WO2022006525A1

WO2022006525A1 - Electrical load for electronic battery tester and electronic battery tester including such electrical load

Info

Publication number: WO2022006525A1
Application number: PCT/US2021/040313
Authority: WO
Inventors: Kevin I. Bertness
Original assignee: Midtronics, Inc.
Priority date: 2020-07-02
Filing date: 2021-07-02
Publication date: 2022-01-06
Also published as: DE112021003562T5

Abstract

An apparatus (10) for testing a storage battery (12) in an automotive vehicle (300) includes a controllable electrical load (70) configured to electrically couple to the storage battery (12) of the vehicle (300). A current sensor is configured (304) to electrically connect to a terminal (22) of the battery (12) and measure flow of current through the battery (12). A controller (56) is arranged to apply an electrical load (RE) to the battery (12) using the controllable load (70) and adjust the electrical load (RE) while monitoring the electrical current sensed by the current sensor (70) to determine a charge current applied to the battery (12) by an alternator of the vehicle (300) and further configured to perform a test on the battery (12). A method for testing a storage battery (12) in an automotive vehicle (300) includes connecting a controllable electrical load (70) to the storage battery (12), connecting a current sensor (304) to a connection to a terminal (22) of the battery (12), applying an electrical load (RE) to the battery (12) using the controllable electrical load (70), adjusting the electrical load (RE) while monitoring an output from the current sensor (304) to determine a charge current applied to the battery (12) by an alternator of the vehicle (304), and performing a test on the battery (12).

Description

ELECTRICAL LOAD FOR ELECTRONIC BATTERY TESTER AND ELECTRONIC BATTERY TESTER INCLUDING SUCH ELECTRICAL LOAD

BACKGROUND

[0001] The present invention relates to storage batteries. More specifically, the present invention relates to electronic battery testers used to test storage batteries.

[0002] Storage batteries, such as lead acid storage batteries, are used in a variety of applications such as automotive vehicles and standby power sources. Typical storage batteries consist of a plurality of individual storage cells which are electrically connected in series. Each cell can have a voltage potential of about 2.1 volts, for example. By connecting the cells in the series, the voltages of the individual cells are added in a cumulative manner. For example, in a typical automotive storage battery, six storage cells are used to provide a total voltage of about 12.6 volts. The individual cells are held in a housing and the entire assembly is commonly referred to as the “battery.”

[0003] It is frequently desirable to ascertain the condition of a storage battery. Various testing techniques have been developed over the long history of storage batteries. For example, one technique involves the use of a hygrometer in which the specific gravity of the acid mixture in the battery is measured. Electrical testing has also been used to provide less invasive battery testing techniques. A very simple electrical test is to simply measure the voltage across the battery. If the voltage is below a certain threshold, the battery is determined to be bad. Another technique for testing a battery is referred to as a load test. In a load test, the battery is discharged using a known load. As the battery is discharged, the voltage across the battery is monitored and used to determine the condition of the battery. More recently, techniques have been pioneered by Dr. Keith S. Champlin and Midtronics, Inc. of Willowbrook, Ill. for testing storage battery by measuring a dynamic parameter of the battery such as the dynamic conductance of the battery.

SUMMARY

[0004] An apparatus for testing a storage battery in an automotive vehicle includes a controllable electrical load configured to electrically couple to the storage battery of the vehicle. A current sensor is configured to electrically connect to a terminal of the battery and measure flow of current through the battery. A controller is arranged to apply an electrical load to the battery using the controllable load and adjust the electrical load while monitoring the electrical current sensed by the current sensor to determine a charge current applied to the battery by an alternator of the vehicle and further configured to perform a test on the battery. A method for testing a storage battery in an automotive vehicle includes connecting a controllable electrical load to the storage battery, connecting a current sensor to a connection to a terminal of the battery, applying an electrical load to the battery using the controllable electrical load, adjusting the electrical load while monitoring an output from the current sensor to determine a charge current applied to the battery by an alternator of the vehicle, and performing a test on the battery. [0005] An electrical load assembly is provided for use by an electronic battery tester used to perform an electronic battery test on a storage battery. The electrical assembly comprises a load wire providing an electrical load resistance and a housing which at least partially encloses the load wire. An airflow passageway is provided in the housing adjacent the load wire. Electrical terminals connected to the load wire are configured to connect to the electronic battery tester. [0006] An electronic battery tester for testing a storage battery includes first and second Kelvin connections configured to couple to the battery. A forcing function applies a time varying signal to the battery through the first and second Kelvin connections. Further, the electrical and assembly is configured to couple across the first and second terminals of the battery and draw a relatively large current. The storage battery is tested as a function of a dynamic parameter measured through the first and second Kelvin connections and as a function of a response of the storage battery to the relatively large current drawn through the resistive load.

