Abstract:
A battery pack includes a plurality of battery modules mounted within a casing. A heat exchanger receives a fluid and a valve selectively connects one of two sources of fluid to the heat exchanger. One of the two sources is at a higher temperature for providing heating fluid to the heat exchanger, and a second of the sources is at a lower temperature to provide cooling fluid to the heat exchanger.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a multi-cell battery pack for use in vehicle applications, wherein a liquid heat exchanger within the battery pack is alternatively provided with a source of heated fluid, or a source of cooling fluid, dependent on operational conditions. 
         [0002]    More and more vehicles are being provided with electric drivelines. Electric motors may be utilized to drive axles, actuate brakes, etc. Large battery packs are required for such systems. 
         [0003]    Heavy vehicles have been proposed which include battery packs assembled from hundreds of individual cells and grouped in modules. Of course, it is desirable to maintain and extend the battery life for such vehicles. With so many cells in a pack, the currents, voltages, and temperature of the several cells should be kept as constant with each other as is possible to evenly load the cells. If the cells are unevenly loaded, early failure could result. 
         [0004]    One challenge with maintaining constant load on the cells is that the temperature of the cells will increase with use. It is known to provide cooling structure for the cells. As an example, fans have been proposed to circulate cooling air over the battery packs. The fans have typically been provided on an outer edge of the battery packs. 
         [0005]    Another challenge with the use of the battery pack is operating in cold environments. If the battery pack is in an environment below 0° C., battery operation becomes more challenging. If the temperature drops even further, such as below −25° C., self-heating of the battery pack becomes minimal. 
       SUMMARY OF THE INVENTION 
       [0006]    A battery pack includes a plurality of battery modules mounted within a casing. A heat exchanger receives a fluid and a valve selectively connects one of two sources of fluid to the heat exchanger. One of the two sources is at a higher temperature for providing heating fluid to the heat exchanger, and a second of the sources is at a lower temperature to provide cooling fluid to the heat exchanger. 
         [0007]    An electronic driveline for a vehicle, including the battery pack, and a method of cooling a battery pack are also disclosed and claimed. 
         [0008]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows a battery pack including a fan structure in a first condition. 
           [0010]      FIG. 2  shows a subsequent condition. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0011]    A battery pack  20  is illustrated in  FIG. 1  having a plurality of multi-cell battery modules  22  and  24 . As shown, the cell modules  22  and  24  are positioned on opposed sides of central fans  34  and  36 . 
         [0012]    The battery pack  20  drives electric motors  26 , shown schematically. The electric motors  26  can be associated with heavy vehicle electric drive trains, and can include an axle drive, as an example. This portion of the invention may be as known in the art. 
         [0013]    A battery management system  28  monitors voltage and provides feedback to a central vehicle control through an input/output connection. 
         [0014]    A fan control  30  provides control signals to the fans  34  and  36 . A disconnect  32  allows a manual electric disconnect, as is known. 
         [0015]    A housing  50  surrounds the fans  34  and  36 , and the modules  22  and  24 . 
         [0016]    Due to the central location of the fans  34  and  36  between the modules  22  and  24 , more even cooling will be provided than is the case in the prior art. While the fans  34  and  36  are shown at a central location with even numbers of modules  22  and  24  on both sides, other locations within the battery pack may come within the scope of this invention. In addition, the fan control  30  controls the fans  34  and  36  such that they flow in a first direction (left to right as shown in  FIG. 1 ) for a period of time. After the passage of a period of time, the fan direction changes and the fans are reversed such that the airflow is from right to left, as shown in  FIG. 2 . 
         [0017]    The airflow reversal time may be selected to be less than a cell thermal time constant of the multi-cell battery modules. The flow reversal cycles can be such that the direction changes at a time period less than one minute, and even less than every 30 seconds. In one disclosed embodiment, the reversal may occur every 10 seconds. 
         [0018]    A challenge with the operation of a battery pack such as is illustrated in  FIGS. 1 and 2  is maintaining desired temperatures. A liquid heat exchanger  100  is put in the intermediate location, and in proximity to the fans  34  and  36 . The liquid heat exchanger cools or heats the air moved by the fans, and over the battery modules  22  and  24 . As shown, a solenoid valve control  106  alternatively connects the engine cooling loop  102 , or an electric drive cooling loop  104  to the heat exchanger  100 . Other sources of liquid to be delivered into the heat exchanger  100  can be utilized. 
         [0019]    Essentially, the engine cooling loop  102  will tend to be at higher temperatures, and the electric drive cooling loop  104  will tend to be at lower temperatures. The control  30 , and/or the solenoid valve control  106 , communicate with a vehicle controller, as an example, and determine whether heated or cooling liquid should be delivered into the heat exchanger  100 . 
         [0020]    Should cooling of the battery modules  22  and  24  be desired, then the solenoid valve control moves to connect the electric drive cooling loop  104  to the heat exchanger  100 . Air moving over the heat exchanger  100  is cooled, and thus the modules  22  and  24  will be cooled. 
         [0021]    On the other hand, if a vehicle receiving the battery pack  20  is in a cold environment, then the control moves to connect the engine cooling loop  102  to the heat exchanger  100 . The air passing over the heat exchanger  100  will now be heated, as will be the battery modules  22  and  24 . 
         [0022]    While a worker of ordinary skill in this art can determine the temperatures at which to connect the two fluids, generally, cooling of the battery pack is desirable when internal temperatures are above 55° C., and heating is desirable when temperatures drop below 0° C. Generally, the engine cooling loop can become hot after continued operation, and could be at a temperature that would be undesirably high. As such, the control should ensure that the temperatures do not exceed desired limits. It may well be that under many conditions of operation, neither source of fluid is connected to the heat exchanger  100 , and cooling is left to the fans  34  and  36 . 
         [0023]    The fans may use brushless, electronically commutated motors. A microprocessor control may be built into the fan drive. 
         [0024]    The battery modules may be of the sort available from Energy Innovation Group (EiG), and as described at www.eigbattery.com. Of course, other battery modules would benefit from this invention. 
         [0025]    In addition, co-pending and co-assigned patent applications entitled “Heavy Vehicle Battery Pack With Improved Cooling Scheme,” filed on even date herewith, and assigned Ser. No. ______, and “Battery Pack With Extended Operating Temperature Range,” filed on even date herewith, and assigned Ser. No. ______ should be studied as being somewhat related to the instant invention. 
         [0026]    While the figures show a first layer of battery modules  22  and  24 , and fans  34  and  36 , it should be understood that there could be additional layers of each of these components extending into the plane of the paper. That is, there could be multiple layers within the actual total battery pack. 
         [0027]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.