Abstract:
A method and apparatus for simulating a battery tester with a fixed resistance load, such as a widely used Japanese load tester that rates the strength of Japanese batteries that are categorized under the Japanese Industrial Standard (JIS), are provided. This invention simulates such a device without invoking large current loads, yields familiar results, utilizes an existing database and provides more conclusive testing. The method includes measuring an open circuit voltage (OCV), temperature and a dynamic parameter of the battery. A load voltage of the battery is estimated as a function of the measured battery dynamic parameter, the OCV, the load resistance value of the load tester and the battery temperature. A bounceback voltage (BBV) of the battery is then predicted. The BBV, the load voltage and the battery temperature are utilized to rate the strength of the battery.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to testing storage batteries. More specifically the present invention relates to simulating a battery tester with a fixed resistance load such as a widely used Japanese load tester that rates the strength of Japanese batteries that are categorized under the Japanese Industrial Standard (JIS). The present invention simulates such a device without invoking large current loads, yields familiar results, utilizes an existing database and provides more conclusive testing. 
     Electronic battery testers are used to test storage batteries. Various examples of such testers are described in U.S. Pat. No. 3,873,911, issued Mar. 25, 1975, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 3,909,708, issued Sep. 30, 1975, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 4,816,768, issued Mar. 28, 1989, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 4,825,170, issued Apr. 25, 1989, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE WITH AUTOMATIC VOLTAGE SCALING; U.S. Pat. No. 4,881,038, issued Nov. 14, 1989, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE WITH AUTOMATIC VOLTAGE SCALING TO DETERMINE DYNAMIC CONDUCTANCE; U.S. Pat. No. 4,912,416, issued Mar. 27, 1990, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE WITH STATE-OF-CHARGE COMPENSATION; U.S. Pat. No. 5,140,269, issued Aug. 18, 1992, to Champlin, entitled ELECTRONIC TESTER FOR ASSESSING BATTERY/CELL CAPACITY; U.S. Pat. No. 5,343,380, issued Aug. 30, 1994, entitled METHOD AND APPARATUS FOR SUPPRESSING TIME VARYING SIGNALS IN BATTERIES UNDERGOING CHARGING OR DISCHARGING; U.S. Pat. No. 5,572,136, issued Nov. 5, 1996, entitled ELECTRONIC BATTERY TESTER WITH AUTOMATIC COMPENSATION FOR LOW STATE-OF-CHARGE; U.S. Pat. No. 5,574,355, issued Nov. 12, 1996, entitled METHOD AND APPARATUS FOR DETECTION AND CONTROL OF THERMAL RUNAWAY IN A BATTERY UNDER CHARGE; U.S. Pat. No. 5,585,416, issued Dec. 10, 1996, entitled APPARATUS AND METHOD FOR STEP-CHARGING BATTERIES TO OPTIMIZE CHARGE ACCEPTANCE; U.S. Pat. No. 5,585,728, issued Dec. 17, 1996, entitled ELECTRONIC BATTERY TESTER WITH AUTOMATIC COMPENSATION FOR LOW STATE-OF-CHARGE; U.S. Pat. No. 5,589,757, issued Dec. 31, 1996, entitled APPARATUS AND METHOD FOR STEP-CHARGING BATTERIES TO OPTIMIZE CHARGE ACCEPTANCE; U.S. Pat. No. 5,592,093, issued Jan. 7, 1997, entitled ELECTRONIC BATTERY TESTING DEVICE LOOSE TERMINAL CONNECTION DETECTION VIA A COMPARISON CIRCUIT; U.S. Pat. No. 5,598,098, issued Jan. 28, 1997, entitled ELECTRONIC BATTERY TESTER WITH VERY HIGH NOISE IMMUNITY; U.S. Pat. No. 5,656,920, issued Aug. 12, 1997, entitled METHOD FOR OPTIMIZING THE CHARGING LEAD-ACID BATTERIES AND AN INTERACTIVE CHARGER; U.S. Pat. No. 5,757,192, issued May 26, 1998, entitled METHOD AND APPARATUS FOR DETECTING A BAD CELL IN A STORAGE BATTERY; U.S. Pat. No. 5,821,756, issued Oct. 13, 1998, entitled ELECTRONIC BATTERY TESTER WITH TAILORED COMPENSATION FOR LOW STATE-OF-CHARGE; U.S. Pat. No. 5,831,435, issued Nov. 3, 1998, entitled BATTERY TESTER FOR JIS STANDARD; U.S. Pat. No. 5,914,605, issued Jun. 22, 1999, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 5,945,829, issued Aug. 31, 1999, entitled MIDPOINT BATTERY MONITORING; U.S. Pat. No. 6,002,238, issued Dec. 14, 1999, entitled METHOD AND APPARATUS FOR MEASURING COMPLEX IMPEDANCE OF CELLS AND BATTERIES; U.S. Pat. No. 6,037,751, issued Mar. 14, 2000, entitled APPARATUS FOR CHARGING BATTERIES; U.S. Pat. No. 6,037,777, issued Mar. 14, 2000, entitled METHOD AND APPARATUS FOR DETERMINING BATTERY PROPERTIES FROM COMPLEX IMPEDANCE/ADMITTANCE; U.S. Pat. No. 6,051,976, issued Apr. 18, 2000, entitled METHOD AND APPARATUS FOR AUDITING A BATTERY TEST; U.S. Pat. No. 6,081,098, issued Jun. 27, 2000, entitled METHOD AND APPARATUS FOR CHARGING