Abstract:
Operation of an industrial vehicle, such as one that lifts and transports loads, is controlled based on the weight of a removable battery. A control method involves reading a battery weight value from an electronic memory attached to a battery. That battery weight value is compared to a specified battery weight value for the industrial vehicle. The operation of the industrial vehicle is restricted to less than the normal operating characteristics when the battery weight value is less than the specified battery weight value. For example, the height to which a load can be raised is limited or the speed at which the industrial vehicle is limited when a battery installed on the industrial vehicle weighs less than the specified battery weight for effectively counterbalancing a load.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Not applicable. 
       STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to battery powered industrial vehicles, such as lift trucks; and more particularly to monitoring the performance of the battery. 
         [0005]    2. Description of the Related Art 
         [0006]    Electric lift trucks employ large lead-acid batteries to power their traction and lift drives. Many lift trucks are operated almost continuously throughout three work shifts a day. When the battery becomes discharged, it is replaced and the truck is immediately put back into service. The battery that was removed is then recharged off the truck and prepared for use on another truck. In a warehouse serviced by many such trucks, batteries continuously cycle through stages including: recharging (typically 7 to 8 hours); cool down period (typically another 7 to 8 hours); and use (typically 7 to 8 hours). Therefore a typical warehouse many have 2 or 3 times the number of batteries as the number of industrial vehicles. Because is takes some time to replace these relatively large batteries, during which time the truck is out of service, an objective in this industry is to operate the truck as long as possible on a battery charge. To do this, however, one must accurately know the state-of-charge or present capacity of the battery. 
         [0007]    It also is desirable to know when a particular battery is approaching the end of its useful life at which time it may no longer be recharged to a level sufficient for a reasonably long working period. Nevertheless it is undesirable from an economic perspective to take a battery out of service before absolutely necessary. In order to determine when a particular battery is approaching the end of its useful life operational data has to be gathered over days or weeks to be able to detect a performance degradation trend. 
         [0008]    In addition, a need exists to be able to detect several operating conditions that indicate a need to perform maintenance or repairs on a battery. For example, repeated disconnection and connection of the battery to a truck and recharging equipment cause wear of the battery cable. That wear often results in power losses in the cable and thus inefficient battery use. Electric current leakage also can occur between the battery and the frame of the lift truck which may be disadvantageous. 
         [0009]    Therefore, a need exists for a system and method that monitors performance of each battery for a fleet of lift trucks. 
       SUMMARY OF THE INVENTION 
       [0010]    A business has a fleet of industrial vehicles each powered by a rechargeable battery. When recharging is required, the battery is removed from a vehicle and replaced by another fully charged battery. 
         [0011]    The removable battery serves as ballast to counterbalance loads that are being carried by the industrial vehicle. It is incumbent on the user of the industrial vehicle to ensure that an appropriate battery is used. Accordingly, specifications are provided for the necessary characteristics for the removable battery, including the minimum battery weight. As an assist, to the user to ensure an appropriate battery is used, the operation of the industrial vehicle is controlled in response to the actual weight of the battery that is installed. The present control method reads a battery weight value from an electronic memory attached to the installed battery, and compares that battery weight value to a minimum battery weight specified for the industrial vehicle. When the battery weight value is less than the minimum battery weight, operation of the industrial vehicle is limited to less than the normal operating characteristics. 
         [0012]    For example, the height to which the industrial vehicle is able to raise a load may be limited when the installed battery weighs less that the specified is less than the minimum battery weight. As another example, the maximum speed at which the industrial vehicle is able to travel may be reduces when too light weight a battery is installed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of an industrial vehicle that utilizes a battery sensor module according to the present invention; 
           [0014]      FIG. 2  is a block diagram of a control system of the industrial vehicle; 
           [0015]      FIG. 3  depicts an exemplary vehicle fleet management system in which a fleets of industrial vehicles communicate via a network with a central computer in a warehouse that is linked to a remote database to which other computers have access; 
           [0016]      FIG. 4  is a block diagram of the battery sensor module that is mounted on a battery; 
           [0017]      FIGS. 5 through 9  depict tables of different types of data stored in a memory of the battery sensor module; and 
           [0018]      FIG. 10  is a flowchart of a method for restricting operation of the industrial vehicle when an installed battery has insufficient weight to properly counterbalance a load being carried. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]    The present invention relates to the operation of an industrial vehicle. Although the invention is being described in the context of a stand-up, counterbalanced lift truck used at a warehouse, the inventive concepts are applicable to other types of industrial vehicles, and their use in a variety of facilities, such as a factories, freight transfer stations, warehouses, and stores, for example. 
