Power source for burst operation

A system, an electrical combination and a method for powering a load device. The combination may include a burst circuit configured to provide power to the load device to perform a burst operation, the burst circuit including a supercapacitor, a first switch between a power source and the supercapacitor and operable to control whether power is provided from the power source to charge the supercapacitor, and a second switch between the supercapacitor and the load device and operable to control whether power is provided from the supercapacitor to the load device; and an electronic processor configured to control the first switch and the second switch based at least in part on a voltage of the supercapacitor.

FIELD OF THE INVENTION

The present invention relates to power sources and, more specifically, to power sources that provide burst operation.

SUMMARY

Fastener drivers are used to drive fasteners (e.g., nails, staples, tacks, etc.) into a work piece. These fastener drivers operate through various means (e.g. compressed air, gas, powder, electrical energy, a flywheel mechanism, etc.) to provide a burst of power to drive the fastener into the work piece. However, these designs often have power, size, and cost constraints.

In one independent aspect, a battery-powered fastener driver may include a burst circuit with a supercapacitor for providing power to a motor of the fastener driver.

In another independent aspect, a battery pack may include battery cells with different characteristics. The battery cells may be of different physical size (e.g., different diameter, different length, etc.), shape (e.g., cylindrical, prismatic, etc.), chemistry (e.g., different lithium-based or other chemistries), operational characteristics (e.g., Ampere-hour (Ah) capacity, temperature performance, nominal voltage, etc.), combinations thereof.

In yet another independent aspect, a battery charger may execute a method of monitoring a health of a battery pack by determining direct current (DC) internal resistance of the battery pack based on a monitored voltage of the battery pack.

In a further independent aspect, a battery pack may include battery cells coupled by laser welding conductive straps to terminals of the battery cells.

In another independent aspect, an electrical combination for powering a load device may be provided. The electrical combination may generally include a burst circuit configured to provide power to the load device to perform a burst operation, the burst circuit including a supercapacitor, a first switch between a power source and the supercapacitor and operable to control whether power is provided from the power source to charge the supercapacitor, and a second switch between the supercapacitor and the load device and operable to control whether power is provided from the supercapacitor to the load device; and an electronic processor configured to control the first switch and the second switch based at least in part on a voltage of the supercapacitor.

In yet another independent aspect, a method of powering a burst operation of a load device may be provided. The method may generally include determining, with an electronic processor, that a voltage of a supercapacitor is greater than or equal to a burst voltage threshold; controlling, with the electronic processor and in response to determining that the voltage of the supercapacitor is greater than or equal to the burst voltage threshold, a first switch to open to prevent power from being provided by a power source to the supercapacitor, the first switch being between the power source and the supercapacitor; determining, with the electronic processor, that an actuator of the load device has been actuated; and controlling, with the electronic processor and in response to determining that the actuator has been actuated, a second switch to close to allow power to be provided from the supercapacitor to the load device to perform the burst operation, the second switch being between the supercapacitor and the load device.

In a further independent aspect, a battery pack may generally include a housing; a plurality of battery cells supported in the housing, the plurality of battery cells including a first battery cell having a first characteristic and a second battery cell having a second characteristic different than the first characteristic, the first characteristic and the second characteristic being at least one of a physical size, a shape, a chemistry, and an operational characteristic; and a terminal electrically connected to the first battery cell and the second battery cell.

Other independent aspects of the invention may become apparent by consideration of the detailed description, claims and accompanying drawings.

DETAILED DESCRIPTION

Before any independent embodiments of the application are explained in detail, it is to be understood that the application is not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The application is capable of other independent embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

Use of “including” and “comprising” and variations thereof as used herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Use of “consisting of” and variations thereof as used herein is meant to encompass only the items listed thereafter and equivalents thereof. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings.

Also, the functionality described herein as being performed by one component may be performed by multiple components in a distributed manner. Likewise, functionality performed by multiple components may be consolidated and performed by a single component. Similarly, a component described as performing particular functionality may also perform additional functionality not described herein. For example, a device or structure that is “configured” in a certain way is configured in at least that way but may also be configured in ways that are not listed.

Furthermore, some embodiments described herein may include one or more electronic processors configured to perform the described functionality by executing instructions stored in non-transitory, computer-readable medium. Similarly, embodiments described herein may be implemented as non-transitory, computer-readable medium storing instructions executable by one or more electronic processors to perform the described functionality. As used in the present application, “non-transitory computer-readable medium” comprises all computer-readable media but does not consist of a transitory, propagating signal. Accordingly, non-transitory computer-readable medium may include, for example, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a RAM (Random Access Memory), register memory, a processor cache, or any combination thereof.

Many of the modules and logical structures described are capable of being implemented in software executed by a microprocessor or a similar device or of being implemented in hardware using a variety of components including, for example, application specific integrated circuits (“ASICs”). Terms like “controller” and “module” may include or refer to both hardware and/or software. Capitalized terms conform to common practices and help correlate the description with the coding examples, equations, and/or drawings. However, no specific meaning is implied or should be inferred simply due to the use of capitalization. Thus, the claims should not be limited to the specific examples or terminology or to any specific hardware or software implementation or combination of software or hardware.

FIGS. 1-2illustrate a battery-powered device10(i.e., a load device), such as, for example, a nailer that uses “burst operation” to drive nails into a work piece. In other constructions (not shown), the device10may include another fastener-driving device, such as a stapler, to drive staples, tacks, etc., or other power tools that use burst operation. In still other constructions (see, e.g.,FIG. 5), the device10may include another powered device using a burst of power to supply a load, such as a jump starter used to start a vehicle engine.

In the illustrated construction, the device10is powered by a removable, rechargeable battery pack14, such as a power tool battery pack. Alternatively, rechargeable battery cells (not shown) may be permanently housed within and non-removable from the device10.

