Abstract:
A method and apparatus for controlling the temperature of a battery during discharge cycles. Battery temperature is reported to a controller that returns a shunt current indicator. Heat is generated as the battery is discharged according to the shunt current indicator. This heat is then applied to the terminal of a battery.

Description:
BACKGROUND 
       [0001]    There are numerous methods for managing batteries during a charge cycle and during a discharge cycle. Typically, large energy storage systems rely upon series connected batteries to achieve higher voltages for delivery to a load. As such, it is necessary to ensure that each battery included in such a series connected battery pack (SCBP) is charged to a substantially equal level during the charge cycle. Likewise, it is also necessary to ensure that the charge on each battery included in such a series connected battery pack is drained at a substantially equivalent rate during the discharge cycle. 
         [0002]    Is well-known that temperature amongst the individual batteries in an SCBP can vary. It is also well-known that the temperature of a battery is just one of the factors that dictates the effectiveness of a battery. In an SCBP, variation of the battery temperatures means that different batteries in the SCBP will be charged at different rates and, of course, will be discharged at different rates because of the temperature variation amongst individual batteries in the SCBP. The SCBP, as a whole, is also affected by the ambient temperature it is subject to during operation. Because batteries are not as effective at colder temperatures, batteries around the peripheral of the SCBP may not be charged or discharged as effectively as other batteries in the SCBP that may be surrounded by other batteries. As such, the overall effectiveness of the SCBP is compromised. 
         [0003]    In order to manage the thermal characteristics of an SCBP, some implementations use temperature sensors that are placed in between batteries so that the temperature at different points in the SCBP can be monitored. Then, based on the temperature, adjustments can be made in charging and discharging profiles of the battery pack as a whole. In yet other implementations, heating elements are distributed within a battery pack based on empirical observations of the temperature profile as the battery pack operates in its ambient environment. This, of course, does not consider that individual batteries in an SCBP may be operating at different temperatures because of their positioning within the battery pack or because of the self-heating that each battery exhibits during its charge or discharge cycles. More problematic is the fact that only a few temperature sensors are typically included in an SCBP and only a handful of heating elements are distributed within the battery pack. In these prior art implementations, there is simply no mechanism by which variations of temperature within the SCBP can be accounted for. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    Several alternative embodiments will hereinafter be described in conjunction with the appended drawings and figures, wherein like numerals denote like elements, and in which: 
           [0005]      FIG. 1  is a pictorial of a plan view of one example embodiment of a battery management module; 
           [0006]      FIG. 2  is a flow diagram that depicts one example method for managing battery charge and discharge with concurrent thermal control; 
           [0007]      FIG. 3  is a flow diagram that depicts one alternative example method for discharging a battery; 
           [0008]      FIG. 4  is a flow diagram that depicts one alternative example method for applying heat to a battery; 
           [0009]      FIG. 5  is a flow diagram that depicts one alternative example method for managing excessive battery temperature; 
           [0010]      FIG. 6  is flow diagram that depicts one alternative example method for removing heat from a battery terminal; 
           [0011]      FIG. 7  is a flow diagram that depicts yet another alternative example method for removing heat from a battery terminal; 
           [0012]      FIG. 8  is a pictorial diagram that depicts one illustrative use scenario for a battery management module; 
           [0013]      FIG. 9  is a pictorial diagram that depicts yet another illustrative use scenario for a battery management module; 
           [0014]      FIG. 10  is a block diagram that depicts one alternative embodiment of a module manager that is based on a processor; and 
           [0015]      FIG. 11  is a data flow module that depicts the operation of a processor based module manager. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  is a pictorial of a plan view of one example embodiment of a battery management module. It should be appreciated that, in one alternative example embodiment, the battery management module  100  is structured on a printed circuit board. In such an alternative example embodiment, the battery management module  100  includes a battery terminal connector  120 . Typically, the battery management module  100  includes a positive battery terminal connector  120  and a negative battery terminal connector  122 . According to this one example embodiment, a battery management module  100  includes a module manager  125 . The battery management module  100  includes a data interface  130 . In one alternative example embodiment, the data interface  130  is bidirectional. As such, a bidirectional data interface  130  may be used to convey information from the module manager  125  and may also be used to receive information into the module manager  125 . In one alternative example embodiment, a second data interface  135  is also included. In this alternative example embodiment, the first interface  130  is used to convey information from the module manager  125  and the second data interface  135  is used to receive information into the module manager  125 . 
