoming aware that the battery is being almost discharged. For example, when power is consumed for roughly five hours at 7 amperes, the remaining charge of a typical battery can be insufficient to start an engine. A five-hour-power-consumption period is not uncommon on watercraft, especially during offshore fishing activities or when using the watercraft for recreation without the engine running. 
     One way to prevent an untimely shortage of battery charge is to provide two batteries for the watercraft. One battery is used exclusively for starting the engine, and the other battery is used to provide power to other electrical devices. Some systems use two batteries that are arranged to be switchable to ensure sufficient power to always start the engine. However, in such systems, the batteries can be falsely switched, which may cause a shortage in the charge of the battery that is intended to provide power to start the engine. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a watercraft battery control system to prevent the dissipation of the remaining charge in a battery to reduce or eliminate problems in engine starting. 
     One aspect of an embodiment in accordance with the present invention is a watercraft battery control system for monitoring a battery charge. The system informs the watercraft operator when the battery charge is below a predetermined value, and the system automatically starts the engine to cause a generator to replenish the battery charge when the battery charge has fallen below a predetermined value. 
     One aspect in accordance with embodiments of the present invention is a watercraft battery monitoring system that comprises an integrating unit that integrates the current extracted from a battery and the current provided to a battery to provide a net integrated current value. A charge determining unit is responsive to the net integrated current value and determines whether a remaining charge in the battery is less than a predetermined value. An alarm unit is responsive to the charge determining unit to output a perceptible alarm when the charge determining unit determines that the remaining charge in the battery is less than the predetermined value. In particular, embodiments, the perceptible alarm is visual. Alternatively, the perceptible alarm is audible. As a further alternative, the perceptible alarm is both audible and visual. 
     Another aspect in accordance with embodiments of the present invention is a watercraft battery monitoring system that comprises an integrating unit that integrates the current extracted from a battery and the current provided to a battery to provide a net integrated current value. A charge determining unit is responsive to the net integrated current value to determine whether a remaining charge in the battery is less than a first predetermined value. An engine control unit is responsive to the charge determining unit to automatically start an engine when the charge determining unit determines that the charge in the battery is less than the first predetermined value. The engine is coupled to a generator that provides electrical current to charge the battery to a charge level greater than the first predetermined value. Preferably, the charge determining unit also determines whether the remaining charge of the battery is greater than a second predetermined value, and the engine control unit is responsive to the charge determining unit to automatically stop the engine when the charge determining unit determines that the charge in the battery is greater than the second predetermined value. Also, preferably, the watercraft battery monitoring system further comprises an input unit that receives an input by an operator to set or reset an automatic start enable command. A storage unit receives the input and stores a value representing whether the automatic start enable command is set or reset. The engine control unit is responsive to the value representing the automatic start enable command in the storage unit to automatically start the engine only when the automatic start enable command is set. 
     Another aspect in accordance with embodiments of the present invention is a watercraft battery monitoring system that comprises an integrating unit that integrates the current extracted from a battery and the current provided to a battery to provide a net integrated current value. A charge determining unit is responsive to the net integrated current value to determine whether a remaining charge in the battery is less than a first predetermined value. An engine control unit is responsive to the charge determining unit to automatically increase a speed of an engine from an initial engine speed to an increased engine speed when the charge determining unit determines that the charge in the battery is less than the first predetermined value and the engine control unit determines that the engine is already running. The engine is coupled to a generator that provides electrical current to charge the battery to a charge level greater than the first predetermined value. Preferably, the charge determining unit also determines whether the remaining charge of the battery is greater than a second predetermined value, and the engine control unit is responsive to the charge determining unit to automatically reduce the engine speed from the increased engine speed to the initial engine speed when the charge determining unit determines that the charge in the battery is greater than the second predetermined value. Also preferably, the watercraft battery monitoring system further comprises an input unit that receives an input by an operator to set or reset an automatic speed control enable command. A storage unit receives the input and stores a value representing whether the automatic speed control enable command is set or reset. The engine control unit is responsive to the value representing the automatic speed control enable command in the storage unit to automatically increase the speed of the engine only when the automatic speed control enable command is set. 
