Abstract:
A battery supervisor system having an integral smart winch controller is provided for a vehicle equipped with an electric winch system and especially for off-road vehicles such as all-terrain-vehicles (ATVs), utility-task-vehicles (UTVs). and extreme-terrain-vehicles (XTVs) which are generally equipped with small batteries. The purpose of this invention is to prevent over discharge of the vehicle battery to a point where it would be difficult or impossible to start the vehicle engine and to prevent damage to the electric winch system, either of which has the potential of stranding an operator in a remote area. The battery supervisor monitors the state-of-charge of the vehicle&#39;s battery to automatically control the power to the winch and the vehicle&#39;s accessory loads. In addition, the smart winch controller takes a unique approach to protecting the winch by controlling the short term pulse (or pulses) of energy delivered to the winch and by forcing a fixed off time for the winch system to cool down, in lieu of trying to determine if components in the winch system are experiencing excessive temperatures and then turning the winch off.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to motor vehicle electrical systems, and more specifically, to a control system that incorporates a battery supervisor having an integral smart winch controller for driving an electric winch system. 
     BACKGROUND OF THE INVENTION 
     Rechargeable lead-acid batteries have become the standard energy source used for starting motor vehicles and powering various electrical loads on the vehicle. If this battery is allowed to be discharged to a very low state-of-charge (SOC), the operator may be unable to start the vehicle engine. The problem is exacerbated when a high current load such as an electric winch is operated, whether or not the vehicle engine is running. Repeated, deep discharging a battery will also reduce the number of charge/discharge cycles the battery can perform and may even permanently damage the battery. Many efforts have been made to avoid over discharge of a vehicle battery and examples are commonly assigned U.S. Pat. No. 3,395,288 (Von Brimer), U.S. Pat. No. 3,646,354 (Von Brimer), U.S. Pat. No. 4,039,903 (Russell), U.S. Pat. No. 4,080,560 (Abert), U.S. Pat. No. 4,493,001 (Sheldrake), U.S. Pat. No. 4,902,956 (Sloan), U.S. Pat. No. 5,089,762 (Sloan), U.S. Pat. No. 5,136,230 (Gayler), U.S. Pat. No. 5,140,250 (Morland), U.S. Pat. No. 5,200,877 (Betton, et al.), U.S. Pat. No. 5,272,380 (Clokie), U.S. Pat. No. 5,321,389 (Meister), U.S. Pat. No. 6,037,749 (Parsonage), U.S. Pat. No. 6,242,891(Parsonage), U.S. Pat. No. 7,262,947 (Heravi, et al.), U.S. Pat. No. 7,791,310 (Luz, et al.) and U.S. Pat. No. 7,898,219 (Felps). The invention disclosed in U.S. Pat. No. 7,898,219 by Felps has proven itself to perform well in “real world” applications and is the basis for the present disclosure. 
     The need for a smart winch controller becomes apparent when one experienced in the art realizes an electric winch can draw up to hundreds of amperes (A) of current, which can quickly drain a battery. Even with the vehicle engine is running, the alternator will seldom be able to deliver sufficient current to maintain the battery&#39;s charge. This is especially true in small off-road vehicles such as all-terrain-vehicles (ATVs), utility-task-vehicles (UTVs) and extreme-terrain-vehicles (XTVs) that typically have small batteries with low ampere-hour (AH) ratings (generally ranging from 15 to 45 AH) and low output alternators (generally 40 A and sometimes much less). This is not as much of a problem on larger vehicles such as sport-utility-vehicles (SUVs), large 4-wheel drive pickups and trucks that have high output alternators. But even then, some of these vehicles have electric winches with much higher pull ratings; and therefore, much higher winch current requirements. Another problem is at the high load currents winches can draw, the AH rating of the battery is significantly reduced (as much as 35% or more) because of the Peukert effect (a measure of how well a battery holds up under heavy loads). An ATV/UTV/XTV winch rated at 4500 to 5000 pounds (lbs.) can draw as much as 330 A of current. The SOC on a 28 AH battery delivering 85 A of current can drop by more than 19% in 2.5 minutes. So care must be exercised to preserve the battery&#39;s SOC when a winch is being operated. Battery choice for off-road vehicles is very important because their environment can be extreme and those equipped with an electric winch place special demands on the battery. An absorbed-glass-matt (AGM), lead-acid battery is best since it is more rugged than a flooded, lead-acid battery. The Odyssey line of AGM batteries seem to be in a “league all their own” since their batteries can be purchased with a metal casing (for high heat applications), have extreme vibration resistance, have a higher energy density than spiral wound batteries and are certified as “dry cell” (for shipping and mounting purposes). 
     A second reason for needing a smart winch controller is that winch manufacturers generally design vehicle electric winches for intermittent use. The reason for this is to keep the size, weight and cost to a minimum. But, continuous use of these winches will result in overheating of the motor windings, synthetic rope, relays, wiring and wiring connections. A difficulty in solving that problem is that winch manufacturers are inconsistent about rating the cycle times of their winches. Most adhere to a 15 minute cycle time, but some rate fixed off times that can be as little as 10 minutes. The off time is to allow the winch time to cool down. Most specify a maximum on time of 2.5 minutes for any level of winch current and a maximum on time of 10 to 45 seconds at the maximum rated winch current. The specifications for winches include the maximum pull rating in lbs. for the first layer of wire rope on the winch drum and the maximum current the winch requires for pulling that weight. This maximum current rating can be used for controlling the winch. In practice, few operators use their winches when they are unwound to the first layer and they might be pulling on something that won&#39;t move (e.g. removing a tree stump). And, under these conditions, it is easy to overload the winch (i.e. sudden excessive current). 