The nailing device10includes an onboard drive mechanism18. In the illustrated construction, the drive mechanism18includes a gas-spring drive mechanism. In other constructions (not shown), the nailing device10may include another type of onboard drive mechanism, such as an air compressor, a vacuum pump, a mechanical energy storage element (e.g., a coil spring), etc.

The device10generally includes a housing20connectable to and operable to support the battery pack14and supporting the drive mechanism18. An electric motor22(FIG. 1) is supported by the housing20and operable to drive the drive mechanism18. Fasteners are supported in a magazine24.

The gas spring-powered drive mechanism18includes a cylinder26and a movable piston30positioned within the cylinder26(FIG. 2). A driver blade34is attached to and movable with the piston30. The drive mechanism18does not require an external source of air pressure but, rather, includes a storage chamber cylinder38of pressurized gas in fluid communication with the cylinder26. In the illustrated embodiment, the cylinder26and movable piston30are positioned within the storage chamber cylinder38.

With reference toFIG. 2, during a driving cycle, the driver blade34and the piston30are movable between a ready position (i.e., top dead center; seeFIG. 2) and a driven position (i.e., bottom dead center; not shown). A lifting assembly42, which is powered by the motor22, is operable to move the driver blade34from the driven position to the ready position.

In operation, the lifting assembly42drives the piston30and the driver blade34to the ready position by energizing the motor22. As the piston30and the driver blade34are driven to the ready position, the gas above the piston30and the gas within the storage chamber cylinder38is compressed. Once in the ready position, the piston30and the driver blade34are held in position until released by user activation of a trigger46.

When released, the compressed gas above the piston30and within the storage chamber38drives the piston30and the driver blade34to the driven position, thereby driving a fastener into a workpiece. The illustrated drive mechanism18therefore operates on a gas spring principle utilizing the lifting assembly42and the piston30to further compress the gas within the cylinder26and the storage chamber cylinder38.

In other constructions, on actuation of the trigger46, a full driving cycle may be completed. More specifically, when the user actuates the trigger46, the motor22is powered to cause the lifting assembly42to lift the piston30and the driver blade34and compress the gas. Upon reaching the ready position, the piston30and the driver blade34are immediately released to drive the fastener.

The structure and operation of the device10and the drive mechanism18may be similar to that disclosed in U.S. Patent Application Publication No. US 2016/022904 A1, published Aug. 11, 2016, the entire contents of which is hereby incorporated by reference.

When driving a nail into a work piece, the motor22is energized for a short period of time to cause the drive mechanism18to drive a nail and is de-energized until another nail is to be driven into the work piece. The operation of the device10may thus be referred to as a “burst operation” in which power is supplied (e.g., the motor22is energized) for short periods of time. For example, when the device10is used to drive twenty nails into a work piece over a one minute period, the motor22may be energized twenty times in bursts of one second or less (e.g., from about 0.05 seconds to about 0.10 seconds) to drive each nail into the work piece.

FIG. 3Aillustrates a block diagram of the device10. The device10includes an electronic processor305(for example, a microprocessor, or other electronic controller), a memory310, an indicator (e.g., one or more light-emitting diodes (LEDs)315), and the motor22.

The memory310may include read only memory (ROM), random access memory (RAM), other non-transitory computer-readable media, or a combination thereof. The processor305is configured to receive instructions and data from the memory310and execute, among other things, the instructions. In particular, the processor305executes instructions stored in the memory310to perform one or more methods described herein. The processor305is also configured to control the LEDs315(for example, to indicate an operating state of the device10, a condition of the battery pack14, a voltage of the supercapacitor(s)340, or the like) and receive electrical signals relating to the motor22(for example, a speed of the motor22as detected by Hall sensors and/or a current drawn by the motor22as detected by a current sensor).

The battery pack14provides power to the processor305, the LEDs315, and other control circuitry for the device10. The battery pack14also charges the supercapacitor(s)340of a burst circuit325, as explained in greater detail below.

Due to high current requirements of a burst operation, the battery pack14does not generally provide power for a burst operation (e.g., to drive a fastener into a work piece). For example, a burst operation of the device10, such as the nailer, may require between approximately 100 A and 120 A to power the motor22to cause the lifting assembly42to move the piston30and the driver blade34to the ready position. A partially-charged battery pack and/or a battery pack with increased internal resistance (due to numerous charge-discharge cycles, damage, etc.) may not be able to provide the current required to power a burst operation.

Additionally, while a battery pack with sufficient charge and/or with a minimum internal resistance may be able to provide the necessary current for a burst operation, during such high current discharge, the voltage of the battery pack may decrease below the operating voltage of the processor305and other control circuitry. In such conditions, the processor305and the control circuitry may shut down, causing the device10to stop operating.

Accordingly, the device10is generally unable to operate or function properly when the battery pack14itself delivers the high current for a burst operation.

To provide the burst operation, the illustrated device10includes a burst circuit325for supplying a burst of power to the motor22(or other load). In some embodiments, the burst circuit325is located within the battery pack14. In some constructions (such as the illustrated construction), the load (e.g., the motor22) is powered solely by the burst circuit325. In such constructions, battery cells of the battery pack14power the processor305, the LEDs315, and other control circuitry during a burst operation. In some constructions where the burst circuit325is located within the battery pack14, the battery pack14includes different sets of terminals to respectively provide power from the burst circuit325and the battery cells. In other constructions, the battery pack14provides power from the burst circuit325and the battery cells through the same set of terminals and includes a switch to control whether the burst circuit325or the battery cells provide power (e.g., similar to the dual-powered device embodiment described below).

As shown inFIG. 3A, the illustrated burst circuit325includes a first switch330, a second switch335, and one or more supercapacitor(s)340. In some embodiments, the supercapacitors340are connected in parallel (seeFIG. 3B). Although the supercapacitors340are described and shown (inFIG. 3B) in the plural form, in some embodiments, the burst circuit325may include a single supercapacitor340. It should also be understood that, in other embodiments (not shown), more than two supercapacitors340may be provided.

