Trolling motor battery gauge

A battery gauge for an electric trolling motor is disclosed. The battery gauge includes a battery that is configured to supply power to the trolling motor. The battery gauge also includes a motor speed setting switch that is configured to supply a signal representative of the motor speed setting. The battery gauge also includes an electronic circuit configured to sense at least one battery parameter that is representative of the battery charge. The electronic circuit is also configured to receive an electrical signal that is representative of the speed setting. The electronic circuit further is configured to determine the remaining battery charge time based on the at least one battery parameter and the speed setting.

FIELD OF THE INVENTION
 The disclosure relates to a battery gauge for a battery-powered electric
 trolling motor of the type which is commonly mounted to the bow of a
 fishing boat. Further, the disclosure relates to a battery gauge for an
 electric trolling motor which displays the amount of running time
 remaining at the current speed setting of the motor before the battery
 loses its charge, thereby allowing the user to adjust the speed setting
 accordingly.
 BACKGROUND OF THE INVENTION
 Fishing boats and vessels are often equipped with a trolling motor for
 providing a relatively small amount of thrust to slowly and quietly propel
 the boat or vessel while the operator is fishing. The motor is typically
 mounted to the bow of the boat (alternatively the motor may be mounted at
 other locations in the boat, for example the motor may be transom mounted
 at the stern of the boat) so that the thrust pulls the boat through the
 water. The power source for the trolling motor is usually a lead-acid
 marine battery having a limited capacity measured by the amount of
 amp-hours that the battery is capable of providing. The limited battery
 capacity limits the combination of trolling motor speed and time available
 to the fisherman. For a predetermined state of charge on the battery, the
 fisherman can troll for a relatively long amount of time at low speed
 (i.e., low-power usage), or for a relatively short amount of time at high
 speed (i.e., high-power usage). When the battery is discharged, the
 fisherman needs to stop his trolling operations until such time that the
 battery can be charged. Unfortunately, prior art trolling motors do not
 provide these fisherman with a reliable way of determining how long the
 battery will last until it needs to be recharged. Thus, the fisherman may
 find that the battery power is depleted well before the end of the fishing
 day.
 Some trolling motors provide information related to the trolling motor
 battery condition, to the operator, by measuring and displaying the
 percentage charge of the battery. The display may be in the form of a bar
 graph having a number of segments corresponding to the percentage of
 charge (e.g., four out of ten segments may be lighted to indicate a 40
 percent charge), or alternatively the display may be in a numerical
 percentage charge of the battery. Based on the display, an operator may
 attempt to roughly estimate the amount of running t me remaining based on
 his prior experience with the boat and trolling motor at different
 operating speed conditions. The display, however, does not provide an
 accurate indication of the amount of running time remaining before the
 battery will be discharged. This defect results from the fact that the
 amount of current drawn from the battery will depend on the speed settings
 of the trolling motor. As the speed setting, and thus propeller speed,
 changes, the current usage will vary in a very wide range (e.g., from 1
 amp to 50 amps). Thus, for example, a 40 percent charge may last two hours
 with the motor operating at its maximum speed, but may last for eight
 hours if the speed is cut back to a slower trolling speed. Therefore, even
 an experienced operator will be able to make only a very inaccurate
 estimate of the amount of running time left using existing battery gauges,
 and will only be able to guess what speed setting will correspond to the
 amount of time that he wishes to continue trolling.
 Accordingly, there is a need for an improved battery gauge for an electric
 trolling motor which determines the amount of running time remaining at
 the current speed setting of the trolling motor before the battery loses
 its charge, and displays this running time. Further, there is a need for a
 battery gauge in which the operator will know how much longer he may
 continue to troll at the current speed setting. Further still, there is a
 need for a battery gauge for an electric trolling motor which provides
 information of which the user can use to adjust the speed setting to
 decrease the current draw and conserve battery power if insufficient
 running time is available at the current speed setting, avoiding the
 possibility of running out of battery power too early.
