Abstract:
An uninterruptible power supply (UPS) system using a battery pack may be potentially hazardous in its design, and in particular when users themselves connect or disconnect the battery from the UPS while the UPS is still active. A battery cap is provided that attaches to the battery to cover parts where the lead wires meet the terminals of the battery.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention pertains to a battery assembly and in particular to a battery assembly in an uninterruptible power supply (UPS) system that protects users from hazardous voltages.  
           [0003]    2. Background of the Invention  
           [0004]    Users of uninterruptible power supply (UPS) system having a battery pack may be subjected to hazardous voltages when users themselves connect or disconnect the battery from the UPS while the UPS is still active. For instance, certain UPS system designs do not use an isolating transformer to isolate high input AC voltage from the UPS circuit. Therefore, a failure of one or more components of the UPS may result in a hazardous condition where high AC voltage is present at the battery leads. Any exposed battery leads or terminals may expose the user to this dangerous voltage. Furthermore, under various safety standards in various countries, battery connections need to provide protection that meet certain standards such as UL finger test and VDE probe test. The UTL finger test mandates that a human finger should not come in contact with any live parts during normal operation of a device. The VDE probe test requires that a specified probe should not be able to touch the active contacts of the battery or its connectors.  
           [0005]    Typically, the battery used in the UPS system are generally cells that have metal electrodes and electrolytic liquid, typically sulfuric acid. During battery operation, the electrolysis of water produces Hydrogen and Oxygen gases, which accumulate within the battery. These gases are typically vented through a vent cap that is provided at the battery. Otherwise, accumulation of these gases creates a highly volatile situation and a spark or flame could ignite these gases creating an explosion that can cause serious damage to the UPS system and/or cause injury to a user of the UPS.  
           [0006]    Accordingly, it is desired to provide a method and apparatus that resolves these and other shortcomings of UPS systems that use battery packs.  
         SUMMARY OF THE INVENTION  
         [0007]    In one general aspect, the present invention features an uninterruptible power supply for providing AC power to a load. The uninterruptible power supply includes an input to receive AC power from an AC power source, an output that provides AC power, an inverter to receive DC power and to provide AC power, a first connector electrically coupled to the inverter, an energy storage device that provides the DC power, the energy storage device including a plurality of terminals, a plurality of lead wires, each lead wire having a first end connected to one of the terminals of the energy storage device, a second connector adapted to connect to the first connector of the inverter, each lead wire having a second end connected to the second connector, an energy storage device cap attached to the energy storage device and covering the terminals and the first end of each of the lead wires, and a transfer switch constructed and arranged to select one of the AC power source and the energy storage device as an output power source for the uninterruptible power supply.  
           [0008]    Other features may include one or more of: a portion of the energy storage device cap is configured to provide strain relief to the lead wire; the strain relief portion of the energy storage device cap is a plurality of posts in which a lead wire can be weaved; the energy storage device cap is made of an insulating material; the energy storage device cap provides impact protection to the terminals of the energy storage device; the first and second connector are constructed to mate without a use of a tool; an insulating tube formed around the plurality of lead wires of the energy storage device; and a shrink wrap material that attaches the energy storage device cap to the energy storage device.  
           [0009]    In another general aspect, the uninterruptible power supply includes an input to receive AC power from an AC power source, an output that provides AC power, an inverter to receive DC power and to provide AC power, a first connector electrically coupled to the inverter, an energy storage device that provides the DC power and having a second connector to connect to the first connector of the inverter, the energy storage device having a plurality of terminals and a plurality of leads wires, a first end of each of the lead wires connected to one of the terminals, means for covering the terminals and the first end of each of the lead wires, and a transfer switch constructed and arranged to select one of the AC power source and the energy storage device as an output power source for the uninterruptible power supply. Other features may include means for attaching the means for covering the energy storage device.  
