Patent Publication Number: US-11660952-B2

Title: Energy storage system for electric vehicles

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/548,942 filed Aug. 23, 2019, which is a continuation of U.S. patent application Ser. No. 16/124,606 filed Sep. 7, 2018, which is a continuation of U.S. patent application Ser. No. 15/095,217 filed Apr. 11, 2016, which is a continuation of U.S. patent application Ser. No. 13/489,797 filed Jun. 6, 2012, which is a continuation of International Application No. PCT/US2011/063695, filed Dec. 7, 2011, which claims the benefit of U.S. Provisional Patent Application No. 61/420,389 filed Dec. 7, 2010, all of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     The present invention generally relates to an energy storage system and, more particularly, to an energy storage module to be incorporated into a hybrid electric motor vehicle to store high voltage energy. 
     Over the past few years, there has been a growing concern over global climate change due to an increase in carbon dioxide levels as well as oil supply shortages. As a result, some automobile manufactures and consumers are beginning to have a greater interest in motor vehicles having low emissions and greater fuel efficiency. One viable option is a hybrid electric vehicle (HEV) which allows the vehicle to be driven by an electric motor, combustion engine, or a combination of the two. 
     Though various features are important to the overall HEV design, the system which stores the energy available for use by the vehicle is a key component. The energy storage system is provided within the HEV to store the energy created by a generator in order for that energy to be available for use by the hybrid system at some later time. For example, the stored energy may be used to drive an electric motor to independently propel the motor vehicle or assist the combustion engine, thereby reducing gasoline consumption. 
     However, energy storage systems face a variety of design complications, such as over-heating, weight, complexity, ease of incorporation into the vehicle, ease of service, and cost, just to name a few. Additionally, known energy storage systems utilize only a specific and known number of battery packs or modules designed to meet a particular HEV design specification. For example, a battery pack may be specifically designed to provide a specific amount of energy for a 300V vehicle. However, when a different amount of energy is required, such as a 600V system, a different battery pack must be designed to meet the needs of that application. Known battery packs and storage systems can not be utilized or otherwise implemented into different settings without a considerable amount of re-engineering and re-working. 
     Some known systems allow for separate battery packs to be electrically connected to a separate and distinct control box. Though the independent battery packs may be added to or removed from the overall system, the separate control box is still required. However, because available space for HEV components is at a premium, the inclusion of a separate and distinct control box should be avoided. Additionally, in the event the separate control box fails, the entire energy storage system is unable to function. 
     Thus, there is a need for improvement in this field. 
     SUMMARY 
     The energy storage system described herein addresses several of the issues mentioned above as well as others. For example, an energy storage system according to one embodiment of the present disclosure has a plurality of energy storage modules. The energy storage modules include, among other things, a plurality secondary battery arrays adapted to store high voltage energy. An energy storage controller module is electrically connected to various components within an energy storage module, such as, but not limited to, the battery arrays, a low voltage harness, a thermistor harness, and/or a vehicle signal connector assembly, to name a few examples. 
     According to one aspect of the present disclosure, the energy storage modules within the energy storage system are adapted to communicate with one another. In one embodiment, a pack-to-pack CAN bus is provided between each energy storage module. When multiple energy storage modules are used to comprise the energy storage system, one energy storage module functions as a master energy storage module while the others function as slave energy storage modules. The energy storage controller module within the master energy storage module is adapted to receive information from the slave energy storage modules and communicate with a transmission/hybrid control module and the rest of the hybrid system as a single energy storage system. 
     According to another aspect of the disclosure, the energy storage system comprises at least one energy storage module adapted to supply electrical energy to a hybrid vehicle. The energy storage module comprises a primary enclosure, at least one battery array located within the primary enclosure, and an energy storage controller module located within the primary enclosure and electrically connected to the battery array. The energy storage controller module is further connected to a hybrid control module of the hybrid vehicle by a low voltage connecter. A high voltage junction box is attached to a first end of the primary enclosure and has a plurality of high voltage connection terminals. The high voltage junction box has a first opening which corresponds to a second opening of the primary enclosure such that the primary enclosure and high voltage junction box define a sealed cavity. At least one of the high voltage connection terminals is configured to receive a high voltage conductor connected between the energy storage module and an inverter of the hybrid vehicle. A service disconnect is connected in a current path between the high voltage connection terminals and the at least one battery array. 
     According to other aspects of the present disclosure, the energy storage system includes a thermal pad disposed between the battery arrays and an interior surface of the primary enclosure. A heat sink is disposed on an exterior surface of the primary enclosure. The heat sink comprises a plurality of fins which may be disposed angularly outward in a symmetrical pattern with respect to a longitudinal axis of the primary enclosure. A fan mounted to an exterior surface of a first end of the primary enclosure is operable to direct air across the fins toward a second end of the primary enclosure. The height or length of the fins may be varied relative to the fan location to provide uniform cooling across the battery cells in the battery array. An enclosing plate is mounted exterior to the heat sink and defining an airflow cavity, wherein the enclosing plate further directs air from the fan across the heat sink. 
     According to other aspects of the disclosure, the energy storage system includes a plug-in bussed electrical center, wherein at least a portion of the high voltage connections between the battery array and the bussed electrical center are achieved using blade terminals. The primary enclosure may further comprise a pressure relief panel disposed within the primary enclosure and operable to limit internal pressure within the primary enclosure. 
     According to other aspects of the disclosure, the battery array comprises two parallel side rails and two parallel plates perpendicular to the side rails. The battery array may also include battery retainers between the battery cells. The battery retainers are formed from an insulating material of sufficient thickness to limit thermal transfer between the adjacent battery cells to a level which prevents venting of a first battery cell from causing an adjacent second battery cell to vent. The battery array also includes a voltage sense board having a plurality of bus bars disposed therein. The bus bars connect a positive terminal of a first battery cell to a negative terminal of a second battery cell. The voltage send board has missing final bus bars in designated locations of the voltage sense board to limit the exposed voltage to 50 volts during initial assembly. The final bus bars are installed last in conjunction with safety covers which have overlap portions to cover the installed final bus bars. 
     According to other aspects of the present disclosure, the controller module optionally includes a memory component. The memory component is adapted to record energy storage module usage and status history, such as achieved power levels and duty cycles, to name a few examples. 
     Further forms, objects, features, aspects, benefits, advantages, and embodiments of the present invention will become apparent from a detailed description and drawings provided herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a diagrammatic view of one example of a hybrid system. 
         FIG.  2    illustrates a general diagram of an electrical communication system in the  FIG.  1    hybrid system. 
         FIG.  3    is a front perspective view of an energy storage module according to one embodiment of the present disclosure. 
         FIG.  4    is a rear perspective view of the energy storage module depicted in  FIG.  3   . 
         FIG.  5    is a bottom perspective view of the energy storage module depicted in  FIG.  3   . 
         FIG.  6    is an end view of the energy storage module depicted in  FIG.  3   . 
         FIG.  7 A  is an end view of an energy storage module with the access cover attached according to one embodiment of the present disclosure. 
         FIG.  7 B  is an end view of an energy storage module with the access cover removed and the safety cover in place according to one embodiment of the present disclosure. 
         FIG.  8    is an end view of an energy storage module stacking arrangement according to one embodiment of the present disclosure. 
         FIG.  9    is a top view of an energy storage module with the top cover removed according to one embodiment of the present disclosure. 
         FIG.  10    is a further perspective view the energy storage module of  FIG.  9    with the top cover removed according to one embodiment of the present disclosure. 
         FIG.  11    is a further perspective view of the energy storage module depicted in  FIG.  10    with the top cover removed according to one embodiment of the present disclosure. 
         FIG.  12    is a perspective view of a plenum end cap according to one embodiment of the present disclosure. 
         FIG.  13    is a cross-sectional view of the end cap of  FIG.  12    taken along line A-A according to one embodiment of the present disclosure. 
         FIG.  14    is a bottom perspective view of an energy storage module depicting the cooling air flow according to one embodiment of the present disclosure. 