         [0020]    With initial reference to  FIG. 1 , an industrial vehicle  10 , specifically a lift truck, includes an operator compartment  11  with an opening for entry and exit by the operator. Associated with the operator compartment  11  are a control handle  14 , a floor switch  12 , and steering wheel  16  that collectively serve as operator controls  17 . The industrial vehicle  10  has a load carrier  18 , such as a pair of forks, that is raised and lowered on a mast  19 . As will be described in further detail, a communication system on the industrial vehicle is able to exchange data and commands via an antenna  15  and a wireless signal with an external warehousing system. 
         [0021]      FIG. 2  is a block diagram of a control system  20  for a typical industrial vehicle  10  that incorporates battery monitoring equipment. The control system  20  comprises a vehicle controller  21  which is a microcomputer based device that includes memory  24 , analog to digital converters, and input/output circuits. The input/output circuits receive operator input signals from the operator controls  17  to activate and govern operation of the vehicle functions such as forward and backward travel, steering, braking, and raising and lowering the load carrier  18 . In response to the input control signals, the input/output circuits send command signals to each of a lift motor control  23  and a propulsion drive system  25  comprising a traction motor control  27  and a steer motor control  29 . The propulsion drive system  25  provides a motive force for moving the industrial vehicle  10  in a selected direction, while the lift motor control  23  drives load carrier  18  along a mast  19  to raise or lower a load  35 , such goods being warehoused. 
         [0022]    The industrial vehicle  10  is powered by a multiple cell battery  37  that is electrically coupled to the vehicle by a cable  38  that has two conductors. A connector at a first end of the cable  38  is attached to the battery terminals and another connector  36  at the opposite, second end of the cable is connected to a mating connector  34  on the industrial vehicle. The battery  37  furnishes electrical power to the vehicle controller  21 , propulsion drive system  25 , steer motor control  29 , and lift motor control  23  through a bank of fuses or circuit breakers in a power distributor  39 . 
         [0023]    The traction motor control  27  drives one or more traction motors  43  which is connected to a propulsion wheel to provide motive force to the industrial vehicle. The speed and rotational direction of the traction motor  43  and the associated propulsion wheel are designated by the operator via the operator control handle  14 , and are monitored and controlled through feedback derived from a rotation sensor  44 . The rotation sensor  44  can be an encoder coupled to the traction motor  43  and the signal therefrom is used to measure the speed and distance that the vehicle travels. The propulsion wheel is also connected to friction brake  22  through the traction motor  43 , to provide both a service and parking brake functions for the industrial vehicle  10 . 
         [0024]    The steer motor control  29  is connected to drive a steer motor  47  and associated steerable wheel  49  in a direction selected by the operator by rotating the steering wheel  16 , described above. The direction of rotation of the steerable wheel  49  determines the direction that the industrial vehicle  10  travels. 
         [0025]    The lift motor control  23  sends command signals to control a lift motor  51  which is connected to a hydraulic circuit  53  that forms a lift assembly for raising and lowering the load carrier  18  along the mast  19 . In some applications, the mast  19  can be a telescoping mast, in which case the hydraulic circuit also raises and lowers the mast. As shown here, a height sensor  59  provides a signal to the vehicle controller  21  indicating the height of the load carrier on the mast  19 . Similarly, a weight sensor  57  is provided on the load carrier  18 . A load sensor  58 , such as a radio frequency identification (RFID) tag reader, is mounted on the mast to obtain an identification of the goods being transported. 