           [0010]    In another general aspect, a method pertains to constructing an uninterruptible power supply for providing AC power to a load. The method includes providing an input to receive AC power from an AC power source, providing an output that provides AC power, providing an inverter to receive DC power and to provide AC power, providing a first connector to the inverter, providing an energy storage device that provides the DC power, wherein the energy storage device is formed by providing a plurality of terminals, attaching a first end of each lead wire in a plurality of lead wires to one of the terminals of the energy storage device, providing a second connector adapted to connect to the first connector of the inverter, connecting a second end of each lead wire of the plurality of lead wires to the second connector, attaching an energy storage device cap to the energy storage device, the cap covering the terminals and the first end of each of the lead wires, and providing a transfer switch constructed and arranged to select one of the AC power source and the energy storage device as an output power source for the uninterruptible power supply.  
           [0011]    Other features may include one or more of: forming a strain relief for the lead wires in a portion of the energy storage device cap; using an insulating material to form the energy storage device cap; mating the first and second connectors without use of a tool; forming an insulating tube around the plurality of lead wires of the energy storage device; and using a shrink wrap to attach the energy storage device cap to the energy storage device. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a block diagram of a typical uninterruptible power supply (UPS);  
         [0013]    [0013]FIG. 2 is a battery assembly configured in accordance with an embodiment of the invention;  
         [0014]    [0014]FIG. 3 is another battery assembly configured in accordance with an embodiment of the invention; and  
         [0015]    [0015]FIG. 4 is a bottom view of a battery cap in accordance with an embodiment of the invention showing strain relief posts.  
     
    
     DETAILED DESCRIPTION  
       [0016]    Embodiments of the invention are described below with reference to an uninterruptible power supply (UPS) battery assembly. As understood by those skilled in the art, the method and apparatus described may be used for manufacturing a battery assembly that may be used for other purposes.  
         [0017]    The use of uninterruptible power supplies (UPSs) having battery back-up systems to provide regulated, uninterrupted power for sensitive and/or critical loads, such as computer systems, and other data processing systems is well known. FIG. 1 shows a typical prior art UPS  10  used to provide regulated uninterrupted power. The UPS  10  includes an input filter/surge protector  12 , a transfer switch  14 , a controller  16 , a battery  18 , a battery charger  19 , an inverter  20 , and a DC-DC converter  23 . The UPS also includes an input  24  for coupling to an AC power source and an outlet  26  for coupling to a load.  
         [0018]    The UPS  10  operates as follows. The filter/surge protector  12  receives input AC power from the AC power source through the input  24 , filters the input AC power and provides filtered AC power to the transfer switch and the battery charger. The transfer switch  14  receives the AC power from the filter/surge protector  12  and also receives AC power from the inverter  20 . The controller  16  determines whether the AC power available from the filter/surge protector is within predetermined tolerances, and if so, controls the transfer switch to provide the AC power from the filter/surge protector to the outlet  26 . If the AC power from the rectifier is not within the predetermined tolerances, which may occur because of “brown out,” “high line,” or “black out” conditions, or due to power surges, then the controller controls the transfer switch to provide the AC power from the inverter  20 . The DC-DC converter  23  is an optional component that converts the output of the battery to a voltage that is compatible with the inverter. Depending on the particular inverter and battery used the inverter may be operatively coupled to the battery either directly or through a DC-DC converter.  
         [0019]    The inverter  20  of the prior art UPS  10  receives DC power from the DC-DC converter  23 , converts the DC voltage to AC voltage, and regulates the AC voltage to predetermined specifications. The inverter  20  provides the regulated AC voltage to the transfer switch. Depending on the capacity of the battery and the power requirements of the load, the UPS  10  can provide power to the load during brief power source “dropouts” or for extended power outages.  
         [0020]    [0020]FIG. 2 shows a battery assembly  200  that may be used as the battery  18  in the UPS  10  of FIG. 1. The battery assembly  200  comprises a battery  201 , lead wires  204 , a male connector  208  and a battery cap  214 . The battery  201  may be of a conventional type that is used in a UPS system and has a positive terminal  202  and a negative terminal  203 . Each of the lead wires  204  has a first end attached to one of the terminals  202 ,  203  using a variety of known methods such as terminal locks at the end of the lead wires that lock onto the terminals or the lead wires are simply soldered on to the terminals  202 ,  203 . The lead wires  204  leading away from the battery  201  are contained within an insulator tube  212 . The insulator tube provides supplemental insulation (such as double-insulation) of the lead wires as well as lead wire management by holding the positive and the negative leads together. Each of the lead wires has a second end that is terminated at a male connector  208 .  