         FIG.  15    is an exploded view of a fan assembly according to one embodiment of the present disclosure. 
         FIG.  16    is a perspective view of a bussed electrical center assembly according to one embodiment of the present disclosure. 
         FIG.  17    is an exploded view of a battery array assembly according to one embodiment of the present disclosure. 
         FIG.  18    is a perspective view of a battery cell. 
         FIG.  19    is an end, cross-sectional view of a battery array and plenum assembly according to one embodiment of the present disclosure. 
         FIG.  20    is a further end, cross-sectional view of a battery array and plenum assembly according to one embodiment of the present disclosure. 
         FIG.  21    is a perspective view of an energy storage controller module according to one embodiment of the present disclosure. 
         FIG.  22    is a perspective view of an energy storage module stacking arrangement according to one aspect of the present disclosure. 
         FIG.  23    is a perspective view of an energy storage module vehicle mounting arrangement according to one aspect of the present disclosure. 
         FIG.  24    is a front perspective view of an energy storage module according to one embodiment of the present disclosure. 
         FIG.  25    is a rear perspective view of the energy storage module depicted in  FIG.  24   . 
         FIG.  26    is a rear perspective view of an energy storage module stacking arrangement according to one embodiment of the present disclosure. 
         FIG.  27    is a lower rear perspective view of the energy storage module depicted in  FIG.  24   . 
         FIG.  28    is a lower front perspective view of a heat sink fin arrangement according to one embodiment of the present disclosure. 
         FIG.  29    is an upper rear perspective view of an energy store module having a thermal pad according to one embodiment of the present disclosure. 
         FIG.  30    is a front perspective view of a high voltage junction box of the energy storage module of  FIG.  24   . 
         FIG.  31    is a front perspective view of the high voltage junction box of  FIG.  31    with the access cover removed. 
         FIG.  32    is a front perspective view of the high voltage junction box of  FIG.  31    with the inner safety cover removed. 
         FIG.  33 A  is a front perspective view of a plug-in bussed electrical center of the energy storage module of  FIG.  24   . 
         FIG.  33 B  is a rear perspective view of a plug-in bussed electrical center of the energy storage module of  FIG.  24   . 
         FIG.  34    is an exploded front perspective view of the energy storage module of  FIG.  24   . 
         FIG.  35    is a rear perspective view of the energy storage module of  FIG.  24    with the top cover and fan assembly removed. 
         FIG.  36    is an exploded rear perspective view of the energy storage module of  FIG.  24   . 
         FIG.  37    is a perspective view of a pressure relief panel of the energy storage module of  FIG.  24    according to one embodiment. 
         FIG.  38    is an exploded perspective view of a battery array according to one embodiment of the present disclosure. 
         FIG.  39    is a perspective view of an assembled battery array according to one embodiment of the present disclosure. 
         FIG.  40    is front view of the battery array of  FIG.  39    showing an individual battery cell mounted in the battery array. 
         FIG.  41    is a top view of a voltage sense board assembly according to one embodiment of the present disclosure. 
         FIG.  42    is a front view of the energy storage module of  FIG.  24    mounted to a vehicular frame. 
         FIG.  43    is a perspective view of an isolator adapter for supporting an energy storage module according to one embodiment. 
         FIG.  44    is a front view of a thermistor mounting arrangement according to one embodiment of the present disclosure. 
         FIG.  45    is a perspective view of the thermistor mounting arrangement of  FIG.  44   . 
         FIG.  46 A  is a diagram showing a single energy storage module for use in an energy storage system according to one embodiment. 
         FIG.  46 B  is a diagram showing two energy storage modules connected in parallel according to one embodiment. 
         FIG.  46 C  is a diagram showing two energy storage modules connected in series according to one embodiment. 
         FIG.  46 D  is a diagram showing two pairs of energy storage modules connected in a series/parallel arrangement according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. One embodiment of the invention is shown in great detail, although it will be apparent to those skilled in the relevant art that some features not relevant to the present invention may not be shown for the sake of clarity. 
     The reference numerals in the following description have been organized to aid the reader in quickly identifying the drawings where various components are first shown. In particular, the drawing in which an element first appears is typically indicated by the left-most digit(s) in the corresponding reference number. For example, an element identified by a “100” series reference numeral will first appear in  FIG.  1   , an element identified by a “200” series reference numeral will first appear in  FIG.  2   , and so on. With reference to the Specification, Abstract, and Claims sections herein, it should be noted that the singular forms “a”, “an”, “the”, and the like include plural referents unless expressly discussed otherwise. As an illustration, references to “a device” or “the device” include one or more of such devices and equivalents thereof. 
       FIG.  1    shows a diagrammatic view of a hybrid system  100  according to one embodiment. The hybrid system  100  illustrated in  FIG.  1    is adapted for use in commercial-grade trucks as well as other types of vehicles or transportation systems, but it is envisioned that various aspects of the hybrid system  100  can be incorporated into other environments. As shown, the hybrid system  100  includes an engine  102 , a hybrid module  104 , an automatic transmission  106 , and a drive train  108  for transferring power from the transmission  106  to wheels  110 . The hybrid module  104  incorporates an electrical machine, commonly referred to as an eMachine  112 , and a clutch  114  that operatively connects and disconnects the engine  102  from the eMachine  112  and the transmission  106 . 
     The hybrid module  104  is designed to operate as a self-sufficient unit, that is, it is generally able to operate independently of the engine  102  and transmission  106 . In particular, its hydraulics, cooling and lubrication do not directly rely upon the engine  102  and the transmission  106 . The hybrid module  104  includes a sump  116  that stores and supplies fluids, such as oil, lubricants, or other fluids, to the hybrid module  104  for hydraulics, lubrication, and cooling purposes. While the terms oil or lubricant will be used interchangeably herein, these terms are used in a broader sense to include various types of lubricants, such as natural or synthetic oils, as well as lubricants having different properties. To circulate the fluid, the hybrid module  104  includes a mechanical pump  118  and an electrical (or electric) pump  120 . With this combination of both the mechanical pump  118  and electrical pump  120 , the overall size and, moreover, the overall expense for the pumps is reduced. The electrical pump  120  can supplement mechanical pump  118  to provide extra pumping capacity when required. In addition, it is contemplated that the flow through the electrical pump  120  can be used to detect low fluid conditions for the hybrid module  104 . In one example, the electrical pump  120  is manufactured by  Magna  International Inc. of Aurora, Ontario, Canada (part number 29550817), but it is contemplated that other types of pumps can be used. 
     The hybrid system  100  further includes a cooling system  122  that is used to cool the fluid supplied to the hybrid module  104  as well as the water-ethylene-glycol (WEG) to various other components of the hybrid system  100  which will be described later in further detail. In one variation, the WEG can also be circulated through an outer jacket of the eMachine  112  in order to cool the eMachine  112 . It should be noted that the hybrid system  100  will be described with respect to a WEG coolant, but other types of antifreezes and cooling fluids, such as water, alcohol solutions, etc., can be used. Looking at  FIG.  1   , the cooling system  122  includes a fluid radiator  124  that cools the fluid for the hybrid module  104 . The cooling system  122  further includes a main radiator  126  that is configured to cool the antifreeze for various other components in the hybrid system  100 . Usually, the main radiator  126  is the engine radiator in most vehicles, but the main radiator  126  does not need to be the engine radiator. A cooling fan  128  flows air through both fluid radiator  124  and main radiator  126 . A circulating or coolant pump  130  circulates the antifreeze to the main radiator  126 . It should be recognized that other various components besides the ones illustrated can be cooled using the cooling system  122 . For instance, the transmission  106  and/or the engine  102  can be cooled as well via the cooling system  122 . 