The first switch330connects the battery pack14to the supercapacitor(s)340. The second switch335connects the supercapacitor(s)340to the motor22. In some embodiments, the first switch330and the second switch335are field-effect transistors (FETs) controlled by the processor305. The processor305is configured to control the state of the first switch330and the state of the second switch335to allow or inhibit current to flow through each switch.

In some embodiments, the processor305monitors a voltage of the supercapacitor(s)340. The processor305is also coupled to the battery pack14to monitor one or more characteristics of the battery pack14(e.g., measure a voltage of the battery pack14and/or receive information from the battery pack14indicative of a condition of the battery pack14). For example, the battery pack14may include an electronic processor (not shown) communicating with the processor305through a communication terminal (not shown). Alternatively, the battery pack14may include a terminal (not shown) allowing the processor305to determine the temperature of the battery pack14(e.g., using a thermistor (not shown) within the battery pack14). In some embodiments, the processor305may also monitor one or more characteristics of the load22.

FIG. 3Billustrates how the battery pack14electrically couples to the supercapacitor(s)340and to the processor305. As shown inFIG. 3B, the battery pack14is connected in parallel with the supercapacitor(s)340when the first switch330is closed. However, when the first switch330is open, the battery pack14is not connected to the supercapacitor(s)340and thus, current is unable to flow between the battery pack14and the supercapacitor(s)340.

The first switch330may be closed to charge the supercapacitor(s)340using the battery pack14. In some embodiments, the processor305controls the first switch330using a PWM signal to charge the supercapacitor(s)340. For example, the PWM signal may begin with a relatively low duty cycle to prevent or limit high inrush current from being drawn by the supercapacitor(s)340having a low state of charge. As the voltage of the supercapacitor(s)340increases, the PWM duty cycle also increases until the supercapacitor(s)340are sufficiently charged, as explained in more detail below. In alternate embodiments, a resistor (not shown) in series with the first switch330is used to prevent or limit high inrush current from being drawn by the supercapacitor(s)340.

In some embodiments, a boost converter (not shown) may be used when charging the supercapacitor(s)340. In such embodiments, the voltage output of the battery pack14is matched to the voltage input of the supercapacitor(s)340. The supercapacitor(s)340may thus be charged without controlling the first switch330using the PWM signal described above, reducing the resulting switching losses that occur.

As shown inFIG. 3B, the state of the second switch335determines whether the load22is connected to the supercapacitor(s)340(i.e., whether the load22receives power from the supercapacitor(s)340). In the illustrated construction, when power is supplied from the supercapacitor(s)340to the load22, the first switch330is placed (e.g., by the processor305) in the open state to prevent feedback charging from the supercapacitor(s)340to the battery pack14.

As shown inFIG. 3B, when the first switch330is open, the battery pack14remains connected to the processor305and other control circuitry of the device10. Accordingly, during a burst operation of the device10, power is supplied from the supercapacitor(s)340to power the load22(e.g., to power the motor to cause the drive mechanism18to drive a nail into a work piece); meanwhile, the battery pack14powers the processor305and other control circuitry of the device10. Such a configuration allows for sufficient (high) current to be supplied to the load22to power a burst operation without the processor305and other control circuitry shutting down (e.g., because the voltage of the battery pack14drops below the operating voltage of the processor305and other control circuitry).

Similarly, in embodiments where the burst circuit325is located in the battery pack14, the battery cells of the battery pack14remain connected to the processor305and other control circuitry of the device10when the first switch330is open. Accordingly, during a burst operation of the device10, power is supplied from the supercapacitor(s)340to power the load22(e.g., to power the motor to cause the drive mechanism18to drive a nail into a work piece); meanwhile, the battery cells of the battery pack14power the processor305and other control circuitry of the device10. As mentioned above, such a configuration allows for sufficient (high) current to be supplied to the load22to power a burst operation without the processor305and other control circuitry shutting down. In some embodiments, the electronic processor305that controls the switches330and335and monitors the voltage of the supercapacitor(s)340is located in the battery pack14.

FIG. 4Aillustrates a method400of powering burst operations from the supercapacitor(s)340. In some embodiments, including the illustrated embodiment, the method400is executed by the processor305of the device10. At block405, the device10is turned on. At block410, the processor305opens the first switch330and the second switch335to prevent current from flowing to or from the supercapacitor(s)340.

At block415, the processor305determines whether the voltage of the battery pack14is greater than a battery low voltage threshold. When the voltage of the battery pack14is less than or equal to the battery low voltage threshold, at block420, the processor305indicates low battery voltage (e.g., flashes an LED) and shuts down the device10. In such a circumstance, the voltage of the battery pack14is too low to operate the device10(i.e., too low to charge the supercapacitor(s)340). The flashing LED may indicate to a user that the battery pack14needs to be replaced or recharged.

When the voltage of the battery pack14is greater than the battery low voltage threshold, at block425, the processor305determines whether the voltage of the supercapacitor(s)340is greater than or equal to a burst voltage threshold. In some embodiments, the burst voltage threshold is indicative of whether the charge of the supercapacitor(s)340is sufficient to power a burst operation of the device10. When the voltage of the supercapacitor(s)340is less than the burst voltage threshold, the method400proceeds to a charging sub-method460ofFIG. 4B, explained in greater detail below.

When the voltage of the supercapacitor(s)340is greater than or equal to the burst voltage threshold, the processor305opens the first switch330to prevent current flow between the battery pack14and the supercapacitor(s)340. At block435, the processor305determines whether the trigger46is pressed. When the trigger46is not pressed, the method400proceeds back to block415to continuously monitor the voltage of the battery pack14and the voltage of the supercapacitor(s)340.