[0007] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the Background.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a simplified block diagram showing an electronic battery tester in accordance with one embodiment of the present invention.

[0009] FIG. 2 is a simplified block diagram showing steps in accordance with one aspect of the invention. [0010] FIGS. 3A, 3B, 3C and 3D are perspective, flat plan, side plan and top exploded views of an electrical load assembly for use with, for example, the electronic battery tester discussed above.

[0011] FIG. 4 is a perspective view of an electronic battery tester including an adjustable load in accordance with one example configuration.

[0012] FIG. 5 illustrates an example user interface for use with the electronic battery tester. [0013] FIG. 6 is a cross-sectional view of the electronic battery tester including an adjustable load.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS [0014] Embodiments of the present disclosure are described more fully hereinafter with reference to the accompanying drawings. Elements that are identified using the same or similar reference characters refer to the same or similar elements. Some elements may not be shown in each of the figures in order to simplify the illustrations.

[0015] The various embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. [0016] The present invention includes an electrical load assembly for use with an electronic battery tester used to test a storage battery. The electrical load assembly includes a load wire which provides an electrical load resistance in a housing which at least partially encloses the load wire. An airflow passageway is provided in the housing adjacent the load wire such that air may be passed by the load wire. Electrical terminals are provided for connecting the load wire to the electronic battery tester. In various aspects, also provided is an electronic battery tester which measures a dynamic parameter of a battery such as that described in US Patent No. 6,456,045, issued September 24, 2002. The dynamic parameter is measured in response to a small forcing function applied across the battery. The forcing function includes a time varying component and can be any type of periodic or transient signal with such a component. Typically, the forcing function will have a relatively small amplitude and can be any type of voltage or current signal either drawn from or applied to the battery. The load wire is used to draw a large current from the battery. A battery test is performed on the battery which provides a test result as a function both of the dynamic parameter and a response of the battery of the applied load resistance. The particular response observed or application of the load can vary for various embodiments. In one aspect the dynamic parameter is measured using Kelvin connections across the battery. In some embodiments the resistive load is connected across the battery using the same Kelvin connections. The combination of a test which uses a dynamic parameter as well as a load resistance can provide improved accuracy in determining the condition of the storage battery. The internal resistive load can also apply to alternator and starter testing for testing the charging system and starter motor of an automotive vehicle. A related device is shown in US Publication No. 2018/0113171. However, there is an ongoing need for improved testing techniques.

[0017] FIG. 1 is a simplified block diagram of electronic battery tester 10 in accordance with one aspect of the invention. Tester 10 includes electronic battery test circuit 16 which couples to battery 12 through Kelvin connections 18. Circuitry 16 determines the battery conductance of a battery 12. Circuitry 16 includes forcing function 50, differential amplifier 52, analog-to-digital converter 54 and microprocessor 56. Amplifier 52 is capacitively coupled to battery 12 through capacitance Cl and C2, and has an output connected to an input of analog-to-digital converter 54. Microprocessor 56 is connected to system clock 58, memory 60, and warning indicator 62, an input 66 and provides a data output, such as for a display.

[0018] In operation, forcing function 50 is controlled by microprocessor 56 and provides a current in the direction shown by the arrow in the figure. In one embodiment, this is square wave or a pulse. Typically, source 50 is a small load applied to battery 12. Differential amplifier 52 is connected to terminals 22 and 24 of battery 12 and provides an output related to the voltage difference between these terminals. Amplifier 52 has a high input impedance. Note that circuitry 16 is connected to battery 12 through a four-point connection technique known as a Kelvin connection. Because very little current flows through amplifier 52 which has a large input impedance, the voltage drop through its connections to battery 12 is insignificant. The output of differential amplifier 52 is converted to digital format and provided to microprocessor 56. Microprocessor 56 operates at a frequency determined by system clock 58 according to program instructions stored in memory 60. [0019] Microprocessor 56 determines the dynamic conductance of battery 12 by applying a current pulse with forcing function 50. Forcing function 50 comprises a small load or an active source. The microprocessor determines the change in battery voltage due to the current pulse using amplifier 52 and analog-to-digital converter 54. The amount of current I generated by forcing function 50 is known or can be measured and stored in memory 60. Microprocessor 56 calculates the conductance of battery 12 as follows:

where DI is the change in current flowing through battery 12 due to forcing function 50, and AV is the change in battery voltage due to applied current DI. The relative conductance of battery 12, can be calculated using the equation:

where Gmeasured is the measured battery conductance in accordance with Equation 1 and G_ref_erence is a reference conductance value stored in memory 60 which can be received through input 66. Generally, this reference conductance is determined based upon the type and characteristics of battery 12. Microprocessor 56 can also operate using impedance, admittance, or resistance measurements.

[0020] FIG. 1 also shows a load resistor 70 labeled R_L coupled across terminals 22 and 24 of battery 12 and in series with switch 72. This can be embodied in the electrical load assembly discussed herein. Switch 72 is coupled to and controlled by microprocessor 56 to selectively switch resistive load R_L in series with battery 12. Microprocessor 56 operates to perform the various tests as discussed above to determine the condition of the battery 12. A current sensor 305 is arranged to measure current through resistance R_L 70. In another configuration, sensor 305 can sense voltage drop across resistor 70 to determine current flow.

[0021] FIG. 2 is a simplified block diagram 100 which illustrates steps performed by microprocessor 56 based upon instructions stored in memory 60 in one example embodiment. The test procedure starts at block 102 and control is passed to block 104. A dynamic parameter of battery 12 is measured, using any appropriate technique, such as the technique discussed above. At block 106, load resistance 70 R_L is applied by microprocessor 56 through the actuation of switch 72. Microprocessor 56 observes a response of battery 12. For example, in the embodiment shown in FIG. 1, microprocessor 56 can observe the voltage or voltage change across battery 12 in response to the applied resistance RL using analog to digital converter 54. At block 108, microprocessor 56 provides a test result output, for example on the data output, of the dynamic parameter measured at step 104 and the load resistance 70 and response observed at step 106. The particular order of the steps or tests performed can be changed accordingly. The procedure terminates at block 110.

[0022] The particular test performed using the addition of the load resistance 70 can be any battery test which provides a result which is a function of a dynamic parameter measurement and/or the applied load 70. In one example, the battery test result is a function of the measured dynamic parameter with the resistive load R_L connected to the battery 12. This can be combined with a dynamic parameter measurement with the resistive load disconnected from the battery 12. Other example load measurements which can be combined with the dynamic parameter measurement include monitoring the battery voltage over an adjustable time period while the load 70 is applied. This can be combined with monitoring the voltage during a recovering period after the load 70 is removed. In one embodiment load R_L is a variable load 70 which can be controlled, for example, by microprocessor 56 during the testing process. The response of the battery 12 to the application of the variable load 70 and changing of the variable load 70 can be monitored as well as its response once the load 70 is removed. In a specific example, the relative conductance determined in accordance with Equation 2 can be used as a multiplier against the nominal voltage of the battery, for example 12.7 volts, and again multiplied by a constant. This value can then be compared to the voltage of the battery 12 measured at a particular time during application of the load resistance or after its removal. The various measurements can also be correlated with the state of health and/or the battery life expectancy which can then be provided as an output.

[0023] The voltage when the load 70 is applied can also be compared to a voltage range which can indicate that the battery 12 has a bad cell. This can then be provided as an output or a warning can be indicated using output 62. In a more specific example, a bad cell can be detected if a voltage measured with the load 70 applied at a first time and a voltage measured at a second time are within a range, such as 8.0 volts to 8.8 volts (two bad cells) or 10.1 volts to 10.9 volts (one bad cell), microprocessor 56 can determine that a bad cell exists in battery 12 and provide an appropriate output. Additionally, microprocessor 56 can determine if a battery has an open circuit by using the measured dynamic parameter in conjunction with the change in voltage across battery 12 with and without the resistive load R_L applied. The resistance R_L can also be used to remove a surface charge (a positive voltage polarization) on battery 12. Once the surface charge is removed, microprocessor 56 can compensate the dynamic parameter measurement in determining battery condition based upon the measured voltage after removal of surface charge. [0024] The correlation between the dynamic parameter and measurements taken which are a function of the load resistance R_L to the condition of battery 12 can be determined by repeated laboratory tests to develop trends or equations which describe the relationship. Any appropriate technique can be used including models which model the battery, the use of multiple measurements to develop a model, neural networks, etc. Although the load resistance R_L is shown in FIG. 1 as being coupled to the battery 12 through the Kelvin connections 18, any appropriate electrical coupling technique can be used. This includes the use of fifth or sixth additional electrical contacts to terminals 22 and 24. Additionally, in one embodiment all four of the electrical contacts shown in Kelvin connections 18 are used to couple the resistive load R_L to battery 12. The duration of the application of the resistive load R_L or frequency of the application, can be chosen as appropriate for a desired testing format.

[0025] In one aspect, circuitry 10 provides an alternator tester for testing an alternator of a vehicle. In such an embodiment, the load resistance R_L is used to apply an additional load to the electrical system of the vehicle. The response of the alternator and regulator of the automotive vehicle can be observed and the microprocessor 56 can provide an output indicative of the condition of the alternator and/or regulator. If the load resistance RL is a variable resistor, the voltage across the battery 12, or some other point in the electrical system, can be observed as various resistive loads are placed on the system.

[0026] The dynamic parameter used in the present invention can be obtained in accordance with any appropriate technique.

[0027] In various aspects, the dynamic parameter is measured prior to, during or subsequent to application of the load resistance 70 across terminals of the battery 12. Further, the measured dynamic parameter can be compared with dynamic parameters measured at other periods in time, for example, dynamic parameters obtained prior to, during or subsequent to application of the load resistance can be compared with each other. Voltage measurements can be obtained and a slope of the voltage measurement can be calculated and used in the battery test. In one example, the battery test is a function of a slope of the voltage measured while the load resistance is applied to the battery. The change in voltage slope can be used in the battery test. The voltage slope can be measured subsequent to disconnection of the load resistance from the battery. The battery test can be based upon a change in the voltage measured subsequent to disconnection of the load resistance from the battery. The battery test can be a function of a difference in voltage measured while the load resistance 70 is applied to the battery and a voltage measured after disconnection of the load. In one aspect, the output from the battery test can provide an indication that the battery has become sulfated. The voltage slope measured before, during or after removal of the load resistance can be used in the battery test. The voltage slope, particularly the voltage slope after disconnection of the load from the battery, can be used as an indication of an open circuit. In one embodiment, the load resistance 70 shown in FIG. 1 is located external to the battery tester. For example, the load resistance 70 is placed directly in the cable assembly used for Kelvin connections 18.

[0028] FIGS. 3A, 3B, 3C and 3D are perspective, flat plan, side plan and top exploded views of an electrical load assembly 200for use with, for example, the electronic battery tester 10 discussed above. The assembly 200 shown in FIGS. 3A-D includes a housing 202 having a cover 204 which supports a load wire 208 formed from a coiled nichrome wire. This provides the load resistance 70. The housing 202 provides a spacing area 206 around the wire 208 which provides an airflow passageway therethrough. End terminals 210,212 are provided for electrically connecting the load wire 208 to the electronic battery tester. The terminals 210,212 may also include a thermistors 214,216 for measuring the temperature at the terminal locations. Other types of temperature sensors 214,216 may be employed and/or positioned at other locations. Typically, each temperature sensor 214,216 will require two electrical connections 220,222, however, these connections may be shared with other electrical connections in certain configurations. As illustrated in FIG. 3A, connectors 230,232 are provided for connecting to the load wire 208 as well as to the thermistors 214,216. One or more fans 240 may be positioned adjacent the electrical load assembly to provide a constant and/or controllable airflow through the housing 202. The fan may operate independently or may operate under the control of the electronic battery tester 10.

[0029] The electrical load 70 provided by the load assembly 200 can be used in a number of configurations. A conductance profiling technique can be employed in which a load (for example, 10-20 amps) is drawn while observing the behavior and combining the measurement with a dynamic conductance measurement. The load assembly 200 can be positioned inside or outside of the battery tester 10, for example, near an electrical connection to the tester 10. During operation, the load assembly 200 will generate a substantial amount of heat. However, the air passageway 200, including the optional fan 240, can be used to dissipate this heat. The fan 240 can be any appropriate fan including a box or muffin fan. The load wire 208 can be formed of any appropriate wiring material such as a nichrome wire and the tunnel 206 and the housing 202,204 should be heat resistant. The housing 202,204 may be formed of a high temperature plastic such as ryton, metal, or ABS plastic with a mica paper insulator liner.

[0030] The various components such as the electrical connectors, thermistors, and connections to the load wire, can be partially or completely fabricated on one or more printed circuit board 250. This PCB boards may include screw terminals to mount the thermistors and can be used to support the various components in the housing.

[0031] The temperature sensors 214,216 can be used to measure temperature of the device 200. The temperature sensors 214,216 can be used for diagnostics, for example, to determine if a particular location is getting too hot, or is not heating sufficiently. Additionally, a temperature differential between two locations can also be used for diagnostic purposes such as for determining airflow or to provide feedback for fan control. This also can be used to determine if the passageway 206 has become blocked or if the fan 240 has failed. Although only one fan 240 and passageway 206 are shown, multiple fans 240 and/or multiple air passageways 206 may also be implemented. Thermo insulators 260 can be provided between the load wire 208 and the housing 202. This can comprise, for example mica paper.

[0032] In yet a further configuration, the battery tester 10 can be configured to operate with relatively high accuracy with minimal decision making required by the operator even while connected to a vehicle with the engine running. For example, in many instances, a car owner will bring their vehicle to a service station indicating that they have difficulty starting the vehicle. The owner may be reluctant to shut off their vehicle as a jump start was required, or the owner had great difficulty in getting the engine started. Service stations or automotive parts stores may have limited personnel and only a few minutes for an employee to diagnose a vehicle. In such a situation, there may not be sufficient time, or knowledge, for an operator to enter battery rating or other information.

[0033] The battery tester of FIG. 1 can be configured as a small lightweight, programmable discharger that connects to the battery under test and does not require an external power source. FIG. 4 shows a configuration of battery tester 10 in which a plurality of coils 306 are arranged in a housing 350. A large fan (see fan 240 in FIG. 3A) is arranged in the housing and blows air across the coils 306. The coils 306 operate as load 70 shown in FIG. 1 and the fan is powered with power from the battery under test. For example, such a configuration can dissipate 3,600 Watts and the air exiting the device is only slightly warm. The electrical connections 18 used to couple to the battery, or couple the load 70 to the battery, are preferably short and able to conduct high current, such as AWG4 wiring. Additionally, the circuitry in battery tester 10 should be configured to operate regardless of the polarity of the connection to the battery 12. In the example configuration, the eight individual 35 amp loads 306 are provided and can be individually controlled. Additionally, an individual 10 amp load can be provided to match current battery profiling data.

[0034] In such a configuration and referring to FIG. 1, battery tester 10 can include an amp clamp or other current sensor 304 configured to measure the current flowing into or out of the battery 12 from an electrical system 302 of an automotive vehicle 300. Another amp clamp/current sensor 305 can be used to measure the current flowing through resistive load 70. [0035] In order to test the battery 12, it is desirable to determine the current flowing into the battery tester 10 due to the battery due to testing and eliminate any current flowing into (or out of) the battery 12 due to the electrical system 302 of the vehicle including the alternator of the vehicle. For example, at idle speed, a typical vehicle alternator can provide on the order of 50 amps of charging current. By increasing the value of R_L of load 70 until the current sensed by current sensor 304 stops changing, it can be determined that the maximum amount of current that the alternator is capable of providing has been reached. At this point, an additional state or time varying load (forcing function) can be applied to the battery 12 in order to determine conductance as discussed herein or perform other tests. This can be using in forcing function 50 or load 70.

[0036] Under heavy load, it is also possible to determine whether battery 12 has a shorted cell. For example, in a battery with a shorted cell, the battery voltage will drop significantly under load.

[0037] Using the adjustable load provided by load 70, it is also possible to characterize batteries in order to infer or predict the battery state of charge as well as reserve capacity. For example, the voltage and/or current can be monitored as the applied load is increased or decreased and correlated to an approximate value of battery state of charge of reserve capacity. This correlation may also include measurement of a dynamic parameter using an applied forcing function 50 and/or time during adjustment of resistive load 70.

[0038] The load 70 can be used to at least partially discharge the battery. When the load is removed, the charging current provided by the alternator can be measured using sensor 304 and the charge acceptance rate of the battery 12 can be monitored. The charge acceptance rate of the battery 12 can be used as an indication as the condition of the battery 12.

[0039] Additionally, by monitoring the current flowing into the battery 12 using sensor 304, it can be determined whether the alternator is functioning at full capacity.

[0040] As the microprocessor 56 requires power for operation, if the voltage provided by battery 12 drops significantly when the load 70 is applied, it is possible that the microprocessor 56 will power down and restart. In order to avoid such an occurrence, a large capacitor can be included in power supply circuitry 309 which allows the microprocessor 56 to “ride out” the temporary voltage drop while the load 70 is removed.

[0041] In order to increase the simplicity of operation, the output 62 can be a series of lights showing the progress of the testing. During initial connection, a first light may come on and stay on. While the device is increasing the load 70 to address the current provided by the alternator, a second light may come on, or the first light may begin blinking and go solid when this step is complete. An additional code or additional lights may be used to provide additional information. Finally, at the test completion a red or green light can provide a pass/fail indication. Additional information can be provided to indicate health of the alternator, or other test information. If desired, the data output from microprocessor can be provided wirelessly to a point of sale system or other data collection device using I/O 67. This can also be used to provide specific information about the vehicle or battery to the tester which can be downloaded if available.

[0042] In order to provide a simple method of supplying additional information about the battery 12, the input 66 can be used. For example, the input 66 could simply be a three position switch which an operator sets to indicate whether the vehicle has an engine which is 4, 6 or 8 cylinders. Such information can be generally associated with the appropriate size of the battery 12 as it relates to the engine size.

[0043] The device set forth herein can determine the condition of a battery using load testing and/or optional conductance based testing in a very short period of time and without requiring that the battery 12 be disconnected from the vehicle. The device can be powered from the battery 12 itself and does not need an external power source. The memory 60 can include a non-volatile memory such that the device 10 does not require any internal batteries. Further, there is no requirement that the vehicle be shut off for testing. This is particularly advantageous in situations where an operator may be concerned that the battery does not have enough reserve capacity to start the vehicle. A very simple user interface can be provided using input 66 and output 62 such that no training is required. The output 62 can be any type of user output including a display, audio output, series of visual components, etc. The connectors 18 can be configured such that they may be connected to either the plus or minus polarity of the battery 12. The input 66 and data I/O 67 can include a wireless component such as Bluetooth, WiFi, etc. allowing data to be uploaded or downloaded as desired.

[0044] In some situations high accurate testing is not required. In such situations, a technician is not required to enter in any specific information regarding the particular battery 12 under test. Instead the device operates using generally acceptable parameters for vehicles. In one configuration, the load 70 can be of sufficient size such that all of the current generated by an alternator of the vehicle used to charge the battery is shunted away from the battery and through the load 70. In such a configuration, the load 70 can then be further increased or decreased such that the battery 12 itself is discharged or charged. During this discharge, additional current, voltage and dynamic parameter measurements can be obtained in order to test the battery 12. [0045] In order to perform a conventional conductance test on an automotive battery, the battery is typically tested in isolation, without any significant external parallel paths which will effectively decrease or alter the observed resistance of the battery under test. This is an issue behind “system noise” that makes accurate testing difficult in certain scenarios. An alternator in parallel on a running engine presents approximately an ideal voltage source. The defining characteristic of an ideal voltage source is that it provides the same voltage, regardless of the current extracted. This effectively presents an impedance of zero across the battery, or an “infinite” conductance which renders a conventional conductance measurement impossible. In contrast, an “ideal current source” provides a constant current regardless of the impressed voltage. This presents as an infinite impedance, and when connected in parallel, is effectively removed from the circuit under test. If the running alternator could be transitioned from ideal voltage source, to ideal current source, it could be removed from the battery virtually.

[0046] Any given automotive alternator has a maximum operating current. This current is achieved when the alternator rotates above a certain minimum RPM, and the alternator is full- fielded (demand is set to 100%). Typical automotive alternator maximums are 60-140 amperes. When the engine is at idle, the maximum output of the alternator remains the same (depending on alternator type) or is substantially less, typically in the range of 40-60 amperes.

[0047] Kirchhoff s current law states that the algebraic sum of a current flowing through a junction is zero. Therefore, if we can provide an equal and opposite current to that supplied by the alternator, the battery is effectively sitting open circuit.

[0048] Using one example configuration having the following parameters:

• Alternator Output -91.3 amps

• Second Load Box Pulse Current = 84 amps

• Delta Battery Voltage = 0.48 VDC

• Conductance = 84 / 0.48 =175 mho

• CCA(100)=(100/12)* 500/160=26 CCA o (Estimated overcurrent past null)

• CCA = (175*500/160)-26 = 521 CCA o 15% high

[0049] In another example test:

• Alternator Output -14.2 amps

• Second Load Box Pulse Current = 83 amps • Delta Battery Voltage = 0.40 VDC

• Conductance = 83 / 0.40 =208 mhos

• CCA(100)=(100/12)* 500/160=26 CCA

•(Estimated overcurrent past null)

CCA = (208*500/160)-26 = 624 CCA •11% high

[0050] In one specific example, the invention can be used for determining the approximate CCA (Cold Cranking Amps) of the battery 12 using the following Equations:

^■ Open circuit voltage (can’t be measured directly since alternator is running) o Vbat= (V1*I2-V2*I1)/(I2-I1)

^■ CCA o Rbat= (Vbat-V2)/I2 o CCAbat= (1/Rbat)* 500/160

^■ Definitions: o Preload

^■ load current I_I > alternator maximum current

^■ Pulse o Approximately 100 amp step load above preload current

^■ VI = preload voltage, Kelvin connection

^■ V2 = pulse voltage, Kelvin connection

^■ II = Imdt-ABS(Ialt) during preload

^■ 12 = Imdt-ABS(Ialt) during pulse

^■ Imdt= internal current measured by sensor 305

^■ Ialt= external current measured by amp clamp sensor 304.