     The eMachine  112  in the hybrid module  104 , depending on the operational mode, at times acts as a generator and at other times as a motor. When acting as a motor, the eMachine  112  draws alternating current (AC). When acting as a generator, the eMachine  112  creates AC. An inverter  132  converts the AC from the eMachine  112  and supplies it to an energy storage system  134 . The eMachine  112  in one example is an HVH410 series electric motor manufactured by Remy International, Inc. of Pendleton, Ind., but it is envisioned that other types of eMachines can be used. In the illustrated example, the energy storage system  134  stores the energy and resupplies it as direct current (DC). When the eMachine  112  in the hybrid module  104  acts as a motor, the inverter  132  converts the DC power to AC, which in turn is supplied to the eMachine  112 . The energy storage system  134  in the illustrated example includes three energy storage modules  136  that are daisy-chained together to supply high voltage power to the inverter  132 . The energy storage modules  136  are, in essence, electrochemical batteries for storing the energy generated by the eMachine  112  and rapidly supplying the energy back to the eMachine  112 . The energy storage modules  136 , the inverter  132 , and the eMachine  112  are operatively coupled together through high voltage wiring as is depicted by the line illustrated in  FIG.  1   . While the illustrated example shows the energy storage system  134  including three energy storage modules  136 , it should be recognized that the energy storage system  134  can include more or less energy storage modules  136  than is shown. Moreover, it is envisioned that the energy storage system  134  can include any system for storing potential energy, such as through chemical means, pneumatic accumulators, hydraulic accumulators, springs, thermal storage systems, flywheels, gravitational devices, and capacitors, to name just a few examples. 
     High voltage wiring connects the energy storage system  134  to a high voltage tap  138 . The high voltage tap  138  supplies high voltage to various components attached to the vehicle. A DC-DC converter system  140 , which includes one or more DC-DC converter modules  142 , converts the high voltage power supplied by the energy storage system  134  to a lower voltage, which in turn is supplied to various systems and accessories  144  that require lower voltages. As illustrated in  FIG.  1   , low voltage wiring connects the DC-DC converter modules  142  to the low voltage systems and accessories  144 . 
     The hybrid system  100  incorporates a number of control systems for controlling the operations of the various components. For example, the engine  102  has an engine control module  146  that controls various operational characteristics of the engine  102  such as fuel injection and the like. A transmission/hybrid control module (TCM/HCM)  148  substitutes for a traditional transmission control module and is designed to control both the operation of the transmission  106  as well as the hybrid module  104 . The transmission/hybrid control module  148  and the engine control module  146  along with the inverter  132 , energy storage system  134 , and DC-DC converter system  140  communicate along a communication link as is depicted in  FIG.  1   . 
     To control and monitor the operation of the hybrid system  100 , the hybrid system  100  includes an interface  150 . The interface  150  includes a shift selector  152  for selecting whether the vehicle is in drive, neutral, reverse, etc., and an instrument panel  154  that includes various indicators  156  of the operational status of the hybrid system  100 , such as check transmission, brake pressure, and air pressure indicators, to name just a few. 
     As noted before, the hybrid system  100  is configured to be readily retrofitted to existing vehicle designs with minimal impact to the overall design. All of the systems including, but not limited to, mechanical, electrical, cooling, controls, and hydraulic systems, of the hybrid system  100  have been configured to be a generally self-contained unit such that the remaining components of the vehicle do not need significant modifications. The more components that need to be modified, the more vehicle design effort and testing is required, which in turn reduces the chance of vehicle manufacturers adopting newer hybrid designs over less efficient, preexisting vehicle designs. In other words, significant modifications to the layout of a preexisting vehicle design for a hybrid retrofit requires, then, vehicle and product line modifications and expensive testing to ensure the proper operation and safety of the vehicle, and this expenses tends to lessen or slow adoption of hybrid systems. As will be recognized, the hybrid system  100  not only incorporates a mechanical architecture that minimally impacts the mechanical systems of pre-existing vehicle designs, but the hybrid system  100  also incorporates a control/electrical architecture that minimally impacts the control and electrical systems of pre-existing vehicle designs. 
       FIG.  2    shows a diagram of one example of a communication system  200  that can be used in the hybrid system  100 . While one example is shown, it should be recognized that the communication system  200  in other embodiments can be configured differently than is shown. The communication system  200  is configured to minimally impact the control and electrical systems of the vehicle. To facilitate retrofitting to existing vehicle designs, the communication system  200  includes a hybrid data link  202  through which most of the various components of the hybrid system  100  communicate. In particular, the hybrid data link  202  facilitates communication between the transmission/hybrid control module  148  and the shift selector  152 , inverter  132 , the energy storage system  134 , the low voltage systems/accessories  144 , and the DC-DC converter modules  142 . Within the energy storage system  134 , an energy storage module data link  204  facilitates communication between the various energy storage modules  136 . However, it is contemplated that in other embodiments the various energy storage system modules  136  can communicate with one another over the hybrid data link  202 . With the hybrid data link  202  and the energy storage module data link  204  being separate from the data links used in the rest of the vehicle, the control/electrical component of the hybrid system  100  can be readily tied into the vehicle with minimum impact. In the illustrated example, the hybrid data link  202  and the energy storage module data link  204  each have a 500 kilobit/second (kbps) transmission rate, but it is envisioned that data can be transferred at other rates in other examples. Other components of the vehicle communicate with the transmission/hybrid control module  148  via a vehicle data link  206 . In particular, the shift selector  152 , the engine control module  146 , the instrument panel  154 , an antilock braking system  208 , a body controller  210 , the low voltage systems/accessories  144 , and service tools  212  are connected to the vehicle data link  206 . For instance, the vehicle data link  206  can be a 250 k J1939-type data link, a 500 k J1939-type data link, a General Motors LAN, or a PT-CAN type data link, just to name a few examples. All of these types of data links can take any number of forms such as metallic wiring, optical fibers, radio frequency, and/or a combination thereof, just to name a few examples. 
     In terms of general functionality, the transmission/hybrid control module  148  receives power limits, capacity available current, voltage, temperature, state of charge, status, and fan speed information from the energy storage system  134  and the various energy storage modules  136  within. The transmission/hybrid control module  148  in turn sends commands for connecting the various energy storage modules  136  so as to supply voltage to and from the inverter  132 . The transmission/hybrid control module  148  also receives information about the operation of the electrical pump  120  as well as issues commands to the auxiliary electrical pump  120 . From the inverter  132 , the transmission/hybrid control module  148  receives a number of inputs such as the motor/generator torque that is available, the torque limits, the inverter&#39;s voltage current and actual torque speed. Based on that information, the transmission/hybrid control module  148  controls the torque speed and the pump  130  of the cooling system. From the inverter  132 , it also receives a high voltage bus power and consumption information. The transmission/hybrid control module  148  also monitors the input voltage and current as well as the output voltage and current along with the operating status of the individual DC-DC converter modules  142  of the DC-DC converter system  140 . The transmission/hybrid control module  148  also communicates with and receives information from the engine control module  146  and in response controls the torque and speed of the engine  102  via the engine control module  146 . 
     Turning to  FIG.  3   , certain embodiments of the energy storage module  136  will now be discussed. As depicted, energy storage module  136  comprises a primary enclosure  301  having a lower housing  302  and an upper cover  304 . The lower housing  302  and upper cover  304  are constructed and arranged to withstand large vibrations and high shock loads. In order to provide heavy duty strength for operation in certain environments (i.e., heavy duty trucking) while also being mindful of weight, lower housing  302  and upper cover  304  are constructed of aluminum in one embodiment, though other materials, such as steel, may also be used. According to one embodiment, the energy storage module  136  is constructed to withstand  100 G shock loads and 25G vibration loads. 
     A plurality of mounting feet  306  are located on the bottom of lower housing  302  to assist in the mounting of the energy storage module  136  to the HEV body or frame. Additionally, a plurality of indentations  316  are provided around the periphery of lower housing  302  to also assist in the optional stacking of multiple energy storage modules. 
