Patent Publication Number: US-2005118465-A1

Title: Multiple voltages DC battery power supply system

Description:
This application claims the benefit of U.S. provisional application Ser. No. 60/526,255 filed Dec. 2, 2003. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      One aspect of the present invention relates generally to a multiple voltages DC electric power battery power supply system for a vehicle.  
      2. Background Art  
      Most engine driven vehicles utilize an internal combustion engine as the primary power source for propelling a vehicle. However, numerous modules and devices for the vehicle as well as the engine require electrical power. Typically, a rechargeable battery is provided with the vehicle as a basic power supply. The battery power supply system provides power for starting the vehicle engine and power for operating certain electrical loads when the vehicle is not running. The battery is recharged to maintain power by an alternator coupled to and driven by the engine when the vehicle is running. Concurrently, the alternator also provides power to the vehicle electrical loads.  
      With the advent of electronics in today&#39;s modern vehicle, the amount of electrical loads which require power has significantly increased. Moreover, many of the various electrical loads generally operate more efficiently at higher voltages. For example, many military vehicles, heavy trucks, and buses utilize 24-volt battery power supply systems. Such systems require half the current than standard 12 volt battery power supply systems to produce the same power output. The result is a significant reduction in power loss. However, numerous vehicle electrical loads still operate more effectively from a standard 12-volt battery power supply system.  
      Various systems have been proposed that provide a dual voltage output to maintain a 12-volt supply for certain accessories and a 24-volt supply for operating other selected electrical loads. One such system utilizes a single 12-volt battery for supplying power to certain 12-volt electrical loads and a single 24-volt battery for supplying power to 24-volt electrical loads. A single alternator and complex electronics are implemented to switch back and forth between a 12-volt and a 24-volt load.  
      Another dual voltage system utilizes two 12-volt batteries connected in series wherein 12-volt loads can be connected across the terminals of a single 12-volt battery while 24-volt loads can be connected across the series combination of both batteries. A single alternator is used to recharge the entire system, however, no single battery can be continuously charged by the alternator to maintain a constant voltage. Moreover, load requirements can drain one battery more rapidly than another without complex electronics to control and balance the loads.  
      Still other multiple voltage power supply systems use two 12-volt batteries connected in series for providing power to both 12-volt and 24-volt loads. In this instance, a single alternator is utilized having electrically isolated, multiple-phase, stator windings which feed full wave rectifiers for each battery to continuously supply power to selected voltage level outputs and the corresponding batteries. However, the multiple-phase windings share a common magnetic field resulting in an equal amount of current being induced in each phase winding. Therefore, this system has its disadvantages with unbalanced loads and may require complicated electronics to balance the system.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an aspect according to the present invention to provide a multiple voltage battery power supply system for operating a plurality of electrical loads at selected voltage output levels.  
      It is a further aspect according to the present invention to provide a multiple voltage battery power supply system for maintaining continuous power to each battery and battery output, while continuously monitoring each battery independently to provide constant battery voltage.  
      It is still a further aspect according to the present invention to provide a multiple voltages DC electric power supply system that utilizes separate alternators for each battery in the system, wherein each alternator is electrically isolated from a common ground.  
      Accordingly, a multiple voltages DC electric power supply system for vehicle devices having multiple electrical load requirements of different voltages is provided. The system includes at least two electrical blocks connected in series. Each individual block comprises a set of output terminals and a battery having a required voltage which defines the block voltage. Within the block, the battery is connected in parallel with an alternator and a voltage regulator. Optionally, an alternate DC electrical power source can be connected in parallel with the battery, instead of or in addition to, the alternator. The alternator in each block comprises a series of power windings which feed a full wave rectifier to convert alternating current into direct current. Moreover, the alternator in each block contains a field winding. The voltage regulator monitors the block voltage and adjusts the voltage on the field winding accordingly such that the alternator maintains a specified output voltage level. Only one output terminal of only one block not connected to other blocks with both terminals can be connected to the system ground. In case the system utilize negative pole ground, the said block grounding can be executed through the alternator with negative pole designed connected to the alternator body connected to the ground (regular alternator). In case the system utilize positive pole ground, the said block grounding can be executed through the alternator with positive pole designed connected to the alternator body connected to the ground. The output terminals of each block alternator are electrically isolated to prevent the common ground of each individual block alternator from shorting out the remainder of the at least one electrical block.  
      The above aspects and other aspects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings wherein like reference numbers correspond to like components. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic view of a multiple voltages DC electric power supply system according to a preferred embodiment of the present invention;  
       FIG. 2  is a partial section view of an alternator according to a certain embodiment of the present invention;  
       FIG. 3  is a schematic view of a multiple voltages DC electric power supply system according to an alternate embodiment of the present invention; and  
       FIG. 4  is a schematic view of a multiple voltages DC electric power supply system according to another alternate embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)  
       FIG. 1  illustrates a schematic view of a multiple voltages DC electric power supply system  10  suitable for powering vehicular devices having electrical loads requirements of differing voltages in accordance with a preferred embodiment of the present invention.  