A BATTERY; U.S. Pat. No. 6,091,245, issued Jul. 18, 2000, entitled METHOD AND APPARATUS FOR AUDITING A BATTERY TEST; U.S. Pat. No. 6,104,167, issued Aug. 15, 2000, entitled METHOD AND APPARATUS FOR CHARGING A BATTERY; U.S. Pat. No. 6,137,269, issued Oct. 24, 2000, entitled METHOD AND APPARATUS FOR ELECTRONICALLY EVALUATING THE INTERNAL TEMPERATURE OF AN ELECTROCHEMICAL CELL OR BATTERY; U.S. Pat. No. 6,163,156, issued Dec. 19, 2000, entitled ELECTRICAL CONNECTION FOR ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,172,483, issued Jan. 9, 2001, entitled METHOD AND APPARATUS FOR MEASURING COMPLEX IMPEDANCE OF CELL AND BATTERIES; U.S. Pat. No. 6,172,505, issued Jan. 9, 2001, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,222,369, issued Apr. 24, 2001, entitled METHOD AND APPARATUS FOR DETERMINING BATTERY PROPERTIES FROM COMPLEX IMPEDANCE/ADMITTANCE; U.S. Pat. No. 6,225,808, issued May 1, 2001, entitled TEST COUNTER FOR ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,249,124, issued Jun. 19, 2001, entitled ELECTRONIC BATTERY TESTER WITH INTERNAL BATTERY; U.S. Pat. No. 6,259,254, issued Jul. 10, 2001, entitled APPARATUS AND METHOD FOR CARRYING OUT DIAGNOSTIC TESTS ON BATTERIES AND FOR RAPIDLY CHARGING BATTERIES; U.S. Pat. No. 6,262,563, issued Jul. 17, 2001, entitled METHOD AND APPARATUS FOR MEASURING COMPLEX ADMITTANCE OF CELLS AND BATTERIES; U.S. Pat. No. 6,294,896, issued Sep. 25, 2001; entitled METHOD AND APPARATUS FOR MEASURING COMPLEX SELF-IMMITANCE OF A GENERAL ELECTRICAL ELEMENT; U.S. Pat. No. 6,294,897, issued Sep. 25, 2001, entitled METHOD AND APPARATUS FOR ELECTRONICALLY EVALUATING THE INTERNAL TEMPERATURE OF AN ELECTROCHEMICAL CELL OR BATTERY; U.S. Pat. No. 6,304,087, issued Oct. 16, 2001, entitled APPARATUS FOR CALIBRATING ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,310,481, issued Oct. 30, 2001, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,313,607, issued Nov. 6, 2001, entitled METHOD AND APPARATUS FOR EVALUATING STORED CHARGE IN AN ELECTROCHEMICAL CELL OR BATTERY; U.S. Pat. No. 6,313,608, issued Nov. 6, 2001, entitled METHOD AND APPARATUS FOR CHARGING A BATTERY; U.S. Pat. No. 6,316,914, issued Nov. 13, 2001, entitled TESTING PARALLEL STRINGS OF STORAGE BATTERIES; U.S. Pat. No. 6,323,650, issued Nov. 27, 2001, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,329,793, issued Dec. 11, 2001, entitled METHOD AND APPARATUS FOR CHARGING A BATTERY; U.S. Pat. No. 6,331,762, issued Dec. 18, 2001, entitled ENERGY MANAGEMENT SYSTEM FOR AUTOMOTIVE VEHICLE; U.S. Pat. No. 6,332,113, issued Dec. 18, 2001, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,351,102, issued Feb. 26, 2002, entitled AUTOMOTIVE BATTERY CHARGING SYSTEM TESTER; U.S. Pat. No. 6,359,441, issued Mar. 19, 2002, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,363,303, issued Mar. 26, 2002, entitled ALTERNATOR DIAGNOSTIC SYSTEM, U.S. Pat. No. 6,392,414, issued May 21, 2002, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,417,669, issued Jul. 9, 2002, entitled SUPPRESSING INTERFERENCE IN AC MEASUREMENTS OF CELLS, BATTERIES AND OTHER ELECTRICAL ELEMENTS; U.S. Pat. No. 6,424,158, issued Jul. 23, 2002, entitled APPARATUS AND METHOD FOR CARRYING OUT DIAGNOSTIC TESTS ON BATTERIES AND FOR RAPIDLY CHARGING BATTERIES; U.S. Pat. No. 6,441,585, issued Aug. 17, 2002, entitled APPARATUS AND METHOD FOR TESTING RECHARGEABLE ENERGY STORAGE BATTERIES; U.S. Pat. No. 6,445,158, issued Sep. 3, 2002, entitled VEHICLE ELECTRICAL SYSTEM TESTER WITH ENCODED OUTPUT; U.S. Pat. No. 6,456,045, issued Sep. 24, 2002, entitled INTEGRATED CONDUCTANCE AND LOAD TEST BASED ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,466,025, issued Oct. 15, 2002, entitled ALTERNATOR TESTER; U.S. Pat. No. 6,466,026, issued Oct. 15, 2002, entitled PROGRAMMABLE CURRENT EXCITER FOR MEASURING AC IMMITTANCE OF CELLS AND BATTERIES; U.S. Pat. No. 6,534,993, issued Mar. 18, 2003, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,544,078, issued Apr. 8, 2003, entitled BATTERY CLAMP WITH INTEGRATED CURRENT SENSOR; U.S. Pat. No. 6,556,019, issued Apr. 29, 2003, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,566,883, issued May 20, 2003, entitled ELECTRONIC BATTERY TESTER; U.S. Pat. No. 6,586,941, issued Jul. 1, 2003, entitled BATTERY TESTER WITH DATABUS; U.S. Pat. No. 6,597,150, issued Jul. 22, 2003, entitled METHOD OF DISTRIBUTING JUMP-START BOOSTER PACKS; U.S. Ser. No. 09/780,146, filed Feb. 9, 2001, entitled STORAGE BATTERY WITH INTEGRAL BATTERY TESTER; U.S. Ser. No. 09/756,638, filed Jan. 8, 2001, entitled METHOD AND APPARATUS FOR DETERMINING BATTERY PROPERTIES FROM COMPLEX IMPEDANCE/ADMITTANCE; U.S. Ser. No. 09/862,783, filed