Abstract:
A distributed battery control network ( 14 ) for a battery string ( 12 ) has a plurality of sensing modules (SM) each associated with one of the batteries in the battery string ( 12 ). Each of the sensing modules has a respective sequencing input (SI) and a sequencing output ( 50 ). Said plurality modules have a sequencing input with a predetermined signature type, storing said address in a particular one of said plurality modules with said sequencing input equal to said signature type, and generating an identifying signature at an output of said particular one of plurality modules with said sequencing input equal to said signature type. A network ( 22 ) is coupled to each of the sending modules. A controller ( 24 ) is coupled to the bus and communicates with each of the sensing modules. The controller ( 24 ) loads each of the sensing modules with an address and a signature type.

Description:
TECHNICAL FIELD 
     The present invention relates generally to battery strings particularly for use in electric vehicles, and more particularly, to a method and circuit for detecting the position of a battery within a string relative to the other batteries in the string. 
     BACKGROUND 
     In electric vehicles or hybrid electric vehicles, high voltage battery packs or battery strings are used to provide electric power to the powertrain of the vehicle. High voltage battery packs typically comprise a plurality of lower voltage batteries connected in series. At times, the batteries are charged and discharged. Eventually, over extended use, the performance of one or more batteries of the string may degrade. For example, this may be manifested in a failure to hold a charge in a similar manner to the other batteries in the string. Eventually, the particular battery may require servicing. 
     In order to provide service for a particular battery in the battery string, it is desirable to identify the particular battery subject to degradation. In many current systems, a service technician, through trial and error testing of the individual batteries, is used to identify the degraded battery. This process is time and labor intensive because this often means removal of the battery from the system may be performed. 
     In U.S. Pat. No. 5,850,351, a distributed management apparatus for a battery pack is described that has battery monitoring modules for each battery. All of the battery monitoring modules are identified by an address. However, this system does not identify the relative position of each individual battery with respect to the others. Identity in the &#39;351 patent merely identifies the presence of a particular battery module rather than its relative position within the battery pack. 
     It would therefore be desirable to provide a battery pack control system wherein the relative position of each battery is recorded so that upon the degradation of operation of a particular battery, that battery may be easily removed and replaced from the battery pack. 
     SUMMARY OF THE INVENTION 
     It is therefore one object of the invention to provide a distributed battery control system that allows the relative location of each battery in the string to be identified. 
     In one aspect of the invention, a distributed battery control network for a plurality of batteries comprises a plurality of sensing modules. One of each of the plurality of sensing modules is associated with a respective one of said plurality of batteries. Each sensing module has a sequencing input and a sequencing output. A bus interconnects the plurality of sensing modules. A controller is coupled to the bus and communicates with each of the sensing modules via a network. 
     In a further aspect of the invention, a method for identifying batteries in a distributed battery control network comprises the steps of: 
     providing a string of a predetermined number of batteries having said predetermined number of sensing modules associated therewith, each battery having a respective sensing module; 
     determining the relative location of each battery and sensing module within the string; and 
     assigning a unique address to each sensing module. 
     One advantage of the invention is that by knowing the location of the battery better control and diagnostics of the battery string may be achieved. Another advantage of the invention is that by knowing a position of a suspect battery, service personnel may easily locate the suspect battery so that it may be quickly replaced. This reduces time and therefore reduces cost in replacing a battery. 
     Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an automotive vehicle having a distributed battery control network according to the present invention. 
     FIG. 2 is a schematic view of a control network according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following figures, the same reference numerals are used to identify the same components in the various views. The present invention is described with respect to an electric vehicle. However, those skilled in the art would recognize that the present invention is applicable to various types of electric vehicles including hybrid electric vehicles that run on both electricity and internal combustion engine power. Also, the present invention is suitable for use in various types of automotive vehicles including but not limited to cars, trucks, and trains and in non-automotive uses requiring a battery string. 
