Abstract:
A battery tester engages a power tool battery and includes a housing having a cavity for receiving a stem of the power tool battery. The battery tester has a plurality of electrically conductive contacts disposed in the cavity and is configured to engage corresponding battery electrodes on the stem. A processor is mounted within the housing and communicates with the battery through the electrically conductive contacts. The processor measures a voltage level of the battery, and a loading circuit electrically loads the battery during measuring. One or more indicators are controlled by the processor. The processor activates the loading circuit for a predetermined period of time to measure a voltage level of the battery while under load, and then activates the indicators to provide a visual indication of remaining battery life. The battery tester is a stand-alone device where housing does not have a motor or a battery charger.

Description:
BACKGROUND 
       [0001]    This disclosure relates to a device for testing batteries. In particular, this disclosure relates to a battery tester for testing power tool batteries. 
         [0002]    Cordless power tools generally use batteries that are rated at 9.6 volts, 14.4 volts, 18 volts, or 24 volts. Often, a user may have several batteries that can fit or be used with the same power tool. When the user has several batteries in the field, it is helpful to be able to determine which of the batteries are charged, and to what degree. 
         [0003]    Battery testers exist in various forms. Analog and/or digital voltmeters (DVMs) typically have two long wires or leads with metal probes at each end. The user touches the probes to an electrical source, such as a battery or battery terminals, to measure the battery voltage. Based on the user&#39;s analysis of the measured battery voltage relative to the maximum expected battery voltage, the user may infer the amount of remaining battery life. 
         [0004]    However, this process is physically cumbersome because the user must maneuver the probes to make electrical contact, while at the same time adjusting the knobs on the meter. This is certainly not a one-handed operation. In some circumstances, two people may be needed to perform the task. While this may provide an indication of the actual voltage level, some level of technical sophistication is required to determine the meaning of the measured voltage. For example, if a fully charged battery has a voltage of 14.2 volts, what does a measured voltage level of 10 volts mean? The user must be able to correlate the measured voltage relative to the maximum expected voltage and arrive at a value representing the remaining battery life. 
         [0005]    Some battery testers are in the form of a box with a plurality of slots or cradles. The slots are configured to receive small batteries, such as D-cell batteries, C-cell batteries, AA-cell batteries, and AAA-cell batteries. The battery is placed in the slot between two metal contacts, and a meter or display provides an indication whether the battery is good, bad, or somewhere in between. However, such testing boxes are relatively large and cumbersome, and are not adapted to testing power tool batteries. It is often difficult to remove the battery from the slot once inserted. 
         [0006]    Accordingly, a battery tester for a power tool battery is needed that provides the user with an indication of remaining battery life, and which can easily and conveniently engage and disengage the power tool battery. 
       SUMMARY 
       [0007]    According to one specific embodiment, a battery tester engages a power tool battery, and includes a housing having a cavity for receiving a stem of the power tool battery and a plurality of electrically conductive contacts disposed in the cavity configured to engage corresponding battery electrodes on the stem. A processor is mounted within the housing and communicates with the battery through the electrically conductive contacts. The processor measures a voltage level of the battery, and a loading circuit electrically loads the battery during measuring. One or more indicators disposed on or in the housing are controlled by the processor. The processor activates the loading circuit for a predetermined period of time to measure a voltage level of the battery while under load, and then activates the indicators to provide a visual indication of remaining battery life. The battery tester is a stand-alone device where housing does not have a motor or a battery charger. 
         [0008]    According to another specific embodiment, a stand-alone battery tester engages a slide-type power tool battery. The battery tester includes a housing having a connector configured to slidingly receive battery terminals of the slide-type power tool battery, and a plurality of electrically conductive contacts disposed in the connector configured to biasingly engage the corresponding battery terminals. A processor is mounted within the housing and communicates with the battery through the electrically conductive contacts. The processor measures a voltage level of the battery, and a loading circuit electrically loads the battery during measuring. One or more indicators disposed on or in the housing are controlled by the processor. The processor activates the loading circuit for a predetermined period of time to measure a voltage level of the battery while under load, and then activates the indicators to provide a visual indication of remaining battery life. The battery tester is a stand-alone device where housing does not have a motor or a battery charger. 