     Another aspect in accordance with embodiments of the present invention is a watercraft battery monitoring system that comprises an integrating unit that integrates the current extracted from a battery and the current provided to a battery to provide a net integrated current value. A charge determining unit is responsive to the net integrated current value to determine whether a remaining charge in the battery is less than a first predetermined value. An engine control unit is responsive to the charge determining unit to automatically start an engine when the charge determining unit determines that the charge in the battery is less than the first predetermined value and the engine control unit determines that the engine is stopped. The engine is coupled to a generator that provides electrical current to charge the battery to a charge level greater than the first predetermined value. The engine control unit is further responsive to the charge determining unit to automatically increase a speed of the engine from an initial engine speed to an increased engine speed when the charge determining unit determines that the charge in the battery is less than the first predetermined value and the engine control unit determines that the engine is already running to thereby increase the electrical current provided to the battery. Preferably, the charge determining unit also determines whether the remaining charge of the battery is greater than a second predetermined value, and the engine control unit is responsive to the charge determining unit to automatically reduce the engine speed from the increased engine speed to the initial engine speed when the charge determining unit determines that the charge in the battery is greater than the second predetermined value and the engine speed was increased by the engine control unit. The engine control unit is further responsive to the charge determining unit to automatically stop the engine when the charge determining unit determines that the charge in the battery is greater than the second predetermined value and the engine was automatically started by the engine control unit. Also preferably, the watercraft battery monitoring system further comprises an input unit that receives an input by an operator to set or reset an automatic engine start enable command and that receives an input to set or reset an automatic speed control enable command. A storage unit receives the inputs and stores a value representing whether automatic engine start enable command is set or reset and stores a value representing whether the automatic speed control enable command is set or reset. The engine control unit is responsive to the value representing the automatic start enable command in the storage unit to automatically start the engine only when the automatic start enable command is set. The engine control unit is further responsive to the value representing the automatic speed control enable command in the storage unit to automatically increase the speed of the engine only when the automatic speed control enable command is set. 
     Another aspect in accordance with embodiments of the present invention is a method of maintaining a charge in watercraft battery. The method comprises integrating the current extracted from a battery and the current provided to a battery to provide a net integrated current value; determining from the net integrated current value whether a remaining charge in the battery is less than a predetermined value; and outputting a perceptible alarm when the remaining charge in the battery is less than the predetermined value. Preferably, the perceptible alarm is visual, audible or both visual and audible. 
     Another aspect in accordance with embodiments of the present invention is a method of maintaining a charge in watercraft battery. The method comprises integrating the current extracted from a battery and the current provided to a battery to provide a net integrated current value; determining from the net integrated current value whether a remaining charge in the battery is less than a predetermined value; and automatically starting an engine when the charge in the battery is less than the first predetermined value. The engine is coupled to a generator that provides electrical current to charge the battery to a charge level greater than the first predetermined value. Preferably, the method further comprises determining whether the remaining charge of the battery is greater than a second predetermined value, and automatically stopping the engine when the charge in the battery is greater than the second predetermined value. In particularly preferred embodiments, the method further comprises receiving an input by an operator to set or reset an automatic start enable command and storing a value representing whether the automatic start enable command is set or reset. The method automatically starts the engine only when the stored value represents the automatic start enable command being set. 
     Another aspect in accordance with embodiments of the present invention is a method of maintaining a charge in watercraft battery. The method comprises integrating the current extracted from a battery and the current provided to a battery to provide a net integrated current value; determining from the net integrated current value whether a remaining charge in the battery is less than a predetermined value; and automatically increasing a speed of engine from an initial engine speed to an increased engine speed when the charge in the battery is less than the first predetermined value. The engine is coupled to a generator that provides electrical current to charge the battery to a charge level greater than the first predetermined value. Preferably, the method further comprises determining whether the remaining charge of the battery is greater than a second predetermined value; and automatically decreasing the engine speed from the increased engine speed to the initial engine speed when the charge in the battery is greater than the second predetermined value. In particularly preferred embodiments, the method further comprises receiving an input by an operator to set or reset an automatic speed control enable command and storing a value representing whether the automatic speed control enable command is set or reset. The method automatically increases the speed of the engine only when the stored value represents the automatic speed control enable command being set. 