     Located at one end  307  of the energy storage module  136  is a high voltage junction box  308 . As will be described in more detail below, a series of high voltage cables  310  are connected to the high voltage junction box  308  to deliver high voltage power to and from energy storage module  136 . The high voltage junction box  308  may be formed integral to the primary enclosure  301  or as a separate unit. 
     Also provided on the end  307  of the energy storage module  136  are a service disconnect  312  and a low-voltage vehicle signal connector  314 . The service disconnect  312  is provided to break the current path between the high voltage energy sources within the primary enclosure  301  and the electronics within the high voltage junction box  308 . The service disconnect  312  ensures user safety during service operations of the energy storage module  136 . The vehicle signal connector  314  allows for the energy storage module  136  to be in electrical and communicative connection with other components of the hybrid system, such as, but not limited to, the transmission/hybrid control module  148 . In one embodiment, the vehicle signal connector  314  is a forty seven (47) way connector which includes gold terminals. According to one aspect of the present disclosure, the vehicle signal connector  314  is also designed and validated for heavy duty applications. Though the embodiment illustrated in  FIG.  3    includes a single vehicle signal connector  314 , other embodiments may include two or more signal connectors. 
       FIG.  4    depicts a perspective view of the other end  315  of the energy storage module  136 . As shown, a plenum inlet cover  402  and a plenum outlet cover  404  are provided at the same end  315  of the energy storage module  136 . The covers  402 ,  404  are constructed and arranged to guide the air entering and exiting the energy storage module  136 . In some embodiments, covers  402 ,  404  may be connected and have a unitary design. An exhaust vent  406  is provided to allow for the safe exhaustion of potentially harmful gases and fumes in the event of a failure of a battery cell, as will be discussed in greater detail below. A plurality of recesses  408  is provided on the upper cover  304  to assist in the optional stacking and mating of multiple energy storage modules. 
     In some embodiments, the energy storage module  136  has a physical dimension of 1100 mm×470 mm×235 mm, though larger and smaller dimensions may be warranted depending upon a particular HEV design and are within the scope of the present disclosure. In some embodiments, the energy storage module has a weight between 50 and 100 kilograms, though lighter and heavier weights are within the scope of the present disclosure. 
       FIG.  5    provides a perspective view of the underside of the lower housing  302  of energy storage module  136 . As depicted, lower housing  302  includes a plurality of protrusions  502  on its bottom surface. In the illustrated embodiment, recesses  408  correspond to the configuration of the protrusions  502  in order to provide a stable arrangement when an additional energy storage module is stacked on top of the upper cover  304 . 
       FIG.  6    provides a more detailed view of the end  307  of the energy storage module  136  including the high voltage junction box  308 . In the illustrated embodiment, all electrical connections are made available on the same end  307  of the energy storage module  136 . The high voltage junction box  308  includes two auxiliary direct current (DC) connections  602  and corresponding auxiliary fuses  604 . These components provide additional sources of high voltage DC power to be used by the hybrid system and/or vehicle accessories. In one embodiment, one DC connection  602  allows the energy storage module  136  to be connected to the DC-DC converter system  140 . The high voltage junction box  308  also includes a high voltage interlock (HVIL)  606  which safely isolates the high voltage components from the rest of the vehicle when triggered. 
     As noted above, a series of high voltage cables  310  connect a series of peripheral components to the high voltage junction box  308  via high voltage connectors  616 . More specifically, a positive inverter cable  608  provides the positive connection to inverter  132 , whereas a negative inverter cable  610  provides the negative connection to inverter  132 . A positive mating cable  612  provides the positive connection to an additional, stacked energy storage module or other high voltage device and a negative mating cable  614  provides the negative connection to an additional, stacked energy storage module or other high voltage device. Positive cables  608 ,  612  are electrically connected to positive terminal  618  and negative cables  610 ,  614  are electrically connected to negative terminal  620 . 
     In one embodiment, the ends of cables  310  and connectors  616  are keyed in order to prevent connection error. In one arrangement, each cable is provided with an individual key. In another embodiment, the positive cables  608 ,  612  are keyed the same, while the negative cables  610 ,  614  are keyed the same but different from positive cables  608 ,  612 . 
       FIGS.  7 A,  7 B  depict the high voltage junction box  308  safety access features according to one embodiment of the present disclosure. As shown in  FIG.  7 A , the high voltage junction box  308  is a sealed unit protected by an access cover  702 . In order to gain access to inside the junction box  308 , fasteners  704  must be removed and the access cover  702  may be lifted away. 
       FIG.  7 B  depicts the high voltage junction box  308  with the access cover  702  removed. For precautionary purposes, a safety cover  706  is provided to act as a further barrier to the high voltage terminals behind it. In order to access the electronics depicted in  FIG.  5   , an HVIL resistor  708  must be removed in order to disconnect the HV power to the positive terminal  618  and the negative terminal  620 . Additionally, the fasteners  710  must be taken out before the safety cover  706  can be removed. Once those actions are completed, the electronics within the high voltage junction box  308  as illustrated in  FIG.  5    can then be safely accessed. 
       FIG.  8    illustrates the HV power connections between stacked energy storage modules. As shown, one energy storage module  802  functions as the master module. Master module  802  is connected to the hybrid system inverter  132  via cables  608 ,  610 . A second energy storage module  804  functions as a slave module. In the illustrated embodiment, slave module  804  is not connected to the inverter  132  but is only connected to the master module  802  via cables  612 ,  614 . Therefore, master module  802  essentially contains two sets of main power connections: one to the hybrid system, one to the slave module  804 . 
       FIG.  9    depicts a top view of the energy storage module  136  in which the upper cover  304  has been removed in order to show various components. In the illustrated embodiment, energy storage module  136  includes a first battery array  902  and a second battery array  904 . The battery arrays  902 ,  904  allow for both (a) the high voltage energy received from the inverter  132  to be stored and (b) to provide high voltage energy to the inverter  132  in order to power an appropriate hybrid system component, as well as other system components via auxiliary DC connections  602 . Each battery array  902 ,  904  is connected to a high voltage harness  906  which is electrically connected to a controller module  908 . The battery arrays  902 ,  904  are also electrically connected to a bussed electrical center (BEC)  918 , which is constructed and arranged to, among other things, properly distribute the high voltage energy to the high voltage junction box  308  and cables  310 . 
     In addition to the high voltage harness  906 , the controller module  908  is also electrically connected to a low voltage harness  910 . The low voltage harness  910  provides a communicative connection between the controller  908  and various components within the energy storage module  136 , such as, but not limited to, fan assembly  912 , vehicle signal connector assembly  914 , and BEC  918 . A high voltage interlock switch  916  is also provided inside the energy storage module  136  as a further safety precaution. The high voltage interlock switch  916  is in electrical and communicative connection with BEC  918 . BEC  918  is adapted to trigger switch  916  and disconnect the high voltage power from the high voltage junction box  308  if the high voltage electrical conditions become unsafe. 
     In other, non-illustrated embodiments, the various components may be rearranged and relocated, such as, but not limited to, BEC  918  and portions of fan assembly  912 . In one embodiment, the fan assembly  912  may be positioned outside of primary enclosure  301 . In other embodiments, BEC  918  may be located inside high voltage junction box  308 . As appreciated by those of ordinary skill in the art, these modifications and others may be implemented to reduce high voltage exposure under service conditions. 
       FIGS.  10  and  11    provide a more detailed overview of the components within the energy storage module  136 . As illustrated, the high voltage junction box  308  includes both a positive header assembly  1002  and negative header assembly  1004 . Disposed underneath the access cover  702  is access cover seal  1006  which ensures that particles and moisture are kept out of the high voltage junction box  308 . Also provided is high voltage interlock conductor  1008 . In certain embodiments, the back of the high voltage junction box  308  may be open with respect to the lower housing  302  to allow the various electrical connections between the high voltage junction box  308  and the BEC  918  or controller  908 . In other embodiments, the back of the high voltage junction box may be sealed with respect to the lower housing  302 , with the wiring connections between the high voltage junction box  308  and the BEC  918  being individually sealed to prevent contaminants from entering the primary enclosure  301  via the high voltage junction box  308 . 
