Abstract:
An electrical storage device heater system according to an exemplary aspect of the present disclosure includes, among other things, an electrical storage device, a heater configured to regulate a temperature of the electrical storage device and a controller configured to actuate the heater using power sourced from a location separate from the electrical storage device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/115,564, filed on May 25, 2011, which is a continuation of U.S. patent application Ser. No. 10/897,695, filed on Jul. 23, 2004. 
     
    
     TECHNICAL FIELD AND BACKGROUND 
       [0002]    This disclosure relates generally to thermal controls for an electrical storage device in a vehicle. More particularly, the present disclosure relates to a system and method for heating the electrical storage device. 
         [0003]    Electric and hybrid electric vehicles have become increasingly popular to meet the demand for fuel-efficient, environmentally-friendly transportation. Such vehicles often include an electrical storage device, such as a high-voltage traction battery, for powering an electric motor to drive the vehicle, either alone or in conjunction with an internal combustion engine, fuel cell engine, or other prime mover. 
         [0004]    Currently available electric and hybrid electric vehicles tend to operate more effectively in moderate and warm climates and less effectively in extremely cold climates. This is because high voltage traction batteries tend to lose power as battery cell temperature drops (e.g., below approx. 20° C.). This power decrease results in reduced vehicle performance, fuel economy and drivability. At extremely low temperatures, the traction battery may have insufficient power to even start the vehicle. 
         [0005]    Maintaining a proper battery temperature is desirable to ensure optimal vehicle performance in many different climates. Sustaining the battery temperature at a desired level can be challenging because the battery temperature can be affected by many factors, such as the battery condition, the battery cell temperature, the battery charge condition when the vehicle is turned off, and the ambient temperature. Self-powered battery heaters are able to maintain a minimum battery temperature level only for short time periods because the amount of power available for heating is limited by the storage capacity of the battery itself. Thus, self-powered battery heaters are unsuitable when the battery needs to be heated for an extended time period and/or when the battery needs to be warmed to a higher temperature to ensure optimal vehicle performance. 
         [0006]    As such, there is a need for a system that can maintain a battery temperature to a level that ensures reliable starting of an electric or hybrid vehicle. There is also a need for a system that can maintain a proper battery temperature in a controlled manner to ensure optimum vehicle performance. 
       SUMMARY 
       [0007]    An electrical storage device heater system according to an exemplary aspect of the present disclosure includes, among other things, an electrical storage device, a heater configured to regulate a temperature of the electrical storage device and a controller configured to actuate the heater using power sourced from a location separate from the electrical storage device. 
         [0008]    In a further non-limiting embodiment of the foregoing system, the electrical storage device is a battery cell. 
         [0009]    In a further non-limiting embodiment of either of the foregoing systems, the electrical storage device is an ultra-capacitor. 
         [0010]    In a further non-limiting embodiment of any of the foregoing systems, a converter is connected between an external power source and the electrical storage device. 
         [0011]    In a further non-limiting embodiment of any of the foregoing systems, the controller controls operation of the heater between an OFF and an ON condition. 
         [0012]    In a further non-limiting embodiment of any of the foregoing systems, the controller is configured to actuate a switch to couple or decouple an external power source to the electrical storage device. 
         [0013]    In a further non-limiting embodiment of any of the foregoing systems, the controller is powered by a power source separate from the external power source. 
         [0014]    In a further non-limiting embodiment of any of the foregoing systems, the external power source includes a battery located on-board of a vehicle. 
         [0015]    In a further non-limiting embodiment of any of the foregoing systems, the external power source is completely remote from the electrical storage device. 
         [0016]    In a further non-limiting embodiment of any of the foregoing systems, a connector is configured to connect the heater to the external power source. 
         [0017]    A vehicle according to an exemplary aspect of the present disclosure includes, among other things, an external power source located on-board of the vehicle and a battery system powered by the external power source. The battery system includes an electrical storage device, a heater that selectively heats the electrical storage device, and a switch that selectively couples the heater to the external power source. A controller controls the operation of the heater by actuating the switch to couple the heater to the external power source. 
         [0018]    In a further non-limiting embodiment of the foregoing vehicle, the controller is powered by an alternative power source that is separate from the external power source. 