     Referring now to FIG. 1, an automotive vehicle  10  has a battery string  12  therein. The battery string  12  is used to provide electric power to the powertrain of the vehicle. A distributed battery control network  14  is coupled to battery string  12  and may provide many functions including charging of the battery string  12 . The distributed battery control network  14  is also used to provide identification of the relative positions of each of the batteries within the battery string  12 . An interface  16  may include a display  18  or a diagnostic connector  20 . Interface  16  identifies to the driver or a service technician of the operation of the batteries within the battery string  12 . For example, display  18  signal the operator of the vehicle that service of the battery string is required. Display  18  may also be used to provide the vehicle operator or service technician with the identity of a suspected performance degraded battery. Display  18  may include an indicator light or warning buzzer or a LCD display message on an instrument panel of the vehicle. Likewise, a diagnostic connector  20  may be used to couple to a service diagnostic testing device to indicate to a service technician which of the batteries in the battery string  12  are suspect. Other information may be included as part of the information through connector  20 . Of course, those skilled in the art would recognize that various types of interfaces may be used. Also, both display  18  and diagnostic connector  20  may be implemented. 
     Referring now to FIG. 2, a battery string  12  and distributed battery control network  14  are shown in further detail. Battery string  12  is comprised of a known number of batteries. The number of batteries depends on the desired output of the system and will vary depending on the particular vehicle. In one application, for example, 39 batteries are coupled together. As illustrated, however, for illustrative purposes, N batteries are shown. Battery  1 , battery  3 , battery N−1, and battery N. In this arrangement battery  1  is the first battery, battery N is the last battery in the string, and batteries  2  through N−1 are intermediate batteries. Each battery has a positive voltage terminal V+ and a negative ground terminal. Batteries battery  1  through battery N are coupled in series. That is, the negative terminal of each battery is coupled to the positive terminal of the adjacent battery, except for battery  1  whose negative terminal provides the overall B− terminal of the battery string  12  and battery N whose positive terminal provides the B+ terminal for the battery string  12 . 
     Distributed battery control network  14  has a sensing module (SM) for each battery. That is, sensing module SM  1  is coupled to battery  1 , sensing module SM  2  is coupled to battery  2 , sensing module SM  3  is coupled to battery  3 , sensing module SM N−1 is coupled to battery N−1 and sensing module SM N corresponds to battery N. 
     Each sensing module SM  1  through SM N is coupled to a communication network  22 . Communication network  22  may be one of a various number of types of networks. In the preferred embodiment, a two-wire communication network is employed. Communication network  22  couples each sensing module to a controller  24 . Controller  24  is preferably microprocessor-based and may perform various functions including assigning addresses and recording the relative position of each sensing module within battery string  12 . Of course, other monitoring and control functions may be performed. Controller  24  may have a memory  26  for storing the addresses and corresponding locations therein. 
     Each sensing module SM  1  through SM N has a microprocessor  30  therein. Microprocessor  30  is coupled to network  22 . Microprocessor  30  may have a number of battery monitoring functions that are beyond the identification function as would be evident to those skilled in the art. Each microprocessor  30  is coupled to a sequencing input SI and has an output that is coupled to the sequencing output SO of its respective sensing module. Each sensing input and sensing output is hereafter referred to as SI# or SO# respectively, where # is the sensing module number. The output of microprocessor  30  is coupled to a controllable switch  32 . As will be further described below, microprocessor  30  may be used to open and close switch  32  in a desirable manner or provide other suitable outputs from its respective sensing module. Switch  32  may be coupled to a ground terminal  34 , to a voltage within the sensing module, or to an output of microprocessor  30 . Upon operation of switch  32 , sequencing output may oscillate between the voltage and ground signal to provide a square wave output. 
     Each sensing module is coupled to its adjacent modules. That is, the sequencing output SO is coupled to the sequencing input of the adjacent module. This is true except for sensing module SM  1  whose sequencing input is coupled to B− and for SM N whose sequencing output may be left floating. 
     Each sensing module has an address memory  36  and a signature memory  38 . Address memory  36  is used to store a unique address for the module (and therefore the battery) that is assigned by controller  24 . Signature memory  38  stores the signature type for which the module is looking. 
     Each sequencing module has a V+ terminal coupled to the positive terminal of the associated battery and a ground terminal (GND) coupled to the negative terminal of its associated battery. 