 SUMMARY OF THE INVENTION
 An exemplary embodiment relates to a battery gauge for an electric trolling
 motor. The battery gauge includes a battery configured to supply power to
 the trolling motor. The battery gauge also includes a motor speed setting
 switch configured to supply a signal representative of the motor speed
 setting. Further, the battery gauge includes an electronic circuit
 configured to sense at least one battery parameter representative of the
 battery charge. The electronic circuit is configured to receive an
 electrical signal representative of the speed setting. The electronic
 circuit is configured to determine the remaining battery charge time based
 on the at least one battery parameter and the speed setting.
 Another exemplary embodiment relates to an electric trolling motor. The
 electric trolling motor includes a propulsion unit configured to provide
 thrust and having a motor. The electrical trolling motor includes a
 steering unit, coupled to the propulsion unit for steering the propulsion
 unit. The electric trolling motor further includes a battery configured to
 supply power to the propulsion unit. Further still, the electric trolling
 motor includes a motor speed setting switch coupled to the motor and
 configured to supply a signal representative of the motor speed setting.
 Yet further still, the electric trolling motor includes an electronic
 circuit configured to sense at least one battery parameter representative
 of the battery charge, and the electronic circuit is configured to receive
 an electrical signal representative of the speed setting. The electronic
 circuit is configured to determine the remaining battery charge time based
 on the at least one battery parameter and the speed setting.
 Yet another exemplary embodiment relates to a method of providing an
 indication of battery charge for a trolling motor. The method includes
 sensing at least one battery parameter of a trolling motor battery. The
 battery parameter is representative of battery charge. The method also
 includes receiving, by a processing circuit, the at least one battery
 parameter. The method further includes, receiving, by the processing
 circuit, a signal representative of a trolling motor speed setting.
 Further still, the method includes computing, by the processing circuit, a
 battery charge time based on the at least one battery parameter and the
 trolling motor speed setting.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
 Referring to FIG. 1, a trolling motor system 100, is depicted. Trolling
 motor system 100 includes a battery 110 for providing electric power to a
 prop motor 120, a steering motor 130, a lift motor 140, and a display 150.
 Trolling motor system 100 also includes a foot pedal assembly 160 with
 input devices for controlling the operation of trolling motor system 100.
 Trolling motor system 100 further includes a chassis 170 for mounting
 trolling motor system 100 to a boat. Further still, trolling motor system
 100 includes a head 180 coupled to prop motor 120 via a rotatable shaft
 190.
 In an exemplary embodiment, battery 110 is a 12 volt lead-acid marine
 battery with limited capacity (typically 105 amp-hours). Also, in an
 exemplary embodiment, foot pecal assembly 160 includes a pedal direction
 (tilt) potentiometer 161 for sensing the rotational position of a foot pad
 used to set a desired steering direction. Foot pedal assembly 160 also
 includes a prop motor speed potentiometer 162 for sensing the rotation of
 an actuatable knob used to select a prop motor speed.
 Further, in an exemplary embodiment, foot pedal assembly 160 includes ten
 actuatable switches 200. Switches 200 include a master switch 210 used to
 control a relay in the chassis which, in turn, controls application of
 power from the battery to the rest of system 100. Other switches include,
 a prop on/off switch 220 for turning the prop on and off; a momentary prop
 on switch 225 for turning the prop on momentarily; a foot presence switch
 230 which indicates whether the operator's foot is on or off foot pedal
 assembly 160; a mode select switch 235 for selecting an operating mode; a
 jog left switch 240 for allowing a user to make small or large corrections
 to the desired bearing, jog left switch 240 being a momentary switch which
 operates steering motor 130 at a reduced speed; a jog right switch 245
 which allows a user to make small or large corrections to the desired
 bearing, jog right switch 245 being a momentary switch which operates
 steering motor 130 at a reduced speed; a trim-up stow switch 250, which is
 a momentary switch allowing upward trim of the motor or stowage of the
 motor; a trim down-deploy switch 255 providing trim down of the motor or
 deployment of the motor if stowed; and an anchor switch 260 configured to
 toggle on or off the power anchor function.