     Various attempts have been made to prevent damage to an electric winch. Some examples of these winch controllers are: U.S. Pat. No. 4,873,474 (Johnson) and U.S. Pat. No. 6,046,893 (Heravi), all having some form of current limiting; U.S. Pat. No. 5,214,359 (Herndon, et al.), having current limiting and thermal protection (in the relay module used for winch direction); U.S. Pat. No. 8,076,885 (Heravi, et al.), having current limiting and under voltage protection; and, U.S. Pat. No. 6,864,650 (Heravi, et al.) and U.S. Pat. No. 8,213,137 (Fregoso), both being much more complex and having current limiting, under voltage protection, over temperature protection as well as other protection features. U.S. Pat. No. 5,648,887 (Herndon, et al.) has a complex current limit protection feature that takes into account multiple states of winch operation (including detecting the battery voltage) to adjust the current limit feature. Herndon addresses excessive energy delivered to a winch but fails to address the time required for the winch to cool down after normal winch use. All of these inventions provide different methods and levels of protection for the winch system and a controller to perform these functions, but all fail to address the maximum duty cycle rating of the winch, the minimum cycle time and the SOC of the battery. The patents that do monitor the battery voltage (except U.S. Pat. No. 5,648,887), have a single, minimum voltage limit that is not compensated for the internal resistance of the battery. In U.S. Pat. No. 8,213,137, Fregoso mentions “current vs time readings” in both his ABSTRACT and DETAILED DESCRIPTION OF THE INVENTION, but makes no CLAIMS about the phrase. Certainly it is advantageous not to damage the winch system, but either a dead battery or a damaged winch system has the potential of stranding an operator in a remote area. 
     SUMMARY OF THE INVENTION 
     In a preferred embodiment of the present invention, the dual output version of the on-board battery supervisor in prior invention, U.S. Pat. No. 7,898,219 (Felps), has been modified to perform a winch drive function. Modifications include replacing the trolling motor output with a winch drive output (along with its smart controller) plus other performance improvements. The two outputs, accessory drive and winch drive, are automatically switched off when the state-of-charge (SOC) of the 12 volt, absorbed-glass-mat (AGM) lead-acid, vehicle battery decreases to a predetermined threshold and back on when the SOC increases a predetermined amount. Monitoring of the vehicle&#39;s battery voltage and the total battery current (discharging or charging) are used to determine the SOC of the battery. This feature is disabled during the time the winch drive is delivering current to the winch (i.e. winch on time). The reason for disabling the SOC measurement during winch on time is because of the difficulty in predicting the resistance (at such high currents) internal to the battery, of the wiring, of the electrical connections and of the relays. Therefore, the battery supervisor must determine, beforehand, if sufficient energy (typically greater than 42% SOC) remains in the battery to allow a winch on cycle. The SOC of the battery is monitored at all times during winch off time. 
     The preferred embodiment of the present invention takes a completely different approach for providing protection to the electric winch system. Rather than try to determine if components in the winch system are overheating and then turning the winch off, the present invention only provides energy to the winch system that is specified not to cause overheating in the first place. One experienced in the art knows that applying a term called “I 2 T” is one of the best means of limiting short term, pulse (or pulses) energy to an electric motor that is subject to overheating. Simply measuring the increase in resistance of the motor winding does not detect hot spots in the winding. In the term “I 2 T”, the “I” is the current delivered to the winch motor and the “T” is the amount of time it is delivered. It can be noted that if the current “I” is doubled, the “I 2 T” term increases by a factor of 4. For example, if a winch is specified for a maximum current of 330 A for 10 seconds, then its “I 2 T” is 1,089,000; it can draw 165 A for 40 seconds and 85.2 A for 2.5 minutes. Therefore; to limit the maximum pulse energy going to the winch, the preferred embodiment of the present invention uses an instantaneous, power monitor, integrated circuit (IC) to “square” the winch current to determine the allowable winch on time, having a maximum winch on time of 10 seconds at maximum winch current, a maximum on time of 150 seconds (2.5 minutes) at any winch current level and a fixed, forced winch off time of 15 minutes. The fixed, forced winch off time occurs immediately following a maximum winch on time event. SOC monitoring is enabled during this forced off time. 
     Even if the operator is manually switching the winch off and on as he or she monitors the winch wire rope and the load (a common practice), the present invention keeps track of the total of the on times and off times to determine if and when a forced off time needs to occur. 
     Additional protection features are still required during winch on time. The battery is monitored for excessive voltage dip and the winch is monitored for excessive current. If either event occurs, the winch is cycled off for 4 seconds. 
     To match the winch and the battery to the present invention, the operator must make a one-time adjustment (based upon manufacturer&#39;s specifications) for maximum winch current and for battery ampere-hour (AH) rating. 
     The output, intelligent switch ICs provide short circuit and over temperature protection for the output drives. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings presented in the present disclosure provide a better understanding of the present invention, but are not intended to limit the scope or use of the invention. The components in the drawings do not necessarily adhere to conventional symbols, emphasis being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views and in which: 
         FIG. 1  is a simplified schematic of a typical vehicle electrical system equipped with an electric winch that is being driven by a preferred embodiment of the present invention comprising a battery supervisor and a current sense resistor; 
         FIG. 2  is a block diagram of the battery supervisor in  FIG. 1  showing the six smaller functional blocks and their interconnecting signals; 
         FIG. 3  is a schematic of the bias and protection circuitry in the block diagram in  FIG. 2 ; 
         FIG. 4  is a schematic of the smart winch controller circuitry in the block diagram in  FIG. 2 ; 
         FIG. 5  is a schematic of the output drive circuitry in the block diagram in  FIG. 2 . 