         [0026]    In addition to providing control signals to the drive and lift control systems, the vehicle controller  21  furnishes data to an operator display  55  that presents information to the vehicle operator. In addition, the display indicates vehicle operating parameters, such as for example, the speed of travel, battery charge level, hours of operation, time of day, and maintenance needed to be performed. Although not shown here, temperature sensors can also be included to monitor the temperature of the motors and other components. Alert annunciations are presented on the operator display  55  to alert the operator of vehicle conditions requiring attention. 
         [0027]    Referring still to  FIG. 2 , a number of data input and output devices can also be connected to the vehicle controller  21 , including, for example, a vehicle power sensor  60  that measure the voltage and electric current received at the industrial vehicle from the battery  37 . As will be elaborated upon hereinafter, a battery sensor module (BSM) communication interface  62  exchanges data with a battery sensor module  64  that is mounted on the battery  37 . Each battery  37  for the fleet of industrial vehicles has a battery sensor module  64  mounted thereon to gather and store data regarding that particular battery. The industrial vehicle  10  also has a communication port  69 , and a maintenance service port  65  by which the vehicle controller  21  communicates with external devices. The communication port  69  is connected to a wireless communication device  66  that includes a transceiver  68  connected to the antenna  15  for exchanging data and commands with a communication system in the warehouse or factory in which the industrial vehicle  10  operates. Any one of several communication protocols such as Wi-Fi, can be used to exchange messages and data via that communication link. Each industrial vehicle  10  has a unique identifier, such as its manufacturer&#39;s serial number or a communication network address, that enables messages to be specifically communicated to that vehicle. 
         [0028]    The vehicle controller  21  stores data regarding the operation of the industrial vehicle  10 . That data can include number of hours in operation, battery state of charge, and fault codes encountered. In addition, load lifting operations are monitored using the time that the lift motor  51  is active. Various speed parameters, such as speed and acceleration of the vehicle and of the mast  19 , can also be monitored. The vehicle operational data are collected and stored in a memory  24  in the vehicle controller  21 . 
         [0029]    Referring now to  FIG. 3 , a warehouse  100 , in which one or more industrial vehicles  10  operate, includes a communication system  102  that links the vehicles to a warehouse computer  104 . The communication system  102  includes a plurality of wireless access points  106  distributed throughout the warehouse  100 , such as in the shipping dock and goods storage areas. The wireless access points  106  are wireless transceivers that are connected via a conventional local area network  105  or a TCP/IP communications link to the warehouse computer  104 . Alternatively the wireless access points  106  can be wirelessly coupled, such as through a Wi-Fi link, to the warehouse computer  104 . The warehouse  100  has one or more battery charging stations  101  where the batteries  37  are removed from the industrial vehicles and recharged by equipment  103 . The charging equipment  103  also is connected to the local area network  105  for exchanging data with the warehouse computer  104 . 
         [0030]    The warehouse computer  104  is connected to the Internet  108 . 
         [0031]    The warehouse computer  104  communicates with a management computer system  114  at the headquarters of the warehouse company via the Internet  108 . That connection enables the management computer system  114  to receive data regarding the operation of the fleet of industrial vehicle at all the warehouses in the company. Both warehouse computer  104  and the warehouse management computer system  114  execute software for storing, analyzing and reporting the operating information for the industrial vehicles. 
         [0032]    The connection of the warehouse computer  104  to the Internet  108 , or other external communication network, enables the warehouse computer to access a database  110  that stores vehicle specific data provided by the manufacturer from a manufacturer computer  112 . The data gathered from the industrial vehicles at the warehouses also is uploaded and stored in the database  110 . Selected data can also be accessed by, for example, warehouse management personnel or vehicle dealers, who can connect to the database  110  through the Internet  108 . The various computers can analyze and compare the data gathered from all the industrial vehicles at a given warehouse, at all facilities of the warehouse company, or all the vehicles made by the manufacturer. 
         [0033]    As shown in  FIG. 2 , every battery  37  for use on an industrial vehicle has a battery sensor module  64  mounted thereto. The battery sensor module  64  may be built into the battery so as to be permanently integrated therewith. Alternatively, the battery sensor module  64  may be removable, in which case it remains attached to a particular battery as long as that battery remains in service at the warehouse  100 . The battery sensor module  64  gathers operational data while the battery is powering any one of the industrial vehicles  10  and while the battery is being recharged at the charging station  101 . 
