Patent Publication Number: US-2015079427-A1

Title: Case system, battery and battery rack with improved stacking

Description:
The present invention relates to a case system for lead batteries, a lead battery and a lead battery rack layout according to the preambles of the independent claims. 
     Lead batteries are a common type of battery, where the electrodes are composed of lead and/or lead dioxide and the electrolyte is formed by sulfuric acid. A lead battery essentially is made up of an acid resistant case and at least two sheets of lead of which one functions as a positive, whereas the other functions as a negative electrode. 
     The sheets are submersed into a sulfuric acid solution. 
     This most generic type of lead battery is equipped with a gas opening at the top to prevent gas pressure build up. Gas pressure increases, when hydrogen and oxygen are produced through electrolysis. 
     Understandably such batteries can only be stored and operated in an orientation that ensures that the gas opening is on the top of the case, such as to ensure venting and prevent spilling of the acid. They require refilling with H 2 O on a regular basis. 
     One particular type of lead batteries, so called VRLA type batteries (Valve Regulated Lead Acid Battery) are sealed with a pressure regulating valve and do not require a refilling of water to keep the battery functioning. 
     Furthermore, such batteries can be designed with absorbent glass mats to have the acid in an absorbed state on glass fibers. These types of lead batteries have significant advantages as they can be operated in any orientation and have a reduced maintenance requirement, i.e. no refilling of H 2 O is necessary. 
     One commonly used design is the so-called 19 inch or 23 inch rack system with the battery terminals accessible from the front. Four individual 12V batteries are arranged such as to fit a 19-inch or 23-inch wide and 400 or 600 mm deep drawer of an electrical cabinet or rack. These elements are configured such as to present the terminal accesses at the frontside. Cases adapted for racks in the 19 inch/23 inch front access layout have an essentially box shaped case element with 6 compartments in a 2×3 configuration (i.e. two rows of three compartments) for the electric cells and a cover for the terminals. The electrical cells are placed into the compartments, such as to extend top down inwardly into the compartments and presenting their individual terminals on the topside. 
     This configuration has been found to carry a number of disadvantages. For one part, the top down arrangement of the cell leads, due to the large vertical height of the cells, to stratification of the sulfuric acid, which in turn leads to a decrease in capacity and service life of the battery. Furthermore, as both terminals of the electrical cells are on the same side of the cell plate, the ohmic losses in the plate cause that the effective and reactive surface is restricted to the upper third of the electrical cell. One further disadvantage in respect to said set up is a consequence of the 2×3 arrangement of the compartments. It requires comparatively thicker outside sidewalls of the individual cells so to keep up the compression of the absorbent glass mat between the plates, especially when operating the battery at high temperatures. 
     A further disadvantage is that the cabling and connection of the individual batteries in a rack is complicated and prone to short circuits. 
     It was thus an object of the present invention to provide a solution to the problems of the state of the art. it was a particular object of the present invention to provide a case system, a battery and a battery rack layout that is easy and cheap to produce and has an improved service life and capacity as well as easier to install compared to the state of the art. 
     The problem is solved with a case system for lead batteries, a lead battery and a battery rack layout according to the characterizing portions of the independent claims. 
     One aspect of the present invention relates to a case system for lead batteries. The case system comprises a one piece, essentially box shaped cell housing part with at least four sidewalls. In the context of the present invention, a one-piece cell housing part shall mean that said cell-housing part has been manufactured in as a monolithic way. An exemplary suitable manufacturing process to produce such a one-piece cell housing part would be injection molding. The cell housing part is thus integrally formed. In the context of the present invention, essentially box shaped means that the said cell housing part has a roughly rectangular shape with a height, a length and a depth such as to encompass a volume. The essentially box shaped cell housing has at least four sidewalls. The four sidewalls enclose an interior volume. At least two of the four sidewalls are arranged in parallel to each other. Said interior volume is further divided. The cell housing part comprises at least one division plane for dividing said interior volume, such that a plurality of compartments is formed. Each of said compartments is adapted for storing an electrical cell or element. The case system according to the present invention further comprises an access wall part with electrical conductor (terminals) feed throughs. The access wall part further comprises at least one fluid channel opening. Preferably it comprises a gas opening. The cases according to the present invention further comprise a closure wall part for sealing off the casing system. 