         [0009]    According to another specific embodiment, the battery tester further includes a voltage divider configured to provide a scaled voltage signal to an input of the processor, where the scaled voltage signal corresponds to remaining battery life. The processor activates the loading circuit for a first predetermined period of time to measure a voltage level of the battery while under load, and then activates the indicators to provide a visual indication of remaining battery life. The indicators are then deactivated after a second predetermined period of time. The battery tester is a stand-alone device where housing does not have a motor or a battery charger. 
         [0010]    According to another specific embodiment, a battery testing circuit includes a processor having an input configured to receive a battery voltage level, and a regulated power supply configured to provide regulated power to the processor. A loading switch is operatively coupled to the processor, and a load is coupled between the battery and the switch. The processor activates the loading switch for a predetermined period of time to operatively couple the load between the battery and ground so as to load the battery. The processor measures a voltage level of the battery while under load and activates indicators disposed on the housing to provide a visual indication of remaining battery life. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a perspective view of a battery tester according to one specific embodiment; 
           [0012]      FIG. 2  is a perspective view of a battery tester and a power tool battery according to one specific embodiment; 
           [0013]      FIG. 3  is a partial sectional view of the battery tester shown engaging a stem of the power tool battery according to one specific embodiment; 
           [0014]      FIG. 4  is an enlarged partial sectional view of the battery tester of  FIG. 3 ; 
           [0015]      FIG. 5A  is a perspective view of a battery tester with a lanyard; 
           [0016]      FIG. 5B  is a perspective view of the battery tester of  FIG. 5A  in operation; 
           [0017]      FIG. 6A  is a perspective view of a slide-type battery; 
           [0018]      FIG. 6B  is a perspective view of one embodiment of a battery tester configured to engage a slide-type battery; 
           [0019]      FIG. 7  is a schematic diagram of a battery tester circuit according to one specific embodiment; and 
           [0020]      FIG. 8  is a schematic diagram of a battery tester circuit according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0021]    The invention is described with reference to the drawings in which like elements are referred to by like numerals. The relationship and function of the various elements of this invention are better understood by the following description. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. The embodiments described below are by way of example only, and the invention is not limited to the embodiments illustrated in the drawings. 
         [0022]      FIG. 1  is a perspective view of a battery tester  100 . The battery tester  100  includes a housing  106  having a contoured grip portion  112  for user-convenience and ergonomic considerations. The housing  106  may be formed of plastic or other suitable material. A plurality of light-emitting diodes (LEDs)  116  may be provided on or in a surface portion  120  of the battery tester housing  106 . The LEDs  116  may be placed in any convenient position on the battery tester  100 , such as on the top surface  120  or a side surface  130 . The LEDs  116  may be recessed as shown in the illustrated embodiment. The LEDs  116  may also be flush with the surface  120  of the housing  106 , or they may protrude relative to a surface of the housing. The LEDs  116  may indicate the remaining charge of the battery. 
         [0023]    In one specific embodiment, the housing  106  may include four separate LEDs  116 , such as, for example, a green LED  136 , a blue LED  138 , a yellow LED  140 , and a red LED  142 . Any suitable number and colors of LEDs  116  may be used depending on the application. The LEDs  116  may provide the user with a visual indication of the remaining battery charge depending on which of the LEDs or combination of LEDs is illuminated. Other suitable visual displays may be included, such as an LCD display that displays a bar chart, alphanumeric characters, graphic characters, or other indicia of battery life. In some embodiments, an audio indicator may provide an audio indication of the remaining battery life. For example, an audio transducer, such as a speaker, piezoelectric transducer, or other transducer, may emit a series of audio “beeps” or tones corresponding to the measured battery life. Various tones may correspond to the battery life level. 
         [0024]      FIG. 2  shows the battery tester  100  in operation in a position engaging a stem  206  of the power tool battery  212 , while  FIG. 3  shows the battery tester  100  in partial sectional view engaging the battery stem  206 . The power tool battery  212  may be a commercially available power tool battery, such as a nickel-cadmium or a lithium-ion power tool battery. The power tool battery  212  includes a housing  220  having a base  226 , and the stem  206  projecting from the base. The housing  220  may be formed of plastic or other suitable material. The base  226  may include two laterally opposed spring-loaded side clips  230  configured to engage corresponding tabs in the power tool (not shown) to which it attaches so as to lock the battery  212  to the power tool. The stem  206  may include two electrodes partially recessed relative to an outside periphery of the stem. The two electrodes may provide positive and negative battery contact. A third stem electrode, which may also be partially recessed, may provide battery identification (nickel-cadmium v. lithium-ion). 