         [0017]    In this example embodiment, the battery management module  100  also includes a heating element  105 . In one alternative example embodiment, the heating element comprises a resistor. In this example embodiment, the module manager  125  controls the heating element  105  by means of an enablement signal  106 . In this example embodiment, the battery management module  100  also includes a thermal sensor  115 . In this example embodiment, the module manager  125  receives thermal information from the thermal sensor  115  by way of a thermal sensor interface  116 . In operation, the module manager  125 , in this example embodiment, conveys the thermal information to an external controller by way of the data interface  130 . Using the same data interface  130 , or in an alternative example embodiment, a second data interface  135 , the module manager  125  receives a shunt current indicator from the external controller. In this alternative example embodiment, the module manager  125  then enables the heating element  105  according to the shunt current indicator received by the module manager  125 . 
         [0018]    It should be appreciated that, according to various illustrative use cases, the data provided to the external controller and received from the external controller can in fact be conveyed to any type of device that satisfies particular requirements for determining a particular shunt current value based on a thermal value provided by the module manager  125 . As such, the claims appended hereto are not intended to be limited in scope by the type of external controller or other device with which the module manager  125  included in the battery management module  100  is in communication with. 
         [0019]      FIG. 2  is a flow diagram that depicts one example method for managing battery charge and discharge with concurrent thermal control. It should be appreciated that, according to this example method, a temperature of a battery is determined by determining the temperature at a battery terminal connector (step  5 ). As depicted in  FIG. 1 , one alternative example embodiment of a battery management module  100  includes a thermal sensor  115  that is physically proximate to a battery terminal connector  120 . It should be appreciated that the thermal sensor  115 , according to one alternative example embodiment, is disposed proximate to at least one of a positive battery terminal connector  120  and a negative battery terminal connector  122 . According to this example method, the temperature at the battery terminal connector is then conveyed to a controller (step  10 ). Although not part of the battery management module method per se, the controller determines a shunt current value based on the thermal reading it receives from the battery management module. Continuing with the present method, a shunt current indicator is received from the controller (step  15 ). 
         [0020]    In this example method, the battery which is being controlled by the battery management module  100  is then discharged according to the shunt current indicator (step  20 ). Heat is then generated using the current drained from the battery according to the shunt current indicator (step  25 ). The heat that is generated is then applied to the battery terminal connector (step  30 ). It should be appreciated that, by applying heating directly to the battery terminal connector, the heat transfer to the core of the battery is much more effective than prior art methods where heating elements are simply disposed at a surface of a battery, for example on a plastic case that is used to enclose the battery core. 
         [0021]      FIG. 3  is a flow diagram that depicts one alternative example method for discharging a battery. In this alternative example method, a pulse width modulated signal is generated according to the shunt current indicator (step  35 ). It should be appreciated that the pulse width modulated (PWM) signal comprises a duty cycle based signal where the signal is enabled for a period of time and then disabled for a second period of time on a periodic basis. In this alternative example method, a resistance is applied across the battery according to the pulse width modulated signal (step  40 ). 
         [0022]      FIG. 4  is a flow diagram that depicts one alternative example method for applying heat to a battery. In this alternative example method, heat generated by the resistor that is enabled by the PWM signal is directed to the battery terminal connector (step  45 ). In this alternative example method, losses in the heat path from the resistor to the battery terminal connector are minimized (step  50 ) in order to provide for more efficient heating of the battery. 
         [0023]      FIG. 1  further illustrates that the battery management module  100 , in one alternative embodiment, includes a heat conduction structure  110  that facilitates the flow of heat from the heating element  105  to the battery terminal connector  120 . It should be appreciated that this structure, in an alternative embodiment, is disposed about at least one of the positive battery terminal connector  120  and the negative battery terminal connector  122 . 