     The service disconnect  312  comprises service disconnect plug  1010  and base  1012 . The service disconnect plug  1010  of service disconnect  312  is provided to break the current path between the high voltage energy sources within the energy storage module  136  and the electronics within the high voltage junction box  308 . 
     A seal  1014  is disposed underneath the upper cover  304  to ensure that particles and moisture are kept out of the energy storage module  136 . A series of bolts  1016  are utilized to fix the upper cover  304  to the lower housing  302 , though other known techniques may be utilized. Around the outer periphery of both the upper cover  304  and the lower housing  302  are a plurality of holes  1024  adapted to facility both the lifting of the energy storage module  136  as well as the stacking of multiple energy storage modules  136 . 
     A safety cover  1018  is positioned on top of the battery array  902 . The safety cover  1018  protects the battery cells comprising the battery array  902  from damage and contact with the other components within the energy storage module  136 . A battery end plate seal  1032  is provided at each end of the battery arrays  902 ,  904  to further protect the arrays from contamination and damage. 
     Positioned between the plenum inlet cover  402  and the fan assembly  912  is a plenum/fan interface  1020 . An inlet air sensor  1022  is located downstream of the plenum/fan interface  1020  and is adapted to monitor the air flow into the energy storage module  136 . A fan housing seal  1030  is also provided adjacent to the fan assembly  912 . 
     As discussed with respect to  FIG.  9   , the controller module  908  is electrically and communicatively connected to low voltage harness  910 , as well as a thermistor high harness  1026  and a thermistor low harness  1028 . As appreciated by those of skill in the art, a thermistor is a resistor whose resistance varies with changes in temperature. Accordingly, the thermistor harnesses  1026 ,  1028  may communicate temperature data related to the BEC  918 , inlet air, outlet air, the battery arrays  902 ,  904 , the fan assembly  912 , etc. 
     Looking now at  FIG.  11   , BEC  918  includes a positive high voltage conductor  1102  electrically connected to the positive header assembly  1002  and a negative high voltage conductor  1104  electrically connected to the negative header assembly  1004 . BEC  918  further includes a negative conductor  1106 . 
     A high voltage interlock header pass through  1108  is provided adjacent to high voltage junction box  308 . Referring now also to  FIGS.  9  and  10   , the HVIL pass through  1108  electrically connects the HVIL conductor  1008  with the HVIL switch  916 . Accordingly, when the HVIL resistor  708  is removed from the HVIL  606 , the HVIL pass through  1108  indicates an open circuit and the HVIL switch  916  is tripped to disconnect the high voltage power from the electronics within the high voltage junction box  308 . 
     During operation, various components within energy storage module  136  generate a considerable amount of heat, particularly the battery arrays  902 ,  904 . In order for the components to properly function, the heat must be adequately dissipated. Pursuant to the illustrated embodiment, the battery arrays  902 ,  904  and other components within the energy storage module  136  are air cooled. In order to guide and provide a separate air flow along the battery arrays  902 ,  904 , a plenum cover  1110  is provided between the battery arrays  902 ,  904 . The plenum cover  1110  has a fan end  1112 , which is positioned adjacent to the fan assembly  912 , and a BEC end  1114 , which is located near the BEC  918 . In the illustrated embodiment, the fan end  1112  is taller than the BEC end  1114 . The tapering of plenum cover  1110  ensures that the air flow through the plenum maintains an adequate velocity as it flows away from the fan assembly  912 . A plenum air seal  1116  is disposed beneath the plenum cover  1110 . 
     A mid pack conductor  1118  electrically connects the first battery array  902  with the second battery array  904 . The mid pack conductor  1118  allows the controller module  908  to monitor the battery arrays  902 ,  904  as if they were a single array. 
     As previously discussed, the plenum inlet cover  402  and the plenum outlet cover  404  are provided at one end  315  of the primary enclosure  301 . In order to ensure no debris or moisture is introduced into the energy storage module  136 , an inlet cover seal  1120  is provided between the outer periphery of the plenum inlet cover  402  and the lower housing  302 . Similarly, an outlet cover seal  1122  is provided between the outer periphery of the plenum outlet cover  404  and the lower housing  302 . 
     In one embodiment, potentially harmful and noxious gases which may vent when under abuse or failure from the battery cells within the battery arrays  902 ,  904 , exhaust vent manifold  1124  is provided along the length of the battery arrays  902 ,  904 . The vent tubes comprising manifold  1124  are connected at a vent tee  1126 , with the exhaust gases then being delivered to the exhaust vent  406 . Known techniques can then be implemented to treat or otherwise dispose of the exhaust gases. 
       FIG.  12    provides a perspective view of a plenum end cap  1200 . The plenum end cap  1200  may be used as plenum inlet cover  402  and/or plenum outlet cover  404 . The end cap  1200  comprises a body  1202  and a plurality of mounting flanges  1204 . The mounting flanges  1204  are constructed and arranged to lay flat against and provide a surface to be affixed to the lower housing  302 . In the illustrated embodiment, the end cap  1200  is affixed to the lower housing  302  by a plurality of fasteners placed through the holes  1206 . In other embodiments, the end cap  1200  may be held to the lower housing  302  through other known techniques, such as, but not limited to, nails, welding, glue, etc. A filter  1208  is provided to limit the amount of debris that enters the air plenum. 
       FIG.  13    is a cross-sectional view of end cap  1200  taken along line  13 - 13  of  FIG.  12   . As illustrated, the bottom end of the cap body  1202  is open to provide an external air flow opening  1302 , which assists in limiting the amount of debris entering the air plenum. However, in order to further ensure that debris does not enter the air plenum, a particle screen  1304  is optionally provided within the opening  1302 . Within end cap  1200  is an air deflector  1306 . The area within the mounting flanges  1204  defines an air inlet opening  1308 , which is optionally filled with the filter  1208 . The air inlet opening  1308  is positioned adjacent to the plenum/fan interface  1020 . In one embodiment, the air inlet opening  1308  has a dimension of 100 mm×75 mm, though other dimensions may be appropriate depending on design specifications. 
     According to one embodiment of the present disclosure, a heating and/or cooling unit is positioned adjacent to plenum/fan interface  1020 . In such an embodiment, the controller module  908  works in conjunction with the thermistor harnesses  1026 ,  1028  to determine if the introduction of hot or cold air into the energy storage system is warranted. In yet other embodiments, the inlet cover  402  and the outlet cover  404  are in fluid connection, which allows the air to be re-circulated throughout the energy storage module  136  in cold weather conditions. In further embodiments, the plenum inlet cover  402  and plenum outlet cover  404  are connected to a snorkel-type device. The snorkel device provides a means to keep the energy storage module  136  free of water in the event it becomes submerged. The snorkel device may also be used to transport cool air to the plenum inlet cover  402  of the energy storage module  136 . 
       FIG.  14    generally depicts the cooling air flow through the energy storage module  136 . As previously discussed, the plenum inlet cover  402  and the plenum outlet cover  404  are provided on the same end  315  of the energy storage module  136 . When fan assembly  912  is powered on, external air is drawn into the energy storage module  136 , as indicated by arrow  1402 . The air is forced along the battery array  902 , around the BEC  918 , and back up along the battery array  904 . The exhaust air is generally indicated by arrow  1404 . The cooling air flow is guided along by the plenum cover  1110  in a U-shape pattern as indicated by arrow  1403 . As appreciated by those of skill in the art, the battery arrays  902 ,  904  generate a considerable amount of heat during operation. If the heat is not dissipated, the arrays may overheat and malfunction. Accordingly, the air flow provided by the present disclosure adequately dissipates that heat. 