When the trigger46is pressed, at block440, the processor305closes the second switch335to allow current to flow to the motor22from the supercapacitor(s)340. This closing of the second switch335starts a burst operation of the device10to, in the illustrated construction, drive a nail into a work piece. In some embodiments, the processor305controls the second switch335using a PWM signal during the burst operation.

At block445, the processor305may determine whether an operation of the device10has been completed (e.g., whether the nail has been driven into a work piece by the device10). If the operation has not been completed (e.g., if the fastener has not yet been fully driven into the work piece) and if further driving of the fastener is possible, the method remains at block445until completion or until discharge of the supercapacitor(s)340below the burst voltage threshold. If further driving is not possible, the processor305may alert the user (e.g., through the LEDs) of an incomplete or failed fastener driving operation.

When the operation has been completed, at block450, the processor305opens the second switch335to prevent current from flowing to the motor22from the supercapacitor(s)340, ending the burst operation.

After the second switch335is opened to end the burst operation at block450, the method400returns to block415to repeat the method400. Repetition of the method400allows for numerous burst operations of the device10powered by the supercapacitor(s)340. In between these burst operations, the supercapacitor(s)340are charged by the battery pack14when the voltage of the supercapacitor(s)340is below a threshold (e.g., the burst voltage threshold).

FIG. 4Billustrates the sub-method460for charging the supercapacitor(s)340. As explained above, at block425(seeFIG. 4A), when the voltage of the supercapacitor(s)340is less than the burst voltage threshold, the method400proceeds to the charging sub-method460shown inFIG. 4B.

At block465, the processor305determines whether the second switch335is open to prevent current flow to the motor22from the supercapacitor(s)340. If the second switch335is closed, at block470, the processor305opens the second switch335to prevent current flow to the motor22from the supercapacitor(s)340. The charging sub-method460then proceeds to block475. At block465, when the second switch335is already open, the charging sub-method460also proceeds to block475.

At block475, the processor305closes the first switch330to allow current flow from the battery pack14to the supercapacitor(s)340to charge the supercapacitor(s)340. As explained above, in some embodiments, the processor305controls the first switch330using a PWM signal to charge the supercapacitor(s)340.

At block480, the processor305determines whether the voltage of the supercapacitor(s)340is greater than or equal to the burst voltage threshold. When the voltage of the supercapacitor(s)340remains below the burst voltage threshold, at block485, the processor305continues to control the first switch330to allow current to flow from the battery pack14to the supercapacitor(s)340to charge the supercapacitor(s)340. The charging sub-method460then returns to block480to continue monitoring the voltage of the supercapacitor(s)340.

When the voltage of the supercapacitor(s)340is greater than or equal to the burst voltage threshold, the method400returns to block430(seeFIG. 4A) to continue operation as described above. Thus, the method400and the sub-method460allow the supercapacitor(s)340to power burst operations of the device10and to be charged between burst operations of the device10. The battery pack14is used to charge the supercapacitor(s)340between burst operations and to power the processor305and other control circuitry of the device10during and between burst operations.

In alternate embodiments, at block435, a burst operation of the device10occurs upon a monitored characteristic of the device10exceeding a predetermined threshold while, at other times, operational power is provided by the battery pack14. Such a device10is a dual-powered device—the load22is powered by the battery pack14and/or by the supercapacitor(s)340. For example, in some embodiments, the device10may include a reciprocating saw, a circular saw, a drill, etc., (not shown) having a load sensor (not shown; e.g. a current sensor for the motor22). The burst operation is provided to operate under an increased load (e.g., the saw “bogging down” or binding on the work piece).

For most operations (e.g., “normal” operations), the battery pack14is capable of supplying the required discharge current to power the load22while maintaining sufficient voltage to also power the processor305and the other control circuitry as necessary during operation. Under normal operating conditions, the load22of the dual-powered device (e.g., the saw, drill, etc.) is powered by the battery pack14.

When the load sensor senses a load above a predetermined “burst load” threshold, the processor305may initiate a burst operation powered by the supercapacitor(s)340. In other words, the processor305may disconnect the battery pack14from the load22and connect the supercapacitor(s)340to the load22to provide a burst of power.

When the load sensor senses that the load is below a “normal load” threshold, the processor305may re-initiate “normal” operations of the load22powered of the battery pack14. The processor305may disconnect the supercapacitor(s)340from the load22and connect the battery pack14to the load22to provide “normal” power.

FIG. 5illustrates a block diagram of a burst device500(or burst adapter) including a burst circuit505(similar to the burst circuit325) to provide power to an external load (e.g., a burst-receiving device535). Such a burst device500may be a jumpstarting device for jumpstarting a vehicle battery. Alternatively, the burst device500take the form of an “adapter” configured to receive a battery pack (such as the battery pack14) and separate from and connectable (e.g., at least electrically) to a load (e.g., a fastener-driving device (as disclosed in U.S. Patent Application Publication No. US 2016/022904 A1), another power tool, a non-motorized device, etc.) to provide burst power to a load.

In some embodiments, the burst device500is integrated into the battery pack14. In other words, the battery pack14may include a burst circuit505that functions in a similar manner as the burst device500described below. In some embodiments, the electronic processor525that controls the switches540and545and monitors the voltage of the supercapacitor(s)530is located in a device outside of the burst device500(e.g., in the burst receiving device535, in the battery pack14, or the like).

The separate burst device500allows the supercapacitor(s)530of the burst circuit505to provide power to loads/devices that do not include a burst circuit505,325. In some embodiments (e.g., when the burst device500is a jump starting device for a vehicle battery), the burst device500is capable of providing between approximately 300 Amps and 600 Amps (or more depending on the number and characteristics of the supercapacitor(s)530) to the burst-receiving device535.

