Abstract:
An end-to-end cell connection system for a battery assembly uses a conductive interconnector with an inner portion welded to an end of one cell, a standoff portion contiguous with the ring portion, tabs extending from the standoff portion, with the tabs welded to an end of another cell. By placing an insulator between the interconnector and the one cell, an electrical short is prevented in the event that a longitudinally coupled cell group is jostled. At the cell connections, there is a recess. To hold the cell group in place, the housing has a tab extending into the recess. The tab is at the center so that any dimensional variations are accommodated on each side of the tab. The interconnector also may include a receptacle for a thermistor to obtain a measure of battery assembly temperature. Diverter ribs may be provided in the housing to distribute flow to all cells.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a power supply system or battery system, which can be used in a hybrid electric vehicle. 
     2. Background Art 
     A battery for a hybrid electric vehicle may include many cells electrically connected. To attain a battery of a sufficiently high voltage, cells are electrically connected serially. Groups of several cells can be coupled longitudinally and then placed in a housing with groups arranged in parallel compartments. And, although cell groups are physically arranged in a parallel fashion, they may be electrically coupled either in series or in parallel. Groups of individual cells within a housing can be called a brick. A plurality of bricks are arranged in an array and electrically connected via bus bars to provide the desired voltage and current characteristics for the particular application. Such connected plurality of bricks forms a battery. 
     To avoid shorts among cells within a group due to longitudinal bending within a cell group, it is known to place insulating sleeves over the connection points. Such sleeves increase the diameter of the battery group and thus the compartments within the housing. As the battery includes many cells arranged in an array, any increase in diameter is multiplied and causes the housing to be larger than it might otherwise be. 
     To ensure a robust connection, the longitudinally-arranged cell groups may be welded together. When cells are combined longitudinally to form a group, any manufacturing variation in length of the cells and any variation in the length of the cell group in forming the joint between cells will result in an overall increase in cell group stackup variation. Bus bars, which are used to electrically connect cell groups, may be forced to bend to accommodate differences in length between connecting cells groups. By forcing the bus bar to bend, the connection may be compromised and harm the integrity of the battery. It is desirable to minimize the amount of stackup tolerance that the bus bar bending accommodates. 
     During charging and discharging of the battery, energy is generated within the cells. The battery is cooled to maintain the temperature within individual cells below a temperature at which cells are damaged. Typically, temperature sensors are provided at various locations within the battery from which temperature within the cells is estimated. It is important to locate the temperature sensors at locations that provide a good indication of the maximum temperatures experienced within battery cells. Also, it is desirable for the temperature sensors to be located in a position that is readily accessible after much of the assembly of the battery is completed because wires from the temperature sensor may be damaged during assembly. 
     SUMMARY 
     To address at least one problem, an end-to-end cell connection system is enclosed which has a conductive interconnector with: an inner ring portion welded to an end of a first cell; a standoff portion contiguous with the inner ring portion; and two tabs extending from the standoff portion. The two tabs are welded to an end of a second cell. A washer-shaped insulator located between the conductive interconnector and the first cell. The insulator has an inside diameter large enough to slide over an exterior surface of the standoff portion. The insulator is fitted over the standoff portion prior to welding the first cell to the conductive interconnector. In some embodiments, the tabs comprise two portions: a first portion which extends outward from the standoff portion in a radial direction and a second portion which extends from the first portion in a direction toward the second cell. The first portion of the tabs is welded to an end cap of the second cell in one alternative. In another embodiment, the second portion of the tabs is welded to a cylindrical casing of the second cell. In yet another alternative, both portions of the tabs are welded to the cell. 
     By providing an interconnector, the diameter of a cell group, is less than using an insulator sleeve. The insulator can be a snap ring insulator which provides advantages in assembly or a conveniently-shaped disk. By decreasing the overall diameter, size of the battery assembly can be reduced. 
