Abstract:
Redundant power supplies and redundant channels of communication maximize the probability that a controller will trigger a battery disconnect switch to open when commanded to do so.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to electrical systems of motor vehicles. More particularly, the invention relates to circuits that include a battery disconnect switch for disconnecting a battery or battery bank from the electrical system. 
     BACKGROUND OF THE INVENTION 
     Motor vehicles that are propelled by internal combustion engines have electrical systems that include one or more D.C. storage batteries. In order to crank the engine at starting, an ignition switch is turned to a start, or crank, position that causes the engine to be cranked by an electric starter motor. When the engine has started, the switch is released from start position to assume a run position. In start position, electric current flows from the battery, or battery bank, to an electric starter motor that cranks the engine through a set of gears. The amount of current is typically very large, and consequently, heavy electrical cable is typically employed to conduct the current without the presence of any circuit protection device to protect against a short in the cable or the starter motor. 
     The electrical system has other circuits that are fed from the battery, or battery bank. Those individual circuits may be protected by their own individual circuit protection devices, such as fuses or circuit breakers, but there may be no circuit protection between the battery and the circuit protection devices themselves unless a battery disconnect switch is present. 
     Various types of battery disconnect switches are known. One type is a mechanical switch that requires manual operation. Because it may not be feasible to access such a switch in a hazardous situation, such as after a vehicle has been involved in an accident, automatic remote control systems for operating battery disconnect switches have been developed. 
     When a vehicle is equipped with a passenger airbag system, a signal that calls for airbag deployment may also be used to remotely operate a battery disconnect switch. A medium or heavy truck that may have a battery disconnect switch, typically does not have an airbag system, and so the same type of control remote control that would be present in an airbag equipped vehicle would not be present in the truck. 
     SUMMARY OF THE INVENTION 
     The inventors have recognized that failure to open a battery disconnect switch that connects the battery bank with a vehicle&#39;s electrical system may in certain situations have serious negative consequences. The inventors therefore believe that it is important to minimize, and ideally reduce to zero, the probability that the switch will fail to open when commanded to do so. Failure of the switch to open may be due to no fault in the design or quality of the switch itself or the vehicle&#39;s electrical system, but rather may be due to circumstances of a particular situation, such as a crash. 
     The inventors therefore propose that the system for operating the battery disconnect switch employ certain features that will maximize the probability that a battery disconnect switch will open when commanded to do, even if the vehicle is not equipped with an airbag system that is intended to open the disconnect switch in the event of a crash. 
     These features include redundant channels of communication through which a command to open the switch is transmitted from one or more sources of the command to a controller, and redundant power supplies for the switch and the controller. 
     It is a general objective of the invention to provide an electrical system connected through a battery disconnect switch to a bank of one or more DC storage batteries. A battery disconnect switch controller will open the battery disconnect switch in response to a command to disconnect the battery bank from the electrical system. The system has redundant channels of communication through which the command is transmitted from one or more sources of the command to the controller. 
     It is another general objective of the invention to provide an electrical system connected through a battery disconnect switch to a bank of one or more DC storage batteries. A battery disconnect switch controller will open the battery disconnect switch in response to a command to disconnect the battery bank from the electrical system. The system has redundant power supplies for the switch and the controller. 
     The foregoing, along with further aspects, features, and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. The disclosure includes drawings, briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a general schematic electrical diagram of a first circuit embodying principles of the present invention. 
         FIG. 2  is a general schematic electrical diagram of a second circuit. 
         FIG. 3A  is a schematic electrical diagram of a first type of battery disconnect switch that can be controlled in accordance with principles of the invention. 
         FIG. 3B  is a schematic electrical diagram of a second type of battery disconnect switch that can be controlled in accordance with principles of the invention. 
         FIG. 3C  is a schematic electrical diagram of a third type of battery disconnect switch that can be controlled in accordance with principles of the invention. 
         FIG. 4  is more detailed schematic diagram of a version of the circuit of  FIG. 1  that is used with disconnect switch trigger circuits shown in  FIGS. 5A and 5C . 