         [0021]    The male connector  208  is designed such that contacts within the male connector  208  cannot be contacted by a finger. The male connector  208  is keyed to polarize a connection with a female receiver connector  209  located within the UPS. Because hazardous voltage may be present at female receiver connector  209 , according to one embodiment, the female receiver connector  209  needs to conform to the VDE probe test. One method of conforming to the VDE probe test is to provide a 5 mm clearance from a VDE probe to the contacts within the female receiver connector  209 . The male connector  208  and the female connector  209  are designed for easy mating with each other and do not require any tools for connection. This feature is an improvement over known battery connectors that typically require a tool to connect them to the UPS. It should be noted that the positioning of the female connector of the UPS and the male connector of the battery are interchangable.  
         [0022]    The battery cap  214  is welded, adhered with epoxy or mechanically strapped to the battery  201  to cover the area where the lead wires  204  meet the terminals  202 ,  203 . The battery cap  214  may be molded to fit the contour of the battery  201  and preferably, the battery cap  214  is designed to fit batteries from multiple vendors and therefore is universal in its design to reduce complexity and cost. The material used to manufacture the battery cap  214  is preferably one with insulating properties such as thermoplastics or thermosets. The battery cap  214  seals the terminal connecting end of the leads wires  204  and the terminals  202 ,  203  to prevent access by the user to protect the user from potentially hazardous voltages at the lead wires and terminals. The battery cap  214  may also serve as an impact protector for the terminals  202 ,  203  of the battery  201 .  
         [0023]    A second embodiment of a battery assembly  300  will now be described with reference to FIG. 3. the battery cap  314  is adhered to the battery  301  using a piece of commercially available plastic shrink tubing  316  that shrink wraps around the battery assembly  300 . However, it should be noted that the battery cap may be welded or adhered with epoxy to the battery and a shrink wrap is placed around the combination. Typically, the plastic shrink tubing  316  is thermally sensitive and shrinks when heat is applied to it. Because of the insulating nature of the plastic shrink tubing  316 , it provides an additional protection layer on the battery assembly  300 . Furthermore, because the shrink tubing  316  wraps tightly around the contour of the battery cap  314  and the battery  301  a simple but effective attachment of the battery cap to the battery is formed. The battery cap  314  has a plurality of vents  318  that provide discharge of Hydrogen and Oxygen gases that accumulate during battery operation. The vents  318  eliminate a potential hazard that occurs when an explosive combination of Hydrogen and Oxygen gases are present. To ensure that the vents  318  operate properly, the vents  318  should not be sealed or covered by the shrink wrap during the shrink wrap process.  
         [0024]    [0024]FIG. 4 shows a bottom view of a battery cap  414  in accordance with an embodiment of the invention which may be implemented in the battery caps illustrated in FIG. 2 and FIG. 3. The battery cap  414  has a strain relief portion  420 ,  422  that, in one embodiment comprises a plurality of posts in which each of the lead wires  404  can be woven or wrapped around. An insulator tube  412  containing the lead wires  404  enters through an opening of the battery cap  414 . Each lead wire  404  is wrapped around a first post  420  and a second post  422  forming an “S” shape around the posts  420 ,  422 . The end of the lead wire  404  is connected to the terminal of the battery (not shown). The strain relief portion  420 ,  422  allows the lead wires to be pulled without exerting pressure on the leadwire-battery terminal connection. In one embodiment, the strain relief portion is designed to be able to absorb a pull force of 100 Newtons on the lead wires  404 .  
         [0025]    Having thus described at least one illustrative embodiment of the invention, various alterations, modifications and improvements will readily occur to those skilled in the art. Such alterations, modifications and improvements are intended to be within the scope and spirit of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The scope of the invention should be defined by the following claims and the equivalents thereof.