 In an exemplary embodiment, foot pedal assembly 160 also includes a
 micro-controller 265 that is configured to read the settings of
 potentiometers 161 and 162 and switches 200 (except, in an exemplary
 embodiment, for the master power switch which may not be coupled to
 microcontroller 265), and is configured to communicate data representative
 of switch 200 positions via a serial communications link 270 to chassis
 170. Any of a variety of configurations to communicate information from
 foot pedal 160 may be used, including, but not limited to, serial link
 270, which is shown as an RS-232 communications link, however other
 configurations such as parallel communications links, and the like, may
 also be used.
 Chassis 170 houses a motherboard including a second microcontroller 300
 which is configured to receive input data from foot pedal 160 along serial
 link 270. Micro-controller 300 is also configured to receive signals from
 an auto pilot compass circuit 305 and a global positioning system (GPS)
 path track circuit 310 in chassis 170. Micro-controller 300 further is
 configured to receive heading and depth signals from a heading sensor 315
 and a sonar module 320 which are mounted in head 180. Chassis
 microcontroller 300 is configured to execute appropriate control
 algorithms to process various inputs, generate control signals for
 controlling the steering motor 130, lift/trim motor 140, and prop motor
 120, via appropriate output drive circuits. In an exemplary embodiment,
 micro-controller 300 has access to random access memory (RAM) and
 electronically erasable programmable read only memory (EEPROM), also
 generates control signals to produce visible indicia, such as, but not
 limited to, the available amount of running time at the current prop motor
 speed setting before the battery needs to be recharged, on LCD display
 150.
 In an exemplary embodiment, remaining running time is displayed (in tenths
 of an hour) on LCD display 150 based on the "no load battery voltage"
 (i.e., open-circuit voltage), time, and prop speed currently selected by
 the setting of the prop motor speed potentiometer. To determine remaining
 running time, in an exemplary embodiment, certain assumptions are made.
 For example, battery 110 is assumed to be a 105 amp-hour marine battery in
 good condition at a temperature of 80 degrees Fahrenheit. The accuracy of
 any calculations of remaining run time are diminished to the extent that
 the assumptions are not met. For example, the accuracy may be diminished
 if the battery is new or nearly worn out (i.e., in poor condition), if a
 different type or size (i.e., capacity) a battery 110 is used, or if
 battery 110 is operated at a different temperature. In alternative
 embodiments, one or more sensors may be added to detect some of these
 conditions (e.g., temperature), and make appropriate corrections in the
 software.
 When prop motor 120 is turned off (i.e., prop on/off and momentary prop on
 switches are in their off positions), and after delay time (determined as
 described below), micro-controller 300 measures the "no load battery
 voltage" (i.e., open-circuit voltage from the battery), and uses this
 value as an index to lookup a "state of charge" (SOC) in amp-hours from an
 "SOC table" stored in memory (e.g., EEPROM). Micro-controller 300 also
 reads the selected prop motor speed setting from potentiometer 162, and
 uses this value as an index to lookup a "motor current" in a "motor
 current table" stored in the memory. In an exemplary embodiment, a 100
 millisecond loop, remaining run time (in tenths of hours) is computed and
 displayed using equation:
 ##EQU1##
 In an exemplary embodiment, the "SOC table" contains "state of charge"
 values in amp-hours times 100 for improved accuracy, providing 0.01 hour
 resolution across a range from 0.1 hours (i.e., 10 in the table) to over
 200.0 hours (i.e., 20,000 in the table). The table itself contains twenty
 entries, or one entry for each of the twenty possible no load voltages
 from 11.7 volts to 12.7 volts that an 8-bit A/D converter can measure with
 a resistor divider network which divides the input battery voltage by
 2.54.
 In an exemplary embodiment, the "motor current table" contains motor
 currents in amps times 100 for improved accuracy, thereby providing 0.01
 amp resolution across the range of 1 amp (i.e., 100 in the table) to 50
 amps (i.e., 5,000 in the table). The table will contain 256 entries, one
 for each of 256 possible prop motor speed settings. The value of the
 "motor current" values depends on prop motor 120 being used, and different
 tables may be used for different motors.