         [0034]    With reference to  FIG. 4 , the battery sensor module (BSM)  64  comprises a microcomputer  150  that includes a digital processor input/output circuits and analog to digital converters. The microcomputer  150  is connected to a memory  152  that stores a software program which is executed by the microcomputer to govern the operation of the battery sensor module  64 . In addition, data which is used or produced by that program are stored with the memory  152 , as will be described. 
         [0035]    A memory  152  contains a table with manufacturer specification data related to the battery  37  as depicted in  FIG. 5 . That specification data table  160  contains a first field  161  in which a unique serial number is stored which identifies and distinguishes that associated battery  37  from all the other batteries in the warehouse  100 . A second field  162  stores a value denoting the battery&#39;s nominal voltage. The data in a third field  163  indicates the rated capacity of the battery as specified by its manufacturer. Battery capacity is a measure of the charge stored by the battery and represents the maximum amount of energy that can be extracted from the battery under certain stated conditions. The actual energy storage capability of a battery, however, can vary significantly from the rated capacity, because the actual battery capacity depends strongly on the age and past history of the battery, e.g., the charging or discharging regimes and the temperature to which the battery has been exposed. Battery capacity is commonly denoted in terms of ampere hours (Ah) or kilowatt-hours (kWh). Ampere hours is defined as the number of hours for which a battery can provide an electric current equal to the discharge rate at the nominal voltage of the battery. For example, a 400 Ah battery can deliver 40 amperes of current for 10 hours or 20 amperes of current for 20 hours. The kilowatt-hour capacity is approximated by multiplying the ampere hour capacity by the nominal battery voltage. Thus a 24 volt, 400 Ah battery has a 9.6 kWh capacity. Depending upon the particular industrial vehicle, the battery can have a nominal voltage of 24, 36 or 48 volts and typical capacities of 4-32 kWh for a 24 volt battery, 16 to 54 kWh for a 36 volt battery, and 22 to 43 kWh for a 48 volt battery. 
         [0036]    The data in a fourth field  164  indicates the battery&#39;s weight. A fifth field  165  stores an identification of the chemistry type of the battery and the sixth field  166  stores the date on which the battery was manufactured. Alternatively the sixth field  166  could contain an indication of the date on which the battery was first put into service in the warehouse  100 . A seventh field  167  is provided to store a count of the number of times that the battery has been recharged, referred to as the charging cycle count. This count is incremented by the microcomputer  150  in battery sensor module  64  each time the battery is recharged. 
         [0037]    Returning to  FIG. 4 , the battery sensor module  64  has several sensors located on the battery  37 . A voltage and current sensor  154  measures the voltage and electric current at the terminals  156  of the battery to which a first end of the battery cable  38  connects. The voltage and current sensor  154  detects a level of electric current flowing in either direction at those terminals and thus the current used to power an industrial vehicle as well as the current that recharges the battery. Alternatively, the voltage may be detected in each of the individual cells of the battery  37 . A temperature sensor  158  detects the temperature of the battery  37  and a fluid level sensor  159  detects the battery&#39;s electrolyte level. 
         [0038]    Periodically, the microcomputer  150  in the BSM reads the signals produced by the battery sensors  154 ,  158  and  159  and stores the measurement data in other data tables within memory  152 . Specifically,  FIG. 6  depicts a temperature table  170  in the BSM memory  152  that stores a plurality of measurements from (T 1 ) through (Tn). Similarly,  FIGS. 7 and 8  represent data tables  172  and  174  for the output voltage (V) and output current (I), respectively. Another data table  176 , depicted in  FIG. 9 , stores data indicating the condition of the battery at different points in time, such as each time that recharging occurs. As will be described, this data designate by the symbol X may be any of several parameters, such as battery capacity, state of charge or battery resistance, for example. 