         FIG. 6  is a schematic of the current sense and control circuitry in the block diagram in  FIG. 2 ; 
         FIG. 7  is a schematic of the battery voltage monitor and dual timer circuitry in the block diagram in  FIG. 2 ; 
         FIG. 8  is a schematic of the status circuitry in the block diagram in  FIG. 2 ; 
         FIG. 9  is a mechanical drawing of the 250 micro-ohm (μΩ) current sense resistor in  FIG. 1 ; 
         FIG. 10  is a partial view drawing of the battery supervisor label in  FIG. 1  showing typical marking for the maximum winch current adjustment; 
         FIG. 11  is a partial view drawing of the battery supervisor label in  FIG. 1  showing typical marking for the battery ampere-hour (AH) adjustment; 
         FIG. 12  is a typical voltage and timing diagram of the integrator output and the 0.2V/4.8V node of the smart winch controller in  FIG. 4  when the winch is being operated at no load; 
         FIG. 13  is a typical voltage and timing diagram of the integrator output and the 0.2V/4.8V node of the smart winch controller in  FIG. 4  when the winch is being switched on, off, and then back on again and then the load increases rapidly. 
         FIG. 14  is a table that shows the status of the accessory and winch drive outputs of the battery supervisor in  FIG. 1  via the red-green-blue (RGB) LED in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure describes how this preferred embodiment of the present invention operates, but is not intended to limit the scope, other applications or uses of the present invention. The present disclosure is primarily for all-terrain-vehicles (ATVs), utility-task-vehicles (UTVs) and extreme-terrain-vehicles (XTVs), but is not limited to these vehicles or limited in its chosen output current or voltage capabilities. Battery supervisor  12  in  FIG. 1  consists of a printed circuit board (PCB) assembly with all components being surface mount devices (SMDs) and with the PCB being attached to a heat sink (not shown) with electrical isolation and thermal conduction being provided via a thermal pad (not shown). The heat sink is oversized to minimize temperature rise. In this preferred embodiment, the present invention is integrated into a single unit, battery supervisor  12 , except for current sense resistor  18  in  FIG. 1 . This approach lends itself to “after market” applications, but one might choose to place part of the circuitry internal to the winch in new designs. Since this invention is for a vehicle application, all devices should be rated to withstand an automotive temperature range of at least −40 to +125° C. 
     To begin, refer to  FIG. 1 , which represents a typical vehicle electrical system having a battery  14  (AGM, Odyssey PC925 recommended), a battery supervisor  12 , an engine current sense resistor  18  (250μΩ, refer to  FIG. 9 ), an electric winch  24 , a winch  24  reversing, relay module  22  and a momentary control switch  20  (that turns winch  24  on and off for in or out operation). An ATV application will often have two momentary control switches (similar to switch  20 ) with the second switch being mounted on the handlebars of the ATV. The handlebar switch (not shown) often has an ignition connection that can be connected to WINCHDRIVE to reduce ignition switch current. Connection  16  works best if resistor  18  is bolted directly to the positive terminal on battery  14 . A short brass spacer may be required to mount resistor  18  on the top of battery  14  and out of the way. Battery supervisor  12  monitors the voltage of battery  14 , internally monitors the current of the accessory drive and monitors the engine current (charging or discharging) via current sense resistor  18  so as to properly control (turn off and on) ACCDRIVE and WINCHDRIVE outputs to prevent over discharge of battery  14 . In addition, battery supervisor  12  also internally monitors winch  24  drive current for use in controlling winch  24 . The preferred way to power battery supervisor  12  is from the engine ignition switch (IGN) that connects to a terminal on battery supervisor  12 . Total bias current is typically 17 mA with the outputs on and typically &lt;200 μA in the idle state (ignition switch and battery supervisor  12  switch off). Label  26  provides information for the connections, adjustments and the circuit breakers of battery supervisor  12 . 
     Referring to  FIG. 2 , BATTERY SUPERVISOR BLOCK DIAGRAM, this block diagram shows the six main circuit blocks  100 ,  200 ,  300 ,  400 ,  500  and  600  that make up battery supervisor  12  in  FIG. 1 , each to be described in more detail, later. 