     In some embodiments, a barrel-style female receptacle is coupled to one of the tabs. The receptacle is configured to accept a temperature sensor such as a thermistor. The temperature sensor is placed proximate the conductive interconnector thereby indicating the temperature of the conductive interconnector. In some embodiments, the thermistor has a clip lock to maintain the thermistor position. 
     To ensure proper cooling, the battery is aided by a temperature estimate from a temperature sensor. According to an embodiment of the present disclosure, the temperature proximate the interconnector provides a good indicator of the internal temperature of the cells. Thus, one advantage of such embodiment is improved cooling. By providing the receptacle for a thermistor, or other temperature sensor, contiguous with the interconnector, no additional hardware is required. Yet another advantage is that the receptacle may be accessed from outside the brick, i.e., after the brick is assembled and after multiple bricks are connected together to form a battery system. This reduces the potential for breakage of electrical leads from the temperature sensor. 
     In an alternative to the washer-shaped insulator, the first cell has a cylindrical case and a terminal end crimped onto the cylindrical case to form a crimp joint. A snap insulator ring snaps onto the crimp joint and substantially covers the crimp joint. Additionally, a crimp joint insulator is disposed within the crimp joint to electrically insulate the cylindrical case from the terminal end. The snap insulator ring has the shape of a surface of revolution generated by revolving a substantially C-shaped figure in three-dimensional space about an axis coplanar with the C-shaped figure. 
     The diameter of the snap insulator ring is approximately equal to the diameter of the crimp joint so that the snap insulator ring can be snapped onto the crimp joint without inadvertently slipping off. In one embodiment, the entirety of the snap insulator ring is disposed on a side of the tabs proximate the first cell. 
     A first assembly of cells mechanically coupled longitudinally and having a circumferential recess at the coupling forms a first group. A housing is provided that has a first tubular compartment configured to receive the first assembly. The housing with the cells installed into the housing is called a brick. The first compartment has a tab extending inwardly to index with the recess. In one embodiment, the cells of the first assembly are mechanically coupled by welding. In one embodiment, there are four cells in the first assembly, three couplings between the four cells thereby defining three recesses, and the tab indexes with the middle of the three recesses. The brick may also have a second assembly of cells mechanically coupled longitudinally and have a circumferential recess at the coupling. The housing further includes a second tubular compartment configured to receive the second assembly. The second compartment has a tab extending inwardly to index with the recess in the second assembly. 
     Another embodiment of a brick includes a first assembly of cells coupled longitudinally and a second assembly of cells coupled longitudinally. The cell assemblies define a circumferential recess at each coupling. A housing has first and second tubular compartments to hold the first and second cell assemblies. The compartments have a tab extending inwardly from an interior surface, the tab configured to index with one such recess in a cell assembly. In one embodiment, the tab is located approximately equidistant from ends of the housing. In one alternative, the housing includes first and second shells configured to snap together to allow installation of the cells in the compartments. 
     The width of the tab is less than the width of the recess to allow the tab to index in to the recess. The housing may be a clam-shell having first and second sections which are configured to receive the first and second assemblies of cells and snap together to retain the assemblies. The first and second sections are prevented from snapping together when the tab is indexed with a cylindrical case of the cell. 
     A battery assembly includes: a plurality of cell groups, each group comprising a plurality of cells coupled longitudinally, a plurality of cell housings each having at least one cell group within with the cell housings arranged in an array. A pair of indexing tabs extends from an outside surface of each cell housing so that a groove in a cover placed over the array mates with the indexing tabs. The indexing tabs are configured to receive the groove and the groove is V shaped in one embodiment, and rectangular in another embodiment. 
     The battery assembly also has a first end plate coupled to a first end of the array, the first end being a side of the array adjacent to the cover, and a second end plate coupled to a second end of the array, the second end being opposite to the first end. The first and second end plates define multiple clamping holes and the battery assembly also includes a nut coupled to the cover configured to align with the clamping hole when the array, cover, and end plates are in position to be assembled and a bolt passing through the clamping hole and engaged with the nut. The cover, in some embodiments, further includes a tab extending substantially perpendicularly toward an exterior surface of the cover. The tab defines an alignment hole, and the bolt further passes through the alignment hole. In some alternatives, the tab is proximate the groove and extends from a bottom of the groove to, at most, the top of the cover. 