         [0039]    The BSM  64  has a power line communication circuit  153  that enables the microcomputer  150  to exchange messages bidirectionally with the vehicle controller  21 , when the battery  37  is attached to the industrial vehicle. At other times, when the battery is at the charging station  101 , the power line communication circuit  153  communicates with the controller of the charging equipment  103 . The power line communication circuit  153  is a well known device for sending digital communication signals over a power line, in this instance the battery cable  38 . When the microcomputer  150  has data to send to the industrial vehicle  10  or to the charging equipment  103 , that data modulates an oscillating carrier signal produced in the power line communication circuit  153 . The modulated carrier signal then is sent through the battery cable  38 . In another technique, the digital data are transmitted serially as pulses of a high frequency signal. The serial number of the battery is transmitted along with the data in order for the recipient device to identify which battery is associated with the data. 
         [0040]    With reference to  FIG. 2 , the control system  20  for the industrial vehicle  10  has a BSM communication interface  62  electrically attached to a connector  34  that mates with the connector  36  of the battery cable  38 . The BSM communication interface  62  receives the information sent through the battery cable  38  by power line communication circuit  153 . The BSM communication interface  62  also is able to transmit data and operating commands through the battery cable  38  to the power line communication circuit  153  in the BSM  64  using the same power line communication protocol. 
         [0041]    Periodically or when specifically queried, the battery sensor module  64  sends the acquired battery data and its serial number to the BSM communication interface  62  on the industrial vehicle  10 . That battery information is forwarded via the communication port  69  to wireless communication device  66  and then onward through the local area network  105  to the warehouse computer  104 . In this manner, the warehouse computer stores the performance for all the batteries  37  that are available for use on the industrial vehicles  10  at that facility. The warehouse computer  104  also can forward the battery data to the database  110  and other computer systems, such as computers  112  and  114  for example. 
         [0042]    When the battery  37  is connected to the charging equipment  103  in the warehouse  100  as shown in  FIG. 3 , a similar BSM communication interface  62  within that equipment enables bidirectional communication with each battery sensor module  64  using that same power line communication protocol. This enables the charging equipment  103  to monitor the parameters, such as temperature, electrolyte fluid level and battery current and voltage, that are measured by the sensors in the BSM  64 . The charging equipment  103  also is able to send the acquired battery data to the warehouse computer  104 . 
       Battery Allocation Method 
       [0043]    The electrical parameters of the battery  37  that are measured by the BSM  64  and by the battery charging equipment  103  are used to calculate the battery capacity, state of charge and internal resistance, which provide an indication of the present condition of the associated battery. When a battery ages or is not maintained properly, the lead plates become “sulfated.” Deposits of lead sulfate form on the plates which effectively reduces the active area of each plate. This action reduces battery capacity and increases internal resistance. The calculation of one or more of the actual battery capacity, state of charge or battery resistance is performed by at least one of the microcomputer  150  within the BSM, the vehicle controller  21 , a controller within the battery charging equipment  103 , or the central warehouse computer  104 . 
         [0044]    The capacity of a battery is defined as the electric current load divided by the charge or discharge rate. Any of several well known techniques can be employed to derive the present, or actual, capacity of a given battery. That calculation is performed by the battery sensor module  64 , each time the associated battery is recharged, and the calculated value then is stored in data table  176  in the BSM memory  152 . The present battery capacity derived at the end of recharging may be used as a direct indication of battery aging or can be compared to the battery capacity rating stored in field  163  within the BSM memory  152  to determine the degree of aging. The battery capacity rating represents the capacity of the battery when newly manufactured. A significant decrease (e.g. 20%) in the actual battery capacity from the specified rating indicates that the battery has reached the end of its useful and thus when the battery should be taken out of service. 
         [0045]    Alternatively the present condition of the battery  37  can be indicated by the state of charge at the end of recharging or the present internal resistance. These parameters can be determined utilizing any one of several well-know techniques, such as the one described in U.S. Pat. No. 6,556,020, the description of which is incorporated herein by reference. Thus each time a particular battery is recharged one or both of these parameters is calculated by the battery sensor module  64  and then stored in data table  176  in the BSM memory  152 . Thus any one of several parameters can be employed to indicate the present condition of a battery and the degree of deterioration of the operational ability of the battery. 