         [0019]    In a further non-limiting embodiment of either of the foregoing vehicles, the controller is configured to actuate the switch based on at least one of a temperature of the electrical storage device, an output from a converter, and/or a key on/off condition of the vehicle. 
         [0020]    In a further non-limiting embodiment of any of the foregoing vehicles, an engine block heater is coupled to the battery system by the external power source. 
         [0021]    In a further non-limiting embodiment of any of the foregoing vehicles, the external power source is a supplemental electrical power source on-board the vehicle. 
         [0022]    A method according to another exemplary aspect of the present disclosure includes, among other things, checking whether a battery system is connected to an external power source, checking a temperature of an electrical storage device of the battery system, connecting a heater to the electrical storage device if the temperature is below a temperature threshold, and disconnecting the heater from the electrical storage device if the temperature is above the temperature threshold or if the battery system is disconnected from the external power source. 
         [0023]    In a further non-limiting embodiment of the foregoing method, the method includes checking whether a vehicle is in a key ON or key OFF condition prior to the step of checking whether the battery system is connected to the external power source. 
         [0024]    In a further non-limiting embodiment of either of the foregoing methods, the method includes periodically awakening from a sleep mode to re-check the temperature of the electrical storage device. 
         [0025]    In a further non-limiting embodiment of any of the foregoing methods, the method includes remaining in the sleep mode for a selected time period, awakening from the sleep mode after the selected time period, and rechecking whether the battery system is connected to the external power source after the step of awakening from the sleep mode. 
         [0026]    In a further non-limiting embodiment of any of the foregoing methods, the method of connecting includes closing a switch and the step of disconnecting includes opening the switch. 
         [0027]    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 
         [0028]      FIG. 1  is a block diagram illustrating a battery heater system according to one embodiment of the invention; 
           [0029]      FIG. 2  is a block diagram illustrating a battery heater system according to another embodiment of the invention; 
           [0030]      FIG. 3  is a block diagram illustrating an example of the battery heater system in conjunction with an engine block heater; and 
           [0031]      FIG. 4  is a flow diagram illustrating a method for controlling the battery heater according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  is a block diagram illustrating components of a battery heater system  100  according to one embodiment of the invention. Generally, the invention is directed to a vehicle battery heater system  100  that is powered by an external power source e.g., a 120V AC power source outside the vehicle or a supplemental low-voltage or accessory battery on-board the vehicle) outside a high-voltage battery system  102  or other electrical storage device. The battery system  102  includes one or more battery cells  103 . By using an external power source that is separate from the high-voltage battery system  102  to operate the heater system  100 , the invention can keep the battery system  102  warm and regulate the temperature of the battery system  102  reliably when the vehicle is exposed to a cold environment. 
         [0033]    As shown in  FIG. 1 , the battery heater system  100  includes a heater  104  for warming the battery cells  103 . The heater  104  itself may have any configuration known and appreciated in the art that is appropriate for regulating the temperature of the battery cells  103 . In one embodiment, a plurality of resistive or other thermoelectric heater elements disposed in the battery system  102  act as the heater  104 . The heater  104  is coupled to the battery cells  103 . The battery cells  103  themselves can be, for example, nickel metal hydride cells, lithium-ion cells, lead acid cells, or any equivalent electric energy storage device. Although the description below focuses on battery cells, the heater system may apply to other electrical storage devices, such as ultra-capacitors, without departing from the scope of the invention. 
         [0034]    The heater system  100  also includes a converter  108 . In the example shown in  FIG. 1 , the converter  108  is an AC/DC converter that converts an AC voltage output from an external AC power source  110  to a lower level DC voltage output. The AC power source  110  can be, for example, power from a wall outlet in a garage. A connector  112 , such as a conventional three-pronged plug, connects the battery heater system  100  to the AC power source  110 . The output of the AC/DC converter  108  or a suitable control signal may also be sent to a controller  114  that controls operation of the heater  104  via one or more switches  116 , such as relays, mechanical switches, field effect transistors, etc. In one embodiment, the controller  114  also receives signals indicating a battery temperature, a key on/off condition (e.g., whether a key is in the vehicle ignition), and an AC/DC active signal as inputs and controls operation of the switch  116  based on these inputs. 