As shown inFIG. 5, the burst device500includes a housing502defining a battery connection portion503(e.g., a terminal block and a battery support) for electrical and/or mechanical connection to the battery pack14and a load connection portion504(e.g., a terminal block and a support) for electrical and/or mechanical connection to the load. The housing502supports a burst circuit505, an actuator510(e.g., a button, a trigger, a signal-receiving unit, etc.), a memory515, an indicator (e.g., one or more LEDs520), and an electronic processor525. These components are similar to the corresponding components described above with respect to the device10(seeFIG. 3).

In the burst device500, the processor525may monitor the actuator510to initiate a burst of power from supercapacitor(s)530to the burst-receiving device535. The processor525may also control the LEDs520to indicate a status of the burst device500(for example, whether the supercapacitor(s)530are charged and capable of providing a burst of power), the battery pack14and/or the burst-receiving device535.

Generally, the processor525controls operation of the burst circuit505in a similar manner to the operation of the burst circuit325of the device10. For example, the processor525may execute the method400ofFIG. 4Ato provide one or more bursts of power from the supercapacitor(s)530to the load (the burst-receiving device535) electrically coupled to the burst device500.

The processor525may also execute the charging sub-method460ofFIG. 4Bto charge the supercapacitor(s)530using the battery pack14electrically coupled to the burst device500. The processor525controls charging and discharging of the supercapacitor(s)530by controlling the first switch540and the second switch545in a similar manner to that of the burst circuit325of the device10.

FIGS. 6A-6Billustrate a battery pack600including a number of first battery cells602(e.g., three; illustrated as being arranged vertically in a stem605of a housing of the battery pack600) and a number of different second battery cells604(e.g., three; illustrated as being arranged horizontally in a base610of a housing of the battery pack600). In some embodiments, the battery pack600operates in a similar manner as described above with respect to battery pack14and may be used to power the device10. In some embodiments, the stem605is inserted into a battery receptacle (not shown) of a power tool (for example, the device10). In such embodiments, the base610generally remains external to a housing (not shown) of the power tool.

The battery cells602,604may be connected in any combination with each other to provide desired voltage and current outputs for a desired application. For example, in some embodiments, two battery cells602in the stem605are connected in parallel, two battery cells604in the base610are connected in parallel, and one battery cell602in the stem605and one battery cell604in the base610are connected in parallel. In such an exemplary configuration, the three sets of parallel battery cells602,604may be connected in series. In some embodiments, the battery cells602,604are “18650” (18 mm in diameter by 65 mm in length) lithium-ion batteries.

In some embodiments, larger-sized battery cells (e.g., “26700” (26 mm by 70 mm) cells or “21700” (21 mm by 70 mm) cells compared to 18650 cells) may be used to provide increased ampere-hour capacity of a battery pack. Due to size constraints of the battery receptacle of the associated power tools, use of larger-sized battery cells in the stem605of the battery pack600may be limited. Specifically, increasing the size of the stem605to accommodate larger-sized battery cells would require increasing the size of the battery receptacle of the power tools to receive such a larger stem. However, use of larger-sized battery cells in the base610of the battery pack600would not generally require modification of the battery receptacle of power tools as the base610remains external to the power tool when the battery pack600is inserted.

FIG. 7Aillustrates a cut-away view of a battery pack705including different types of battery cells (i.e., battery cells that include one or more different characteristics than each other). The battery cells may be of different physical size (e.g., different diameter, different length, etc.; seeFIG. 7A), shape (e.g., cylindrical, prismatic, etc.), chemistry (e.g., different lithium-based or other chemistries), operational characteristics (e.g., Ampere-hour (Ah) capacity, temperature performance, nominal voltage, etc.), combinations thereof. In some embodiments, the battery pack705operates in a similar manner as described above with respect to the battery pack14and may be used to power the device10.

Similar to the battery pack600shown inFIGS. 6A and 6B, the battery pack705includes a stem710and a base715. The stem710houses a number of smaller-sized battery cells720(for example, three 18650 lithium-ion battery cells). The base715houses a number of larger-sized battery cells725(for example, three 21700 lithium-ion battery cells). In some embodiments (as illustrated), the battery cells720,725have different diameters and different lengths (18650 compared to 21700; as shown inFIG. 7A). In other embodiments (not shown), the battery cells720,725have only different diameters (18 mm compared to 21 mm) or different lengths (65 mm compared to 70 mm).

As mentioned above, in some embodiments, the battery cells720,725have different operational characteristics (e.g., Ampere-hour (Ah) capacity, temperature performance, nominal voltage, etc.). For example, the battery cells720,725may have different ampere-hour capacities. As illustrated, the larger-sized battery cells725(e.g., the 21700 cells) have a greater ampere-hour capacity than the smaller-sized battery cells720(e.g., the 18650 cells).

As another example, the battery cells720,725may have different temperature performance characteristics (e.g., one set of battery cells may have a wider range of temperatures in which it may properly function or one set of battery cells may function better at low temperatures or high temperatures). The battery controller (not shown) may determine, based on the conditions (e.g., ambient and/or operational conditions), which battery cells720,725to use to supply power.

In some embodiments, each smaller-sized battery cell720in the stem710is connected in parallel with one larger-sized battery cell725in the base715. In alternate embodiments, multiple smaller-sized battery cells720may be connected in parallel with multiple larger-sized battery cells725. The parallel combinations of battery cells720and725may be connected in any series combination with each other to provide desired voltage and current outputs for a desired application.

AlthoughFIG. 7Ashows the battery pack705as including six battery cells, in some embodiments, the battery pack705includes more or fewer battery cells that may be connected in a similar manner to the battery cells720,725. For example,FIG. 7Billustrates a battery pack730including eight larger battery cells735and eight smaller battery cells740in a base745of the battery pack730. As shown inFIG. 7B, the smaller battery cells740may be positioned between rows of larger battery cells735and/or along a bottom of the base745. Using battery cells of different sizes allows for space within the base745to be optimized to make the battery pack730less bulky and easier to manipulate.