         [0024]      FIG. 5  is a flow diagram that depicts one alternative example method for managing excessive battery temperature. In this alternative example method, when the temperature of at least one of the positive battery terminal connector and the negative battery terminal connector exceeds a pre-established threshold (step  80 ), then heat is removed from at least one of the positive battery terminal connector and the negative battery terminal connector (step  60 ). 
         [0025]      FIG. 6  is flow diagram that depicts one alternative example method for removing heat from a battery terminal. In this alternative example method, heat from the battery terminal is directed to a heat sink (step  65 ). In order to remove heat from the heat sink, airflow across the heat sink is increased (step  75 ) so as to promote dissipation of heat from the heat sink into the ambient environment. In one example embodiment, increasing airflow across the heat sink is accomplished by means of a fan. It should be appreciated that the increase of airflow is enabled when the temperature of at least one of the positive battery terminal connector and the negative battery terminal connector exceeds a pre-established threshold, as depicted in Step  80  in  FIG. 5 . 
         [0026]      FIG. 7  is a flow diagram that depicts yet another alternative example method for removing heat from a battery terminal. In this alternative example method, heat from the battery terminal is encouraged to flow into a heat sink (step  70 ). This, in one alternative embodiment, is accomplished by means of a device that can be enabled and which operates as a heat pump. In one alternative embodiment, such a device comprises a thermoelectric cooler that, upon application of electric current to the thermoelectric cooler, encourages the migration of heat from a first surface to a second surface, said surfaces disposed in opposition to each other. Accordingly, one surface of the thermal electric cooler is mechanically coupled to the battery terminal and the second surface of the thermoelectric cooler is mechanically coupled to a heat sink. 
         [0027]      FIG. 8  is a pictorial diagram that depicts one illustrative use scenario for a battery management module.  FIG. 8  also depicts one alternative example embodiment of a battery management module. It should be appreciated that a battery  165  includes at least two terminals by which charge is directed into the battery or drawn from the battery. It is common knowledge that batteries store a direct current (DC) charge and that at least one terminal of the battery is dedicated to a positive terminal and at least one terminal of the battery is dedicated to a negative terminal. In this illustrative use scenario, a power bus  140  is mechanically coupled to at least one of a positive battery terminal and a negative battery terminal. For the purpose of illustration, the terminals of either polarity are identified by reference designator  160 . 
         [0028]    The battery management module  100 , in this illustrative diagram, is placed on top of the power bus  140 . To ensure proper mechanical and electrical connection between the battery terminal connector included in a battery management module  100 , the power bus  140  and the battery terminal  165  a force is a applied by means of a fastener  147 , for example a threaded machine screw. By ensuring good mechanical connection between the battery terminal  165  and the power bus  140 , heat may be removed from the battery terminal  160  and directed through the power bus  140  to a heat sink  155 , which is mounted to the power bus  140 . It should be appreciated that various alternative illustrative uses are contemplated and the example of a threaded machines screw is merely one example of a fastener that is used to provide mechanical retention of the battery management module  100 , the power bus  140  and the battery terminal  160 . Accordingly, the claims appended hereto are not intended to be limited in scope to any particular example thus far described. 
         [0029]      FIGS. 1 and 8  also depict an alternative example embodiment of a battery management module  100  that further includes a fan  150 . In yet another alternative example embodiment, the battery management module  100  further includes a high-power output  180 . It can be appreciated that, according to various illustrative use scenarios, the high-power output can be used to enable a fan that is used to increase airflow across a heat sink. 
         [0030]      FIG. 9  is a pictorial diagram that depicts yet another illustrative use scenario for a battery management module. In this alternative use scenario, a heat sink  155  is installed upon a thermoelectric cooler  185 . In this illustrative use scenario, the thermoelectric cooler  185  is then mounted upon the power bus  140 . To enable the thermoelectric cooler  185 , the high-power output  180  from the battery management module  100  is used in this illustrative use scenario. 