         [0025]      FIG. 3  shows a partial sectional view of the battery tester  100  shown engaging the stem  206  of the power tool battery  212  according to one specific embodiment. The battery tester  100  may be releasably connected to a loop  304 , which may in turn, be connected to a ring  306 , a key chain or fob, or carabineer-type connector to permit the battery tester to be easily and conveniently affixed to a support or carrier, such as a belt loop, handle of a carrying case, or other fixed or temporary structure. The loop  304  may engage a circular spindle  310  or boss formed in the housing  106 , and may swivel or rotate around the spindle. 
         [0026]    The housing  106  may be formed with an interior cavity  320  that may have a contour that generally corresponds to the outside contour of the battery stem  206 . The cavity may be configured to receive the battery stem  206 , as shown in  FIG. 3 . An internal portion or structure  326  within the battery tester housing  106  is configured to support a circuit board  332 , such as a printed circuit board. The circuit board  332  may support and interconnect various electrical components (“the circuit”) to facilitate battery testing, as described below. An electrode clip holder  340  may be formed of plastic or other non-conducting material, and may be mounted in an upper portion of the battery tester  100 , or may be integrally formed with the housing  106 . The electrode clip holder  340  may include a plurality of flexible electrode clips or contacts  346  configured to engage the corresponding stem electrodes. 
         [0027]    Once the electrode clips  346  engage the battery electrodes, the circuit is energized and the battery tester operation begins. No mechanical switch or micro-switch is used to activate the circuitry or trigger measurement of remaining battery life. Such mechanical switches may be prone to failure. Once the battery tester  100  engages the battery  212 , the battery is electrically “loaded” for a predetermined period of time of about one to about five seconds (described below). During that time, the battery condition (voltage level) is measured. After the voltage level has been measured, and the LEDs  116  are illuminated to provide the user with an indication of battery life. 
         [0028]    In operation, the battery tester  100  is placed over the battery stem  206 . The battery tester  100  does not engage the side clips  230  of the battery housing  106 . Rather, a gentle frictional fit permits the battery tester  106  to engage the battery stem  206  and make positive electrical contact with the stem electrodes. The amount of friction is sufficient to maintain electrical continuity, while permitting single-handed operation. Accordingly, the battery tester  100  may be placed over the battery stem  206  and removed from the stem with a single hand. For example, if the battery  212  is resting on a fixed surface with the battery tester  100  engaged, the battery tester may be removed from the battery stem  206  without “lifting” the battery from the fixed surface. In other words, the amount frictional force between the battery tester  100  (or electrode clips) and the battery stem  206  is less than the weight of the power tool battery  212 . 
         [0029]      FIG. 4  shows the partial sectional view of the battery tester  106  in greater detail. In one specific embodiment, the electrode clip holder  340  may include the three electrode clips or contacts  346 , where each electrode clip may be separated from the adjacent electrode clip by about ninety degrees. In some embodiments, only two electrode clips may be provided. The electrode clips  346  may be formed of spring steel or other metal capable of flexing and maintaining its shape under deformation. 
         [0030]    Each electrode clip  340  may be bent in the form of a “V” or may be curved so as to be able to be displaced by a distal portion of the battery stem  206  as the battery tester  106  receives the battery stem. The electrode clips or contacts  346  may have any suitable shape or geometric configuration. The stiffness of the metal and the geometric arrangement of the electrode clips  346  may determine the amount of friction between the electrode clips  340  and the battery stem  206 , and hence the amount of force required to remove the battery tester  106  from the battery stem. As explained above, a frictional force that permits single-handed operation is preferred. 