May 21, 2001, entitled METHOD AND APPARATUS FOR TESTING CELLS AND BATTERIES EMBEDDED IN SERIES/PARALLEL SYSTEMS; U.S. Ser. No. 09/960,117, filed Sep. 20, 2001, entitled IN-VEHICLE BATTERY MONITOR; U.S. Ser. No. 09/908,278, filed Jul. 18, 2001, entitled BATTERY CLAMP WITH EMBEDDED ENVIRONMENT SENSOR; U.S. Ser. No. 09/880,473, filed Jun. 13, 2001; entitled BATTERY TEST MODULE; U.S. Ser. No. 09/940,684, filed Aug. 27, 2001, entitled METHOD AND APPARATUS FOR EVALUATING STORED CHARGE IN AN ELECTROCHEMICAL CELL OR BATTERY; U.S. Ser. No. 60/330,441, filed Oct. 17, 2001, entitled ELECTRONIC BATTERY TESTER WITH RELATIVE TEST OUTPUT; U.S. Ser. No. 60/348,479, filed Oct. 29, 2001, entitled CONCEPT FOR TESTING HIGH POWER VRLA BATTERIES; U.S. Ser. No. 10/046,659, filed Oct. 29, 2001, entitled ENERGY MANAGEMENT SYSTEM FOR AUTOMOTIVE VEHICLE; U.S. Ser. No. 09/993,468, filed Nov. 14, 2001, entitled KELVIN CONNECTOR FOR A BATTERY POST; U.S. Ser. No. 09/992,350, filed Nov. 26, 2001, entitled ELECTRONIC BATTERY TESTER, U.S. Ser. No. 60/341,902, filed Dec. 19, 2001, entitled BATTERY TESTER MODULE; U.S. Ser. No. 10/042,451, filed Jan. 8, 2002, entitled BATTERY CHARGE CONTROL DEVICE, U.S. Ser. No. 10/073,378, filed Feb. 8, 2002, entitled METHOD AND APPARATUS USING A CIRCUIT MODEL TO EVALUATE CELL/BATTERY PARAMETERS; U.S. Ser. No. 10/093,853, filed Mar. 7, 2002, entitled ELECTRONIC BATTERY TESTER WITH NETWORK COMMUNICATION; U.S. Ser. No. 60/364,656, filed Mar. 14, 2002, entitled ELECTRONIC BATTERY TESTER WITH LOW TEMPERATURE RATING DETERMINATION; U.S. Ser. No. 10/098,741, filed Mar. 14, 2002, entitled METHOD AND APPARATUS FOR AUDITING A BATTERY TEST; U.S. Ser. No. 10/112,114, filed Mar. 28, 2002; U.S. Ser. No. 10/109,734, filed Mar. 28, 2002; U.S. Ser. No. 10/112,105, filed Mar. 28, 2002, entitled CHARGE CONTROL SYSTEM FOR A VEHICLE BATTERY; U.S. Ser. No. 10/112,998, filed Mar. 29, 2002, entitled BATTERY TESTER WITH BATTERY REPLACEMENT OUTPUT; U.S. Ser. No. 10/119,297, filed Apr. 9, 2002, entitled METHOD AND APPARATUS FOR TESTING CELLS AND BATTERIES EMBEDDED IN SERIES/PARALLEL SYSTEMS; U.S. Ser. No. 60/379,281, filed May 8, 2002, entitled METHOD FOR DETERMINING BATTERY STATE OF CHARGE; U.S. Ser. No. 60/387,046, filed Jun. 7, 2002, entitled METHOD AND APPARATUS FOR INCREASING THE LIFE OF A STORAGE BATTERY; U.S. Ser. No. 10/177,635, filed Jun. 21, 2002, entitled BATTERY CHARGER WITH BOOSTER PACK; U.S. Ser. No. 10/207,495, filed Jul. 29, 2002, entitled KELVIN CLAMP FOR ELECTRICALLY COUPLING TO A BATTERY CONTACT; U.S. Ser. No. 10/200,041, filed Jul. 19, 2002, entitled AUTOMOTIVE VEHICLE ELECTRICAL SYSTEM DIAGNOSTIC DEVICE; U.S. Ser. No. 10/217,913, filed Aug. 13, 2002, entitled, BATTERY TEST MODULE; U.S. Ser. No. 60/408,542, filed Sep. 5, 2002, entitled BATTERY TEST OUTPUTS ADJUSTED BASED UPON TEMPERATURE; U.S. Ser. No. 10/246,439, filed Sep. 18, 2002, entitled BATTERY TESTER UPGRADE USING SOFTWARE KEY; U.S. Ser. No. 60/415,399, filed Oct. 2, 2002, entitled QUERY BASED ELECTRONIC BATTERY TESTER; and U.S. Ser. No. 10/263,473, filed Oct. 2, 2002, entitled ELECTRONIC BATTERY TESTER WITH RELATIVE TEST OUTPUT; U.S. Ser. No. 60/415,796, filed Oct. 3, 2002, entitled QUERY BASED ELECTRONIC BATTERY TESTER; U.S. Ser. No. 10/271,342, filed Oct. 15, 2002, entitled IN-VEHICLE BATTERY MONITOR; U.S. Ser. No. 10/270,777, filed Oct. 15, 2002, entitled PROGRAMMABLE CURRENT EXCITER FOR MEASURING AC IMMITTANCE OF CELLS AND BATTERIES; U.S. Ser. No. 10/310,515, filed Dec. 5, 2002, entitled BATTERY TEST MODULE; U.S. Ser. No. 10/310,490, filed Dec. 5, 2002, entitled ELECTRONIC BATTERY TESTER; U.S. Ser. No. 10/310,385, filed Dec. 5, 2002, entitled BATTERY TEST MODULE, U.S. Ser. No. 60/437,255, filed Dec. 31, 2002, entitled REMAINING TIME PREDICTIONS, U.S. Ser. No. 60/437,224, filed Dec. 31, 2002, entitled DISCHARGE VOLTAGE PREDICTIONS, U.S. Ser. No. 10/349,053, filed Jan. 22, 2003, entitled APPARATUS AND METHOD FOR PROTECTING A BATTERY FROM OVERDISCHARGE, U.S. Ser. No. 10/388,855, filed Mar. 14, 2003, entitled ELECTRONIC BATTERY TESTER WITH BATTERY FAILURE TEMPERATURE DETERMINATION, U.S. Ser. No. 10/396,550, filed Mar. 25, 2003, entitled ELECTRONIC BATTERY TESTER, U.S. Ser. No. 60/467,872, filed May 5, 2003, entitled METHOD FOR DETERMINING BATTERY STATE OF CHARGE, U.S. Ser. No. 60/477,082, filed Jun. 9, 2003, entitled ALTERNATOR TESTER, U.S. Ser. No. 10/460,749, filed Jun. 12, 2003, entitled MODULAR BATTERY TESTER FOR SCAN TOOL, U.S. Ser. No. 10/462,323, filed Jun. 16, 2003, entitled ELECTRONIC BATTERY TESTER HAVING A USER INTERFACE TO CONFIGURE A PRINTER, U.S. Ser. No. 10/601,608, filed Jun. 23, 2003, entitled CABLE FOR ELECTRONIC BATTERY TESTER, U.S. Ser. No. 10/601,432, filed Jun. 23, 2003, entitled BATTERY TESTER CABLE WITH MEMORY; U.S. Ser. No. 60/490,153, filed Jul. 25, 2003, entitled SHUNT CONNECTION TO A PCB FOR AN ENERGY MANAGEMENT SYSTEM EMPLOYED IN AN AUTOMOTIVE VEHICLE, which are incorporated herein in their entirety. 