      The system  10  in  FIG. 1  is comprised of a first block  12  connected in series with a substantially electrically similar second block  14 . Each block  12  and  14  contains a battery  16 ,  18 , which is connected in parallel with an alternator  20 ,  22 , respectively. The batteries  16 ,  18  can be standard 12-volt vehicle batteries, or rather, they can be any type of battery having a different voltage. As non-limiting examples, batteries  16 ,  18  can be a 3-volt, 6-volt, 9-volt, or even 24-volt battery. Moreover, each battery  16  and  18  are not required to have the same voltage. That is, battery  16  can maintain a voltage which differs from battery  18 . For example, battery  16  can be a 12-volt battery, while battery  18  can be a 6-volt battery.  
      Preferably, the alternators  20 ,  22  each comprise of a three-phase alternating current generator  24 ,  26  coupled to a full wave rectifier  28 ,  30 , respectively. Each three-phase generator  24 ,  26  further comprises power windings  32 ,  34  affixed to a stator (not shown) and field windings  36 ,  38  affixed to a rotor (not shown). The power windings  32 ,  34  are electrically connected to the full wave rectifiers  28 ,  30 , respectively.  
      Each power block  12 ,  14  further comprises a voltage regulator  40 ,  42  also connected in parallel with batteries  16 ,  18  and alternators  20 ,  22 , respectively. Moreover, each voltage regulator  40 ,  42  is electrically coupled to the field winding  36 ,  38  and a relay  44 ,  46 . Each relay  44 ,  46  is normally open preventing current from being supplied to the field winding  36 ,  38 . Each relay  44 ,  46  is also connected to a suitable electric power source, such as the ignition switch, through leads  48 ,  50 . Accordingly, when the ignition switch is in the OFF position, the relay contact remains open and no current is supplied to the field windings  36 ,  38 . Correspondingly, when the ignition switch is turned ON, each relay  44 ,  46  is energized closing the normally open contacts, which in turn provides current from each battery  16 ,  18  to the field winding  36 ,  38 , respectively. The current in each field winding  36 ,  38  generates an electric field which induces current in the power windings  32 ,  34 . The current in the power windings  32 ,  34  is passed through the rectifiers  28 ,  30  and distributed to vehicular electrical loads.  
      Each voltage regulator  40 ,  42  monitors the corresponding voltage of each battery  16 ,  18  and adjusts the current in each field winding  36 ,  38 , accordingly. Under normal load conditions, sufficient current is supplied to the field windings  36 ,  38  in order to continuously charge each battery  16 ,  18  such that each battery maintains their rated voltage level (e.g., 13.6 volts for a 12-volt battery). Should the output power requirements increase, thereby lowering the voltage, increasing the drain on each battery, the voltage regulator increases the voltage and current supplied to the field windings. As a result, each alternator  20 ,  22  charges keep each batteries  16 ,  18  on charge and provides required output power. The net result is that a virtually constant voltage is maintained at each battery  16 ,  18  regardless of the output power requirements (except severe overloading).  
      It is important to note that each voltage regulator  40 ,  42  monitors each corresponding batteries  16 ,  18  terminals independently. That is, each voltage regulator dictates the current in the corresponding field winding, and ultimately the rectified power supplied to the corresponding battery and parallel electrical loads. Therefore, each battery can drain at different rates without interfering with the overall power supplied by system  10  through each block  12  and  14 , or series combination thereof. Thus, each block  12 ,  14  is a self sufficient, independent source of power that when connected in series can provide even greater power (voltage) and the currents consumed by the electrical loads fed by the series blocks voltages are felt by the each block like an additional parallel electrical load on the block output terminals.  
      It is fully contemplated that each block  12 ,  14  can contain an alternate DC power source  52 ,  54  instead of the alternator  20 ,  22 . The alternate power source  52 ,  54  is connected in parallel with the corresponding battery  12 ,  14  rated for the same voltage. As non-limiting examples, the alternate power source  52 ,  54  can be an additional battery, an alternator, a DC generator, a fuel cell, or the like. Moreover, the alternate power source  52 ,  54  can be added in parallel, in addition to the alternator  20 ,  22 , to help meet power requirements of the electrical loads.  
      The system  10  further comprises three alternating vehicular electrical loads  56 ,  58 ,  60 . The alternating loads  56 ,  58 ,  60  can be vehicle accessories such as lights, electric seats, car audio, or the like. Alternating load  56  is fed by the voltage supplied by block  12 , while alternating load  58  is fed by the voltage supplied by block  14 . Alternating load  60  is fed by the sum of the voltages supplied by blocks  12  and  14 . The three varying loads are represented as alternating loads because it is contemplated that additional loads, in excess of the three shown and described, can be powered by each individual block  12  and  14 , or sum thereof.  
      Accordingly, each individual block  12  and  14  is an independent, self-maintained battery power supply subsystem capable of operating individual vehicular loads which have voltage requirements commensurate with the output voltage of each block. Moreover, the cascading of block  12  and  14  together in series provides system  10  with the ability to supply adequate voltage to vehicle electrical loads having higher voltage requirements. Accordingly, system  10  described herein provides for greater power versatility than traditional single voltage/single alternator systems.  