         [0035]    Alternatively, the controller  114  may be powered by, for example, a separate low-voltage battery  120  or other alternative power source. The low-voltage battery  120  may be, for example, a conventional accessory battery having a nominal voltage output of approximately 10V-15V. If the controller  114  is powered by the low-voltage battery  120 , the controller  114  can monitor the temperature of the battery system  102  even when the battery heater system  100  is not connected to the AC power source  110 . The controller  114  preferably draws a very small current during operation (e.g., on the order of less than 1 mA). Moreover, by intermittently placing the controller  114  into a sleep mode where it draws minimal current, as will be described in greater below, the controller  114  avoids draining the low-voltage battery  120 . The components of the heater system  100  may be connected together via any connection structure, such as an electrical harness (not shown). 
         [0036]    In the example shown in  FIG. 1 , the controller  114  and the switches  116  are disposed in the battery system  102 , while the AC/DC converter  108  may be placed at any location in the vehicle outside the battery system  102 . The AC/DC converter  108  tends to be an expensive component; by placing the AC/DC converter  108  outside of the battery system  102 , the battery heater system  100  can be marketed as a separate component as part of a vehicle heating package and can be omitted in vehicles that do not require cold weather assistance. Note that other components in the system (e.g., the controller  114  and/or the switch  116 ) may be placed outside the battery system  102  as well, if desired, to further enhance modularity by placing these components only in vehicles that require it.  FIG. 2  illustrates another embodiment of the battery heater system  100  where both the AC/DC converter  108  and the controller  114  are disposed outside the battery system  102 . 
         [0037]    Moreover, by placing the AC/DC converter  108  outside the battery system  102  (e.g., near a vehicle engine), only low voltage DC electrical lines, as opposed to high voltage AC lines, need to be passed through a passenger compartment of the vehicle, eliminating possible safety concerns. Keeping the AC/DC converter  108  separate from the battery system  102  makes UL certification simpler because certification is needed only for the AC/DC converter  108 , as opposed to the entire battery system  102  if the AC/DC converter  108  were included within the battery system  102 . 
         [0038]    Connecting the battery heater system  100  to the AC power source  110  allows the battery system  102  to be heated for an unlimited time period as long as the connection lasts. This creates a distinct advantage over self-powered battery heaters, which can heat the battery only for a finite time period. Also, the unlimited nature of the AC power source  110  allows the battery system  102  to be heated to a higher temperature without risking power supply drainage, making it possible to maintain the battery temperature to a level that allows the vehicle to start. In another embodiment, the temperature level may be selected to ensure optimum battery performance. 
         [0039]    Note that if the supplemental battery is used as the external power source, the converter  108  may be a DC/DC converter. Of course, the converter  108  may also be omitted altogether. 
         [0040]      FIG. 3  illustrates the battery heater system  100  coupled with an engine block heater  200 . In extremely cold regions, vehicles are typically equipped with the engine block heater  200  to keep an engine in good working condition in cold climates. Like the inventive battery heater system  100 , the engine block heater  200  is designed to be connected to the AC power source  110 . The modular design of the inventive battery heater system  100  allows it to be easily coupled to the engine block heater  200 . 
         [0041]    As shown in  FIG. 3 , both the battery heater system  100  and the engine block heater  200  may be connected to the same AC power source  110  through a single connector  112  (e.g., a single plug) as opposed to two separate connectors. The single connector  112  is appropriate because the battery heater system  100  and the engine block heater  200  are usually both needed at the same time in extremely cold climates. This streamlines the vehicle heating package  202  and simplifies connection of the battery heater system  100  and the engine block heater  200  to the AC power source  110 . The battery heater system  100  and the engine block heater  200  may be offered together as a modular vehicle heating package  202 . 
         [0042]      FIG. 4  is a flow diagram illustrating a control process  250  used by the controller  114  to control the battery temperature according to one embodiment of the invention. As noted above, the controller  114  may receive inputs corresponding to battery temperature and a key on/off condition. The controller  114  also checks whether it is receiving the AC/DC active signal to determine whether the battery heater system  100  is connected to the AC power source  110 . 