     In general, battery state of health decisions are based on battery rating standards. Japanese battery manufacturers design and manufacture batteries according to Japanese Industrial Standards (JIS). Lead-acid storage batteries used for purposes such as starting, lighting and ignition of automobiles are defined by standard JIS D 5301. This standard defines performance, testing, construction, and labeling criteria for JIS rated batteries. 
     One type of Japanese battery tester uses measurements of battery voltage under a resistive load and subsequent recovery voltage to access the viability of JIS rated batteries for further service. This tester encompasses several ranges of battery sizes grouped by JIS numbers and multiple temperature ranges. Depending on the response, the battery is diagnosed, as “good,” “replace soon,” “replace,” etc. 
     Because this tester has a fixed load resistor that discharges batteries at sizable rates (for example, 150 amperes for 5–6 seconds), the tester is rather bulky and may get hot with repeated tests. Also, waiting for the completion of the load and the recovery time takes a moderate amount of time and further depletes battery charge. Further, this tester has voltage sensing leads that are not directly connected to the battery, and therefore the cables must be ohmically perfect and the current must be exactly known to give the correct voltage reading at the battery terminals. Furthermore, if the tester is to be powered by the battery to be tested, then heavy loads can drain a weak or discharged battery causing the tester to lose sufficient power to keep its control circuits running thereby causing a reset. 
     Thus, it is desirable to obtain load test results, that the above-described Japanese load tester, and other such load testers, are capable of providing, using a more amenable testing technique. 
     SUMMARY OF THE INVENTION 
     A method and apparatus for simulating a battery tester with a fixed resistance load, such as a Japanese load tester that rates the strength of Japanese batteries that are categorized under the Japanese Industrial Standard (JIS), are provided. The method includes measuring a dynamic parameter of the battery and obtaining an open circuit voltage of the battery. A temperature of the battery is then obtained. A load voltage of the battery is estimated as a function of the measured battery dynamic parameter, the open circuit voltage of the battery, a load resistance value of the load tester and the temperature of the battery. A bounceback voltage of the battery is then predicted. The bounceback voltage, the load voltage and the battery temperature are utilized to rate the strength of the battery by categories of JIS group size numbers for JIS rated batteries. In addition, the apparatus and method of the present invention can be employed for non-JIS batteries by using reference CCA (cold cranking amps) ranges for each group size. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified schematic diagram showing battery test circuitry in accordance with the present invention. 
         FIG. 2  is a simplified block diagram showing the steps of a method of programming a battery tester in accordance with the present invention. 
         FIG. 3  is a simplified block diagram showing the steps of a method of testing a battery in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention provides an apparatus and method for simulating a battery tester with a fixed resistance load, such as a Japanese load tester that rates the strength of Japanese batteries that are categorized under the Japanese Industrial Standard (JIS). A battery tester of the present invention assesses a dynamic parameter, such as conductance, of a battery rated according to Japanese Industrial Standards (JIS) and, together with the resistance of the tester load to be simulated, an open circuit voltage and the temperature of the JIS rated battery, outputs calculated values that are used to rate the strength of the JIS rated battery by categories of JIS group size numbers. In addition, the tester can be used for non-JIS batteries by using reference CCA (cold cranking amps) ranges for each group size. 
       FIG. 1  is a simplified block diagram of battery test circuitry  16  in accordance with an embodiment of the present invention. Apparatus  16  is shown coupled to battery  12 , which includes a positive battery terminal  22  and a negative battery terminal  24 . Battery  12  may be a JIS rated battery or a non-JIS rated battery such as a CCA rated battery. 