       FIG.  15    is an exploded view of the fan assembly  912  according to one embodiment. As illustrated, the fan assembly  912  comprises a first fan housing  1502 , inlet air sensor  1022 , second fan housing  1504  and brushless fan  1506 . The first fan housing  1502  is positioned adjacent to the plenum/fan interface  1020  and mounted directly to the lower housing  302 . The inlet air sensor  1022  is constructed and arranged to monitor the inlet air flow coming into the cooling plenum. The information is communicated to the controller module  908 . 
     The first fan housing  1502  is constructed and arranged to receive the second fan housing  1504 . The fan  1506  is mounted to the second fan housing  1504  by a plurality of screws  1508 . The fan  1506  includes a communication connector  1510  which allows the controller module  908  to monitor and control the operation of the fan  1506 . In one embodiment, the fan  1506  is brushless and operates at 12V, although other types of fans and voltage levels may be used. 
       FIG.  16    provides a more detailed view of the BEC  918 . According to the illustrated embodiment, the BEC  918  is a single serviceable unit which can be replaced as a whole. The BEC  918  comprises a positive contact  1602 , a negative contact  1604 , and a pre-charge contactor  1606 . The contacts  1602 ,  1604 ,  1606  connect the battery arrays  902 ,  904  to the appropriate electrical connections within the high voltage junction box  308 . Accordingly, the contacts  1602 ,  1604 ,  1606  work in conjunction with the HVIL  606  to disconnect the high voltage from the rest of the vehicle. A pre-charge resistor  1608  is provided to slowly charge the inverter  132  when energy is delivered from the energy storage module  136  during vehicle start-up. A Y-cap  1610  is provided to reduce high frequency noise from the DC wires. A current sensor  1612  monitors the amount of high voltage current flowing in or out of the energy storage module  136 . That information is optionally provided to the controller module  908 . If the current exceeds a certain threshold, the high voltage interlock  606  is triggered and the high voltage power is disconnected from the electronics within the high voltage junction box  308 . In one embodiment, current sensor  1612  is a dual range sensor. 
       FIG.  17    is an exploded view of a battery array  1700 . The battery array  1700  comprises a plurality of battery cells  1702  separated from one another by a cell retainer  1704 . The battery cells  1702  are secondary batteries capable of being repeatedly charged and discharged, such as, but not limited to, nicad (Ni—Cd), nickel-hydride, and/or lithium-ion types. Battery cells manufactured by Samsung, Sanyo and GS Yuasa Corporation have been found to be acceptable depending upon design and size considerations. 
     At each end of the battery array  1700  is an end plate  1706 , which works in conjunction with two side rails  1708  to hold the battery cells  1702  and the cell retainers  1704  in place. Once the battery cells  1702 , cell retainers  1704 , end plates  1706 , and side rails  1708  are properly aligned, the structure is held together by a series of screws  1710 , though other known means may be used. In one embodiment, the battery array  1700  is made up of forty six individual battery cells  1702 . 
     A series of seals  1712  is sandwiched between vent manifold sections  1714 . The ends of the vent manifold sections  1714  are constructed and arranged to connect with the exhaust vent manifold  1124 . Above the vent manifold assemblies  1714  are positioned a voltage sense board  1716 , followed then by a safety cover  1720 . The voltage sense board  1716  includes a harness connection  1718  which is constructed and arranged to connect with the high voltage harness  906 . 
       FIG.  18    is a perspective view of an individual battery cell  1702 . The battery cell  1702  includes two terminals  1802  and a vent  1804 . The terminals  1802  provide a contact point upon which high voltage energy can be passed in order to be stored within the cell  1702 . The terminals  1802  also provide a contact point upon which high voltage energy can be extracted from the battery cell  1702  in order to provide power to the hybrid vehicle system. The vent  1804  provides a specific location in which exhaust gases may be expelled in the event the battery cell  1702  is abused, overheats, or malfunctions. 
       FIGS.  19  and  20    illustrate an end view of the battery array  1700  when installed within the energy storage module. Buss bars  1902  provide an electrical connection between the voltage sense board  1716  and the cell terminals  1802 . Additionally, it is noted that cell vent  1804  is positioned directly beneath the vent manifold section  1714 , which is in turn connected to the vent manifold  1124 . Such an arrangement ensures that any harmful or noxious gases expelled from the battery cell  1702  are properly exhausted from the energy storage module  136 . 
       FIG.  21    is a perspective view of the controller module  908 . Disposed along one edge of the controller module  908  is a plurality of high voltage connections  2102 . As discussed hereinabove, the high voltage connections  2102  are principally used to receive the high voltage harness  906  which is connected to the battery arrays  902 ,  904 . Through the high voltage harness  906 , the controller module  908  can individually monitor the state of charge of each individual battery cell  1702  within the battery arrays  902 ,  904 . The controller module  908  can also control the charge and discharge of the battery arrays  902 ,  904 . 
     Disposed along a different edge of the controller module  908  is a plurality of low voltage connections  2104 . The low voltage connections  2104  are connected to various components within the energy storage module  136 , such as, but not limited to, low voltage harness  910 , thermistor high harness  1026  and a thermistor low harness  1028 . The low voltage harness  910  is communicatively connected to the vehicle signal connector assembly  814 . Additional components within the energy storage module may also be communicatively connected to the controller module  908  via high voltage harness  906 , low voltage harness  910 , or through other harnesses or connections. 
     According to one aspect of the present disclosure, the energy storage modules  136  within the energy storage system  134  are adapted to communicate with one another. In order to provide the communicative connection, the energy storage module data link  204  is provided between each energy storage module  136 . In one embodiment and generally referring also to  FIG.  8   , one energy storage module  136  functions as the master energy storage module  802  while the others function as the slave energy storage modules  804 . The controller module  908  within the master energy storage module  802  then receives information from the slave energy storage modules  804  and communicates with the transmission/hybrid control module  148  and the rest of the hybrid system as a single energy storage system  134 . As discussed herein, the transmission/hybrid control module  148  receives power limits, capacity available current, voltage, temperature, state of charge, status, and fan speed information from the energy storage system  134  and the various energy storage modules  136  within. The transmission/hybrid control module  148  in turn sends commands for connecting the various energy storage modules  136  so as to supply voltage to and from the inverter  132 . 
     Because the controller modules  908  within the energy storage modules  136  are identical, it does not matter which energy storage module is in the “master” position. According to one embodiment of the present disclosure, the controller modules  908  are adapted to periodically verify that the master energy storage module  802  is still functional. If not, a slave energy storage module  804  then begins to function as the master energy storage module and communicates with the transmission/hybrid control module  148 , thereby providing system redundancy. According to the principles of the present disclosure, a separate controller box or structure is not necessary and energy storage modules  136  can be easily interchanged. Additionally, the principles of the present disclosure further provide an energy storage system  134  in which the entire system remains functional even in the event that the master module  802  becomes inoperable. In one embodiment, the energy storage modules  136  are instructed to be a master or slave module based upon a received address which is programmed by the jumpers within low-voltage signal connector  314 . 
     Though not illustrated, controller module  908  optionally includes a memory component. The memory component may be any known memory device, such as, but not limited to, non-volatile memory, a hard disk drive, magnetic storage device, optical storage device, RAM, or ROM, just to name a few examples. Non-volatile memory is adapted to record energy storage module usage and status history, such as achieved power levels and duty cycles, to name a few examples. The memory provides an effective serviceability tool in which energy storage module component performance can be quickly obtained and evaluated. The controller  908  may include additional components, such as a microprocessor capable of performing the various control, communication, and switching functions. 
     In order to stack multiple energy storage modules  136  on top of one another, various embodiments are contemplated.  FIG.  22    illustrates one such embodiment. While  FIG.  8    and the associated discussion primary dealt with the electrical connections between the master energy storage module  802  and the slave energy storage module  804 ,  FIG.  22    concerns the physical arrangement and connection of the two. As shown, the slave energy storage module  804  is stacked upon the master storage module  802 . A plurality of bolts  2202  are provided through mounting holes  1024  of both storage modules  802 ,  804 . The indentations  316  are located near holes  1024  and run along the height of the energy storage modules  136  to provide sufficient clearance for the torque wrench or other device used to tighten the bolts  2202  during the stacking of the storage modules  802 ,  804 . With four bolts  2202  in place, the stacked arrangement is strong enough to withstand considerable vibration and shock loads. As can be appreciated by those of skill in the art, more or less bolts  2202  and mounting holes  1024  may be provided. 