[0051] As illustrated in FIG. 4, multiple loads 306 can be included and selectively switched in using switch 72. Multiple switches 72 can be provided an operated by the microprocessor 56 and arranged for connecting the loads 306, in series and/or parallel as desired to achieve the desired resistive load RL 70. A large capacitor in power supply circuitry 309 can also be provided to smooth the power used by the device 10 during operation and more power if desired. [0052] In one configuration, it is possible to eliminate the need for an external current sensor or amp clamp to measure current flowing from the vehicle in the battery. This can be achieved by incrementally increasing the current through the load applied to the battery and measuring the conductance at each point. The conductance measurement can be a dynamic parameter based measurement or can be a static based measurement by increasing the applied load and measuring the resultant voltage change. Once a stable conductance value is observed, it can be determined that the alternator is supplying a maximum amount of current and any resultant change in voltage is the result of the battery alone. Once the load current from the alternator filling into the battery has been eliminated, a battery test can be conducted as described above including conductance, load, or other tests. In another example configuration, the current drawn through the load applied to the system is incrementally increased as discussed above. The voltage across the battery is measured after each increase. Once a substantial change in the voltage measured across the battery is observed, it can be inferred that the alternator has reached a maximum output and any further voltage changes will be due to the battery alone.

[0053] FIG. 5 shows an example user interface 400 which can be formed using components 62 and 66 of FIG. 1. In the example user interface, an operator can select different testing standards based upon the number of cylinders of the vehicle by pressing the appropriate button 402 illustrated in FIG. 5. This information can be used by the tester to determine the appropriate battery rating for the vehicle based upon engine size. Visual outputs are provided to indicate that the device is powered up and show testing progress. Finally, a test result is provided which illustrates that the battery is either good, should be replaced or should be recharged. Preferably the user interface 400 is waterproof. Further, a power indicator 404 can be arranged to only turn on when the Kelvin connectors 18 are properly connected to the battery terminals 22, 24. In one specific configuration, once the amp clamp 304 is properly connected the 4-6-8 CYL buttons 402 can illuminate sequentially indicating that one of them needs to be pressed in order to initiate the test, at which time that particular button 402 will remain illuminated.

[0054] Various progress bars 406 indicated in the test progress portion of the user interface 400 can be used to display different steps in the testing process. This can include, for example, current null, alternator test, conductance testing, current pulsing, ramp testing, load cool down, etc. As mentioned previously, once the test is complete one of the three test result icons 408 will illuminate.

[0055] FIG. 6 is a cross-sectional view of the electronic battery tester 10 and illustrates the arrangement of fan 250 which is a rotary fan positioned within a cylindrical housing 350. As discussed above, coils 306 provide the load 70 and are arranged within the housing 350. Switches 72 and arranged to selectively connect the coils 306 to the battery 12 such that a desired load R_L is achieved as desired. The coils may be arranged in parallel, series and/or series parallel as desired to achieve particular resistance values. FIG. 6 also illustrates the display 400 as being carried in a handle 450 of the tester 10. This allows the display to be easily visible during operation. Various cable connections are also provided for the current sensor 304 and the Kelvin connections 18.

[0056] 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. Although specific embodiments describe increasing the load or current, it should be understood that the change in applied load or current drawn can be either increasing or decreasing

Claims

WHAT IS CLAIMED IS:

1. An apparatus for testing a storage battery in an automotive vehicle comprising: a controllable electrical load configured to electrically couple to the storage battery of the vehicle; a current sensor configured to electrically connect to a terminal of the storage battery and configured to measure flow of current; a controller arranged to apply an electrical load to the storage battery using the controllable load and adjust the electrical load while monitoring the electrical current sensed by the current sensor to determine a charge current applied to the storage battery by an alternator of the vehicle and further configured to perform a test on the storage battery.

2. The apparatus of claim 1 wherein the current sensor includes a first current sensor arranged to measure current delivered from an electrical system of the vehicle.

3. The apparatus of claim 1 wherein the current sensor includes a first current sensor arranged to measure current flowing through the controllable electrical load.

4. The apparatus of claim 1 wherein the controller adjusts the controllable electrical load such as that substantially all of the charge current flows through the controllable electrical load.