     In preferred embodiments, circuitry  16  operates, with the exceptions and additions as discussed below, in accordance with battery testing methods described in one or more of the United States patents obtained by Dr. Champlin and Midtronics, Inc. and listed above. Circuitry  16  operates in accordance with one embodiment of the present invention and determines the conductance (G) of battery  12 , the open circuit voltage (OCV) between terminals  22  and  24  of battery  12  and the bounceback voltage (change in voltage after the battery is initially released from a load until some time later (for example, 3 seconds)) of battery  12 . Circuitry  16  includes current source  50 , differential amplifier  52 , analog-to-digital converter  54  and microprocessor  56 . Amplifier  52  is capacitively coupled to battery  12  through capacitors C 1  and C 2 . Amplifier  52  has an output connected to an input of analog-to-digital converter  54 . Microprocessor  56  is connected to system clock  58 , memory  60  and analog-to-digital converter  54 . Microprocessor  56  is also capable of receiving an input from input devices  66  and  68 . Microprocessor  56  also connects to output device  72 . 
     In operation, current source  50  is controlled by microprocessor  56  and provides a current I in the direction shown by the arrow in  FIG. 1 . In one embodiment, this is a square wave or a pulse. Differential amplifier  52  is connected to terminals  22  and  24  of battery  12  through capacitors C 1  and C 2 , respectively, and provides an output related to the voltage potential difference between terminals  22  and  24 . In a preferred embodiment, amplifier  52  has a high input impedance. Circuitry  16  includes differential amplifier  70  having inverting and noninverting inputs connected to terminals  24  and  22 , respectively. Amplifier  70  is connected to measure the OCV of battery  12  between terminals  22  and  24 . The output of amplifier  70  is provided to analog-to-digital converter  54  such that the voltage across terminals  22  and  24  can be measured by microprocessor  56 . 
     Circuitry  16  is connected to battery  12  through a four-point connection technique known as a Kelvin connection. This Kelvin connection allows current I to be injected into battery  12  through a first pair of terminals while the voltage V across the terminals  22  and  24  is measured by a second pair of connections. Because very little current flows through amplifier  52 , the voltage drop across the inputs to amplifier  52  is substantially identical to the voltage drop across terminals  22  and  24  of battery  12 . The output of differential amplifier  52  is converted to a digital format and is provided to microprocessor  56 . Microprocessor  56  operates at a frequency determined by system clock  58  and in accordance with programming instructions stored in memory  60 . 
     Microprocessor  56  determines the conductance of battery  12  by applying a current pulse I using current source  50 . The microprocessor determines the change in battery voltage due to the current pulse I using amplifier  52  and analog-to-digital converter  54 . The value of current I generated by current source  50  is known and is stored in memory  60 . Microprocessor  56  calculates the conductance of battery  12  using the following equation: 
                   Conductance   =     G   =       Δ   ⁢           ⁢   I       Δ   ⁢           ⁢   V                 Equation   ⁢           ⁢   1               
where ΔI is the change in current flowing through battery  12  due to current source  50  and ΔV is the change in battery voltage due to applied current ΔI. In a preferred embodiment of the present invention, the temperature of battery  12  is input by a tester user through input  66 , for example. In other embodiments circuitry  16  also includes a temperature sensor  74 , coupled to microprocessor  56 , that can be thermally coupled to battery  12  to thereby measure a temperature of battery  12  and provide the measured battery temperature value(s) to microprocessor  56 . In one embodiment, the battery temperature is measured using an infrared signal from the outside of the battery. Microprocessor  56  can also use other information input from input device  66  provided by, for example, an operator. This information may consist of the particular type of battery, location, time, the name of the operator, battery group size number, battery temperature, etc.
 
     Under the control of microprocessor  56 , battery tester  16  estimates a load voltage of battery  12  as a function of the battery conductance G (Equation 1), the OCV, the resistance of the simulated tester load and the battery temperature. Further, battery tester  16  predicts, as mentioned above, a bounceback voltage of the battery. The bounceback voltage, the load voltage and the battery temperature are utilized by microprocessor  56  of battery tester  16  to rate the strength of the battery by categories of JIS group size numbers. Details regarding the derivation of an example algorithm utilized by battery tester  16  to estimate the bounceback voltage and load voltage of battery  12  are provided below. The algorithm included below was derived by analyzing a popular Japanese battery load tester. 
     Analysis of Japanese Load Tester 
     The Japanese load tester requires the user, after connecting the cable clamps to a battery, to input the size of the battery and the temperature. The user then pushes a start button. The tester puts a load on a battery for 5–6 seconds and then records the load voltage (LV). It then looks at the bounceback or recovery voltage 2.5 seconds later and makes a decision about the battery. 
     As mentioned above, the user inputs battery size. Specifically, batteries are input in 10 group size ranges (0–9) that go in increasing cranking power range. Each range, however, is strictly associated with various JIS battery numbers printed on the tester(s). Table 1 below shows the different group size ranges. 
                             TABLE 1                       Cold       Group       Cranking Amp       Size   JIS BATTERY NUMBER   (CCA) range                   0   26A17, 26A19, 26B17, 28A19, 28B17, 28B19,   200–250 CCA           32C24       1   30A19, 32A19, 34A19, 34B17, 34B19, 36B20,   251–300 CCA           48B26       2   38B19, 40B19, 38B20, 40B20, 46B24, 50D20,   301–350 CCA           55D26       3   42B19, 42B20, 44B19, 50B24, 55D23, 65D31   351–400 CCA       4   55B24, 65D23, 65D26, 75D31   401–450 CCA       5   60B24, 70D23, 75D23, 75D26, 80D23, 80D26,   451–600 CCA           85D31, 95E41, 100E41, 105E41, 110E41       6   90D26, 95D31, 105D31, 115E41, 115F51   601–750 CCA       7   115D31, 120E41, 130E41, 130F51, 145F51,   751–900 CCA           145G51, 155G51       8   150F51, 170F51, 165G51, 190H52   901–1050 CCA       9   180G51, 195G51, 210H52, 225H52, 245H52   1051+ CCA                    
As mentioned above, in addition to group size, the user inputs temperature. The temperature is input by the user in four ranges (shown in Table 2):
 