     Referring to  FIG. 3 , BIAS &amp; PROTECTION  100 , it can be seen that power to bias battery supervisor  12  in  FIG. 1  comes from one of two sources, the threaded, ignition terminal  101  through diode  103  (⅓ of IMN10) or from battery  14  in  FIG. 1  via BATTERY+, diode  104  (⅓ of IMN10) and switch  105 . It is always preferred that the engine be running when winch  24  in  FIG. 1  is operated. Therefore, switch  105  is normally off to minimize battery  14  current drain when the vehicle is not being used. To reset any latched protection features of battery supervisor  12 , both the vehicle ignition switch (not shown) and switch  105  have to be turned off, momentarily. Capacitor  102  (0.1 μF) is primarily for electrostatic-discharge (ESD) protection. Diodes  103  and  104  block current from flowing back to IGN or BATTERY+. Note! BATTERY+ can be a negative voltage if battery  14  is installed reversed. PTC thermistor switch  106  (PRG18BB330 MB1RB, 33Ω, 85 mA) provides a low voltage drop and short circuit protection for VCC  108 . Voltage transient suppressor  107  (SMF16 A) clamps over-voltage transients. Precision reference integrated circuit (IC)  110  (MAX6035B, 5V±0.5%) provides 5V  112  power and a reference voltage to the circuits in battery supervisor  12 . Capacitors  109  and  111  (both 1 μF) provide input and output filtering for IC  110 , respectively. Resistors  114  (1MegΩ) and  115  (62.5 kΩ) and power-on-reset (POR) IC  116  (MAX16052) monitor BATTERY+ for excessive voltage dip (+8.5V threshold) and if it occurs, will hold ˜RESET low for 4 seconds (which turns winch  24  off), the timing being determined by capacitor  117  (1 μF). The +8.5V threshold also ensures all circuits in battery supervisor  12  have sufficient voltage to function properly. Capacitor  113  (1 μF) filters voltage transients. Resistors  119  (82.5 kΩ) and  120  (10 kΩ) and POR IC  121  (MAX16052) form a POR function (until 5V&gt;+4.65V) via ˜RESET to hold the WINCHDRIVE output in  FIG. 5  off until 4 seconds after sufficient voltage is reached. Capacitor  122  (1 μF) determines the 4 second delay. The over-current signal, ˜CL, from SMART WINCH CONTROLLER  200  in  FIG. 4  also initiates a POR function in the event a winch  24  over current condition occurs. Resistor  118  (100 kΩ) is the pull-up resistor for ˜RESET. 
     Referring to  FIG. 4 , SMART WINCH CONTROLLER  200 , this circuitry performs all of the on time and off time timing functions for driving winch  24  in  FIG. 1  via the “heart” of this circuit, integrator operational amplifier (opamp) IC  226  (LMP2011, chosen for its low offset voltage, 60 μV over temperature, even for the output coming out of saturation from the positive and negative voltage rails). A resistive divider comprised of resistors  201  (182 kΩ),  202  (332 kΩ),  203  (5.76 kΩ) and  204  (806Ω) provide the following reference voltages: 3.25V, 63 mV and 7.74 mV. READY is a “wired-and” function and can be pulled low by either open drain CMOS comparator IC  205  or  206  (both MCP6546s) or N-channel MOSFET  208  (½ of DMN5L06DMK). Resistor  207  (100 kΩ) is the pull-up resistor. IC  205  is active low if ˜RESET is &lt;3.25V. IC  206  is active low if CAP is &gt;63 mV ((an indication a pending low state-of-charge (SOC) in battery  14  in  FIG. 1  may exist)). MOSFET  208  is active when FORCEOFF is high. Also when ˜RESET is low, switch S1 in CMOS analog switch IC  209  (STG719) is on, rapidly driving integrator output  225  to +5V (a POR function). Integrator capacitor  227  (4 each 10 μF, 50V, X7R capacitors in parallel) has a high voltage rating to minimize its voltage coefficient of capacitance. The integrator input resistance during winch  24  on time (integrating from +5V towards 0V) is the combined resistance of resistors  210  (37.4 kΩ),  212  (825Ω) and  214  (825Ω) for 39.05 kΩ. N-channel MOSFET  233  (½ of DMN5L06DMK) is off during winch  24  on time, but CMOS opamp IC  229  (MCP6051) and low leakage diode  228  (⅓ of CMDX6001) will pull node  211  up to the voltage at node  230 , if it is not already that high. During winch  24  on time, the integrator  226  is driven by instantaneous power monitor IC  216  (INA223). The programmable feature of IC  216  is not used. Instead, its POR state is used, which is: output mode=“supply power”, current shunt voltage gain=20V/V and bus voltage gain=0.2 V/V. These settings yield an output “power gain” (in this case, “current squared”) of VISW (voltage proportional to winch  24  current, with 2.5V being full scale) times 1/11 of VISW. VISW connects to VIN+ (bus voltage input) of IC  216  and the junction of attenuator resistors  217  (75Ω) and  218  (750Ω) connect 1/11 of VISW (228 mV full scale, which includes 1 mV caused by input bias current) to VIN—(current shunt input) of IC  216 . 1/11 of VISW was chosen so as to not saturate the current shunt input amplifier of IC  216  until VISW reaches ˜2.74V. With this circuit, the full scale output  215  of IC  216  is 760 mV (2.5V*228 mV*1.333). During winch  24  on time integrator output  225  will integrate from +5V down to 0.2V (0.2V threshold of 0.2V/4.8V switched reference  223 ) where FORCEOFF from CMOS comparator IC  224  (MCP6541) switches to 5V. At this point, READY goes low and forced winch  24  off time begins. READY is held low until integrator  226  integrates up to the new threshold  223 , 4.8V, taking 15 minutes (i.e. forced off time). During this forced off time, winch  24  has no power and VISW=0V. Switched voltage reference  223  (0.2V/4.8V) is provided by resistors  220  (1 MegΩ),  221  (1 MegΩ) and  222  (43.2 k). 