      In a preferred embodiment, the voltage of battery  16  of block  12  and the voltage of battery  18  of block  14  is the same. For example, each battery  16 ,  18  can be 12-volts. Accordingly, certain accessories or devices having 12-volt voltage requirements may be connected to either block  12  or block  14  as loads  56  or  58 , respectively. Moreover, certain vehicle devices and accessories may require much higher voltage, for example, 24-volts, to be fully operable. These such devices can be connected at across blocks  12  and  14  as represented by load  60 . The result is that 24-volts is supplied to load  60 . Each individual alternator  20 ,  22  in each corresponding block  12 ,  14  individually maintains constant battery charge. The result is a constant output voltage across block  12 , block  14 , and the series combination of both block  12  and block  14 .  
      In an alternate embodiment, the voltage of battery  16  of block  12  differs from the voltage of battery  18  of block  14 . For example, battery  16  can be 12-volts, while battery  18  can be 24-volts. Accordingly, vehicular loads having as many as three different voltage requirements can be operable by system  10 . Block  12  can operate 12-volt loads, while block  14  can operate 24-volt loads. Moreover, the series combination of block  12  and block  14  can feed loads requiring 36 volts.  
      An important feature of the present invention is that the negative output terminal  70  of block  14  must be electrically isolated from the alternator body to maintain proper function. This isolation prevents block  14  from shorting out block  12  to a common ground when connected in series. For example, typical vehicle alternators have an isolated positive plate (diods radiator) connected to the isolated positive output terminal and a non-isolated plate (diods radiator) affixed to the alternator body, a conductor in order to save on not building the terminal. In turn, the alternator body is mounted directly to the engine (i.e. essentially vehicle ground). If an additional alternator is added in series, but is of the same regular design and construction of the first alternator, then special care must be taken to ensure that the traditionally non-isolated terminal of the second alternator is electrically isolated from the engine. Otherwise, the first alternator would effectively be shorted out.  
      In a certain embodiment, best shown in  FIG. 2 , the isolation of the negative output terminal  70  of block  14  can be accomplished by placing an insulating sheet  72  between negative plate (diods radiator)  74  of the rectifier  30  and the alternator body  75 . The insulating sheet  72  is preferably a high temperature, non-conducting plastic sheet. The negative plate (diods radiator)  74  of the rectifier  30  is a conductor on which three diodes  80 ,  82 ,  84  are physically and electrically connected. Typically, the negative plate  74  is formed from aluminum to provide an aspect of cooling to the alternator  22 . However, it is fully contemplated that other conductive materials are usable. Further, insulating washers  76  are provided to electrically insulate each bolt  78  used to mount the negative plate (diods radiator)  74  to the alternator body  75 . This arrangement will effectively isolate the rectifier  30  from the common ground alternator body  75  preventing block  14  from shorting block  12 . In this case the wire providing the contact with the block circuit is connected directly to the plate (diods radiator)  74 .  
      In an alternate embodiment, the alternators  20 ,  22  would vary from standard alternators in that they would be designed such that both output terminals are already electrically isolated from the alternator body. To provide the ground one would place a conductor between the negative output terminal of block  12  and the any sufficiently grounded convenient vehicle part. The advantages of modified alternators having this design will be better appreciated in systems having greater than two blocks, as described below.  
      Referring now to  FIG. 3 , an alternate embodiment of the multiple voltage battery power supply system  90  is shown. Please note that similar elements retain the same reference numbers, while new elements are assigned new reference numbers. In particular, a third block  92  has been added and connected in series with blocks  12  and  14  to comprise the system  90 . Again, block  92  is essentially electrically identical to blocks  12  and  14 . In this arrangement, three additional alternating loads  94 ,  96 ,  98  may be powered by system  90 . Alternating loads  56 ,  58 ,  60  remain electrically coupled to the blocks  12  and  14 , or combination thereof, while alternating loads  94 ,  96 ,  98  can be connected to block  92  or across a combination of blocks  12 ,  14 , and  92 , as shown in  FIG. 3 .  
      Again, it is fully contemplated that each block  12 ,  14 , or  92  can supply equivalent voltages, or rather, each block can maintain different voltages. In the former, as many as three alternating loads having different voltage requirements can be operated by system  90 . With respect to the latter, as many as six alternating loads having different voltage requirements can be operated by the system  90 . This allows for a multitude of accessories having different voltage requirements to be simultaneously operated by system  90 .  
      It is fully contemplated that an indefinite number of electrical blocks can be connected in series together, so long as the negative output terminals remain electrically isolated to prevent the short-circuit condition of the other blocks to a common ground. With regard to  FIG. 4 , a system  110  in accordance with yet another alternate embodiment of the present invention is illustrated. A fourth block  112  has been added to system  110  to provide as many as 10 different output voltages for various alternating loads. There is no limit to the number of electrical blocks that can be added to the system. The only limit is to the cost and space available for system  110  and safe voltage level.  
      While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.