     A method to assemble a battery, includes arranging bricks containing cells in an array, the bricks having indexing tabs extending outwardly with the indexing tabs forming a channel when arranged in the array and placing a cover over a first side of the array such that a groove formed in the cover engages into the channel of the indexing tabs. In some embodiments, the cover has a tab extending upwardly roughly perpendicularly from the cover with an alignment hole in the tab. The method further includes placing a first end plate with at least one clamping hold adjacent to a second side of the array with the alignment hole, placing a bolt through the alignment hole and the clamping hole, and tightening a nut onto threads of the bolt. 
     A housing for cells of a battery assembly, in some embodiments, include: a first tubular compartment having a first axis, a second tubular compartment having a second axis generally parallel with the first axis, a duct disposed between the compartments, and a plurality of diverter ribs disposed in the duct. The diverter ribs configured to direct flow into the compartments. Flow along the duct is generally parallel to the first and second axes. In one alternative, the first tubular compartment receives a first cell assembly, the second tubular compartment receives a second cell assembly, with each of the assemblies made up by a plurality of cells mechanically coupled longitudinally. A first half of the diverter ribs direct flow toward the plurality of cells associated with the first cell assembly and a second half of the diverter ribs direct flow toward the plurality of cells associated with the second cell assembly. The number of diverter ribs directing flow toward the plurality of cells associated with the first cell assembly equals the number of cells in the first cell assembly. The duct has an inlet and the diverter rib closest to the inlet is shorter than diverter ribs farther from the inlet. The diverter ribs provide an approximately equal flow quantity directed toward each cell in the first and second cell assemblies. The duct has an inlet and incoming flow to the duct is roughly parallel with the first and second axes and a direction of flow into the compartments is turned approximately ninety degrees with respect to a direction of the incoming flow. 
     A brick, which is part of a battery assembly, includes a first group of cylindrical cells coupled longitudinally, a second group of cylindrical cells coupled longitudinally and a housing having: a first tubular compartment into which the first group of cells are placed, a second tubular compartment into which the second group of cells are placed, a duct disposed between the compartments, and diverter ribs disposed in the duct, the diverter ribs configured to direct flow into the compartments. The duct runs approximately parallel with the first and second groups of cells, the duct has an inlet, and incoming flow to the duct is diverted through a turn of about ninety degrees toward the compartments. The first group has four cells, the second group has four cells, and the duct has six diverter ribs with three ribs directing flow into the first tubular compartment and three ribs directing flow into the second tubular compartment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a battery partially assembled. 
         FIG. 2  is an isometric view of a brick, a portion of a battery; 
         FIG. 3  is an exploded view of a brick showing individual cells; 
         FIG. 4  is a detail of a partially formed connection between two cells; 
         FIG. 5  is an isometric view of a cell interconnector and insulator; 
         FIG. 6  is a detail of a partially formed connection between two cells; 
         FIG. 7  is an isometric view of a portion of a snap insulator ring; 
         FIG. 8A  is an isometric view of an interconnector having a barrel receptacle; 
         FIG. 8B  shows a section of the interconnector prior to forming the barrel receptacle; 
         FIG. 9A  is an end view of multiple battery bricks showing a barrel receptacle for a thermistor with a thermistor installed; 
         FIG. 9B  is an isometric view of two bricks showing a holder for the thermistor; 
         FIG. 9C  is a detail of the holder of  FIG. 9B ; 
         FIG. 9D  is a detail of a connector for the thermistor; 
         FIG. 10  is an isometric view of a battery, partially exploded, showing a cover, according to an embodiment of the disclosure; 
         FIG. 11  is an alternative tab structure, according to an embodiment of the disclosure; 
         FIG. 12A  is a portion of a battery cover prior to being bent into shape; 
         FIG. 12B  is an isometric view of a portion of the battery cover; and 
         FIG. 12C  is a cross section of the cover and the end plate of the battery assembly. 