     Continuing with  FIG. 4 , the output of open-drain CMOS comparator  239  (MCP6546) is high via pull-up resistor  238  (205 kΩ) when VISW is &gt;63 mV (which determines winch  24  is on). 63 mV was chosen to be less than the voltage at VISW caused by the unloaded current rating of winch  24 . One purpose of IC  239  (with output high), resistors  231  (13.7 kΩ),  232  (1MegΩ) and  238  (205 kΩ), is to establish a reference voltage of 56.6 mV at node  230  for the 2.5 minute timer (which limits the maximum winch  24  on time). The other purpose is to turn on N-channel MOSFETs  235  and  236  (DMN5L06DMK) and turn off N-channel MOSFET  233  (½ of DMN5L06DMK). MOSFET  236  pulls 600 mV down through resistor  237  (10 kΩ) to disable SOC monitoring during winch  24  on time. 
     Continuing with  FIG. 4 , during winch  24  forced off time, comparator  239 &#39;s output is active low, switching MOSFET  233  on via pull-up resistor  234  (205 kΩ) and enabling SOC monitoring by switching MOSFET  236  off. MOSFET  233  pulls node  213  to very near 0V; therefore, integrator input resistance comprises resistors  210  plus 212 for 38.23 kΩ. MOSFET  233  is necessary because even though IC  216  has a rail-to-rail CMOS output, its output will be a few mV from the supply rails, which is significant when one realizes integrator  229  uses a reference voltage of only 7.74 mV. Integrator  226  timing examples are shown in  FIG. 12  and  FIG. 13 , and will be described later. 
     Continuing with  FIG. 4 , during winch  24  on time, CMOS comparator IC  240  (MCP6541) monitors VISW and if its voltage &gt;3.25V (130% of maximum current rating), initiates current limit by taking ˜CL low. Resistor  219  (100 k) and capacitor  241  (1 μF) provide a time delay to ignore surge currents of winch  24 . 
     Referring to  FIG. 5 , OUTPUT DRIVE  300 , this circuitry provides the two high current outputs, ACCDRIVE and WINCHDRIVE and their current sensing. Input power BATTERY+ comes Battery  14  in  FIG. 1  via threaded terminal  301  (located on battery supervisor  12  in  FIG. 1 ). Capacitor  302  (1 μF in parallel with 0.1 μF) and capacitors  313  and  317  (both 0.1 μF) provide ESD protection and voltage filtering. Transient suppressors  308  (2 each SMDJ8.0 As in parallel) and  309  (2 each 5.0SMDJ14CAs in parallel) limit voltage surges on BATTERY+ in the event there is a loose connection between battery  14  and the vehicle electrical system. The ACCDRIVE circuitry is virtually the same as FIG. 5C in U.S. Pat. No. 7,898,219 and performs the same functions, delivering 30 A to vehicle accessories via ACCDRIVE and threaded terminal  318  (located on battery supervisor  12 ). N-channel MOSFET  310  (½ of DMN601 DMK) turns intelligent switch ICs  303  and  304  (both IR3313Ss) on when SOCGOOD is high and the body diode in MOSFET  310  provides reverse battery  14  protection when BATTERY+ is negative (i.e. battery  14  is reversed). Resistors  311  (316Ω) and  312  (316Ω) force current sharing of the current from the feedback pins (IFB) of ICs  303  and  304 . Diode  325  (½ of IMN10) blocks current from flowing into the IFB pins on ICs  303  and  304 . With potentiometer  326  (2 kΩ) set to minimum resistance, potentiometer  327  (1 kΩ) is adjusted to make VIFBA equal to 1.5V when ACCDRIVE is delivering 30 A. Next, potentiometer  326  is adjusted for a current limit latch to occur in ICs  303  and  304  at a load current of 33 A. Ref. Voltage  320  (200 mV) and resistor  321  (200 kΩ) bias the gate of N-channel MOSFET  324  (½ of DMN5L06DMK) to make its gate threshold voltage 0.29 to 0.8V. Then, sudden output current surges on ACCDRIVE (even when the output current is ˜25 A) cause a voltage transient on IFB on IC  303  that is coupled through capacitor  322  (1 μF) to turn MOSFET  324  on to prevent over-current latching of ICs  303  and  304  for a time determined by capacitor  322  and resistor  321 . If the surge current on ACCDRIVE exceeds ˜200 A, internal latches latch ICs  303  and  304  off. Diode  323  (⅓ of IMN10) discharges capacitor  322  for the next surge event. 
     Continuing with  FIG. 5 , the WINCHDRIVE circuitry uses intelligent power switch ICs  305 ,  306  and  307  (all BTS555s) that are rated to deliver a continuous combined current of 384 A to the load through output WINCHDRIVE and threaded terminal  319 . Internal short circuit latches typically trip at 1200 A at 25° C. (although very difficult to achieve), but the over current feature in smart winch controller  200  in  FIG. 1  current limits at a much lower level. ICs  305 ,  306  and  307  are turned on by N-channel MOSFET  314  (½ of DMN601 DMK) when READY is high. The body diode in MOSFET  314  provides reverse current protection when battery  14  is reversed. The current sense output ISW of ICs  305 ,  306  and  307  is proportional (typically 30,000 to 1) to the WINCHDRIVE output current and is sensed through potentiometers  328  and  329  (both 500Ω). Voltage follower CMOS opamp IC  331  (MCP6051) buffers the sensed ISW voltage. Resister  330  (10 kΩ) limits the current into opamp  331  when the ISW voltage exceeds the supply rails. With potentiometer  329  set to minimum resistance and the WINCHDRIVE output current set to 360 A, potentiometer  328  is set for VISW to be 2.5V. Potentiometer  329  is a one-time adjustment the vehicle owner makes to correspond to the maximum current rating of winch  24  in  FIG. 1  installed on the vehicle. Zener diode  315  (SMAZ6V8) provides voltage clamping for positive and negative voltages on INW and Capacitor  316  (1 μF) provides filtering for INW. Refer to  FIG. 10  to see how markings on label  26  in  FIG. 1  might appear for adjustment of potentiometer  328 .  FIG. 10  will be described in more detail, later. 