         FIG. 5A  is a schematic electrical diagram of a trigger circuit for use in triggering the first type of battery disconnect switch. 
         FIG. 5B  is a schematic electrical diagram of a trigger circuit for use in triggering the second type of battery disconnect switch. 
         FIG. 5C  is a schematic electrical diagram of a trigger circuit for use in triggering the third type of battery disconnect switch. 
         FIG. 6  is a more detailed schematic diagram of a version of the circuit of  FIG. 1  that is used with the disconnect switch trigger circuit shown in  FIG. 5B . 
         FIGS. 7 and 8  collectively form a schematic diagram of the power supply and voltage regulator used in the circuits of  FIGS. 1 and 6 . 
         FIG. 9  is a more detailed schematic diagram of the second circuit shown in  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a circuit that comprises one or more D.C. storage batteries  20 , herein sometimes referred to as a battery bank, a battery disconnect switch  22 , herein sometimes referred to as a BDS, a starter motor  24  for cranking an internal combustion engine that propels a truck, and a control unit  26  for operating BDS  22 . Ignition switch connection to starter motor  24  is not shown. Control unit  26  and BDS  22  are integrated with battery bank  20  on the truck chassis. 
     BDS  22  assumes a normally closed condition for conducting current from battery bank  20  to starter motor  24  when the ignition switch is placed in start position to crank the vehicle&#39;s engine. When control unit  26  receives a signal requesting that BDS  22  be operated to open condition, the control unit delivers a trigger signal to BDS  22  that causes BDS  22  to open and prevent current flow from battery bank  20  to starter motor  24 . 
     Control unit  26  can receive signals from an HMI (human machine interface)  28 , a wired communication channel  30 , and a wireless communication channel  32 . Wired and wireless communication are redundant in the disclosed embodiment, meaning that a signal request to operate BDS  22  to open is concurrently sent by both wire and wireless channels from a location that is remote from the battery bank. HMI  28  is understood to be an operator, such as a pushbutton, at the location of the switch. 
       FIG. 2  shows a second control unit  34  that receives signals from HMI  28  and re-transmits them to control unit  26  both by wire and wireless. Control unit  34  is remote from control unit  26  and is located, for example, in the instrumental panel of the truck cab. 
       FIGS. 3A and 3B  illustrate respective relay type BDS actuators.  FIG. 3C  illustrates a pyroelectric type BDS actuator. These three actuators are present in known battery disconnect switches. 
     In  FIG. 3A , the receipt of a trigger signal T by actuator  36  causes the actuator to open BDS  22 . When no trigger signal is given, BDS  22  is closed. 
     When a voltage whose polarity is represented by numeral  40  in  FIG. 3B  is applied to actuator  38 , BDS  22  is closed. When a voltage of opposite polarity, as represented by numeral  42 , is applied, BDS  22  is open. 
     When a voltage is applied to actuator  44  in  FIG. 3C , BDS  22  is irreversibly opened. 
       FIG. 4  shows control unit  26  to comprise a power supply and voltage regulator  50  powered by battery bank  20  for developing a regulated voltage  52 , such as +12 VDC, that is supplied to BDS  22  and a regulated voltage, such as +5 VDC, for operating a microcontroller system (MCS)  54 . A back-up power supply  56  is provided for power supply and voltage regulator  50  in case the latter&#39;s connection to the battery bank through the vehicle electrical system is somehow lost. 
     MCS  54  will trigger BDS  22  via a trigger circuit  58  when MCS  54  receives a command to disconnect battery bank  20  from the vehicle electrical system. The command may come from any one or more of three sources, namely from the non-remote HMI input directly to MCS  54 , from a remote initiator via wired communication, and from a remote initiator via wireless communication. Wired communication to MCS  54  is through one or more of an SAE J1939 and an SAE J1708 data link. Wireless communication can occur via one or more wireless communication protocols such as Zigbee and Bluetooth. 