         [0043]    In the illustrated control process  250 , the controller  114  assumes that the vehicle key is not in a vehicle ignition; that is, the vehicle is in a key-off condition (block  252 ). The controller  114  then checks whether it is receiving the AC/DC active signal (block  254 ). If not, the controller  114  assumes that the battery heater system  100  is not connected to the AC power source  110  (block  255 ) and therefore maintains the heater  104  in an OFF condition (block  256 ). The controller  114  then enters a sleep mode during which it is inactive. The sleep mode may, for example, reduce the current draw of the controller  114  (block  258 ). During this sleep mode, the controller  114  waits for a selected period of time (e.g.,  2  hours) (block  260 ) before waking up (block  262 ). Note that it may be possible to operate the heater when the vehicle is in a key-on condition, if desired, as long as the battery heater system  100  is connected to the AC power source  110 . 
         [0044]    If the controller  114  is receiving the AC/DC active signal (block  254 ), it knows that the battery heater system  100  is connected to the AC power source  110  (block  263 ). The controller  114  then checks the battery temperature (block  264 ) to determine whether the battery temperature is less than a selected temperature threshold (block  265 ). As noted above, the temperature threshold is selected to ensure that the vehicle will start and/or ensure optimum vehicle performance. 
         [0045]    If the battery temperature is at or greater than the temperature threshold, the controller  114  switches the heater  104  to the OFF condition if it is turned on or leaves the heater  104  in the OFF condition if it is already turned off (block  256 ). The controller  114  then enters the sleep mode (block  258 ) as described above, checking the battery temperature again when it wakes up after the selected time period. 
         [0046]    If the battery temperature is less than the temperature threshold (block  265 ), it indicates that the battery system  102  needs to be heated to reach its desired temperature. The controller  114  turns on the switch  116  to connect the heater  104  to the AC power source  110  (block  268 ). At this point, the heater  104  is in the ON condition (block  270 ). 
         [0047]    The controller  114  then enters a sleep mode (block  272 ). In this example, the amount of current sent to the heater  104  is low enough so that the heater  104  can remain turned on during the sleep mode without any danger of overheating. Alternatively, the controller  114  may turn the switch  116  on only for a predetermined period of time before turning it off again, without waiting for the controller  114  to wake up out of sleep mode. Note that if the controller  114  is powered by the AC power source  110  rather than the low-voltage battery  120 , the controller  114  can monitor the battery temperature continuously rather than only during periodic wake-ups, further optimizing the battery system  102  power without risking overheating. 
         [0048]    In the example shown in  FIG. 3 , the controller  114  remains in sleep mode for the selected time period (e.g., 2 hours) (block  274 ). The controller  114  then wakes up (block  276 ) and checks whether it is receiving the AC/DC active signal (block  277 ). If not, it re-enters the sleep mode (block  272 ). If the controller  114  is receiving the AC/DC active signal, indicating that the battery heater system  100  is connected to the AC power source  110 , the controller  114  then measures the battery temperature (block  278 ). If the battery temperature is at or below the desired temperature threshold (block  280 ), the controller  114  re-enters the sleep mode (block  272 ) with the switch  116  closed, thereby allowing current to continue passing through the heater  104  and keep the heater  104  in the ON condition. Of course, if the controller  114  is no longer receiving the AC/DC signal at this stage, the controller  114  opens the switch  116  to switch the heater  104  to an OFF condition. 
         [0049]    If the battery temperature is above the temperature threshold (block  278 ), it indicates that the battery system  102  is at or above the desired optimum temperature, making it unnecessary to continue operating the heater  104 . The controller  114  therefore opens the switch  116  to disconnect the heater  104  from the AC power source  110  (block  282 ) and place the heater  104  in an OFF condition (block  256 ). The controller  114  then enters the sleep mode (block  258 ) as described above and delays for the selected time period before waking up to check the battery temperature again. 
         [0050]    The inventive battery heater system therefore maintains a desired battery temperature indefinitely by connecting the battery heater to an AC power source rather than relying on its own internal power source. Using the AC power source also allows the battery heater system to work in conjunction with an engine block heater and be powered through the engine block heater&#39;s connection to the power source, eliminating the need for separate power source connections. The modularity of the inventive battery heater system also allows it to be included or omitted from a given vehicle easily. 
         [0051]    It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby.