Battery tester configured to receive a removable digital module

[0002] The present application is a continuation-in-part of and claims priority of U.S. patent application Ser. No. 09/816,768, filed Mar. 23, 2001 now U.S. Pat. No. 6,586,941, the content of which is hereby incorporated by reference in its entirety.

[0003] This application also claims the benefit of Provisional No. 60/192,222 filed on Mar. 27, 2000.

[0004] The present invention relates to battery testers. More specifically, the present invention relates to electronic battery testers used for testing storage batteries.

[0005] Storage batteries are an important component of modern automotive vehicles. Vehicles with internal combustion engines use such batteries to start the engine or run electrical equipment when the engine is not operating. Electric vehicles use such batteries as a source of power. It is frequently desirable to test storage batteries so that a failing battery can be identified and replaced prior to its ultimate failure, so that a battery with a low state of charge can be recharged, etc. Battery testing typically can be reconfigured after their manufacture.

[0006] Many battery testing techniques have been developed through the years. Midtronics, Inc. of Willowbrook, Ill. and Dr. Keith S. Champlin have been pioneers in battery testing and related technologies. Examples of their work are shown 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 METHODS 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. Ser. No. 09/703,270, filed Oct. 31, 2000, entitled ELECTRONIC BATTERY TESTER; U.S. Ser. No. 09/780,146, filed Feb. 9, 2001, entitled STORAGE BATTERY WITH INTEGRAL BATTERY TESTER; U.S. Ser. No. 09/816,768, filed Mar. 23, 2001, entitled. MODULAR 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. 09/483,623, filed Jan. 13, 2000, entitled ALTERNATOR TESTER; U.S. Ser. No. 09/960,117, filed Sep. 20, 2001, entitled IN VEHICLE BATTERY MONITOR; U.S. Ser. No. 09/908,389, filed: Jul. 18, 2001, entitled BATTERY LAMP WITH INTEGRATED CIRCUIT SENSOR; 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. 09/977,049, filed Oct. 12, 2001, entitled PROGRAMMABLE CURRENT EXCITER FOR MEASURING AC IMMITTANCE OF CELLS AND BATTERIES; U.S. Serial No. 60/330,441, filed Oct. 17, 2001, entitled ELECTRONIC BATTERY TESTER WITH RELATIVE TEST OUTPUT; U.S. Serial 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. Serial 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. Serial 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. 10/101,543, filed Mar. 19, 2002, entitled ELECTRONIC BATTERY TESTER; 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/PARALL SYSTEMS; U.S. Ser. No. 10/128,790, filed Apr. 22, 2002, entitled METHOD OF DISTRIBUTING JUMP-START BOOSTER PACKS; U.S. Serial No. 60/379,281, filed May 8, 2002, entitled METHOD FOR DETERMINING BATTERY STATE OF CHARGE; U.S. Ser. No. 10/143,307, filed May 10, 2002, entitled ELECTRONIC BATTERY TESTER; U.S. Serial No. 60/387,046, filed Jun. 7, 2002, entitled METHOD AND APPARATUS FOR INCREASING THE LIFE OF A STORAGE BATTERY; U.S. Serial 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. Serial 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, which are incorporated herein in their entirety.

[0007] An electronic battery tester is provided for testing storage batteries. Battery test circuitry is configured to couple to the storage battery and digital processor determines a condition of the battery using the battery test circuitry. A data bus couples to the digital processor and is configured to carry data. A connector couples to the data bus and is configured to receive a removable digital module. The connector includes electrical connections which couple the data bus to the removable module.

[0008] FIG. 1 is a simplified block diagram of a battery tester and a removable module.

[0009] FIG. 2 is a more detailed block diagram of the removable module shown in FIG. 1.

[0010] FIG. 3 is an electrical schematic diagram showing electrical lines or connections in the connector which couples the battery tester to the removable module illustrated in FIG. 1.

[0011] FIGS. 4A, 4B and 4C show couplings between the battery tester and removable module.

[0012] The present invention provides an electronic battery tester for testing storage batteries in which removable modules can be selectively coupled to the electronic battery tester to extend the functionality of the device. In various aspects, the invention includes an electronic battery tester adapted to couple to a removable module, a removable module itself and a combination of an electronic battery tester and a removable module. The following is a more detailed description of the invention. However, in broad aspects, the present invention is not limited to the specific configurations or example modules set forth herein.

[0013] FIG. 1 is a simplified diagram of a battery tester 100 configured to test a storage battery 102. Storage battery 102 includes terminals 104 and 106 and may comprise a single cell or a plurality of cells. Battery tester 100 includes battery test circuitry 110 which electrically couples to battery 102 to terminals 104 and 106 of battery 102 through Kelvin connections 112 and 114, respectively. In one aspect, the connection between test circuitry 110 and battery 102 can be through any appropriate means and is not limited to Kelvin connections. For example, a split Kelvin configuration, non-Kelvin connections and/or current sensors can be used. In one specific embodiment circuitry 110 includes a forcing function source 120 configured to apply a forcing function signal to battery 102 through Kelvin connections 112 and 114. In such an embodiment, circuitry 110 may also include a response sensor 122 electrically coupled to battery 102 through Kelvin connections 112, 114. The response sensor 122 is configured to sense an electrical response of battery 102 to the applied forcing function signal. The forcing function signal includes a time varying component and can be applied either by injecting a signal or selectively applying a load to the battery 102.

[0014] A digital processor 140 is electrically coupled to circuitry 110 and is configured to test the storage battery 102. Processor 140 operates in accordance with instructions stored in some type of a memory 142 and at a rate determined by clock 144. In one specific embodiment, processor 140 measures a dynamic parameter of battery 102. An optional input/output (I/O) 146 is provided for coupling to other equipment and/or for operation by a user.

[0015] In accordance with the present invention, a data bus 160 is provided which couples processor 140 to a connector 162. The data bus 160 can carry digital or analog data along with analog signals or electrical power as desired. Connector 162 is configured to couple to a removable module 164 which can be selectively coupled to battery tester 100 to add functionality to battery tester 100.

[0016] FIG. 2 is a simplified block diagram of one example of a removable module 164 and shows various component blocks which can be included in module 164. Module 164 includes a connector 180 configured to mate with connector 162 of battery tester 100 and thereby provide a connection to data bus 160. In one aspect, optional digital circuitry 182 is provided and coupled to data bus 160 through connectors 180 and 162. Similarly, in another example aspect, optional analog circuitry 184 is provided and can also couple to data bus 160 through connectors 180 and 162. Another optional circuit is illustrated as input/output circuit 186 which can couple to data bus 160 through connectors 180 and 162. Removable module 164 can include any combination of circuits 182, 184 and 186. Further, these circuits can optionally interconnect with one another.

[0017] FIG. 3 is a electrical diagram showing specific electrical connections provided in one embodiment of connectors 162 and 180. These connections are shown for example only and the present invention is not limited to this particular configuration. The electrical connections shown in FIG. 3 form the data bus 160 illustrated in FIGS. 1 and 2.

[0018] A reset connection 202 carries a reset signal between battery tester 100 and module 164 such that either unit can cause a reset to occur in the other. This is useful if one of the units is not responding. Line 204 carries a circuit ground while lines 206 and 208 carry analog and digital power, respectively, from the battery tester 100 to the module 164. Lines 210 and 212 provide analog inputs from module 164 to battery tester 100. In a specific example, these inputs can range between 0 and 5 and can be configured to represent a variable in an analog format. Line 214 carries a battery center voltage connection and is used to couple to a center terminal of a multi-terminal battery. Unregulated power is provided on line 216. A bar code/IRDA connection is provided on line 218 and an IR driver connection is provided on line 220. The bar codes/IRDA connection can be used to receive data from module 164 and the IR driver line 220 can be used to send data to an external device, such as a printer, through module 164.

[0019] A frequency count line 222 is provided for transferring data relating to frequency. TXD and RXD lines are provided on a serial connection 224 for transferring data serially between module 164 and battery tester 100. Connectors 226 provide a connection through Kelvin connectors 112 and 114 and are identified as A, B, C and D. This allows module 164 to have direct access to the Kelvin connectors 112 and 114.

[0020] A two-line data bus connection 228 is provided in accordance with the I²C standard for bi-directional communication between battery tester 100 and module 164. Additionally, five lines are provided for a data bus 230 which operates in accordance with the SPI standard for data communication between battery tester 100 and module 164. A chassy ground is provided on line 232 and a load control is provided on line 234. Load control line 234 is used to control application of a load contained in module 164.

[0021] The example data bus 160 shown in FIG. 3 provides a number of different electrical connections for sending signals between tester 100 and module 164. Depending on the particular signal lines being employed, tester 100 and module 164 should be configured appropriately. For example, if a serial bus 224 is used, processor 140 of battery tester 100 and digital circuitry 182 from module 164 should have appropriate circuitry to interface with such a serial connection.

[0022] In one embodiment, module 164 comprises a standard battery tester interface. For example, such an interface can provide a direct passthrough connection with no electronics itself and a standard battery interface is built into the main tester body.

[0023] In another example, module 164 comprises a 42 volt battery tester interface. In such an embodiment, the interface can provide voltage and/or conductance scaling by adjusting amplifiers and/or divider networks to scale a 42 volt input voltage, or other measurements such that they can be used with a standard battery tester interface. This allows a single test circuit to be used with differing battery types by scaling applied signals and/or measured values. This is not limited to the measurement of 42 volt batteries and can be applied to other battery sizes. In general, the battery test module can include circuitry which can scale a measurement.

[0024] Module 164 can comprise a hybrid vehicle interface. For example, instead of scaling a 42 volt battery voltage, a much high voltage can be scaled such as those present in hybrid vehicles, for example 250 to 400 volts.

[0025] Module 164 can comprise an OBDII connector such that battery tester 100 can access the OBDII data bus of a vehicle. In another example, module 164 comprises a multimeter to thereby add such functionality to battery tester 100. In such an example, Kelvin connectors 112 and 114 can be used to provide signals to module 164 through connection 226. The signals can be digitized using digital circuitry 182. This information is provided back to processor 140 and displayed or output on I/O 146. For example, voltage resistance or current can be measured. In a similar example, module 164 provides an oscilloscope function.

[0026] Communication functions can be provided through module 164 such as radio frequency or infrared and other wired or wireless communication I/O. For example, module 164 can provide a interface to a printer. In another example, module 164 includes a printer such that information can be printed directly.

[0027] Module 164 can include a memory which carries specific software to add additional software functionality to battery tester 100. Data security, encryption or software unlocking keys can also be provided by a memory in module 164.

[0028] Module 164 can include calibrated values such that specific calibrations can be performed on battery tester 100. For example, a calibration reference can be coupled to the tester 100. The value of the reference can be digitally communicated to the tester 100.

[0029] Module 164 can include additional processing circuitry to further process battery test data.

[0030] In one embodiment, analog circuitry 184 includes a large resistive load which can optionally be applied to battery 102 during a test. The load is configured to draw a large amount of current for performing a load test.

[0031] Removable module 164 can also provide a backup battery connection for operating circuitry of battery tester 100. A barcode reader can be included in module 164 such that module 164 can be used to read bar code information, for example on a vehicle or on a battery. This information can be used by the battery tester 100 or stored for future use. A data port can be included in module 164, such as a USB port or a PCMCIA port. This allows the battery tester 100 to couple to widely available modular devices used with personal computers. The module 164 may contain additional memory for storage or data logging or a real time clock.

[0032] Module 164 can also contain circuitry or stored algorithms for performing additional tests such as testing the alternator of a vehicle or the starter, etc.

[0033] Removable module 164 can be coupled to measure battery tester 100 using any appropriate technique. For example, FIG. 4A is a side view showing battery test module 164 coupling to battery tester 100 through screws 300 and 302. Finger grips 304 and 306 can be used to manually tighten the screws 300, 302, respectively, by an operator. FIG. 4B is a side view shown another attachment technique in which a spring loaded members 310 includes a protrusion 312 which fits into a receptacle 314. A more detailed view is shown in the cross-sectional view of FIG. 4C. Other attachment techniques include separate screws or attachment elements, snap fit techniques, etc. The mechanisms can be separate elements, molded into the cases of battery tester 100 and/or removable module 164, etc.

[0034] 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.