     In a preferred embodiment the case system is configured such that the access wall part and the closure wall part are two opposing walls of an essentially box shaped case system, whose main body is formed by an essentially box shaped cell housing part. 
     In a preferred embodiment, the four sidewalls are outer walls of cell housing part. 
     The closure wall part is used to seal off the front facing away from the access wall part. The box shaped cell housing further comprises division planes on the inside forming compartments. 
     Each of the at least one division planes is essentially perpendicular to the same two opposite sidewalls of the essentially box shaped cell housing. 
     The case system according to the present invention provides a series of advantages. The compartments are constructed to hold the electrical cells with the plates in an orientation that is parallel to the surface the case system is placed on. 
     By having the plates in a horizontal orientation, the path for vertical migration and stratification of the sulfuric acid in the space between the lead sheets of the electrical cell or element is reduced from about 200 mm as in the state of the art for a standard 19″ battery or from 250 mm in a 23″ standard battery to almost negligible 2 mm or less in the present invention 
     One further advantage of the present invention is the provision of an increased volume inside the compartments that can be used by the electrical cells. It is known that during operation the absorbent glass mat in the element requires compression especially at higher temperatures. To ensure continued compression. also at higher operation temperatures, the exterior sidewalls of the compartments, have to be reinforced and thus produced with an increased wall thickness. This reduces the volume available for the internal cell parts and increases manufacturing and parts cost. 
     The case system according to the present invention reduces the lengthwise walls of the compartments in contact with each other. As the walls between compartments are comparatively shorter with the case system according to the present invention, less material needs to be used for stabilizing the walls between the compartments. This directly leads in an increase of compartment volume, where the operative parts, i.e. the plates are stored as well as to lower material and manufacturing costs. 
     In a preferred embodiment, the interior volume is divided into 6 compartments by means of 5 division planes. The division planes are preferably arranged in parallel to each other. 
     In a preferred embodiment, the case system is adapted to hold an electrical cell or element in each compartment. Said electrical cell or element is furthermore adapted to be operated in a horizontal orientation. 
     Electrical cells applicable for the present invention are preferably made of lead sheets separated by absorbent glass fiber sheets saturated with acid electrolyte. Preferably, the plates are configured to have a positive (+) terminal on one side of the short edge of the plate and a negative (−) terminal at the opposite short edge of the plate. In a preferred embodiment such plates would be devised to have a length of 395 mm to 550 mm, preferably 320 mm to 480 mm. The width of the plates ranges from 105 mm to 125 mm, preferably 95 mm to 115 mm 
     In a further preferred embodiment, the electrical conductor openings are located at opposite ends of the access wall part. The access wall part can be arranged as a plate of essentially rectangular shape. The plate as such would be adapted to fit onto the box shaped cell housing part and to serve as a cover of an opening of said essentially box shaped cell housing part on one side. In the context of the present invention the conductor or terminal feed-through would be located at opposite ends of the access wall part and on a symmetrical axis drawn across the middle point of the access wall part. 
     In a preferred embodiment, the fluid, respectively preferred gas channel opening comprises at least one gas vent with a valve. 
     Suitable valves and gas vents for lead batteries with acid electrolyte are discretional for the skilled artisan. 
     In a preferred embodiment, the fluid, respectively preferably gas channel opening is located essentially at the central point of the access wall plate. This central point can be defined in an analogous manner as above, i.e. as the middle point of the plate. 
     In a further preferred embodiment, the access wall part is shaped as a cover panel with a shape adapted to fit the cell housing part. The access wall part has a first proximal surface, facing outwards, when the case system is fully assembled, and a second distal surface, facing the inside when the case system is fully assembled. 
     In a further preferred embodiment, the access wall part has a plurality of gas valves. Even more preferably the access wall part has as many gas valves as the cell housing part has compartments, preferably it has six gas valves. The access wall part furthermore has a gas-collecting duct on the proximal surface. 
     In a preferred embodiment the box shaped cell-housing part, the access wall part and the closure wall part are separately prefabricated parts. Preferably, they are integral parts. 
     The injection molding process can be simplified and unwanted mold core movement/deflection during the injection molding, resulting in uneven thickness of the case walls, can be prevented. 
     The case system can be sealed with a hot plate welding technique or by gluing and any remaining cell cavities can be packed with adapted fillers. 