     
       
         
               
               
             
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Temperature range 
               
               
                   
                 (degrees Celsius(° C.)) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1 
                  0 
               
               
                   
                 2 
                 10 
               
               
                   
                 3 
                 25 
               
               
                   
                 4 
                 “After Driving” (50) 
               
               
                   
                   
               
             
          
         
       
     
     The tester allows the battery to be tested down to 11.5 volts (V) after recovery where it is then reported as low voltage, provided that the battery provides enough voltage to support the tester during the load. If indeed the voltage goes very low, the load tester simply resets and reports nothing. 
     A basic relationship between the group size (0–9) and temperature (° C.) for this type of tester follows the following relationship: 
     Good Voltage (Vg in Volts):
 
 Vg= 8.8+0.1*GroupSize+0.02*TempC  Equation 2
 
Where
         GroupSize=battery group size (Table 1 above)   TempC=battery temperature in degrees Celsius (Table 2 above)
 
Replace Voltage (Vr in Volts):
 
 Vr=Vg− 0.3  Equation 3
 
However, because the battery may be discharged or have other problems, the measured recovery or bounceback voltage (BBV) is assessed and combined with the group size criteria and temperature gives the following (shown in Table 3 below):
       

                         TABLE 3               Comparison   Result                   LV &gt;= Vg AND BBV &gt;= 11.5 V   Good       LV &lt; Vg AND LV &gt;= Vr AND BBV &gt;= 11.5 V   Replace Soon       LV &lt; Vr AND LV &gt;= 7 V AND BBV &gt;= 11.5 V   Replace       LV &gt;= Vr AND LV &lt; Vg AND BBV &lt; 11.5 V   Attention           (Charge Soon)       LV &gt;= 7 V AND LV &lt; Vr AND BBV &lt; 11.5 V   Warning           (Charge and Retest)       LV &lt; 7 V (Normally the tester simply   Fail/Replace       resets for lack of power. In such a   (Charge and       case the battery is retested after   Retest)       charging.)                    
Example Algorithm for Battery Tester of the Present Invention
 
     As mentioned above, the battery tester of the present invention works by predicting the load voltage (LV) using measured values of the battery&#39;s OCV, conductance and temperature (measured or input by the user). 
     To predict the load voltage in Volts, the following relationship is used:
 
 LV=V act −I*R   Equation 4
 
Where
         Vact=activation voltage   I=load current   R=battery resistance
 
The activation voltage (Vact) can be estimated by:
 
 V act =K 1 *OCV   2   +K 2* OCV+K 3*TempC− K 4  Equation 5
 
where K1, K2, K3 and K4 are constants whose values are selected based upon the type of battery tester being simulated.
       

     The battery conductance (G) is measured as described above using Equation 1. Using conductance measured at 100 Hz, the battery resistance can be estimated by:
 
 R=K 5/ G+K 6  Equation 6
 
where K5 and K6 are constants. However, because the Japanese tester uses a fixed resistor for loading, the current will vary with the resistance of the battery. Therefore, the load current must first be estimated. This can be carried out using the following relationship:
 
 I=V act/( R+R 1)  Equation 7
 
where R 1  is the estimated resistance of the load tester in ohms.
 
     It was generally found that the load varies between 110–160 amperes; if below 110 amperes the load tester will reset. Therefore, the load voltage can be predicted and used for assessing the battery strength. 
     In addition, it was found that the recovery or bounceback voltage (BBV) could be predicted with a second order equation using the open circuit voltage and the temperature:
 
 BBV=K 7* OCV+K 8* OCV−K 9 +K 10*(TempC− K 11)  Equation 8
 
where K7, K8, K9, K10 and K11 are constants.
 