         [0046]    The present battery condition, such as the actual battery capacity upon recharging, also is employed to determine with which of the plurality of industrial vehicles  10  within a warehouse a particular battery  37  can be used. In a typical warehouse, certain industrial vehicles are assigned to more strenuous tasks or are used for a greater amount of time during each work shift than other industrial vehicles at that facility. For example, an industrial vehicle  10  at a loading dock may be used almost continuously to load and unload delivery trucks. In contrast, another industrial vehicle may be assigned to a warehouse location in which it is only occasionally used to transport items. Thus, this latter vehicle is used a lesser amount of time during each work shift and does not require a battery that has as great an actual capacity as the battery for a vehicle at the loading dock. Certain industrial vehicles  10  perform more strenuous load handling tasks and thus require a battery with a greater capacity. For example, certain vehicles may be assigned the task of placing goods onto to warehouse shelves which involves lifting heavy loads. In contrast other industrial vehicles may only work at transferring goods from the shelves to the loading dock wherein lowering the goods takes advantage of gravity and is less strenuous that raising the goods onto the shelves. The environment in which an industrial vehicle is used also affects the performance demands placed on its battery and thus whether a lesser capacity battery can be used. For example, an industrial vehicle that works in an extremely cold environment, such as within a freezer area of a warehouse, requires a battery with more actual capacity than a vehicle that is utilized in warmer areas. 
         [0047]    As a consequence, a battery that is aging and can no longer be charged to its full rated capacity may not be satisfactory for use in certain industrial vehicles, but will still provide adequate service in vehicles used less strenuously. Even though a particular battery has aged to the point where it can no longer be charged to its full rated capacity, that battery still can be used in certain industrial vehicles and thereby prolonging the useful life of that battery before it has to be taken out of service completely. 
         [0048]    To prolong the usefulness of each battery, every industrial vehicle  10  within the warehouse is assigned one of several work ratings indicating the relative intensity of its use during each work shift and the relative performance demands that are placed on its battery. Industrial vehicles with a more intense work rating will receive batteries that have been charged to substantially their full capacity rating. In contrast, industrial vehicles with less intensity work ratings typically receive batteries that are charged only to a fraction of their full capacity rating. Thus, upon being recharged, the present, or actual condition of the battery is determined, either in terms of the actual capacity or internal resistance, for example, as noted previously, and that present condition is used to categorize the battery for use with industrial vehicles particular work ratings. As an example, batteries that presently can be charged between 90% and 100% of their capacity rating are assigned for use in industrial vehicles with the highest intensity rating, whereas batteries with a present charge less that 90% of their capacity rating are assigned for use in industrial vehicles with a lower intensity rating. More that two levels of vehicle intensity ratings and more than two battery capacity categories can be employed. 
         [0049]    The association between various capacity batteries and the appropriate industrial vehicles can be accomplished by a color coding scheme, for example, in which the work intensity level of each industrial vehicle is indicated by a colored label and the appropriate batteries for that vehicle based on their present actual capacity are indicated by a similar colored label. Obviously, a battery with a colored label indicating a greater capacity than is required by a particular industrial vehicle can be utilized on that vehicle. 
         [0050]    In addition, the present battery condition can be calculated by the battery sensor module  64  or the vehicle controller  21  periodically during use on an industrial vehicle. When that condition falls below predefined threshold, the vehicle operator is notified that the battery capacity is diminishing to a point where recharging soon will be required. At such times, the operation of the industrial vehicle may be restricted to prolong the operational period so that recharging will not have to occur until the end of a work shift. Because some time is required to replace these very heavy batteries, such reduction in vehicle performance minimizes the down time and prolongs the useful work time. 
         [0051]    The difference between the battery capacity rating for a new battery and the actual battery capacity also is employed to estimate when a particular battery will have to be taken out of service. This capability allows supervisory personnel at a warehouse to order replacement batteries before they are actually needed. 