5. The apparatus of claim 4 wherein the test is performed on the storage battery while substantially all of the charge current flows through the controllable electrical load.

6. The apparatus of claim 5 wherein the storage battery test comprises measuring a parameter of the storage battery while changing a resistance of the controllable electrical load.

7. The apparatus of claim 6 wherein the parameter comprises a dynamic parameter.

8. The apparatus of claim 6 wherein the parameter comprises a voltage measured across terminals of the storage battery.

9. The apparatus of claim 6 wherein the parameter comprises determining a current flowing through the storage battery.

10. The apparatus of claim 1 wherein the test includes identifying a shorted cell in the storage battery.

11. The apparatus of claim 1 wherein the test comprises a charge acceptance rate of the storage battery.

12. The apparatus of claim 1 wherein the test comprises determining a state of charge of the storage battery.

13. The apparatus of claim 1 wherein the test comprises determining a storage battery capacity.

14. The apparatus of claim 1 wherein the test comprises a load test.

15. The apparatus of claim 1 wherein the test is performed on the storage battery while an engine of the vehicle is running.

16. The apparatus of claim 1 wherein the controller is powered by the storage battery.

17. The apparatus of claim 16 including a capacitor to store power from the storage battery.

18. The apparatus of claim 1 including an input configured to receive information regarding an engine of the vehicle.

19. The apparatus of claim 18 wherein the information comprises a number of cylinders of the engine of the vehicle.

20. The apparatus of claim 1 wherein the controllable electrical load couples to the storage battery using Kelvin connections.

21. The apparatus of claim 1 wherein the controllable electrical load is used to apply a forcing function to the storage battery.

22. The apparatus of claim 1 including providing a pass/fail output based upon the test performed on the storage battery.

23. The apparatus of claim 1 including an output configured to indicate progress of the test performed on the storage battery.

24. The apparatus of claim 1 including a cylindrical housing arranged to house the controllable electrical load.

25. The apparatus of claim 24 wherein the housing includes a rotary fan arranged to pass air across the controllable electrical load.

26. The apparatus of claim 1 wherein the controllable electrical load comprises a plurality of wire coils.

27. The apparatus of claim 1 including wireless Input/Output circuitry.

28. The apparatus of claim 1 wherein the controller controls the controllable electrical load to cause a current pulse to flow through the storage battery.

29. The apparatus of claim 1 wherein the controller determines the charge current applied to the storage battery by changing the controllable electrical load and observing a change in a measured parameter of the battery.

30. The apparatus of claim 29 wherein the measured parameter comprises conductance.

31. The apparatus of claim 29 wherein the measured parameter comprises voltage.

32. A method for testing a storage battery in an automotive vehicle, comprising: connecting a controllable electrical load to the storage battery; connecting a current sensor to a connection to a terminal of the storage battery; applying an electrical load to the storage battery using the controllable electrical load; adjusting the electrical load while monitoring an output from the current sensor to determine a charge current applied to the storage battery by an alternator of the vehicle; and performing a test on the storage battery.

33. The method of claim 32 wherein the current sensor includes a first current sensor arranged to measure current delivered from an electrical system of the vehicle.

34. The method of claim 33 wherein the current sensor includes a second current sensor arranged to measure current flowing through the controllable electrical load.

35. The method of claim 32 including adjusting the controllable electrical load such as that substantially all of the charge current flows through the controllable electrical load.

36. The method of claim 35 wherein the test is performed on the storage battery while substantially all of the charge current flows through the controllable electrical load.

37. The method of claim 32 including receiving an input comprising information regarding an engine of the vehicle.

38. The method of claim 37 wherein the information comprises a number of cylinders of the engine of the vehicle.

39. The method of claim 32 wherein the controllable electrical load is used to apply a forcing function to the storage battery.

40. An apparatus for testing a storage battery in an automotive vehicle comprising: a controllable electrical load configured to electrically couple to the storage battery of the vehicle; a current sensor electrically connected to the controllable electrical load and configured to measure current flow through the controllable electrical load; a voltage sensor configured to electrically connect to terminals of the storage battery and measure a voltage across the storage battery; and a controller arranged to adjust the controllable electrical load while monitoring the sensed current and sensed voltage and determine a charge current applied to the storage battery by an alternator of the vehicle based upon the measured voltage and the measured current.

41. The apparatus of claim 40 wherein the charge current is determined based upon a dynamic parameter measurement.

42. The apparatus of claim 40 wherein the charge current is determined based upon a measured conductance.