     Therefore, using these calculations (Equations 1 and 4–8), the values attained by the Japanese load tester can be predicted without invoking a high load. 
       FIG. 2  is a flowchart  100  showing steps of a method of programming battery tester  16  in accordance with an embodiment of the present invention. As shown in flow chart  100 , at step  102 , mathematical relationships to estimate the load voltage from the conductance, temperature and OCV of the battery are established (Equations 1 and 4–7 above). At step  104 , a mathematical relationship to estimate bounceback voltage of the battery is established (Equation 8). At step  106 , the mathematical relationships are programmed into memory  60  of battery tester  16 . At this point, battery tester  16  is ready to estimate battery load voltage and bounceback voltage and to utilize the estimated bounceback voltage, the load voltage and the battery temperature to rate the strength of the battery by categories of JIS group size numbers. 
       FIG. 3  is a flowchart  150  showing steps of a method of testing a battery in accordance with an embodiment of the present invention. At step  152 , a dynamic parameter of the battery is measured. At step  154 , an open circuit voltage of the battery is obtained. At step  156 , a temperature of the battery is obtained. At step  157 , a value of tester load resistance is set. This is a predetermined load resistance value that is appropriate for a load tester being simulated. At step  158 , a load voltage of the battery is estimated as a function of the measured battery dynamic parameter, the open circuit voltage of the battery, the load resistance and the battery temperature. At step  160 , a bounceback voltage of the battery is predicted. At step  162 , the bounceback voltage, the load voltage and the battery temperature are utilized to rate the strength of the battery by categories of JIS group size numbers. Different techniques, some of which are set forth above, can be employed to carry out the steps shown in the flow chart of  FIG. 3  while maintaining substantially the same functionality without departing from the scope and spirit of the present invention. 
     Furthermore, because there is no load from the tester of this invention, the tester can improve upon the standard load tester by making judgements in areas that would reset the standard load tester. In particular, if the bounceback voltage is above 11.5V and the load voltage is very low (&lt;7V), such a battery can be certain to be a cause for “Fail/Replace.” If the bounceback voltage is below 11.5V, the OCV is greater than 11V and the load voltage estimate is less than Vr then a judgement can be deferred and the battery can be put in a “Charge and Retest” category. In addition, the tester can detect batteries with probable shorts by finding significant conductance when the OCV is less than 11V. These can be placed in a “Fail/Replace” category. If little conductance is present when the voltage is very low, the battery can be placed in a “Charge and Retest” category. The improved and more specific comparisons and results are provided in Table 4 below. 
     
       
         
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 Comparison 
                 Result 
               
               
                   
               
             
             
               
                 LV &gt;= Vg AND BBV &gt;= 11.5 V 
                 Good 
               
               
                 LV &lt; Vg AND LV &gt;= Vr AND BBV &gt;= 11.5 V 
                 Replace Soon 
               
               
                 LV &lt; Vr AND LV &gt;= 7 AND BBV &gt;= 11.5 V 
                 Replace 
               
               
                 LV &lt; 7 V AND BBV &gt;= 11.5 V 
                 Fail/Replace 
               
               
                 LV &gt;= Vr AND LV &lt; Vg AND BBV &lt; 11.5 V 
                 Attention 
               
               
                 AND OCV &gt;= 11 V 
                 (Charge Soon) 
               
               
                 LV &lt; Vr AND BBV &lt; 11.5 V AND OCV &gt;= 11 V 
                 Warning (Charge 
               
               
                   
                 and Retest) 
               
               
                 IF OCV &lt; 11 V AND CCA &gt;= f(GROUP SIZE) 
                 Fail/Replace 
               
               
                 (PROBABLE SHORT) 
               
               
                 IF OCV &lt; 11 V AND CCA &lt; f(GROUP SIZE) 
                 Warning (Charge 
               
               
                   
                 and Retest) 
               
               
                   
               
             
          
         
       
     
     Although the example embodiments of the present invention described above relate to estimating load voltage from battery conductance measurements, dynamic parameters other than battery conductance may be utilized without departing from the spirit and scope of the invention. Examples of other dynamic parameters include dynamic resistance, admittance, impedance, reactance, susceptance or their combinations. In preferred embodiments of the present invention, battery tester  16  is relatively small and portable. 
     The above embodiments of the present invention are primarily described in connection with simulating a Japanese load tester. However, the significance of this present invention is not necessarily that it mimics a Japanese tester, but that it mimics, in general, any tester with a fixed resistance load. In general, simulating a tester with a fixed resistance load is a two stage process: (1) determining what current will be drawn from the battery (Equation 7 above) and (2) determine what voltage the battery will achieve under that load (Equation 4 above). Many prior art algorithms assume that the load current is defined and then the voltage is predicted. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.