       Battery Weight Verification 
       [0052]    With reference again to  FIG. 1 , the weight of the battery  37  in a lift type industrial vehicle  10  is important to providing ballast to counterbalance the weight of the load  35  that is being transported on the load carrier  18 . Such ballast gives the vehicle stability especially when the load is raised high on the mast  19 . The manufacturer specification for a particular industrial vehicle includes a minimum battery weight that is required for proper counterbalance. 
         [0053]    Although physically possible, it is improper to install a battery that is less than the specified minimum battery weight. Therefore, whenever a battery is replaced on an industrial vehicle, the vehicle controller  21  executes a battery weight verification software routine  180  depicted in  FIG. 10 . That routine commences at step  181  with the vehicle controller  21  in  FIG. 2  sending an inquiry via the BSM communication interface  62  to the BSM  64  on the battery  37 , requesting the specification data that is stored in data table  160  within the memory  152 . The BSM  64  responds to that inquiry by transmitting the specification data through the battery cable  38  from which it is received by the BSM communication interface  62  and forwarded to the vehicle controller  21 . 
         [0054]    The vehicle controller memory  24  also stores the minimum weight specified for the battery in this vehicle, which is read by the vehicle controller  21 , at step  182 . At step  184 , the actual battery weight is compared to the minimum battery weight to determine whether the presently installed battery is heavy enough to counterbalance the vehicle. If the presently installed battery  37  is not heavy enough, the program execution branches to step  186  at which the industrial vehicle  10  is configured for restricted operation. This may be accomplished by setting a flag within the vehicle controller  21 . As long as that flag remains set, the vehicle controller  21  limits the operation of the vehicle. For example, the height to which a load  35  is raised on the mast  19  may be restricted so that the loads can not be raised to a height which could create an instability condition. In addition or alternatively, the weight of the loads  35  that may be transported can be limited. As noted previously, a weight sensor  57  measures the weight of the load  35  being on the load carrier  18  and provides an indication of that weight to the vehicle controller  21 . Therefore, an attempt to lift an excessively heavy load  35 , in this restricted operating mode, causes the vehicle controller to disable the lift motor control  23  thereby preventing that load from being raised. Another operational restriction, when the installed battery has insufficient weight, involves the vehicle controller  21  limiting the maximum speed at which the traction motor  43  propels the industrial vehicle  10 . In this situation, the vehicle controller  21  may permit a heavy load  35  to be lifted a small amount off the floor, but then limit the vehicle traction speed. The maximum traction speed that now is permitted is significantly less than the maximum speed permitted when a properly sized battery is installed. Other types of operational restrictions may be implemented when a battery of insufficient weight is installed. 
         [0055]    During the periods when vehicle operation is limited, the vehicle controller  21  provides an indication of the load restriction mode to the operator via the operator display  55 . Other types of visual and audible annunciations can be issued. 
       Battery Cable Testing 
       [0056]    Because the batteries  37  are frequently removed from one industrial vehicle  10 , attached to and detached from the charging equipment  130 , and reinstalled on another vehicle, the battery cable is subjected to wear. With reference to  FIG. 2 , in addition to receiving voltage and electric current data from the BSM  64  on a battery  37 , the vehicle controller  21  occasionally receives data from the vehicle power sensor  60 . This latter data indicate the electric current and voltage received from the battery  37  at the connector  34  on the industrial vehicle  10 . This provides a measurement of the voltage and electric current at the second, or vehicle, end of the battery cable  38 . Thus, the vehicle controller  21  receives data regarding the voltage and electric current at both ends of the battery cable  38 . 
         [0057]    By comparing that data from opposite ends of the battery cable  38 , the vehicle controller  21  determines whether a substantial voltage drop occurs in that cable and thereby whether the cable has deteriorated to a degree where replacement is required. The voltage drop in that cable is directly related to the resistance in the cable to the flow of electric current between the battery and the industrial vehicle  10 . A similar comparison of the voltage at opposite ends of the battery cable  38  occurs when the battery  37  is connected to the equipment  103  at the charging station  101 . If the voltage drop across the cable exceeds a predefined threshold, an alert is given to either the operator of the vehicle via the operator display  55  or to personnel at the charging station  101 . Other forms of visual and audible annunciations can be issued. 