     One aspect of the present invention relates to a lead battery. The lead battery comprises a case system as previously described. It is self evident that such a case system can comprise any combination of features described above as preferred embodiments. The case system for a lead battery according to the present invention would at least comprise a one piece, essentially box shaped cell-housing part with at least four sidewalls. The sidewalls enclose an interior volume. The box shaped cell housing part has at least one division plane, dividing said interior volume, such as to form a plurality of compartments. Each of the plurality of compartments is adapted for storing an electrical cell or element. The case system further comprises an access wall part with electrical conductor openings or terminal feed throughs and at least one fluid channel opening. The case system further comprises a closure wall part for sealing off the casing system. Each of the at least one division planes is essentially perpendicular to the same two opposites sidewalls of the essentially box shaped cell housing. The lead battery according to the present invention further comprises at least one electrical cell stored in each compartment. Each electrical cell further comprises a plurality of stacked lead and absorbent glass fiber sheets and an electrolyte. Each electrical cell has a negative (−) terminal and a positive (+) terminal. 
     In a preferred embodiment the negative (−) terminal is positioned opposite of the positive (+) terminal on the electrical cell in respect to a plane in which the lead sheets of the electrical cells are arranged. 
     In a preferred embodiment the electrolyte is fixed in a matrix. In an even more preferred embodiment the holding matrix is an absorbent fiber mat or highly dispersed silica, even more preferably a glass fiber mat. In a preferred embodiment the electrical cells are stored in each compartment alternatingly in respect to the orientation of the terminals. This means that a first electrical cell or element can be placed in the compartment such that the positive (+) terminal faces one direction whereas its negative (−) terminal faces the opposite direction. The successive element or cell is stacked in the next compartment in such a fashion, that its terminal orientation is the opposite of the orientation of the previous. with this opposite terminal orientation arrangement within a cell or element the effects of ohmic losses in the plate group are minimized, and a more even current distributions achieved thereby increasing the effective capacity of the battery. 
     In a preferred embodiment the case system has 6 compartments and each is equipped with an electrical cell or element, such that six electrical cells are in the lead battery. 
     In a further preferred embodiment the electrical cells are placed in a horizontal, so called “pancake” orientation. In operation the case is placed in a horizontal direction. The length for stratification of the acid is preferably not more than 3 mm, preferably less. Stratification is limited to the thickness of the absorbent glass fiber sheets. 
     One further aspect of the present invention is a lead battery layout and associated dimension comprising at least two lead batteries as described above. Said lead batteries can be mounted either in series or in parallel and four units would fit within the 19″ or 23″ wide and 400 mm or 600 mm deep battery tray. 
    
    
     
       The present invention shall be further described by means of drawings and specific examples on the following pages. Further advantages and embodiments become evident to a person of ordinary skill in the art by reviewing these. The invention shall not be limited to these examples. 
         FIG. 1   a  is a schematic drawing of the layout of electrical cells in a case system of the state of the art. 
         FIG. 1   b  is a schematic drawing of the layout of electrical cells in a case system according to the present invention. 
         FIG. 2  is a schematic drawing of a battery according to the present invention. 
         FIG. 3  is a schematic drawing of an electrical cell adapted for use with the present invention. 
         FIG. 4  is a schematic drawing of a battery according to the present invention with a removed front access plate. 
         FIG. 5  is a schematic drawing of a battery according to the present invention with a removed back cover plate. 
         FIG. 6  is a schematic drawing of a lead battery rack consisting of 4 batteries connected according to the present invention and filling a 19″ or 23″ battery tray. 
         FIG. 7   a  is a schematic drawing of a lead battery rack wherefore two time two lead batteries according to the Present invention are connected in parallel. 
         FIG. 7   b  is a schematic drawing wherefore two times two lead batteries are connected in parallel according to the state on the art. 
         FIG. 8   a  shows a schematic drawing of a two-level rack of batteries according to the present invention. 
         FIG. 8   b  shows a two-level rack of lead batteries that are connected as in the state of the art. 
     
    
    
       FIG. 1   a  shows a compartmentation as used in the state of the art batteries. 
     The batteries have six cell compartments in a two times three configuration, meaning that two rows of three compartments are placed in parallel to each other and divided by division planes  103 . Each cell compartment  104  has a width x and a length y. In a typical state of the art battery the length y is 131 mm and the inside width x is 45 mm. 