         [0031]      FIGS. 5A and 5B  show an alternate embodiment of the battery tester with a lanyard. The battery tester form is not limited to a generally rectangular shape shown in  FIG. 1 , and any suitable shape may be adopted.  FIG. 5A  is a perspective view of the battery tester  100 , while  FIG. 5B  shows the battery tester engaging the stem  206  of the power tool battery  212 . The housing  106  of the battery tester  100  may have a relatively flat or “pancake” appearance. The thickness dimension of the housing  106  is sufficient to provide a cavity capable of receiving the stem of the power tool battery  212 . This configuration may be convenient for construction workers, and may permit the worker to carry the battery tester about a job site, where the battery tester may be quickly and easily attached to a tool belt via a clip or lanyard, or hung on a peg or hook. The circuitry of the battery tester of  FIG. 5A  may be similar or identical to the circuitry described in reference to  FIGS. 1-4  and  7 - 8 . 
         [0032]    The battery tester is not limited to engaging stem-type batteries, and may also engage a “slide-type” power tool battery  602 .  FIG. 6  shows a specific embodiment of the battery tester engaging a slide-type battery  602 . The slide-type power tool battery  602  includes a housing and a plurality of battery terminals  610  partially covered by a protective shell  616 . The battery tester includes a connector  620  configured to slidingly receive and mate with the battery terminals  610 . The circuitry of the battery tester of  FIG. 6A  may be similar or identical to the circuitry described in reference to  FIGS. 1-4  and  7 - 8 . 
         [0033]      FIG. 7  is a schematic diagram of a specific embodiment of the battery tester circuitry. The circuit may include a transistor  702  coupled between a positive battery terminal (B+) and a 5 volt regulator  706 . A voltage divider  710 , which includes a first resistor  720  and a second resistor  722 , is coupled between the positive battery terminal (B+) and the negative or ground battery terminal (B−). The 5 volt regulator  706  may supply power to a processor chip  730 , which may be a mixed-signal array processor chip. The mixed-signal array processor chip  730  may be, for example, Model No. CY8C27143, which is commercially available from Cypress Semiconductor Corp. However, any suitable processor may be used, such as a single-chip processor, multi-chip components, and the like. Such devices may include memory, a processing unit, a configurable analog-to-digital converter, a configurable digital-to-analog converter, and a port controller. The processor is not limited to a chip or integrated circuit. Circuitry for determining comparative voltage levels and/or for determining the remaining battery may be formed from discrete components, such as resistors, capacitors, diodes, logic gates (AND, OR, XOR etc.), transistors, or other any suitable components. Such components may be used in place of an integrated processor chip and are interchangeable therewith. 
         [0034]    A Zener diode  732  turns off the transistor  702  if the battery voltage falls below about 9 volts, which is the Zener threshold voltage. When the transistor  702  is turned off, power to the 5 volt regulator  706  and power to all portions of the circuit is turned off. Accordingly, in the illustrated embodiment, the battery tester circuit operates when the battery voltage is above the Zener threshold voltage of about 9 volts. However, any suitable Zener diode may be used to vary the Zener threshold voltage depending upon the application and the specific battery to be tested. 
         [0035]    The voltage divider  710  divides the battery voltage by a factor of about twelve (1K/12K), and provides the scaled voltage to an input port of the processor chip  730 . Any suitable scaling factor may be used depending on the resolution of the processor chip circuitry. Depending upon the input voltage range of the processor chip  730 , different scaling factors may be used. In some applications, a divider may not be included, for example, if the processor chip input port can accept the maximum battery voltage level. 
         [0036]    In one specific embodiment, the processor chip  730  may drive four separate light-emitting diodes  734  (LEDs), for example, a green LED  740 , a blue LED  742 , a yellow LED  744 , and red LED  746 . Any suitable number and colors of LEDs may be used depending on the application. The LEDs  734  may provide the user with a visual indication of the remaining battery charge or remaining battery life. The processor chip  730  may determine the percentage of battery charge based on the scaled voltage level at the input port. For example, the green LED  740  may indicate about an 80% charge or greater, the blue LED  742  may indicate about a 60% charge, the yellow LED  744  may indicate about a 40% charge, and the red LED  746  may indicate about a 20% charge or less. The percentage ranges may vary in other embodiments. In other embodiments, the LEDs may also be arranged in a “bar chart” configuration to indicate the level of charge. 
         [0037]    In some embodiments, the testing circuitry and the LED indicators  734  may be built into a power tool battery. In further embodiments, a single multi-color LED may be provided that indicates the battery charge depending on the illumination color. The multi-color LED may, for example, be configured to provide three or four different colors, where each color corresponds to a specific battery charge range. 