       FIG. 5A  shows how MCS  54  is associated with the actuator  36  of  FIG. 3A . The trigger circuit  58  comprises a transistor driver in which the collector is connected to one terminal of actuator  36 . The other terminal of actuator  36  is connected to battery bank  20  through BDS  22 . When MCS  54  operates the transistor driver, actuator  36  becomes grounded through the transistor. Battery current flows through BDS  22 , actuator  36  and the transistor to ground causing the actuator to open BDS  22  and automatically terminating the current flow to ground through actuator  36 . 
       FIG. 5B  shows how MCS  54  is associated with the actuator of  FIG. 3B . Voltage is applied to actuator  38  in the polarity sense of reference numeral  40  when a first transistor driver  40 A is turned on by MCS  54 . Voltage is applied to actuator  38  in the polarity sense of reference numeral  42  when a second transistor driver  42 A is turned on by MCS  54 . Both battery voltage ( 20 ) and regulated voltage ( 52 ) are supplied to the collector of driver  40 A through respective diodes D 1 , D 2 . Both battery voltage ( 20 ) and regulated voltage ( 52 ) are also supplied to the collector of driver  42 A through respective diodes D 3 , D 4 . Diodes D 5 , D 6  provide reverse polarity protection for the respective driver drivers. 
       FIG. 5C  shows how MCS  54  is associated with the actuator of  FIG. 3C . The trigger circuit  58  comprises a transistor driver in which the collector is connected to one terminal of actuator  44 . The other terminal of actuator  44  is connected to battery bank voltage ( 20 ) and to regulated voltage ( 52 ) through respective diodes D 1 , D 2 . 
       FIG. 6  shows control unit  26  to comprise a microcontroller system (MCS)  70  that is associated with the wired communication channel, the wireless communication channel, and the HMI interface. 
     MCS  70 , like MCS  54 , monitors battery bank voltage as an indicator of the healthy status of the battery bank and the associated battery cable system. Should the battery bank voltage become less than voltage needed to operate the BDS actuator, microcontroller  70  outputs regulated +12V to the trigger circuit (reference  52 ) to provide enough power supply for the BDS to function correctly when the microcontroller is commanded to disconnect the battery bank via the trigger circuits. 
     Microcontroller  70  can receive a command input from the HMI interface, from the wired communication interface, or the wireless communication interface. A J1939 communication is used as a standard wired communication interface. A J1708 is optionally available for a vehicle that has no J1939 network. 
     For redundancy, Zigbee wireless communication technology is implemented. Bluetooth wireless communication technology is used as an option for control interface expansibility. The redundancy of wired communication and wireless communications increases the probability that BDS will be shut off when commanded. 
       FIG. 7  illustrates details of the power supply and voltage regulator  50 . A step up/step down DC/DC converter  90  with burst mode can develop regulated +12 VDC output from input voltages ranging from +4 VDC to +60 VDC. One input to converter  90  is from the battery bank through a diode. Another input is from the back-up power circuit  56 . A voltage regulator  92  develops +5 VDC for the microcontroller system from the output of converter  90 . 
       FIG. 8  illustrates back-up power circuit  56 . It comprises a super-capacitor  100  and a back-up battery pack  102 . The super-capacitor  100  is charged from the battery bank through a diode D 7 . Battery pack  102  parallels super-capacitor  100  and is kept charged from the battery bank. 
       FIG. 9  shows control unit  34 . A microcontroller  104  can read a user command from a push button with energy harvest module  106  and transmit the command to control unit  26  through wired and/or wireless channels. When the push button is pushed, the energy harvest module provides power to assure the microcontroller and Zigbee module both perform the user request. This enables control unit  34  to still send a command to control unit  26  should the power supply to the MHI interface and/or wired communication channel become non-functional, such as in an accident. 
     While a presently preferred embodiment of the invention has been illustrated and described, it should be appreciated that principles of the invention are applicable to all embodiments that fall within the scope of the following claims.