     For ensuring an adequate compression of the absorbent glass mat in the element during operation, the wall over the whole length y needs to be very strong and stable. 
       FIG. 1   b  shows a case system  100  with a compartment configuration according to the present invention. Six compartments, each with an inside width x of 95 mm and a length y of 65.8 mm are stacked onto one another, such that all division, planes are in parallel to each other or perpendicular to the same two opposite side walls  102 . 
     The edge requiring a reinforced wall for ensuring adequate compression during operation is the width x of 105 mm times two walls, and therefore considerably smaller than the six walls with 131 mm edge as shown in figure la. Thereby, an increase in volume can be accomplished without increasing the overall size of the case. This also allows saving on wall material and thus manufacturing and material costs. 
       FIG. 2  shows a battery  120  according to the present invention. The battery has a housing part  101 , which is shown with a cut off window for representation purposes. It has an interior volume divided by 5 division planes  103  such as to form six compartments into which an electrical cell or element  105  can be placed. The housing part  101  is sealed off on the front side by an access wall part  106  with electrical conductor openings or terminal feed throughs  107  and a fluid, respectively gas channel opening  108  for the gas release and a gas valve (not shown). The back part is sealed with a closure wall part  109 . 
     The housing part  101 , the access wall part  106  and the closure wall part  109  can be manufactured of suitable plastic such as SAN,ABS,PC, PP or mixtures thereof, for example. 
     The electrical cells  105  are lead sheet acid absorbent glass mat cells. The electrical cells  105  are placed in the case system  100 , such that one terminal faces the access wall part  106  and the opposite terminal faces the closure wall part  109 . 
       FIG. 3  shows an electrical cell  105  as employed in the battery described in  FIG. 2 . 
     The electrical cell consists of a plurality of stacked lead sheets separated with absorbent glass fiber mat saturated with electrolyte, whereby the electrolyte in the present electrical cell  105  is sulfuric acid of a concentration of 32% in weight, for example. 
     The electrical cell  105  has a positive terminal (+)  122  and a negative terminal (−)  121 . The terminals are located at opposite ends of the electrical cell  105  in the same plane as of the lead sheets. 
       FIG. 4  shows a lead battery according to the present invention with the front access parts removed and the closure wall part affixed to the box shaped cell-housing part  101 . The cell housing part has five parallel division planes  103  subdividing the internal volume into six compartments into which an electrical cell or element  105  can be placed. The access wall part  106  has electrical conductor openings or terminal feed throughs  107  through which adequate electrical contact can be made to the positive cell terminal  122 , or the negative terminal  121  respectively. The front access wall part  106  further has six gas pressure regulation valves and a central gas collection duct (not shown) on the back side (the part facing the electrical cells when mounted) connected to the gas channel opening  108 . 
       FIG. 5  shows a schematic drawing in perspective from the backside of the battery  120  of  FIG. 4  with the same five division planes  103  and the electrical cells  105  in the respective compartments. In contrast to  FIG. 5 , the closure wall part  109  is removed from the case system enclosing the electrical cells  105 . 
       FIG. 7   a  shows how a series of four battery units  120  according to the present invention can be connected in parallel. Four 12V batteries according to the present invention can be linked in parallel with simple flexible cable connectors  131 . 
     By means of comparison, an equally parallel linked rack  130  of four batteries  132  of the state of the art is shown. The batteries cannot be linked without having to use special shaped solid and rigid connectors. 
     By this means, a safer, cheaper and easier way of connecting four 12V batteries to a 2×24V chain in parallel is provided. 
       FIG. 6  shows a battery rack  130  consisting of four lead batteries  120  of a valve regulated lead absorbent glass mat type, configured according to the present invention. The set up of the front access terminals enables connecting the four batteries  120  by means of an easy to use low cost, low profile, rigid and insulated battery connector  134  made from copper. 
       FIG. 8   a  shows a rack  130  equipped with 14 lead batteries  120  according to the present invention. 
     The figure shows how easy it is to connect the batteries  120  by means of the connection means  135  with the front terminal layout according to the present invention. 
     For comparison,  FIG. 8   b  shows a configuration of 14 batteries connected as required in the state of the art. The intertier connection of the state of the art batteries requires a long cable and is associated with danger of short circuits due to the proximity of the intercell connector position with the metallic rack.