The configuration of the battery cells735and740inFIG. 7Bis merely exemplary and other configurations may be used. Although not shown inFIG. 7B, in some embodiments, a stem750of the battery pack730also includes battery cells, as previously explained with respect toFIGS. 6A, 6B, and 7A. In alternate embodiments (not shown), the stem750includes cylindrically-shaped battery cells, and the base745includes prismatic battery cells.

In some embodiments, the battery cells720,725and the battery cells735,740are coupled to each other by laser welding conductive straps to terminals of the battery cells, as explained in greater detail below.

Although several configurations of connections between the battery cells720,725have been explained, the operation of the battery cells720,725will be described with respect to the configuration that includes three parallel combinations of a smaller-sized battery cell720and a larger-sized battery cell725. These three parallel combinations may be connected in series to provide a desired voltage (for example, approximately 12V) at the terminals of the battery pack705.FIG. 7Cillustrates a circuit diagram of the battery cells720,725in such an exemplary configuration.

In the illustrated configuration, the total ampere-hour capacity of the battery pack705is the sum of the capacities of one smaller-sized battery cell720and one larger-sized battery cell725. Accordingly, the total ampere-hour capacity of the illustrated battery pack705is increased compared to a battery pack including only six smaller-sized battery cells720.

Despite the different characteristics of the battery cells720,725, as described above, in some embodiments, the battery cells720,725have substantially the same nominal voltage. Within each parallel combination of a smaller-sized battery cell720and a larger-sized battery cell725, the battery cells720,725balance each other despite having different ampere-hour capacities because they have the same voltage. Thus, existing charging, discharging, and balancing methods of battery packs including battery cells of the same size and ampere-hour capacity may still be used with the battery pack705having different size and ampere-hour capacity battery cells720,725(for example, to monitor and control charging and discharging of the battery pack705).

Within each parallel combination of a smaller-sized battery cell720and a larger-sized battery cell725, the larger-sized battery cell725has a higher impedance and a higher energy than the smaller-sized battery cell720. Accordingly, the larger-sized battery cells725are referred to as energy cells while the smaller-sized battery cells720are referred to as low impedance cells.

With reference toFIG. 7C, in some embodiments, the battery pack705may include switches to disconnect either the battery cells720or the battery cells725depending on monitored characteristics of the battery pack705. In such embodiments, the battery pack705provides power solely from a single type of battery cell intended to operate under the monitored characteristic (e.g., low temperature).

For example, when the battery cells720and725include different temperature characteristics, an electronic processor of the battery pack705may disconnect either the battery cells720or725based on a monitored temperature (e.g., ambient and/or of the battery pack705). For example, when the battery pack705is in a cold environment (e.g., temperature less than a desired operating temperature for one set of battery cells720or725), the processor may disconnect such battery cells. In such embodiments, the battery pack705provides power solely from the battery cells720or725intended to operate at lower temperatures (e.g., having a low temperature characteristic compared to the other cells).

In some embodiments, the battery pack14,600and705includes an electronic processor (not shown) and a memory (not shown) that may be similar to the processor305and the memory310described above with respect to the nailing device10(seeFIG. 3A). The battery pack14,600and705may also include at least one sensor for monitoring an operational characteristic of the battery packs14,600, and705during operation.

For example, the battery pack14,600and705may include a current sensor for monitoring a current provided by the battery pack14,600and705. In some embodiments, the processor of the battery pack14,600and705may monitor an amount of time that the battery pack14,600and705provide current to a device.

In some embodiments, the battery pack14,600, and705determines a type of device to which the battery pack14,600, and705is connected. In such embodiments, the processor of the battery pack14,600and705may make such a determination by communicating with the processor305of the nailing device10or other device.

The memory of the battery pack14,600and705may store monitored operational characteristics of the battery pack14,600and705. The memory of the battery pack14,600and705may also store the type of device to which the battery pack14,600and705is or was connected. Based on this information, the battery pack14,600and705may provide information to a user to improve operation of the battery pack14,600and705.

For example, the battery pack14,600and705may include a wireless communication controller to communicate with an external device (e.g., a smart phone). In such embodiments, the wireless communication controller and the external device may be similar to those disclosed in U.S. Patent Application Publication No. 2016/0342151, filed May 16, 2016, the entire contents of which is hereby incorporated by reference.

The battery pack14,600and705may communicate with the external device to provide usage data of the battery pack14,600and705(e.g., a type of device that the battery pack has been used to power in the past and operational characteristics of the battery pack14,600and705during discharge) and predicted intended future operation of the battery pack14,600and705.

For example, when the battery pack14,600and705is not suitable to the device or power tool to which it is connected, the battery pack14,600, and705may communicate with the external device to recommend an appropriate battery pack be used in place of the battery pack14,600and705in future operations with device or power tool. In turn, the external device may communicate this information to the user (e.g., display this recommendation such that it is viewable by a user).

More specifically, when a low-capacity, discharged and/or damaged battery pack14,600and705is connected to a high-demand power tool, the battery pack14,600, and705may communicate with the external device and/or to the user to recommend that a higher-capacity, fully-charged and/or new battery pack be used in place of the battery pack14,600and705in future operations with the high-demand power tool.

Such a recommendation may extend the useful life of the battery pack14,600and705by informing the user that a different battery pack would last longer than the battery pack14,600, and705when used with the high-demand power tool. Such a recommendation may also improve the functionality of the high-demand power tool by informing the user that a higher-capacity battery pack is better suited to power the high-demand power tool. In some embodiments, a specific alternate battery pack may be recommended based on the type of device being operated by the user.