     
    
    
     DETAILED DESCRIPTION 
     As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated and described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. Those of ordinary skill in the art may recognize similar applications or implementations consistent with the present disclosure, e.g., ones in which components are arranged in a slightly different order than shown in the embodiments in the Figures. Those of ordinary skill in the art will recognize that the teachings of the present disclosure may be applied to other applications or implementations. 
     A battery  10 , in  FIG. 1 , has multiple bricks  12  formed into an array. In  FIG. 1 , an end plate  14  is shown on one end of battery  10 . When fully assembled, an end plate is included on the other end of battery  10 . Furthermore, there is a cover, not shown in this view, which engages with channels formed between tabs  16 . The engagement between the cover and tabs  16  will be discussed in more detail in regards to  FIGS. 10-12 . A single brick  12  of battery  10  is shown in  FIG. 2 . Brick  12  includes multiple cells enclosed in a housing  22 . Housing  22  also provides access for coolant for the cells via notches  21  and slots  23 , with notches  21  providing an entry point and slots  23  providing an exit path, in one embodiment. 
     An exploded view of one embodiment of brick  12 , in  FIG. 3 , has eight cells  20  held within a housing ( 22  in  FIG. 2 ), as assembled. Housing  22  includes two portions  22   a  and  22   b , which snap together. In  FIG. 3 , four cells  20  are shown as a cell group  28  and four cells  20  are shown exploded. Each cell  20  has a positive terminal  24  and a negative terminal  26 . Cell pairs are coupled longitudinally by interconnector  30 , which is welded to the negative terminal  26  of one cell  20  and welded to the positive terminal  24  of an adjacent cell  20 . To protect against a negatively-charged portion of one cell  20  from contacting against a positively-charged portion on an adjacent cell  20 , an insulator  32  is included in the assembly. 
     Between pairs of assembled cells  20  is a recess  34 . A tab  36 , which extends inwardly from housing portion  22   b , indexes with recess  34  when housing  22  halves are assembled. Housing portion  22   a  also has an inwardly extending tab; however, due to the angle at which housing portion  22   a  is illustrated in  FIG. 3 , the tab is not visible. Tab  36  is located between the two center cells of a four-cell group. In alternate embodiments, the groups include fewer or greater numbers of cells. In the case of an even number of cells, tab  36  is located between the two center cells. In the case of an odd number of cells, tab  36  is located on one side or the other of the middle cell. 
     There is stackup tolerance in assembling cell group  28 . There can be subtle differences in the lengths of individual cells, the interconnector dimensions, the details of the welds, etc. Although these may be small differences in each individual dimension, the difference in total length between cell groups can be substantial. Tab  36  slides into recess  34  when housing portions  22   a  and  22   b  are snapped shut to prevent cell group  28  from sliding longitudinally within housing  22 . By indexing at the midpoint of cell group  28 , only stackup tolerance from two cells  20  of cell group  28  is accommodated at one end. In this way, the total dimensional variation is accommodated between the two ends rather than falling to one side or the other. 
     Also shown in  FIG. 3  are diverter ribs  33   a ,  33   b , and  33   c . At an end of housing portion  22   b  proximate rib  33   a , there is a notched opening  21   a  through which air, or other coolant, can be provided. To promote distribution of the air to all of the cells, the first rib  33   a  collects air from the top portion of notched opening  21   a  and directs it upward toward the cell proximate rib  33   a . In  FIG. 3 , there is no cell shown proximate rib  33   a  because  FIG. 3  is an exploded view. However, one of cells  20  is proximate rib  33   a  as assembled. Housing portion  22   b  has no openings along the wall proximate  33   a . Thus air directed upward by rib  33   a  wraps around cell  20  until being expelled from an opening  23  in housing portion  22   a  (i.e., the portion that mates with portion  22   b ). Rib  33   a  extends from the back wall of housing portion  22   b  and is situated just below the top of notch opening  21   a . Thus, only a fraction of the flow into notch  21   a  is directed toward the cell proximate notch  21   a . The rest of the flow that is directed along an underside of rib  33   a  toward rib  33   b . Rib  33   b  extends from the back wall but is situated lower than rib  33   a , so that rib  33   b  grabs a portion of the air directed along housing  22  and directs it toward an adjacent cell. Similarly, rib  33   c , situated even lower, grabs some air. The remaining air is directed toward the cell distally located from notch  21 . Because housing portion  22   b  houses cells  20 , the distance at which ribs  33   a ,  33   b , and  33   c  extend from the back wall is limited. Because rib  33   a  is closer to the widest part of the cell, it is a narrow rib. Rib  33   b  can be made a little wider because it is located lower within housing portion  22   b . Also, as the ribs angle upward, their width decreases as a function of the amount of upward travel. A notch  21   b  is provided in housing portion  22   a  which allows flow into the lower compartment. 