     Another aspect in accordance with embodiments of the present invention is a method of maintaining a charge in watercraft battery. The method comprises integrating the current extracted from a battery and the current provided to a battery to provide a net integrated current value; determining from the net integrated current value whether a remaining charge in the battery is less than a predetermined value; and performing at least one of (1) automatically starting an engine when the charge in the battery is less than the first predetermined value and the engine is stopped and (2) automatically increasing a speed of engine from an initial engine speed to an increased engine speed when the charge in the battery is less than the first predetermined value and the engine is already running. The engine is coupled to a generator that provides electrical current to charge the battery to a charge level greater than the first predetermined value. Preferably, the method further comprises determining whether the remaining charge of the battery is greater than a second predetermined value and performing at least one of (1) automatically decreasing the engine speed from the increased engine speed to the initial engine speed when the charge in the battery is greater than the second predetermined value and the engine speed was automatically increased from the initial engine speed to the increased engine speed and (2) automatically stopping the engine when the charge in the battery is greater than the second predetermined value and the engine was automatically started. In particularly preferred embodiments, the method further comprises receiving an input by an operator to set or reset an automatic start enable command and receiving an input by the operator to set or reset an automatic speed control enable command. The method stores a value representing whether the automatic start enable command is set or reset, and automatically starts the engine only when the stored value represents the automatic start enable command being set. The method stores a value representing whether the automatic speed control enable command is set or reset, and automatically increases the speed of the engine only when the stored value represents the automatic speed control enable command being set. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments in accordance with aspects of the present invention will be described below in connection with the accompanying drawing figures in which: 
         FIG. 1  illustrates a diagram of a watercraft in phantom with components of a battery control system and an engine control system illustrated by a block diagram; 
         FIG. 2  illustrates a block diagram of a watercraft battery control system showing battery monitoring components and engine components; 
         FIG. 3  illustrates a block diagram illustrating various communication paths and components of a watercraft battery control system; 
         FIG. 4  illustrates a flowchart of a control routine performed by the watercraft battery control system that illustrates control of a battery alarm; 
         FIG. 5  illustrates a flowchart of a control routine performed by the watercraft battery control system that illustrates control of an automatic starting mode; 
         FIG. 6  illustrates a flowchart of a control routine performed by the watercraft battery control system that illustrates control of a recharging mode; 
         FIG. 7  illustrates a block diagram of a watercraft battery control system showing battery monitoring components and engine components placed in a predetermined location near an electronic control unit; and 
         FIG. 8  illustrates a block diagram of a watercraft battery control system showing battery monitoring components and engine components placed in a predetermined location near an announcing section. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a watercraft equipped with a watercraft battery control system that comprises a battery consumption warning device and a system for maintaining a battery charge. In the illustrated embodiment, the watercraft battery maintenance system comprises a processing section  17  and an announcing section  13 . Information is communicated between the processing section  17  and the announcing section  13  through a local area network (LAN)  11  provided in the watercraft. Known hardware standards and protocols can be used for the LAN  11 . Direct connections can also be used between the two sections and between other sections described herein instead of using the LAN  11  to interconnect the sections. 
     As shown in  FIG. 1 , the watercraft comprises a hull  1  and an outboard motor  2 . The LAN  11  is positioned in the hull  1  and is connected to an input section  12 , the announcing section  13 , a shift/throttle operating section  15 , and the processing section  17 . The outboard motor  2  includes an engine  21 , which is provided with an engine control unit (ECU)  22 , a starter motor  23 , and a generator  24 . The ECU  22  communicates with various watercraft components via the LAN  11 . 
     The hull  1  also comprises a steering control (steering wheel)  14  for steering the outboard motor  2 . The hull  1  also includes a main switch  16 , a battery  18 , and a starter relay  19 . The main switch  16  generally starts or stops the engine  21  through a key (not shown). When the main switch  16  is closed, the starter relay  19  transfers a voltage from the battery  18  to activate the starter motor  23  to initiate engine operation. An engine stop switch  25  can cause the ECU  22  to cease engine operation. The watercraft may also include other systems for controlling when the engine is stopped, as is well known by persons skilled in the art. 
     The battery  18  also supplies power to other various watercraft components. The battery  18  is charged by the generator  24  mounted on the engine  21 . The generator  24  delivers an AC output voltage to a rectifying circuit (not shown) to supply the battery  18  with a rectified DC input voltage. 
     The electrical current delivered to the battery and the electrical current supplied by the battery  18  are monitored by the processing section  17 . The processing section  17  controls the operation of the starter relay  19  based on the result of the monitoring. For example, in one preferred embodiment, the processing section  17  outputs a signal to start and stop the engine  21  based on a measured battery current. The processing section  17  outputs a signal, such as a warning signal, via the LAN  11  to the announcing section  13  based on the result of monitoring the current delivered to and the current supplied by the battery  18 . The announcing section  13  also advantageously informs the operator visually through a display or audibly through a warning sound. 
     The input section  12  can be in the form of an operational panel, a touch screen, a keyboard, or any input system through which information necessary for the processing by the processing section  17  can be inputted. The inputted information is supplied to the processing section  17  via the LAN  11 . The processing section  17  can be advantageously placed within the input section  12  to allow the overall construction of the watercraft battery maintenance system to be smaller. 