     In operation, the batteries with associated sensing modules are assembled into the battery string  12 . Each sensing module may have a previously stored address contained therein. In this method, the number of sensing modules is known. In carrying through with the present example, N sensing modules are used. The method allows the detection of the location of each battery and sensing module in the string and assigns a unique address to each sensing module and battery to allow for better diagnostics and control of the battery string. As will be described below, because the addresses are sequentially assigned by the controller, the location of each is known. 
     The module identification process is initiated by controller  24  issuing a module sequence start command to all the sensing modules in the battery string  12 . Each of the sensing modules set their respective sequence output to a default state. In the present example, each of the sequencing outputs are placed in a high state. Of course, any suitable state may be implanted as would be evident to those in the art. All the sensing modules also erase their current addresses stored within current address memory  36 . Each sensing module then receives an identical address to check, and an input sequence signature type. Initially this corresponds to the first location. 
     Initially, the first sensing module SM  1  must be identified. As described above, the first sensing module SM  1  has its sequencing input SI  1  coupled to the negative battery terminal B−. The sequencing output state is set to a default high state for each of the sensing modules. Thus, each sequencing input for all the other modules will see a high state. The exception of course is sequencing module  1  whose sequencing input is pulled to a low state. Those skilled in the art would recognize that the unique input required for sense module  1  could also come from the controller. The controller sends a request to each sensing module to inquire what the particular state of each sequencing input is. The controller request is seeking to find the sensing module with a low sequencing input in this example. Because sensing module  1  has the only sequencing input that is low, the sensing module latches the address and thus stores the address within the address memory  36 . An acknowledge signal may be provided to controller  24  to indicate successful identification of the first sensing module and to allow the controller  24  to continue sequencing. The controller thus has the first address and sensing module identified. During this process the communication between the sensing module and the controller takes place between the microprocessor  30  of each sensing module and the controller  24 . 
     The controller  24  must then identify each subsequent sensing module. Each of the unknown sensing units will again receive an identical address to check, and a specific second sequencing input signature type. This address corresponds to the second location. The signature type for the second and subsequent sensing modules may be a toggling input or other input different from the first signature type. The toggling input may be generated by the microprocessor controlled switch  32 . However, various types of signatures may be used. Preferably, the type of signature is one that noise or an error cannot easily produce. The controller  24  instructs each of the remaining sensing modules to look for a toggling input at the sequencing input. The controller instructs the first known module, in this case sensing module  1 , to toggle its sequencing output. The controller  24  instructs the module with the toggling input to latch its address. Thus, sensing module SM 2  will latch the second address because the signature of its sequencing input matches that which the controller  24  is requesting. The second sensing module acknowledges the known address as its own to controller  24 . 
     A third address is then communicated to the remaining unidentified modules. The controller will then tell sensing module SM  2  to apply a signature such as a toggling signal to its sequencing output. In this manner, each of the remaining sensing modules are identified. Because the number of modules are known, all modules will be identified in a similar manner. 
     At the end of the process controller  24  may command all sensing modules to default their sequencing output to a particular state. For example, the sensing modules may all be defaulted to a high or a low signal. 
     Once the sensing modules and their relative locations are known, the controller  24  may be used to monitor the charging and discharging functions of the batteries through each of the associated sensing modules. If a fault is recognized in any one of the sensing modules or associated batteries, one of the interfaces or both of the interfaces such as display  18  or connector  20  may provide an indication as to which sensing module is indicating an error. This will allow a service technician to easily locate the suspect battery and sensing module. 
     If only one of the sensing modules is replaced, the controller  24  need not re-identify each of the sensing modules. Controller  24  issues commands and receives information about the sensing module&#39;s associated battery. Controller  24  keeps track of the commands initiated and if a particular sensing module has not responded in a predetermined number of tries, controller  24  will know that a sensing module and battery has been replaced or has a fault. Controller  24  may then command the non-responsive sensing module because of its known relative location to accept the address provided which is associated with its relative location. 
     While particular embodiments of the invention have been shown and described, numerous variations alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.