         [0038]    Battery power may be supplied to the circuit when the battery tester engages the battery stem electrodes of the battery, such as a power tool battery. When power is provided via the battery electrodes (B+ and B−), at a voltage greater than the Zener threshold, the transistor  702  turns on, and the voltage regulator  706  supplies regulated power to the processor chip  730 . To place the battery under load, the processor chip  730  may couple a load resistor  752  across the battery terminals (B+ and B−). The processor chip  730  may activate a load coupling transistor  754  by outputting a signal on an output port  756  of the processor chip  730 , which effectively places the load resistor  752  between the positive battery terminal (B+) and ground (B−). 
         [0039]    Through a read port or input port  760 , the processor chip  730  may “read” the input voltage while the battery is under load, for example for between about one and five seconds. After a period of about one to five seconds, the processor chip  730  may turn off the load coupling transistor  754  and unload the battery. Based on the input voltage read by the processor chip  730 , and based on the scaling factor of the voltage divider  710 , the processor chip may determine the actual voltage of the battery. The measured battery voltage may be compared to a “curve” or “chart” residing in the memory of the processor chip  730  to determine the remaining battery life. Based on the measured voltage and results of the curve comparison, the processor chip illuminates the appropriate LED or series of LEDs to show the level of charge or remaining life of the battery (for that particular charge). After a predetermined period of time, for example, ten seconds, the processor chip turns off the LEDs. This may conserve battery power should the battery tester inadvertently remain engaged with the power tool battery. 
         [0040]      FIG. 8  is an alternate embodiment of the battery tester circuit. The circuit of  FIG. 8  may be similar to the circuit of  FIG. 7  and may have components in common, where like reference numbers may be used to denote like structures or components. In  FIG. 8 , the voltage divider  710  may be coupled directly across the positive battery terminal (B+) and the negative (B−) or ground battery terminal. Note that in this specific embodiment, the circuit receives power as long as it is coupled to the battery stem. 
         [0041]    A first filter capacitor  810  may smooth the input voltage provided to the voltage regulator  706 , and a second filter capacitor  812  may smooth the output voltage provided by the voltage regulator. A battery ID resistor  816  may be coupled to an input of the processor chip  730  and to a T-pad terminal  820 . The T-pad terminal  820  contacts a third stem electrode of the battery when the battery tester engages the battery. The T-pad terminal  820  permits identification of the battery type, that is, whether the battery is a nickel-cadmium battery or a lithium-ion battery. Because the T-pad terminal  820  is coupled to an ID-input  830  of the processor chip  730 , the processor chip “knows” the type of battery that is being measured, and illuminates the appropriate LEDs based on the voltage-to-lifetime curves of the particular type of battery. 
         [0042]    The battery may be placed under load by the parallel combination of load resistors  840  to provide a load with higher power dissipation. In some embodiments, the processor chip  730  may load the battery by turning the loading transistor  754  on and off at a predetermined duty cycle, for a predetermined period of time, for example, one to five seconds. Turning the loading transistor  754  on and off also causes the red LED  746  to turn on and off or blink, which may provide the user with an indication that the battery tester is performing its measurements. At the end of the battery loading period, the processor chip  730  may sample the scaled voltage generated by the voltage divider  710 . The battery voltage may be scaled by the voltage divider  710  by any suitable scaling factor based on the input voltage range of the processor chip  730 . 
         [0043]    Note that while the battery tester of  FIG. 8  may be configured to test the voltage of a specific battery, for example, a 18 volt battery, the value of the components may be adjusted to test a different voltage battery, for example, a 14.4 volt battery. In an alternate embodiment, the battery tester may include a switch or other selector to permit the user to choose the specific type of battery to measure, such as a 9.6 volt battery, a 14.4 volt battery, an 18 volt battery, a 24 volt battery, or any power tool battery. 
         [0044]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only exemplary embodiments have been shown and described and do not limit the scope of the invention in any manner. The illustrative embodiments are not exclusive of each other or of other embodiments not recited herein. Accordingly, the invention also provides embodiments that comprise combinations of one or more of the illustrative embodiments described above. Modifications and variations of the invention as herein set forth can be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated by the appended claims.