       FIG. 2  illustrates a more detailed block diagram of a preferred embodiment of a watercraft battery control system in combination with watercraft and engine components. 
     The shift/throttle operating section  15  operates a transmission (not shown) to shift the transmission to either a forward, reverse, or neutral position in response to movement of a shift/throttle lever or other shift/throttle control selector. The shift throttle operating section  15  also operates an engine throttle position in response to operator&#39;s torque request. For example, moving the shift/throttle lever in a predetermined direction translates an operator&#39;s torque request to a torque request electrical signal based on the angle of the lever. The shift/throttle operating section  15  communicates the torque request signal and a transmission request signal to the ECU  22  via the LAN  11 . 
     The shift/throttle operating section  15  includes a shift operation signal transmitting section  15   a  and a throttle operation signal transmitting section  15   b . The shift operation signal transmitting section  15   a  delivers the transmission request signal corresponding to a shift/throttle lever position to the ECU  22  via the LAN  11 . The throttle operation signal transmitting section  15   b  delivers the torque request signal to the ECU  22  via the LAN  11 . Although both signals originate within the shift/throttle operating section, the ECU  22  recognizes each signal as a distinct signal that is delivered to the ECU  22  via the LAN  11 . 
     The ECU  22  controls the transmission position and throttle position of the engine  21  based on the electrical signals representative of the operator&#39;s requests. The ECU  22  communicates with the announcing section  13  to inform the operator of various engine and watercraft condition values. For example, the ECU  22  informs the operator of watercraft speed, engine speed, transmission position, and battery condition. Other engine and watercraft component information can also be communicated to the operator via the announcing section, as understood by a person skilled in the art. The announcing section  13  advantageously visually displays the transmitted information or advantageously sounds an audible alarm to inform the operator of watercraft condition. Alternatively both the visual display and the audible alarm can be activated. 
     In the illustrated embodiment, the processing section  17  advantageously comprises a general-purpose computer (e.g., a microprocessor-based computer system); however the processing section  17  may also advantageously comprise an application specific device that implements functions directed to the watercraft battery control system described herein. 
     In one preferred embodiment, the engine  21  can be stopped in response to a control signal from the main switch  16 . In another embodiment, the engine  21  can be stopped by an engine stop switch  25 . Alternatively, either switch can be used to stop the engine  21 . The ECU  22  can also stop the engine in response to battery conditions monitored by the processing section  17 . For example, when the current received by the battery  18  from the generator  24  or when the current delivered to the watercraft and engine components from the battery  18  exceeds a predetermined amount, the ECU  22  can stop the engine  11  to protect the battery  18  and the watercraft and engine components from possible damage. 
     A high voltage ignition system (not shown) provides ignition of an air/fuel mixture through a plurality of spark plugs (not shown). The ignition system can be advantageously controlled directly from the ECU  22  to initiate the spark plugs at predetermined ignition timing points with reference to a crankshaft angle. The ignition system can be deactivated by the ECU  22  when the ECU  22  receives an engine stop signal from the main switch  16  or from the manual engine stop switch  25 . The ECU  22  can also deactivate the ignition when the ECU  22  receives an engine stop signal from the processing section  17 . When the ECU  22  deactivates the ignition, the spark plugs are no longer initiated and the air/fuel mixture is not ignited, to thereby stop the engine  21 . 
     High voltage ignition systems are familiar to persons skilled in the art. Therefore, further explanations of various components of the ignition system, such as, for example, an ignition coil or a triggering circuit of the ignition system are not necessary. 
     In one preferred embodiment, the watercraft battery control system advantageously operates as a battery consumption warning device if the battery  18  is being overcharged or undercharged or if the battery  18  is delivering an inadequate current. Dashed signal lines in  FIG. 2  represent signals that can be advantageously used to initiate the starter relay or to send an engine stop signal to the ECU  22  when the watercraft battery control system monitors battery operations and controls battery consumption. When the watercraft battery control system is used only as a battery consumption-warning device, the dashed signal lines can be omitted. 
       FIG. 3  illustrates exemplary components inside the processing section  17 . The processing section  17  comprises an integrating section  173 , a computing section  172 , a starter operating signal outputting section  171 , an ignition stop signal outputting section  174 , and an interface  175 . The computing section  172  includes a memory  172   a.    