 In an exemplary embodiment, when prop motor 120 is turned on,
 micro-controller 300 stops measuring the "no load battery voltage" and
 retains the last state of charge value which was obtained when prop motor
 120 was turned off. Further, when prop motor 120 is turned on, a memory
 location is cleared that is used to store the total charge used. From the
 initial point when the motor is turned on, every one second,
 micro-controller 300 uses the prop motor speed setting as an index to the
 "motor current table" to lookup the present motor current, and further
 uses the table value to compute the charge used (CU) during that one
 second interval in amp-seconds using equation:
EQU CU(amp-sec)=Motor Current (amp)*1 sec (2)
 Every one second, micro-controller 300 accumulates the total charge used
 (TCU) as follows:
EQU TCU=TCU+CU(amp-sec) (3)
 where TCU is a 3-byte binary result in amp-seconds (1-378,000 amp-seconds,
 where 378,000 amp-seconds equals 105 amp-hours). Then, running time is
 computed every 100 milliseconds in tenths of an hour using the following
 equation:
 ##EQU2##
 Thus, the last measured no load battery voltage (used to determine the
 state of charge) is used repeatedly as long as prop motor 120 is left on.
 It is also assumed that prop motor 120 will be turned off periodically
 (e.g., every 30 minutes) such that the state of charge can be updated
 using a new measured no load battery voltage.
 In an exemplary embodiment, the no load battery voltage is measured using a
 one percent resistor divider network 320 using 2.55 K Ohms and 5.11 K Ohm
 resistors to divide the battery voltage by 3.0039. The divided voltage is
 digitized using a ten-bit A/D interface 330 referenced to 5 volts to
 provide 4.8 millivolt resolution or 14.67 millivolt resolution at the 12
 volt input to the divider to provide 68 A/D readings from 11.7 volts to
 12.7 volts. A/D interface 330 may be provided on micro-controller 300
 itself (if, e.g., an Atmel 8535 micro-computer is used as the chassis
 micro-controller, in an exemplary embodiment), or may be a separate A/D
 converter. A hardware filter 340 is preferably used to reject high
 frequency noise on the 12 Volt battery voltage input. In addition,
 software filtering is performed every 100 milliseconds, performing an A/D
 conversion to measure the present voltage, adding the converted value to
 four previous voltage values already stored in RAM, and dividing the sum
 by five. These steps insure that each measurement of the no load battery
 voltage is the average of five voltage measurements taken at 100
 millisecond intervals which results in filtering out noise and improving
 the accuracy and resolution of the A/D conversion. However, it should be
 noted that any of a variety of filtering techniques, including, but not
 limited to the filtering techniques described above, may be used to
 improve the accuracy and resolution of the A/D conversion. To prepare for
 the next measurement, four previous voltage values stored in RAM are
 shifted (deleting the oldest value) and the present digitized voltage is
 stored as the newest value. By deleting the oldest value, any residual
 affect of a single bad reading will be completely eliminated in 0.5
 seconds. Again, other arrangements and techniques, such as, but not
 limited to integral, filtering, and smoothing techniques, may be used to
 remove the residual affect of any single bad readings.
 As noted above, micro-controller 300, in an exemplary embodiment, waits for
 a delay time after prop motor 120 is turned off, before measuring the no
 load battery voltage and updating the state of charge. The delay time
 allows the no load battery voltage to stabilize after prop motor 120 is
 turned off, which typically takes between 1 and 5 seconds. In an exemplary
 embodiment, micro-controller 300 waits until four voltage values are
 stored in RAM that are all approximately equal (i.e., within plus/minus 44
 milliVolts or three LSB of the A/D) before measuring the no load battery
 voltage. Also, as noted above, the running time is computed and displayed
 every 100 milliseconds on display 150 with prop motor 120 turned on or
 off. When prop motor 120 is on, the state of charge is assumed to decrease
 directly with time. Therefore, if prop motor 120 speed setting is not
 changed, the displayed running time will decrement every 0.1 hours (i.e.,
 every 6 minutes), subject only to the accuracy of the timing circuit of
 micro-controller 300, however, when prop motor 120 is turned off, the
 displayed run time may jump up or down because the actual state of charge
 is measured again, and the measurement may differ from the assumed linear
 (time based) discharge. The displayed run time will be most accurate when
 prop motor 120 is off. Thus, to obtain the most accurate run time, in an
 exemplary embodiment, the operator can simply turn off prop motor 120 and
 wait about five seconds for the no load battery voltage to stabilize. If
 the jump is too large, software filtering may be used to "mask" the actual
 state of charge to avoid having too large a difference from the previous
 value to avoid confusion at the expense of accuracy.