     According to one aspect of the present disclosure, the energy storage modules  136  are constructed such that they may be mounted in any arrangement, direction, or orientation. For example, the master energy storage module  802  may be stacked upon the secondary energy storage module  804 . In other embodiments, the energy storage modules are not stacked upon each other but are positioned in various locations within the HEV. 
       FIG.  23    depicts a frame mounting concept. An energy storage module  2302  comprises a lid  2304  having a receiving element  2306  and a raised element  2308 . The receiving element  2306  and the raised element  2308  allow for additional energy storage modules  2302  to be securely stacked upon one another. The energy storage module  2302  further comprises a housing  2310  constructed and arranged to sit upon and be mounted to the mounting plate  2312 . The mounting plate  2312  includes a plurality of feet  2314  which are fixed to vehicular frame  2316 . In one embodiment, the energy storage module  2302  is dimensioned to fit within the area typically reserved for a heavy duty truck fuel tank. 
       FIGS.  24  and  25    depict another embodiment of an energy storage module  2402 , similar to energy storage module  136 , but with an external fan housing  2416  and heat sink  2418 . The energy storage module  2402  includes an enclosure  2404  having an upper cover  2406  which is secured to lower housing  2407  by screws  2408  as shown, although other methods known in the art may be used to secure the upper cover  2406 . The upper cover  2406  is preferably sealed to lower housing  2407  to prevent outside contaminants from entering the enclosure  2404 . A high voltage junction box  2410 , similar to high voltage junction box  308 , is mounted to one end of the energy storage module  2402 , along with a low voltage connector  2412  and service disconnect  2414 . 
     The energy storage module  2402  employs internal conduction cooling and external convection cooling as will be described further below. The external fan housing  2416  is mounted to an opposite end  2413  of the enclosure  2404  with respect to the high voltage junction box  2410  as shown. Heat sink  2418  having fins  2419  is mounted to or formed integral to the bottom surface  2420  of the enclosure  2404 . An enclosing plate  2422  is mounted to enclosure  2404  as shown to further direct air across the heat sink  2418 . By using an external cooling fan and heat sink, the enclosure  2404  and high voltage junction box  2410  may be individually or collectively sealed from outside contaminants. The enclosure  2404  and high voltage junction box  2410  may be further adapted to be submersible, depending on the needs of the particular application. 
       FIG.  26    depicts an arrangement wherein two energy storage modules  2402  are stacked and electrically connected to provide increased operating voltage or current capacity as needed by the particular application. Again, bolts  2202  are included to secure the energy storage modules  2402  together. 
       FIG.  27    depicts a bottom perspective view of the heat sink  2418  arrangement. As shown, the heat sink  2418  includes a plurality of fins  2419  which are disposed angularly outward with respect to the longitudinal dimension of the energy storage module  2402 . When cooling is required, the fan  2706  directs air through a central cavity  2708  in the direction indicated by arrows  2702 . The air is then directed between the fins  2719  in an angularly outward direction on each side of the energy storage module  2402 . In order to provide a more uniform cooling in each battery cell, the height, length and/or relative spacing of the fins  2419  may be varied with the direction or speed of air flow. For example, the fins nearest the cooling fan  2706  may have a smaller height or length than those farther from the cooling fan  2706 .  FIG.  28    depicts a half-symmetry reverse perspective view of the heat sink  2418  which illustrates the varying height and length of the fins  2419 . 
       FIG.  29    depicts another partial diagrammatic half-symmetry perspective view of an energy storage module housing  2902  in which a battery thermal pad  2904  is disposed for mounting a battery array thereon. The thermal pad  2904  is constructed of a thermally conductive, yet electrically insulating, material such as Sil-Pad®, manufactured by The Bergquist Company. The thermal pad is preferably constructed as a single piece for each battery array to provide maximum thermal transfer. The thermal pad  2904  is preferably sized to be in the range of 70-120 in 2 , although smaller and larger sizes may also be used. When a battery array is mounted on the thermal pad  2904 , the thermal pad  2904  draws heat away from the battery array and into the heat sink  2418  by thermal conduction. As discussed above, the excess heat is then removed from the heat sink  2418  by convection due to the movement of air across the fins  2419 . 
       FIG.  30    provides a more detailed view of one end of the energy storage module  2402  including the high voltage junction box  3010 , similar to high voltage junction box  308 . As shown, the front perimeter  3022  of the high voltage junction box  3010  is sealed and protected by an access cover  3012 . The rear of the high voltage junction box  3010  is preferably open to a corresponding opening  3604  in the lower housing  2407  (see  FIG.  36   ). The rear perimeter  3020  of the high voltage junction box  3010  may also be sealed about the opening  3604  of lower housing  2407  to allow the high voltage junction box  3010  and enclosure  2404  to collectively seal out foreign contaminants and/or be made submersible. High voltage conductors  3014  and  3016  are connected within the high voltage junction box  3010  and also preferably sealed to prevent entry of foreign contaminants. Strain reliefs  3018  and  3024  may be included to further secure the high voltage conductors  3014 ,  3016 . 
       FIG.  31    depicts the high voltage junction box  3010  with the access cover  3012  removed. For precautionary purposes, a safety cover  3110  is provided to act as a further barrier to the high voltage terminals behind it, similar to safety cover  706  of  FIG.  7 B . In order to access the high voltage connections behind the safety cover  3110 , a high voltage interlock (HVIL) resistor  3114  must first be removed. 
       FIG.  32    depicts the high voltage junction box  3010  with the safety cover  3112  and HVIL resistor  3114  removed. In the illustrated embodiment, a plug-in bussed electrical center (BEC)  3210  is located within the high voltage junction box  3010 , and external to the enclosure  2404 . By locating the BEC  3210  outside the enclosure  2404 , the upper cover  2406  does not need to be removed when the energy storage module  2402  is being serviced. This decreases the safety risk to the technician and further prevents contaminants from unnecessarily reaching the components located within the enclosure  2404 . 
     As shown in  FIGS.  33 A and  33 B , the plug-in BEC  3210  offer a further advantage in that it requires less manual connections during assembly or service, further decreasing the safety risk to the technician. More specifically, the high voltage connections between the plug-in BEC  3210  and the live battery arrays are made using bus bar blade terminals  3316  and  3318 , which mate to corresponding receiving terminals in the high voltage junction box  3010  as the BEC  3210  is installed. Then, the terminals  3312  and  3314  which connect the plug-in BEC  3210  to the vehicle power systems may be connected. In other words, the operator does not have to manipulate flexible cables which might be connected to the live battery arrays when installing or removing the BEC  3210  for service. The plug-in BEC may also include a current sensor  3320 , current sensor connector  3321 , fuse block  3222 , high voltage sense connector  3324 , low voltage connector  3326 , and high voltage contactors  3328 . 
       FIG.  34    shows an exploded perspective view of the energy storage module  2402  with the upper cover  2406  removed. As shown, an energy storage controller module  3410 , similar to energy storage+controller module  908  of  FIG.  9   , is mounted within the enclosure  2404  in an alternate arrangement.  FIG.  35    shows a reverse perspective view of the energy storage module  2402  with the upper cover  2406  and fan housing  2416  also removed. As shown, the energy storage module  2402  includes two battery arrays  3510  and  3512 , which are similar in function to the battery arrays  902  and  904  of  FIG.  9   . 