     The integrating section  173  monitors the electrical current delivered from the battery  18  to the watercraft and engine components and also monitors the electrical current delivered to the battery  18  from the generator  24 . The integrating section  173  integrates the current delivered from the battery to various watercraft and engine components (e.g., the battery output current) and advantageously represents the integrated value of the battery output current as a positive value. The integrating section  173  integrates the current delivered to the battery  18  from the generator  24  (e.g., the battery input current) and advantageously represents the integrated value of the battery input current as a negative value. The integrated positive and negative values are used to determine a net integrated current value for the battery  18  wherein a net positive value indicated that more current was output from the battery than was input to the battery during an integration interval. The net integrated current value is delivered to the computing section  172 . 
     The integrating section  173  advantageously comprises an ammeter (not shown) that is configured to measure both positive current values and negative current values. The ammeter is connected so that the ammeter measures the net current flowing from the battery  18 . An analog-to-digital converter (not shown) converts the measured analog current value from the ammeter to a digital value. The converted digital current value is sampled and delivered to the computing section  172 . 
     The computing section  172 , which can also be referred to as a “charge determining unit”, receives the information stored in the memory  172   a , the information outputted from the integrating section  173  and the information obtained from the LAN  11  via the interface  175 . The computing section  172  performs logical operations on the received information to generate processed information. The computing section  172  outputs commands responsive to the processed information to the starter operating signal outputting section  171 , to the ignition stop signal outputting section  174 , and to the interface  175 . 
     The starter operating signal outputting section  171  is responsive to a command output from the processing section  172  to selectively output a signal to activate the starter relay  19 . The ignition stop signal outputting section  174  is responsive to a command output from the processing section  172  to selectively output a signal to deactivate the actuation of the ignition control circuit in the ECU  22 . The interface  175  comprises a communication interface for the processing section  17  to enable the processing section  17  to exchange processed information with watercraft components and engine components via the LAN  11 . 
     It should be understood that the components of the battery control system necessary for the low battery charge warning, such as the processing section  17 , are advantageously powered at all times, even when the boat is anchored with the engine  18  stopped. 
       FIG. 4  illustrates a flowchart that represents the operation of a control routine of the watercraft battery control system illustrated in  FIGS. 1–3 . The control begins and advances to an operation block  41 , wherein the computing section  172  monitors the net integrated current value output from the integrating section  173 . As discussed above, the net integrated current value produced by the integrating section  173  represents the remaining charge in the battery  18 . 
     The control routine then advances to a decision block  42 , wherein the control routine determines whether the net integrated current value output from the integrating section  173  is lower than a predetermined value. If the integrated value from the integrating section  173  is lower than the predetermined value, the control routine advances to an operation block  43 . If the net integrated current value is not lower than the predetermined value (e.g., is equal to or greater than the predetermined value), the control routine advances to an operation block  44 . 
     In the operation block  43 , the control routine requests the announcing section  13  to issue a warning to inform the operator that the remaining battery charge is lower than the predetermined value. Thus, the operator is made aware that allowing the battery  18  to continue to discharge may reduce the remaining charge below the charge needed to start the engine  21 . The control routine then returns to the beginning to repeat the foregoing steps. 
     In the operation block  44 , the control routine resets the request to the announcing section  13  to issue a warning to the operator. The control routine then returns to the beginning to repeat the foregoing steps. 
     The control routine illustrated in  FIG. 4  causes the computing section  172  to monitor the output of the integrating section  173 . The computing section  172  determines whether the remaining charge of the battery  18  is less than a predetermined value. Since, as discussed above, the output from the integrating section  173  indicates the net integrated current consumed from the battery  18 , the computing section  172  can determine how much charge is left in the battery  18  by taking into account the capacity of the battery  18 . 
     The amount of charge needed during normal engine starting is set as the predetermined battery charge value. The remaining charge of the battery is calculated by the computing section  172  from the output of the integrating section  173  and from the capacity of the battery  18 . The capacity of the battery  18  and the predetermined battery charge needed to start the engine are values that may vary with different models of batteries and with different sizes of engines. The capacity and the predetermined battery charge for the particular combination of battery and engine are advantageously inputted through the input section  12  and stored in the memory  172   a.    
     When the remaining charge of the battery  18  is determined to be less than the predetermined value, the signal is outputted to the announcing section  13  through the LAN  11  to output a warning, as described above for the operation block  43 . Because the control routine repeats, the outputted warning continues until the remaining charge of the battery  18  is determined to be as great as the predetermined value in the decision block  42 . When the change in the charge determination occurs (e.g., when the remaining charge of the battery  18  is determined not to be lower than the predetermined value in the decision block  42 ), the request to the announcing section  13  for generating the warning is reset in the operation block  44 , as described above. 