     Ribs  33   a ,  33   b , and  33   c  are located in the upper half of housing portion  22   b , but are not shown in the lower half of housing portion  22   b . Diverter ribs that direct air toward cells installed into the lower compartment of housing  22  are contained in housing portion  22   a  (not visible in  FIG. 3 ). Flow enters through notch opening  21   b  and is directed by diverter ribs, which are analogous to diverter ribs  33   a ,  33   b , and  33   c , into cells  20  which are housed in the lower compartment of housing  22 . 
     A detail of the connection system, according to one embodiment, is shown in  FIG. 4 . A portion of a cell group  40  highlighting the connection system between two cells  20   a  and  20   b , but prior to completely coupling cells  20   a  and  20   b  via interconnector  30 , is shown in  FIG. 4 . The end of cell  20   a  has a crimp joint  42  between positive terminal end  24  and the negatively-charged cylinder case of cell  20   a . To avoid a short between the positively-charged end plate and the negatively-charged case, an insulator  44  separates the two within crimp joint  42 . Interconnector  30  is shown welded to cell  20   a  on the plate having positive terminal  24 . Insulator  32 , shaped like a washer, is placed over interconnector  30  prior to welding on positive terminal  24  at weld joint(s)  46 . To complete the assembly, interconnector  30  is welded to cell  20   b  at surfaces  48  and/or surfaces  50 . 
     A recess  34  between cells is shown in  FIG. 4 . In one embodiment, tab  36  (shown in  FIG. 3 ) indexes with recess  34 . In an alternative embodiment, tab  36  indexes with recess  35  which is associated with crimp joint  42 . As shown in  FIG. 4 , crimp joint  42  is of a slightly smaller diameter than the body of cell  20   a . In an alternative embodiment, crimp joint  42  has substantially the same diameter of the body of cell  20   a.    
       FIG. 5  shows interconnector  30  having an inner ring  52 , stand-off portion  54 , and tabs  56  extending out radially from stand-off portion  54  for a first length and then extend outwardly axially. Four tabs  56  are shown in  FIG. 5 , but, the number of tabs can be fewer or greater. 
     In  FIG. 6 , an alternative embodiment shows a portion of a cell group  62  with a snap insulator ring  64  snapped over crimp joint  42 . Snap insulator ring  64  prevents a short between interconnector  30  and the negative portion of crimp joint  42 .  FIG. 6  shows the portion of the cell group  62  in partial assembly, i.e., with interconnector  30  welded to one cell, but prior to being welded to the adjacent cell. The snap insulator ring  64  is shown in an isometric view in  FIG. 7 . 
     Insulator  30  of  FIGS. 3 and 4  has an inexpensive insulator shape. However, assembly is a bit complicated by having more individual parts that must be assembled at once. Snap insulator ring  64  of  FIG. 6  is a more expensive embodiment. However, snap insulator ring  64  can be assembled onto cell  20  prior to welding. Furthermore, snap insulator ring  64  remains in a fixed position on cell  20  after it is snapped into place, thereby facilitating the assembly process. The choice of insulator is application dependent. Both insulator embodiments provide an advantage over insulators that are placed over the case of the cell in that the latter result in a larger diameter cell group. Because battery  10  is made up of many cell groups, even a small increase in outer diameter of a cell group results in battery  10  being significantly larger than necessary. 