       FIG.  36    shows an exploded view of the fan housing  2416 . Because the energy storage module  2402  is implemented as a sealed or submersible unit, battery gases escaping from the battery cells within battery arrays  3510  and  3512  will be trapped within the enclosure  2404 . The resulting increased pressure may damage the enclosure  2404  and associated seals. A pressure relief panel  3610  is therefore provided to allow the battery gases to escape if the pressure reaches a predetermined threshold. As shown in further detail in  FIG.  37   , the pressure relief panel  3610  includes a compliant seal  3710  which seals a vent opening  3616  in the enclosure  2404 . The pressure relief panel  3610  and seal  3710  are held against the vent opening by bracket  3614  in conjunction with springs  3612 . The bracket  3614  is secured to the enclosure  2404  with fasteners, such as screws  3617 . Springs  3612  are held between the bracket  3614  and pressure relief panel  3610  and hold the pressure relief panel  3610  in place. The springs  3612  may be laterally secured by protrusions  3712  in the pressure relief panel and corresponding protrusions  3615  in the bracket  3614 . The protrusions  3712  and  3615  extend into the interior of springs  3612  when the unit is assembled. The springs are selected to allow the pressure relief panel  3610  to temporarily move outward from the lower housing  2407  at the selected threshold pressure, compressing the springs and relieving the pressure inside the enclosure  2404 . Once the pressure is relieved, the springs force the pressure relief panel  3610  back against the lower housing  2407 , resealing the enclosure  2404 . 
       FIG.  38    shows an exploded view of one of the battery arrays  3510 ,  3512 . As shown, the battery array  3510  includes a plurality of battery cells  3810  separated from one another by cell retainers  3812 , in a similar fashion to the battery cells  1702  of  FIG.  17   . The cell retainers  3812  may be formed from an insulative material, such as plastic or other suitable dielectric, and are of sufficient thickness to limit heat transfer between individual battery cells  3810  to an acceptable level. In the case where a cell  3810  develops an internal short and heats up before venting, the insulative property of the cell retainer  3812  will reduce the amount of heat that propagates to adjacent cells  3810 . This allows the heat in the shorted cell to escape through other cooling paths, preventing nearby cells from heating up and venting themselves. Again, the battery cells  3810  are secondary batteries capable of being repeatedly charged and discharged, such as, but not limited to, nicad (Ni—Cd), nickel-hydride, and/or lithium-ion types. Battery cells manufactured by Samsung, Sanyo and GS Yuasa Corporation have been found to be acceptable depending upon design and size considerations. 
     At each end of the battery array  3510  is an end plate  3814 , which works in conjunction with two side rails  3816  to hold the battery cells  3810  and the cell retainers  3812  in place. An insulation liner  3815  may also be included which improves creepage and clearance of the battery cells  3810  when assembled. Compression limiters  3826  may also be provided to provide additional strength when the side rails  3816  are implemented as trusses, as shown in  FIG.  38   . Once the battery cells  3810 , cell retainers  3812 , end plates  3814 , and side rails  3816  are properly aligned, the structure is held together by pins  3818  and nuts  3819 . The pins  3818  are inserted through holes  3820 ,  3822  in the side rails  3816  and insulation liners  3815 , respectively. The end plates  3814  include flanges  3823  which secure the end plates  3814  behind the pins  3820 . The pin arrangement provides more secure holding and helps prevent torque loosening during operation. In one embodiment, the battery array  1700  is made up of forty six individual battery cells  1702 . 
     Voltage sense board assembly  3830  is installed above the battery cells, followed by safety covers  3032 . The safety covers  3032  are constructed from plastic or other appropriate electrically insulating material. The voltage sense board assembly  3830  includes a harness connection  3834  which is constructed and arranged to connect to the controller module  3410  and/or plug-in BEC  3210 .  FIG.  39    shows a perspective view of the assembled battery array  3510 . 
       FIG.  40    illustrates an end view of a battery cell  3810  mounted within the battery array  3510 . Bus bars  4010  provide an electrical connection between the voltage sense board assembly  3830  and the cell terminals  4012 , connecting the positive terminal of one battery cell to a negative terminal of an adjacent battery cell. This results in a series electrical connection between the battery cells  3810 , collectively providing the desired total array voltage. Thermistor  4020  may be included to monitor the temperature of the battery cell  3810  and communicate the temperature reading to controller module  3410 . 
     In certain embodiments, the voltage sense board assembly  3830  is initially provided with certain bus bars  4010  missing as shown by arrows  4114  in  FIG.  41   . Due to the missing bus bars, the voltage sense board  3830  is electrically divided into voltage sections  4112  until near the end of the assembly process. The covers  3032  include the missing or final bus bars (indicated as  4116  in  FIG.  38   ) which complete the missing connections as each individual cover  3032  is installed in sequence. The covers  3032  include an insulated overlap portion  4118  which covers the final bus bar  4116  of the adjacent cover  3032 . The result is that the technician is only exposed to a limited safe voltage level (e.g., less than 50 volts) from the exposed battery cell terminals until the final connections are made. 
       FIG.  42    depicts a frame mounting concept according to another embodiment of the disclosure. As shown, the enclosure  2404  of energy storage module  2402  is mounted to vehicular frame  4208  using isolator mounts  4210 . The isolator mounts are constructed of a compliant material, such as rubber or silicone, and reduce the vibration transferred from vehicular frame  4208  to the energy storage module  2402 . One example of a suitable isolator mount is the Barry Controls 200 series Cup Mount Isolator. An adapter bracket  4310  may be provided as shown in  FIG.  43    to evenly distribute the weight of the energy storage module  2402  across the support surface  4312  of the isolator mount  4210  and allow connection to the energy storage module  2402  using a single fastener  4314 . 
       FIGS.  44  and  45    illustrate a detailed view of a mounting arrangement for the thermistor  4020  according to one embodiment. The thermistor  4020  needs to maintain mechanical contact with the battery cell  3810  to provide accurate monitoring. However, the battery cells  3810  may vary in height due to manufacturing variations, resulting in a corresponding variation in the distance between the voltage sense board  3830  (in which the thermistor is mounted) and the top surface  4410  of the battery cell  3810 . To account for this variation in distance, the thermistor  4020  may be installed within a flexible clip  4412  as shown. The flexible clip  4412  includes lateral portions  4414  which may flex vertically to hold the thermistor tip  4416  against the top surface  4410  of battery cell  3810 . The clip  4412  further includes vertical portions  4418  which are secured in holes  4420  by tabs  4422 . The thermistor  4020  may be secured to the clip  4412  using a potting material  4424  as shown. Other types of materials may also be used to fix the thermistor within the clip  4412 , such as adhesives, cement, or the like. To provide further adjustability and tolerance, the thermistor tip  4416  may be encased in a compliant material  4426  which provides mechanical flexibility and thermal transfer, such as a thermoplastic elastomer (TPE). The compliant material  4426  and the clip  4412  work in combination to retain the tip of thermistor  4020  against the top surface  4410  of the battery cell  3810 . 
     As can be appreciated by those of skill in the art, a single energy storage module  136  may be used or a plurality of energy storage modules  136  can be connected to one another in a series, parallel, or series/parallel fashion. In one embodiment, multiple energy storage modules  136  may be connected in parallel to provide a 300V system, while two or more pairs of energy storage modules may be connected in series or series/parallel to provide a 600V system. Because the energy storage modules  136  can easily be incorporated into a 300V or 600V HEV application, the electronics are designed to meet the specifications of the higher voltage systems, such as creepage and clearance issues. Accordingly, arcing is of no concern when the energy storage module is used in a 600V setting.  FIG.  46 A  shows an embodiment where a single energy storage module  136  is used.  FIG.  46 B  shows an embodiment where two energy storage modules  136  are connected in parallel.  FIG.  46 C  shows an embodiment where two energy storage modules are connected in series.  FIG.  46 D  shows an embodiment where two pairs of energy storage modules  136  are connected in a series/parallel arrangement. It shall be understood that energy storage module  2402  may also be connected in various series, parallel, or series/parallel arrangements as discussed with respect to energy storage modules  136 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes, equivalents, and modifications that come within the spirit of the inventions defined by following claims are desired to be protected. All publications, patents, and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference and set forth in its entirety herein.