     The initiated warning causes the operator to become aware of the shortage of remaining battery charge. The operator advantageously responds to the warning and starts the engine  21  to begin charging the battery  18 . Charging the battery  18  is intended to prevent the remaining charge of the battery  18  to fall further below the predetermined value such that the battery  18  would have an insufficient charge to start the engine  21 . When the warning is no longer occurring, the operator may then turn of the engine  21 . 
     A flowchart in  FIG. 5  is similar to the flowchart in  FIG. 4 , and similar operation blocks and decision blocks are identified accordingly. The flowchart in  FIG. 5  includes additional control routine procedures to implement another aspect of the watercraft battery control system illustrated in  FIGS. 1–3 . 
     In  FIG. 5 , the control routine begins and advances to the operation block  41 , wherein the output from the integrating section  173  is monitored by the computing section  172 , as discussed above. The control routine then advances to the decision block  41 , wherein the control routine determines whether the net integrated current value from the integrating section  173  is lower than a first predetermined value. If the net integrated current value is lower than the first predetermined value, the control routine advances to the operation block  43 . If the net integrated current value is not lower than the first predetermined value, the control routine advances to the operation block  44 . 
     In the operation block  43 , the control routine requests the announcing section  13  to issue a warning to inform the operator that the remaining charge in the battery  18  is lower than the first predetermined value as described above in connection with  FIG. 4 . The control routine then advances to a decision block  51 . 
     As discussed above, in the operation block  44 , the control routine resets the request to the announcing section  13  to issue a warning to the operator as described above in connection with  FIG. 4 . The control routine then returns to the beginning to repeat the foregoing steps. 
     In the decision block  51 , the control routine determines whether an automatic charging mode is set. If the automatic charging mode is not set, then the control routine returns to the beginning to repeat the foregoing steps. If the automatic charging mode is set, the control routine advances to an operation block  52 . 
     In the operation block  52 , the control routine outputs a starter operating signal which initiates the starter relay  19  to start the engine  21 . Then, the control routine advances to an operation block  53 . 
     In the operation block  53 , the computing section  172  monitors the net integrated current value that is output from the integrating section  173 . As discussed above, the net integrated current value represents the amount of remaining battery charge. The control routine then advances to a decision block  54 . 
     In the decision block  54 , the control routine determines whether the net integrated current value has reached a second predetermined value. If a second predetermined value has not been reached the control routine returns to the operation block  53 . The control routine repeats the operation in the block  53  and the decision process in the block  54  until the second predetermined value is reached. When the second predetermined value is reached, the control routine advances to an operation block  55 . 
     In the operation block  55  the control routine resets the request to the announcing section  13 . The control routine then advances to an operation block  56 . 
     In the operation block  56 , the control routine outputs an ignition stop signal to cause the computing section  172  to issue a command to the ignition stop signal outputting section  174 . The stop signal outputting section  174  responds to the command to generate the ignition stop signal, which deactivates the ignition power supply circuit of the ECU  22  is thereby deactivated to stop the engine  21 . The control routine then returns to the beginning to repeat the foregoing steps. 
     As discussed above, the automatic charging mode automatically starts the engine  21  when a predetermined battery charge is detected in the processing section  17 . No action by the operator is required when the battery control system is in the automatic charging mode. The automatic charging mode can be selectably set by the operator via the input section  12 . Alternatively, the automatic charging mode can be fixedly (unrewritably) stored in the memory  172   a,  which results in the automatic starting of the engine  21  automatically at all times when the remaining charge of the battery  18  decreases below the first predetermined level. 
     When the automatic charging mode is set, the computing section  172  produces the output to the starter operating signal outputting section  171  to deliver the starter operating signal. The starter-operating signal outputting section  171  accordingly delivers the starter-operating signal to the starter relay  19  to start the engine  21 . 
     Preferably, when the engine  21  is automatically started as discussed above, the shift state of the engine  21  is in neutral and the throttle is opened to a degree sufficient to cause the engine  21  to operate at a speed that drives the generator  24  with enough power to output the electrical current required to charge the battery  18 . To accomplish the foregoing, the processing section  17  issues a command to the ECU  22  via the LAN  11 . The ECU  22  is advantageously programmed to automatically generate a shift operation signal to the transmission via the shift operation signal transmitting section  15   a  to cause the transmission to shift into the neutral position and to automatically generate a throttle opening command via the throttle operation signal transmitting section  15   b  to cause the engine  21  to operate at a sufficient speed to adequately charge the battery  18 . Alternatively, the ECU  22  may be advantageously programmed to cause the engine  21  to be in the neutral position and to have an appropriate throttle opening whenever the engine  21  is shut off. 