     Referring to  FIG. 6 , CURRENT SENSE &amp; CONTROL  400 , this circuitry performs the following functions: monitors the vehicle engine current (charging or discharging), combines the engine current with the accessory current at node  406  (i.e. voltages proportional to their currents), provides compensation (i.e. load compensation) for the internal resistance (Rint) of battery  14  in  FIG. 1  for SOC monitoring of battery  14  for a combined current that is discharging battery  14  during off time of winch  24  of  FIG. 1 , provides load compensation for SOC monitoring of battery  14  for a combined current that is charging or discharging battery  14  during forced off time of winch  24  and controls the dual timer in  FIG. 7 . Not providing load compensation for a combined charging current of battery  14  during off time of winch  24  facilitates a fast recovery to a good SOC following a low SOC event. 
     Continuing with  FIG. 6 , the “hard-wired” SENSE cable (jacketed, 3-wire, 16 awg, cable recommended for ruggedness) connects −IN, VSENSE+ and VSENSE− from  FIG. 1  to circuitry  400 . Bi-directional current monitor IC  403  (INA286) monitors −IN and VSENSE+ from current sense resistor  18  in  FIG. 1  and converts the full scale current, ±60 A, to a voltage (2.5V±1.5V) at node  404 . VSENSE− is the ground connection for all the circuits in battery supervisor  12  in  FIG. 1 . Capacitors  401  and  402  (both 0.1 μF) provide ESD protection. VIFBA (0 to 1.5V for 0 to 30 A ACCDRIVE current) is connected through resistor  407  (200 kΩ) to resistor  405  (100 kΩ) to combine node  404  voltage (engine current) with VIFBA (accessory current) to yield the summed voltage at node  406 . The nominal voltage at node  406  for a summed current of 0 A is 1.667V. When battery  14  is being discharged, the voltage at node  406  ranges between 1.667V (0 A load) and 3.17V (90 A load). Open drain CMOS comparator IC  412  (MCP6546) is active low when the voltage at node  406  is &lt;1.710V. The reference, 1.710V, (representing a 2.5 A battery  14  load) is provided by resistors  409  (200 kΩ) and  410  (104 kΩ) and filtered by capacitor  411  (0.1 μF). Capacitor  408  (10 μF) filters ripple voltage caused by the vehicle alternator and the loads. Switch S2 in analog switch IC  413  (STG719) is on when FORCEOFF is high and diode  419  (⅓ of CMDX6001) is shorted. The variable gain, load compensation amplifier circuitry consisting of CMOS opamp IC  417  (MCP6051), voltage divider resistors  414  (252 kΩ) and  415  (126 kΩ), potentiometer  418  (100 kΩ) and diode  419  provides LOADCOMP. Potentiometer  418  provides a variable gain (1.0 for a 45 AH battery  14  and 2.19 for a 15 AH battery  14 ) for LOADCOMP and needs to be set based on the battery  14  installed on the vehicle. When FORCEOFF is low, switch S2 in IC  413  is open and diode  419  is no longer shorted. And, if node  406  is 1.667V (0 A of current), node  416  and LOADCOMP will also be at 1.667V. With FORCEOFF low, resistor  420  (1.04MegΩ) provides the pull-up to hold LOADCOMP at 1.667V when battery  14  is being charged. This compensation was chosen for the Odyssey family of absorbed-glass-mat (AGM) “dry-cell” batteries. At first glance, it seems as though the load compensation should have a gain range of 1.0 to 3.0 for a battery  14  range of 15 to 45 AH. Upon closer examination, one realizes that if you have two identical batteries in parallel operating at a given load current, the paralleled Rint of the batteries is not ½ the Rint of one of the batteries operating at the given load current because each of the two batteries will be operating at ½ the given load current and Rint increases as current decreases in a battery. Typical Rint values for the Odyssey PC925 battery that has been discharged to an SOC of approximately 42% (approximate trip point for a low SOC) are: 25.6 mΩ@3.12 A, 24 mΩ@6.25 A, 22.4 mΩ@12.5 A, 20 mΩ@25 A, 16.2 mΩ@50 A, 14.3 mΩ@85 A and 7.5 mΩ@355 A. Between 3 A and 50 A (approximate range of current the engine and accessories might draw), Rint varies from 25.6 mΩ to 16.2 mΩ, respectively, and a nominal value is approximately 21 mΩ. For a battery of similar construction, a 30 AH battery  14  (mid-range for battery supervisor  12  requirement), Rint would be approximately 20 mΩ. So Rint=20 mΩ is chosen for load compensation, LOADCOMP. As battery  14  ages, Rint will increase, Rint compensation will be insufficient and battery supervisor  12  will shut down at a higher SOC. This is good because it will ensure the engine can still be started, but is a warning that battery  14  may need to be replaced. Refer to  FIG. 11  to see how markings on label  26  in  FIG. 1  might appear for adjustment of potentiometer  418 .  FIG. 11  will be described in more detail, later. 
     Referring to  FIG. 7 , VOLTAGE MONITOR &amp; DUAL TIMER  500 , this circuit is taken from U.S. Pat. No. 7,898,219 with some improvements. It monitors the voltage of battery  14  in  FIG. 1  via VSENSE+ to determine the SOC of battery  14  along with battery  14  load compensation from LOADCOMP through resistor  503  (332 kΩ). Temperature compensation occurs below approximately 70° F. A dual timer (1 minute or 10 minute) prevents nuisance shutdowns (SOCGOOD going low) for engine starting, for battery  14  loads &gt;2.5 A (1 minute) and for battery  14  loads &lt;2.5 A (10 minutes). VSENSE+ voltage is divided down by potentiometer  501  (200 kΩ, typically set at 101 kΩ), resistor  502  (150 kΩ) and resistor  504  (12.1 kΩ). Hysteresis (−270 mV at VSENSE+) is provided by resistor  511  (20 MegΩ) and open drain CMOS comparator IC  506  (MAX6460). The hysteresis internal to IC  506  is typically 6 mV and is asymmetrical about the reference voltage, 600 mV &gt;70° F., on its non-inverting input. i.e. the negative going threshold is 600 mV and the positive going threshold is 606 mV. Capacitor  505  (0.1 μF) filters VSENSE+ voltage. Ambient temperature compensation is provided by “diode-connected” NPN transistor  520  (BC847CW) for temperatures below approximately 70° F., with Ref. Voltage  525  equal to 600 mV above approximately 70° F. and a higher voltage below approximately 70° F. Ref. Voltage  525  has a Thevenin equivalent series resistance  524  (8.87 kΩ). An “ideal diode” circuit consisting of CMOS opamp IC  521  (MCP6051) and diode  522  (⅓ of CMDX6001) prevents compensation above approximately 70° F. This allows a more accurate measurement of the SOC of battery  14  for temperatures &gt;70° F. Transistor  520  is biased at approximately 200 μA by resistor  519  (56.2 kΩ). The VBE voltage of transistor  520  has a negative temperature coefficient of approximately −2.2 mV/° C. (approximately −1.22 mV/° F.) and a typical VBE voltage of 740 mV at −40° F. Therefore, resistor  523  (56.2 kΩ) increases reference voltage, 600 mV, to approximately 619 mV at −40° F. (which represents an SOC of approximately 75% and a voltage of approximately 12.5V for battery  14 ). This voltage compensation was chosen for battery  14  because as temperatures get colder, battery  14  energy decreases and engines are harder to start. The threshold voltage for VSENSE+ is set at 12.1V at no load on battery  14  above 70° F. (which is approximately 42% SOC of battery  14 ) and at approximately 12.37V for the threshold voltage (SOCGOOD going high again). Ref. Voltage  507  is 2.25V. Timing resistor  508  (3.48 MegΩ) and capacitor  510  (4 each 47 μF, 10V, X7R in parallel) provide RC time constant curve at node  509  that open drain comparator IC  512  (MAX6460) compares to a 211 mV threshold when 10MIN is low (1 minute timer selected) and a 1.3V threshold when 10MIN is high (10 minute timer selected). Ref. Voltage  517  (1.3V), resistor  516  (57.8 kΩ, Thevenin equivalent resistance) and resistor  514  (11 kΩ) combine with 10MIN to switch the dual timer. Capacitor  515  (0.1 μF) is a filter capacitor. Resistor  513  (33.2 kΩ) provides pull-up for SOCGOOD. If a low SOC event occurs (SOCGOOD goes low), P-channel FET  518  (MMBJ175) latches the dual timer in the 1 minute state. Therefore, the timer stays latched in the 1 minute state until the voltage on battery  14  is charged up approximately 270 mV (IC  506  hysteresis). 
     Referring to  FIG. 8 , STATUS  600 , and  FIG. 14 , LED STATUS VS. OUTPUT DRIVES, red-green-blue (RGB) LED  610  (LATBT66C) displays (via a light pipe) the status of the various states of the output drives in  FIG. 5 . The table in  FIG. 14  shows the color of LED  610  for various states. For example, status 1 is when battery  14  in  FIG. 1  is reversed and LED  610  color is RED. This is not a normal operating mode, but warns the operator of a fault. The red LED in LED  610  is turned on when current flows through diode  612  (⅓ of IMN10), the red LED, the emitter-base junction of PNP transistor  608  (BC857CW), resistor  606  (2 kΩ) and diode  605  (⅓ of IMN10) into the accessory output ACCDRIVE. ACCDRIVE voltage will be negative and resistor  606  will limit LED  610  current. Under normal operating conditions, when battery  14  polarity is corrected, status 2 is when SOCGOOD is high, WINCHDRIVE and ACCDRIVE will be on and approximately equal to battery  14  voltage, N-channel MOSFET  611  (⅓ of DMN5L06DMK) will be on and current will be flowing from VCC through MOSFET  611 , through the green LED in LED  610  and through resistor  609  (4.02 k) to ground. Pull-up resistor  607  (221 kΩ) biases transistor  608  off. Diode  605  prevents voltage transients from damaging transistor  608 . When WINCHDRIVE is low (during forced winch  24  off time or when a protection feature is activating a 4 second POR), the blue LED in LED  610  will also be on, status 3, causing the color to be aqua. Current will also be flowing through the blue LED, diode  604  (⅓ of IMN10) and resistor  603  (3.01 kΩ) to ground. Diode  602  (⅓ of IMN10) blocks current from flowing into WINCHDRIVE. If battery  14  has insufficient SOC (SOCGOOD is low), status 4, WINCHDRIVE AND ACCDRIVE will be low, LED  610  will be off and there will be no color emitted. In the event an over-temperature or short circuit event has occurred on ACCDRIVE in ICs  303  and  304  in  FIG. 5  causing its output to be latched low, and WINCHDRIVE is functioning normally and is low, status 5, the red and blue LEDs will be on causing the color to be purple. Status 6 is the same as status 5 except WINCHDRIVE is high. Then, only the red LED will be on by resistor  601  (33.2 k). Resistor  601  holds the voltage caused by leakage current from ACCDRIVE low enough to bias transistor  608  on through diode  605  and resistor  606 . Red LED current flows through saturated transistor  608  through resistor  609  to ground. Since the forward voltage drop on the red LED (approximately 2.0V) is much lower than the forward voltage drop on the green LED (approximately 3.5V), the green LED will be off. Status 7 is the same as status 3, except WINCHDRIVE is latched off due to an over-temperature or short-circuit protection feature being activated in ICs  305 ,  306  and  307  in  FIG. 5 . 