As mentioned above, in some embodiments, the battery cells (e.g., the battery cells602,604and/or the battery cells720,725) are electrically coupled by laser welding conductive straps to terminals of the battery cells. Laser welding allows dissimilar metals that may not be capable of being welded together using resistance welding to be welded together. Compared to resistance welding, laser welding may increase pull strength between objects that are welded together. Additionally, laser welding allows for softer metals to be welded together than resistance welding allows.

FIG. 8illustrates conductive straps805electrically coupling a fuse810between battery cells815at laser welds820. In some embodiments, the conductive straps805are made of aluminum or copper and are laser-welded to a stainless steel battery terminal of the battery cells815. The conductive straps805are also laser welded to aluminum or copper terminals of the fuse810. In such embodiments, the conductive straps805and the terminals of the fuse810may also be made of dissimilar metals (e.g., conductive straps805made of aluminum and terminals of the fuse810made of copper or vice versa). In alternate embodiments, the conductive straps805may be made of copper with tin or with cladding layers of at least two materials of the group consisting of copper, stainless steel, and nickel.

In some embodiments, laser welding may allow battery cells with terminals made of dissimilar metals to be welded together. For example, cylindrical battery cells with battery terminals made of a first metal and prismatic battery cells with battery terminals made of a second metal may be electrically coupled by laser welding.

As mentioned above, compared to resistance welding, laser welding may increase pull strength between objects that are welded together (e.g., the conductive straps805and the battery cells815). Different geometries of laser welding patterns may increase the pull strength between welded objects.

FIGS. 9A-9Cillustrate exemplary geometries of laser welding patterns used to weld conductive straps805, fuses810, and/or battery cells815together.FIG. 9Ashows a conductive strap805laser welded between the terminals of two battery cells815using a flower geometry pattern905. As shown inFIG. 9A, the illustrated flower geometry pattern905includes six spot welds that surround a single spot weld. However, in alternate embodiments (not shown), more or fewer spot welds surround the central spot weld.

FIG. 9Bshows a target geometry pattern910with a spot weld surrounded by a circular weld. In some embodiments, the circular weld is completed using overlapping loops as shown by loop pattern912in part of the circular weld ofFIG. 9B. In alternate embodiments, additional spot welds may be included inside the circular weld. In some embodiments, the circular weld may surround the flower geometry pattern905shown inFIG. 9A.

FIG. 9Cshows a spiral geometry pattern915. In some embodiments, the spiral geometry pattern915may be surrounded by the circular weld ofFIG. 9B. The laser welding geometry patterns905,910and915shown inFIGS. 9A-9Care merely exemplary. Additional laser welding geometry patterns may be used in alternate embodiments.

Laser welding may increase the overall pull strength by increasing the pull strength in at least one direction compared to resistance welding. For example, the generally circular shape of the geometry patterns905,910and915shown inFIGS. 9A-9Cprovide similar pull strength in all directions. In contrast, resistance-welding patterns generally include only straight line welds in one or two directions and do not provide similar pull strength in all directions.

When the battery packs14,600and705are depleted, a charger1005(seeFIG. 10) may be used to recharge the battery packs14,600and705. Although the below explanation of the charger1005refers to charging of the battery pack14, the same concepts and methods apply to charging the battery packs600and705and to other battery packs (not shown).

As shown inFIG. 10, the charger1005includes a power cord1010for connecting to a power source (e.g., a wall outlet for AC power) to provide power to the charger1005. The charger1005also includes one or more battery pack receptacles1015(two shown) for receiving battery packs. One receptacle1015ais configured to receive the battery pack14(for example, the stem of the battery pack14inserted into the receptacle1015a) while the other receptacle1015bis configured to receive battery packs of an alternate shape (e.g., a slide-on battery pack).

FIG. 11illustrates a block diagram of the charger1005. In some embodiments, the charger1005includes some similar components as the device10. For example, the charger1005includes an electronic processor1105, a memory1110, and an indicator (e.g., LEDs1115). These components may have similar functionality to the corresponding components described above with respect to the device10(seeFIG. 3A).

The charger1005also includes an AC/DC converter and other conditioning circuitry1120and a charging control switch1125. In some embodiments, the charging control switch1125includes a FET controlled by the processor1105. For example, when the charging control switch1125is closed, current flows from an alternating current (AC) power source1128through the AC/DC converter and other conditioning circuitry1120to charge the battery pack14. In some embodiments, the processor1105controls the charging control switch1125using a PWM signal.

The charger1005also includes a load bank1130and a load bank switch1135. The load bank switch1135is controlled by the processor1105to connect the battery pack14to one or more testing loads instead of to the AC/DC converter and other conditioning circuitry1120and the AC power source1128. WhileFIG. 11shows a single load bank switch1135, in some embodiments, the charger1005includes multiple load bank switches.

In some embodiments, the processor1105executes a method of monitoring battery health by determining a DC internal resistance of the battery pack14. The DC internal resistance of a battery pack is indicative of the health of the battery pack. As a battery pack ages, the DC internal resistance tends to increase which, in turn, decreases performance of the battery pack.

The DC internal resistance affects the capacity of the battery pack—the higher the DC internal resistance of a battery pack, the higher the losses while charging and discharging the battery pack. These losses increase as the charging current or discharging current increase. In other words, the higher the discharge rate of a battery pack, the lower the available capacity of the battery pack.

In some embodiments, the DC internal resistance of the battery pack14is determined by the battery charger1005by monitoring the voltage of the battery pack14as a load connected to the battery pack14is varied. As the load connected to the battery pack14varies, the voltage of the battery pack14will also vary. From the monitored changes in voltage of the battery pack14as the load varies, the DC internal resistance of the battery pack14, which, again, is indicative of the health of the battery pack14, is determined.

FIG. 12illustrates an exemplary method1200of monitoring the DC internal resistance of the battery pack14. At block1205, the processor1105opens the charging control switch1125to ensure that the battery pack14is disconnected from the charging power source1128. At block1210, the processor1105controls the load bank switch1135to connect the battery pack14to a first load of the load bank1130such that the battery pack14applies a first discharge current (e.g., ten amps). The battery pack14remains connected to this load for a time period (e.g., five seconds). During this time, the processor1105monitors the voltage of the battery pack14.