         [0058]    The level of electric current at both ends of the battery cable  38  can also be compared to detect current leakage to the frame or other components of the industrial vehicle as may occur if the insulation of the battery cable has cracks. Here too, a difference in the electric current levels measured at both ends of the battery cable  38  exceeding a predefined threshold causes an alert to be given to the vehicle operator or personnel at the battery charging station  101 . 
         [0059]    Therefore, the present system provides a mechanism for automatically checking the integrity of the battery cable  38  and providing an alert when significant deterioration has occurred. 
       Battery Current Leakage 
       [0060]    Referring to  FIGS. 2 and 4 , a circumstance encountered on these industrial vehicles is electric current leakage from the battery  37  to the metal case  151  that houses the battery. This leakage may occur due to a number of conditions such as unevaporated electrolyte spilled on the cell tops or internal sulfation build-up at the bottom of the cell. Typically, the frame  30  of the industrial vehicle  10  is not connected to the negative terminal of the battery  37  because of this leakage possibility. It is important that operating personnel become aware of this electric current leakage in order that corrective measures can be taken. 
         [0061]    For that purpose, the voltage and current sensor  154  in the battery sensor module  64  includes an input that is connected to the metal battery case  151 . Thus, in addition to detecting the voltage across the output terminals  156  of the battery, the voltage and current sensor  154  periodically measures the resistance between the battery case  151  and each of the positive and negative output terminals  156 . If the resistance level with respect to the battery case  151  and either of these terminals is below a predefined level, an alert message is sent by the BSM  64  to the vehicle controller  21 . The vehicle controller  21  responds to that alert message by providing an alert indication on the operator display  55  or by another visual or audible annunciation. 
         [0062]    An additional or alternative test can be performed by sensing the level of any electric current flow through the voltage and current sensor  154  between the input connected to the battery case  151  and the inputs coupled to the battery terminals  156 . If such electric current exceeds a predefined threshold level, e.g., 1.0 mA, an alert message is sent to the vehicle controller  21  or the charging equipment  103 , which issues an alert to the operator. 
         [0063]    With particular reference to  FIG. 2 , to detect electric current leakage elsewhere on the industrial vehicle  10 , the vehicle power sensor  60  has an input connected to the frame  30  of the industrial vehicle. This enables the vehicle power sensor to detect the level of resistance between the vehicle frame and the B+ and B− conductors of the electrical system. A low resistance indicates a short circuit or current leakage in other components of the vehicle, such as the motors, control circuits or cabling. When such an abnormal condition is found, an appropriate alert is given via the operator display  55 . If an alphanumeric type operator display  55  is used, that alert indicates the nature of the condition, such as current leakage detected by the battery sensor module or by the vehicle power sensor which thus indicates the approximate location and nature of the abnormal condition. 
       Other Operating Conditions 
       [0064]    The various items of operational data received by the vehicle controller  21  from the BSM  64  can be used to detect other abnormal conditions of the battery. When such conditions are found, an appropriate alert is provided to the operator of the vehicle  10  via the operator display  55  or to personnel at the charging station  101  via a similar display on the charging equipment  103 . For example, the temperature data sent from the BSM  64  can indicate that the battery is overheating or has been subjected to freezing temperatures. Similarly, the data produced by the fluid level sensor  159  can be utilized to alert the appropriate personnel that the electrolyte level in the associated battery  37  is abnormally low and additional water needs to be added to the battery. 
         [0065]    As noted previously, all the gathered data from the battery sensor module, other sensors on board the vehicle, and the charging equipment  103  can be transmitted to the central warehouse computer  104  for storage and analysis. The central warehouse computer  104  can also relay that battery related data via the internet to the central database  110  or to other computers, such as those for the vehicle manufacturer, a local dealer, or the warehouse company management. 
         [0066]    The foregoing description was primarily directed to a certain embodiments of the industrial vehicle. Although some attention was given to various alternatives, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from the disclosure of these embodiments. Accordingly, the scope of the coverage should be determined from the following claims and not limited by the above disclosure.