     Referring to  FIG. 9 , SENSE RESISTOR, 25μ OHMS, this mechanical drawing is a two dimensional drawing showing how the 4-terminal sense resistor  18  in  FIG. 1  is manufactured. Resistor  18  is a low cost, practical solution for measuring the current of battery  14  in  FIG. 1 . The bar stock  32  is 0.188×0.750 inches of 304/304L stainless steel. This bar stock was chosen for its low cost, usable resistivity, low temperature coefficient of resistivity, power handling capability and mechanical ruggedness. Power connections are made via holes  28  and  36  (0.25 inches) for 6 mm screw mounting. Threaded holes  30  and  34  (6-32) are sense voltage taps for resistor  18 . The calculated spacing for a 250μΩ resistor of bar stock  32  is 1.124 inches, but, in practice, the stainless steel screw and lug connections and missing material in holes  30  and  34  add a resistance of being approximately 10μΩ; therefore, a dimension of 1.190 inches yields 250μΩ. 
     Referring to  FIG. 10 , WINCH CURRENT LABEL, this is a partial view (p/v) of label  26  on battery supervisor  12  in  FIG. 1  showing a typical marking for the one-time adjustment that needs to be made corresponding to the maximum current rating of winch  24  in  FIG. 1  installed on the vehicle. Sealed potentiometer  329  in  FIG. 5  (500Ω) can be set from 0Ω (360 A) to 500Ω (110 A) to set the current. Potentiometer  329  is exposed for access above potting material  38  (urethane, epoxy or a combination used for moisture protection). Adjustment device  40  is typical for a surface mount potentiometer with the 2 dots indicating that the wiper of the potentiometer is pointing to 165 A. Note the warning that indicates a larger battery  14  in  FIG. 1  is required for maximum winch  24  currents above 165 A. 
     Referring to  FIG. 11 , BATTERY AMPERE-HOUR RATING LABEL, this is a partial view (p/v) of label  26  on battery supervisor  12  in  FIG. 1  showing a typical marking for the one-time adjustment that needs to be made corresponding to the ampere-hour (AH) rating of battery  14  in  FIG. 1  installed on the vehicle. Sealed potentiometer  423  in  FIG. 6  (100 kΩ) can be set from 100 kΩ (15 AH) to 0Ω (45 AH) to set the AH rating. Potting material  38  surrounds potentiometer  423 . 
     Referring to  FIG. 12 , INTEGRATOR TIMING  1 , and  FIG. 4 , SMART WINCH CONTROLLER  200 , this diagram shows the timing for integrator output  225  and switched reference  223  (0.2V/4.8V) for winch  24  in  FIG. 1 , drawing a no load rated current until a forced off time occurs. Integrator output  225  is linear as it decreases from 5V to 0.2V because it has a constant DC voltage input provided by the 2.5-minute timer reference voltage at node  230 . Time begins at t0, where winch  24  has been off, integrator output  225  is at 5V and reference  223  is at 0.2V. Winch  24  is turned on at t1 and is kept on until t2 (2.5 minutes) where reference  223  switches to 4.8V, winch  24  is forced off and integrator output  225  begins its fixed off time ramp. This ramp is always linear because integrator  226  always has a constant 7.74 mV reference during forced off time. The time from t2 to t3 is 15 minutes. At t3, reference  223  switches back to 0.2V and winch  24  could be turned back on (assuming the operator released switch  20  in  FIG. 1  during the forced off time). In this case, winch  24  was not turned back on and integrator output  225  continues to be 5V where it awaits the next time winch  24  is used. 
     Referring to  FIG. 13 , INTEGRATOR TIMING  2 , and  FIG. 4 , SMART WINCH CONTROLLER  200 , this diagram shows the timing for integrator output  225  and switched reference  223  (0.2V/4.8V) for winch  24  in  FIG. 1  being switched on, then off, then on again and after a short time the load on winch  24  increases initiating a forced off time at t5. From t0 to t1, integrator output  225  is at 5V and reference  223  at 0.2V waiting for winch  24  to be turned on. This waveform for integrator output  225  might represent an operator attaching the wire rope of winch  24  to a tree stump, taking up the slack in two steps (t1 to t2 and t3 to t4) and then seeing the load increase (and consequently winch  24  current increase) as the wire rope tightens (t4 to t5) until a forced off time is reached at t5 where reference  223  switches to 4.8V, integrator output  225  begins its forced off time (t5 to t6). The 15 minute timer is operating from t2 to t3, but this is not a forced off time and did not start at 0.2V.