     In  FIG. 8A , an interconnector  70  has a barrel receptacle  72  for insertion of a thermistor. Barrel receptacle  72  can be formed out of the parent material of interconnector  70  and crimped into the barrel shape. In one embodiment, interconnector  70  is formed from a flat piece of material, a portion of which is shown in  FIG. 8B . A portion of a round portion of interconnector  70  is shown with tab  80 . To form interconnector  70 , tab  80  is bent backwards at bend location  75 . Barrel receptacle  72  is formed by bending the material forward at bends  73 . 
     In  FIG. 9A , portions of bricks  73  showing the interconnectors  70  have barrel receptacles  72 . A thermistor  74  can be installed into barrel receptacle  72 . Thermistor  74  is coupled to leads  78  which are coupled to a device for determining the temperature corresponding to a reading from thermistor  74 . Thermistor  74  can have a connector  76  with a clip lock to hold thermistor  74  in place in interconnector  70 . 
     In  FIG. 9B , an exterior view of two brick housings  81  are shown with a front cover  82 . Molded into housings  81  are holders  83 . Holders  83  mate with barrel receptacles  72  (only the upper tips of barrel receptacles  72  are visible in  FIG. 9B .) A detail of holders  83  are shown in  FIG. 9C . Holder  84  is coupled to housing  81  with a rib  84  extending out of housing  81  as a support member. The holder  83  has undercuts  85 , which engage with legs  86  of connector  76  coupled to thermistor  78 , as shown in  FIG. 9D . 
     Thermistor  74  provides an estimate of cell  20  temperature. The highest temperatures occur within cells  20  and in current-carrying tabs  80 . It would be desirable, but not possible, to measure the internal cell temperature. As temperature of tabs  80  mimics the temperature inside cells  20 , tab temperature, as measured by thermistor  74 , is a good indication of internal cell temperature. The location of barrel receptacle  72  is arranged so that thermistor  74  can be inserted after brick  73  is assembled. 
     In  FIG. 1  and  FIG. 2 , battery  10  has tabs  16  with channels formed between the tabs  16 . In  FIG. 10 , a partially-exploded view of battery  88  shows a cover  90  and end plates  92 . Cover  90  has V-shaped grooves  94  which engage with V-shaped channels formed between tabs  96 . The V shape is merely one example. The channels in the cover can be square at the bottom, as shown in  FIG. 11 , to mate with tabs  97  having vertical sides. Other suitable alternatives include any other shape that can be used to hold the cover into the channels. 
       FIG. 12A  shows a portion of cover  102  for the battery. In  FIG. 12A , cover  102  is shown prior to being folded, i.e., as a flat piece. Cover  102  is to be folded along bend lines  103  to form a groove with the middle of the bend lines forming the tip of the vee. Tabs  104  are bent forward along bend lines  101 . A portion of the resulting cover is shown in  FIG. 12B . A square nut is places into the groove formed at bends  103 . Tabs  104 , due to bends  103 , overlap each other. A threaded fastener  112  can engage with nut  110 . A cross-section of a portion of cover  102  is shown in  FIG. 12C . End plate  100  of the battery is coupled to cover  102  when threaded fastener  112  is coupled with nut  110 . 
     In one embodiment, nut  110  is held in place by crimping at least one of tabs  104  around nut  110 . 
     While the best mode has been described in detail, those familiar with the art will recognize various alternative designs and embodiments within the scope of the following claims. Where one or more embodiments have been described as providing advantages or being preferred over other embodiments and/or over prior art in regard to one or more desired characteristics, one of ordinary skill in the art will recognize that compromises may be made among various features to achieve desired system attributes, which may depend on the specific application or implementation. These attributes include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments described as being less desirable relative to other embodiments with respect to one or more characteristics are not outside the scope of the disclosure as claimed.