     In above-described embodiment, when the remaining charge of the battery is determined to be less than the first predetermined value, the starter operating signal is outputted to start the engine  21 . The engine  21  is thus started, and the charging of the battery  18  is initiated by the generator  24  attached to the engine  21 . The first predetermined value is selected so that the battery  18  will have a sufficient charge to start the engine  21  when the automatic starting operation is initiated. The charging of the battery  18  to the second predetermined value causes the battery  18  to have a sufficient charge to operate the electrical components of the watercraft for a time interval before the engine  21  needs to be started again. The second predetermined value can be selected based on the power requirements of the components and based on a desired time interval before again starting the engine  21 . 
     In an alternative to the embodiment of  FIG. 5 , either the engine start operation in the operation block  52  or the engine stop operation in the operation block  56  may be performed manually by the operator. 
     Another alternative embodiment of the control routines of  FIGS. 4 and 5  is illustrated by a flowchart in  FIG. 6 .  FIG. 6  includes the procedure described above, and similar operation blocks and decision blocks are identified accordingly. The flowchart in  FIG. 6  includes additional control routine procedures to implement another aspect of the watercraft battery control system illustrated in  FIGS. 1–3 . 
     The control routine in  FIG. 6  begins and advances to the operation block  41  where the net integrated current value output from the integrating section  173  is monitored by the computing section  172 . The control routine then advances to the decision block  42 , wherein the control routine determines whether the net integrated current value from the integrating section  173  is lower than a first predetermined value. If the net integrated current value is lower than the first predetermined value, the control routine advances to the operation block  43 . If the net integrated current value is not lower than the first predetermined value, the control routine advances to the operation block  44 . 
     In the operation block  43 , the control routine requests the announcing section  13  to issue a warning to inform the operator that the remaining charge in the battery  18  is lower than the first predetermined value, as described above in connection with  FIGS. 4 and 5 . The control routine then advances to a decision block  61 . 
     As discussed above, in the operation block  44 , the control routine resets the request to the announcing section  13  to issue a warning to the operator, as described above in connection with  FIGS. 4 and 5 . The control routine then returns to the beginning to repeat the foregoing steps. 
     In the decision block  61 , the control routine determines whether the engine  21  is already running. If the engine  21  is not running, the control routine advances to the operation block  51  and performs the operations in the blocks  51 – 56  described above in connection with  FIG. 5 . After completing the operations in the blocks  51 – 56 , the control routine returns to the beginning and repeats the foregoing steps. 
     If the engine  21  is already running when the determination is performed in the decision block  61 , the control routine advances to a decision block  62 , wherein the control routine determines whether the recharging mode is set. If the recharging mode is not set, the control routine returns to the beginning and repeats the foregoing steps. If the recharging mode is set, the control routine advances to an operation block  63 . 
     In the operation block  63 , the control routine commands to the ECU  22  to cause the ECU  22  to generate signals to increase the engine speed. The control routine then advances to an operation block  64 . 
     In the operation block  64 , the computing section  172  monitors the net integrated current value output from the integrating section  173 , which represents the amount of remaining battery charge. The control routine then advances to a decision block  65 , wherein the control routine determines whether the net integrated current value has reached a second predetermined value. If the net integrated current value has not reached the second predetermined value, the control routine returns to the operation block  64 . If the net integrated current value has reached the second predetermined value, the control routine advances to an operation block  66 . 
     In the operation block  66 , the control routine resets the request to the announcing section for issuing a warning to cause the warning to the operator to be discontinued. The control routine then advances to an operation block  67 . 
     In the operation block  67 , the control routine resets the request to the ECU  22  for increasing the engine speed. The control routine then returns to the beginning and repeats the foregoing steps. 
     In accordance with the embodiment of  FIG. 6 , when the signal is outputted to the announcing section  13  to output the warning, the processing branches according to whether the engine  21  is running or not. The running condition of the engine  21  can be detected by the ECU  22  through the LAN  11  and the interface  175  to the computing section  172 . 
     The recharging mode is a mode that can be set via the input section  12  and stored in the memory  172   a . When the recharging mode is set and the engine is already running when the remaining charge of the battery  18  decreases below the first predetermined value, the speed of the engine  21  is automatically increased to increase the current generated by the generator  24 . In particular, although power is already being generated by the generator  24 , if the amount of charge in the battery  18  decreases below the first predetermined value, more power is being consumed by the electrical components of the watercraft than is being provided by the generator  24  at the original speed of the engine  21 . 