 When the computed run time reaches zero (with prop motor 120 on or off),
 the display signal from micro-controller 300 will cause LCD display 150 to
 display "RES" for "reserve". At this point, the user will be instructed to
 stop using the battery to prevent a deep discharge cycle that can reduce
 the life of battery 110. Continued use in the reserve domain will reduce
 the battery life by reducing the number of charge/discharge cycles
 remaining. "RES" continues to be displayed as long as the power is left
 on. However, if the user then turns master power switch 210 off,
 micro-controller 300 will lose track of the accumulated time and, when
 power is reapplied, it is possible that display 150 may show a run time
 greater than zero. After being turned back on, the system will measure the
 no load battery voltage and will compute a new run time remaining as
 described above. To prevent this loss of information, in an exemplary
 embodiment, the accumulated time and/or the "reserve" condition is stored
 in non-volatile memory (e.g., EEPROM).
 In an exemplary embodiment described above, motor current is determined
 using the setting of prop motor speed potentiometer 162 as an index to a
 table which correlates speed of prop motor 120 to current being drawn from
 battery 110 under those conditions. In an alternative embodiment, a
 current sensor (e.g., a current-sense resistor and A/D) may be used to
 measure the actual current being drawn from the battery, or the actual
 current being drawn by the prop motor. The advantage of this technique is
 that the accuracy of the motor current measurement may be increased. The
 disadvantage however is that, when the prop motor is turned off (e.g.,
 when the fisherman is still at home with the prop out of the water), the
 run time cannot be determined since no current is being drawn. In another
 embodiment, these two techniques can be combined, with the setting of the
 prop motor speed potentiometer used to determine the current draw with the
 prop motor off, and the measured current draw used with the motor on.
 In an alternative embodiment, micro-controller 300 may be programmed or
 configured to calculate an approximate distance of travel based on the
 remaining battery charge time and the speed setting. The distance of
 travel may then be displayed on display 150. Further, in an exemplary
 embodiment, the distance of travel calculated may also be displayed on a
 display map, which may be shown on display 150, and used, in particular,
 but not limited to a GPS based path tracking system. Further still,
 micro-controller 300 may be programmed to calculate or estimate the
 distance of travel remaining based on the remaining battery charge time
 and the current motor speed (revolutions per minute (rpm)). The estimate
 may be further augmented by utilizing operator input, such as boat size,
 boat weight, wind, wave conditions, etc. Some of the information utilized,
 in particular, boat parameters may be stored in memory or in a look-up
 table. Yet further still, micro-controller 300 may be programmed to
 provide a warning signal to the operator, to notify the operator when it
 is time to begin heading back to home (or any reference point) based upon
 GPS signals and based upon the calculated or estimated distance of travel
 remaining. The system is however not limited to GPS, but may utilize any
 other type of sensed, derived, calculated, or estimated distance from home
 to base the alarm signal on.
 While the detailed drawings, specific examples, and particular formulations
 given describe exemplary embodiments, they serve the purpose of
 illustration only. The materials and configurations shown and described
 may differ depending on the chosen performance characteristics and
 physical characteristics of the trolling motor system and its associated
 electronics. For example, the type of processors, electronic circuits, or
 software used may differ. The systems shown and described are not limited
 to the precise details and conditions disclosed. Furthermore, other
 substitutions, modifications, changes, and omissions may be made in the
 design, operating conditions, and arrangement of the exemplary embodiments
 without departing from the scope of the invention as expressed in the
 appended claims.