         [0031]      FIG. 10  is a block diagram that depicts one alternative embodiment of a module manager that is based on a processor. In this alternative embodiment of a module manager  100 , the module manager comprises a processor based module manager  201 . In this alternative embodiment, the module manager  201  includes a processor  200 , a memory  205 , a data interface  130  and a thermal sensor interface  116 . The memory  205  is used to store various functional modules including a data reception module  305 , a battery control module  300  and a temperature module  310 . 
         [0032]    A functional module is typically embodied as an instruction sequence. An instruction sequence that implements a functional module, according to one alternative embodiment, is stored in the memory  205 . The reader is advised that the term “minimally causes the processor” and variants thereof is intended to serve as an open-ended enumeration of functions performed by the processor  200  as it executes a particular functional module (i.e. 
         [0033]    instruction sequence). As such, an embodiment where a particular functional module causes the processor  200  to perform functions in addition to those defined in the appended claims is to be included in the scope of the claims appended hereto. 
         [0034]    The functional modules (i.e. their corresponding instruction sequences) described thus far that enable battery management according to the present method are, according to one alternative embodiment, imparted onto computer readable medium. Examples of such medium include, but are not limited to, random access memory, read-only memory (ROM), programmable read only memory, flash memory, electrically erasable programmable read only memory, compact disk ROM (CD ROM), floppy disks, hard disk drives, magnetic tape and digital versatile disks (DVD). Such computer readable medium, which alone or in combination can constitute a stand-alone product and can be used to convert a general-purpose computing platform into a device capable of battery management according to the techniques and teachings presented herein. Accordingly, the claims appended hereto are to include such computer readable medium imparted with such instruction sequences that enable execution of the present method and all of the teachings herein described. 
         [0035]      FIG. 11  is a data flow module that depicts the operation of a processor based module manager. In operation, the processor  200 , as it executes the data reception module  305 , is minimally caused to receive a shunt current indicator by way of the data interface  130 . The processor  200 , as it continues to execute the data reception module  305 , makes the shunt current indicator ready for use by the processor  200  as it executes the battery control module  300 . Typically, the data reception module  305 , when executed by the processor  200 , minimally causes the processor  200  to control the hardware aspects of the data interface  130 . The processor  200 , as it continues to execute the battery control module  300 , is further minimally caused to use the current indicator, which may be in the form of a current level value, to establish a pulse with modulation level, which the processor  200  directs to a PWM circuit  225  that is included in this alternative example embodiment of a processor based module manager  201 . 
         [0036]    The battery control module of this particular alternative embodiment, once executed by the processor  200 , further minimally causes the processor to execute the temperature module  310 . The temperature module  310 , as it is executed by the processor  200 , further minimally causes the processor to receive a thermal value from the thermal sensor interface  116 . In various alternative embodiments, the thermal sensor interface comprises an analog and digital converter and the value received from the analog and digital converter must be converted to a temperature value, which is accomplished by the processor  200  as it continues to execute the temperature module  310 . In yet other alternative embodiments, the thermal sensor interface comprises a digital interface, for example an I2C serial data bus. In this alternative embodiment, the temperature module  310 , as it is executed by the processor  200 , further minimally causes the processor  200  to convert an I2C data packet into a temperature value. 
         [0037]    Once the processor  200 , as it continues to execute the battery control module  300 , receives a temperature value from the temperature module  310 , the processor  200  will direct the temperature value to the data interface  130 . This affects the transfer of the temperature value to an external controller, which then can determine a shunt current level based on the temperature it receives. 
         [0038]    In yet another alternative example embodiment, the processor  200 , as it executes the battery control module  300 , further minimally determines if the temperature of the battery exceeds a pre-established threshold. When this condition is present, the processor  200 , as it continues to execute the battery control module  300 , will enable the high-power output  230  so as to enhance heat flow from the battery terminal. As already described, the high-power output  230  can be used to enable a fan or a thermoelectric cooling device. 
         [0039]    While the present method and apparatus has been described in terms of several alternative and exemplary embodiments, it is contemplated that alternatives, modifications, permutations, and equivalents thereof will become apparent to those skilled in the art upon a reading of the specification and study of the drawings. It is therefore intended that the true spirit and scope of the claims appended hereto include all such alternatives, modifications, permutations, and equivalents.