     When the recharging mode is set, the computing section  172  issues a command signal to the ECU  22  via the interface  175  and the LAN  11  to cause the ECU  22  to generate control signals to increase the speed of the engine  21 . In particular, the ECU  22  advantageously outputs a control signal to increase the throttle opening of the engine  21  to cause speed of the engine  21  to increase. 
     After the speed of the engine  21  is automatically increased, the output from the integrating section  173  is continually monitored by repeating the operations in the blocks  64  and  65  until a determination is made that the remaining charge of the battery  18  has reached the second predetermined value. As discussed above, the second predetermined battery charge value is set beforehand to be sufficiently larger than the first predetermined value so that the battery  18  has enough charge to supply power to the electrical components of the watercraft for a time interval when the engine  21  is not running and to have a sufficiently large remaining charge to start the engine  21 . The second predetermined value is advantageously inputted via the input section  12  and is stored in the memory  172   a.    
     When the second predetermined value is reached, the request to the announcing section  13  for generating the warning is reset and the reset of the request for increasing the engine speed is outputted. The computing section  172  issues a command to the ECU  22  via the interface  175  and the LAN  11  to cause the ECU  22  to reset the request for increasing the engine speed, which causes results in the speed of the engine  21  to return to the initial value (e.g., a selected idle speed). 
     The above-described embodiment of  FIG. 6  ensures that a sufficient charge is maintained in the battery  18  when the power is being consumed faster than the battery  18  can supply when being charged at an initial idle speed of the engine  21 . 
       FIG. 7  illustrates another embodiment of a watercraft battery control system in accordance with another aspect of the present invention. In the embodiment of  FIG. 7 , the integrating section  71  communicates with the LAN  11  and replaces the processing section  17  of  FIG. 2 . The integrating section  71  has the same function as of the integrating section  173  of the processing section  17  in the previously described embodiment and is provided with the communication interface (not shown in  FIG. 7 ) to enable the integrating section  17  to be connected to the LAN  11 . Furthermore, in the embodiment of  FIG. 7 , the computing section  172 , the starter operating signal outputting section  171 , and the ignition stop signal outputting section  174  are incorporated with the ECU  22  as a computing section  22   a . Thus, a redundancy of hardware can be avoided by replacing the computing section  172  with a computing function found in the ECU  22 . 
     Although, the locations of the computing sections and integrating section  71  in  FIG. 7  differ from the locations of corresponding sections in  FIG. 2 , the overall operation of the watercraft battery control system in  FIG. 7  is similar to the overall operation of the watercraft battery control system in  FIG. 2 . Therefore, the operations performed by the control routines in  FIGS. 4–6  can also be implemented in the embodiment of  FIG. 7 . 
       FIG. 8  illustrates another embodiment of a watercraft battery control system in accordance with another aspect of the present invention. As in  FIG. 7 , the locations of the computing sections and integrating section  71  in  FIG. 8  differ from the locations of corresponding sections in the embodiment of  FIG. 2 . In contrast to  FIG. 7 , the computing section  172 , the starter operating signal outputting section  171 , and the ignition stop signal outputting section  174  in  FIG. 8  are incorporated with the announcing section  13  as a computing section  13   a.    
     Although, the locations of the computing sections and integrating section  71  in  FIG. 8  differ from the locations of corresponding sections in  FIG. 2 , the overall operation of the watercraft battery control system in  FIG. 8  is similar to the overall operation of the watercraft battery control system in  FIG. 2 . Therefore, the operations performed by the control routines in  FIGS. 4–6  can also be implemented in the embodiment of  FIG. 8 . 
     In the embodiments described herein, the battery control system function can provide additional functions of the announcing section  13 , such as, for example, the display screen. As a further example, the input section  12  can be integrated with the announcing section  13 . 
     According to the embodiments described herein, the power extracted from the battery  18  and the power provided to the battery  18  are monitored by integrating the flow rate of the electrical currents into and out of the battery  18  to determine the remaining charge of the battery  18 . By continuously monitoring the remaining charge of the battery  18 , deep discharge of the battery  18  below the charge required to start the engine  18  can be prevented. 
     Although the present invention has been described in terms of a certain preferred embodiments; other embodiments apparent to those of ordinary skill in the art also are within the scope of this invention. Thus, various changes and modifications may be made without departing from the spirit and scope of the invention. For instance, various steps within the routines may be combined, separated, or reordered. In addition, some of the indicators sensed (e.g., engine speed and throttle position) to determine certain operating conditions (e.g., rapid deceleration) can be replaced by other indicators of the same or similar operating conditions. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present invention. Accordingly, the scope of the present invention is intended to be defined only by the claims that follow.