At block1215, the processor1105controls the load bank switch1135to connect the battery pack14to a second load of the load bank1130such that the battery pack14applies a second discharge current (e.g., one amp). The battery pack14remains connected to this load for a time period (e.g., five seconds). During this time, the processor1105monitors the voltage of the battery pack14.

As indicated by blocks1220and1225, blocks1210and1215are repeated a number of times (e.g., twice), and the voltage of the battery pack14continues to be monitored. After blocks1210and1215are repeated (in other words, after blocks1210and1215have been executed three times in total), at block1230, the processor1105resets a variable N to zero such that the next time the method1200is executed, the blocks1210and1215will be executed once and then repeated the number of times more (in other words, blocks1210and1215are executed three times each time the method1200is executed).

At block1235, the processor1105determines how much the voltage of the battery pack14varied from when the battery pack14was connected to the first load compared to when the battery pack14was connected to the second load. A large variance in the voltage of the battery pack14indicates a higher DC internal resistance and a less healthy battery pack14than does a smaller variance. In other words, the less the voltage of the battery pack14varied when the loads were switched, the healthier the battery pack14.

The variance in voltage may be compared to a variance in the voltage of the battery pack14when the battery pack14was manufactured. An increase in the variance in the voltage of the battery pack14from the time of manufacture beyond a predetermined threshold (e.g., a 50% increase) may indicate that the battery pack14should be replaced or used only for lower power applications.

FIG. 13illustrates a graph that shows exemplary results of the method1200being executed on an exemplary 18V battery pack. InFIG. 13, the x-axis of the graph represents time in seconds. The lower signal on the graph represents a discharge current1305of the battery pack in amps, and the upper signal represents a battery pack voltage1310in volts.

As shown inFIG. 13, the discharge current1305includes a number (e.g., six) of time period (e.g., five second) intervals that alternate between the first discharge current (e.g., ten amps) and the second discharge current (e.g., one amp). As shown inFIG. 13, the battery pack voltage1310varies as the discharge current1305of the battery pack14varies. As mentioned above, the amount of variance of the battery pack voltage1310indicates the health of the battery pack14.

In some embodiments, the method1200is executed by the processor1105of the charger1005before charging of the battery pack14. In other embodiments, the method1200is executed at other times (for example, after the battery pack14has been charged for a predetermined time, after the battery pack14has been charged to a predetermined capacity, after the battery pack14has been fully charged, etc.).

After executing the method1200to determine the health of the battery pack14, the processor1105may control the LEDs1115to illuminate to indicate the health of the battery pack14. For example, in some embodiments, the LEDs1115may include a green LED, a yellow LED, and a red LED. In such embodiments, the processor1105may illuminate the green LED when the battery health is in a first range indicating good health (for example, when the DC internal resistance is within 20% of its initial DC internal resistance). The processor1105may illuminate the red LED when the battery health is in a second range indicating poor health (for example, when the DC internal resistance has increased by 50% or more of its initial DC internal resistance). The processor1105may illuminate the yellow LED when the battery health is in a third range between the first range and the second range. It should be understood that these ranges are merely exemplary and may be different in other embodiments.

In alternate embodiments, the LEDs1115may include a plurality of single-color LEDs that the processor1105controls to illuminate in a similar manner as described above with respect to the green, yellow, and red LEDs. For example, in an embodiment with five single-color LEDs, the processor1105may illuminate all five LEDs when the battery pack14is in good health and may only illuminate one single-color LED when the battery pack14is in poor health. Accordingly, the charger1005may determine and notify a user (through the LEDs1115) when the battery pack14is in poor health.

In some embodiments, the charger1005includes a wireless communication controller to communicate with an external device (e.g., a smart phone). In such embodiments, the wireless communication controller and the external device may be similar to those disclosed in U.S. Patent Application Publication No. 2016/0342151.

In some embodiments, the charger1005provides information to the external device using the wireless communication controller after the health of the battery pack14(i.e., the DC internal resistance of the battery pack14) is determined. For example, when the DC internal resistance of the battery pack14increases above a predetermined threshold (i.e., when the measured variance in voltage during load switching increases above a predetermined threshold), the charger1005may provide a recommendation to the external device that the battery pack14should be replaced or that the battery pack14should only be used to power low-demand devices (e.g., light duty tools and devices such as a work light). In turn, the external device communicates this information to a user (e.g., displays this recommendation such that it is viewable by the user).

As mentioned above, such a recommendation may increase the useful life of the battery pack14and/or may increase the performance of devices (e.g., high-demand devices) by informing the user of an ideal use for the battery pack14based on its health. Thus, newer battery packs with good health may be used to power high-demand devices while older battery packs with diminished health are more appropriate to power low-demand devices.

While the charger1005is described as including the wireless communication controller above, in some embodiments, the battery pack14and/or the nailing device10may include a wireless communication controller to communicate with the external device. In such embodiments, the processor1105of the charger1005may communicate with the battery pack14such that the battery pack14stores battery health information in its memory. The battery pack14may then communicate the battery health information to the external device. In alternate embodiments, the battery pack14may communicate battery health information to a power tool/device when coupled to the power tool/device, and the power tool/device, in turn, may communicate the battery health information to an external device.

It should be understood that each block diagram is simplified and in accordance with the illustrated exemplary embodiment. The components and connections illustrated in the block diagrams are exemplary, and additional or fewer components/connections may be provided. For example, inFIG. 3A, the device10may include additional circuitry (for example, circuitry between the second switch335and the motor22to drive the motor22in a predetermined manner). Similarly, the flowcharts are simplified and exemplary, and additional or fewer steps may be provided.