CN101416330A - Protection method, protection circuit and protection device for secondary battery, electric tool, charger and battery pack suitable for providing protection against fault conditions in battery pack - Google Patents

Abstract

In a cordless power tool system, protection methods, circuits and/or devices are provided that provide protection against fault conditions within a battery pack operatively attached to a power tool or charger to prevent internal or external damage to the battery pack or an accessory tool or charger. These exemplary methods, circuits, and devices address fault conditions such as overcharge, overdischarge, overcurrent, excessive temperature, and the like.

Description

Protection method, protection circuit and protection device for secondary battery, electric tool, charger and battery pack suitable for providing protection against fault conditions in the battery pack

Cross Reference Related Applications

This application claims domestic priority under 35 U.S.C. § 120 to the following related U.S. Provisional Patent Applications filed with the U.S. Patent and Trademark Office: U.S. Provisional Application Nos. 60/510,128, filed October 14, 2003, and U.S. Provisional Application No. 60/551,803 filed on the 11th. The disclosure of each of these provisional applications is hereby incorporated by reference in its entirety.

technical field

The present invention relates to protection methods, protection circuits and protection devices for rechargeable batteries, to power tools and chargers suitable for providing protection to batteries attached to battery packs, and to battery packs including protection controls, each of which is Protects battery packs against a variety of potential failure conditions.

Background technique

Over the past few years, lithium ion (Li ⁺ ) batteries have begun to replace nickel cadmium (NiCd), nickel metal hydride (NiMH), and lead acid batteries in low voltage portable electronic devices such as notebook personal computers. Compared with NiCd and NiMH batteries, lithium-ion batteries are lighter, but have a larger capacity per unit volume. For this reason, lithium-ion batteries are generally suitable for low-voltage equipment that is best lightweight and required to withstand long periods of continuous use. However, in the over-discharge state, the lithium-ion battery deteriorates rapidly, therefore, the lithium-ion battery needs over-discharge protection.

Battery packs used in portable electronic devices typically contain multiple cells connected in series. The maximum number of cells connected in series in a battery pack is determined by the output voltage of the battery pack. For example, the typical output voltage of a NiCd battery or a NiMH battery is 1.2V. The maximum number of NiCd or NiMH cells in series in a battery pack is 15, assuming the 18V output voltage from the battery pack is suitable for most general purpose electronics. On the other hand, the typical output voltage of a Li-ion battery is about 3.6V. Therefore, the maximum number of Li-Ion cells in series in a hypothetical 18V Li-Ion battery pack is 5.

Unlike NiCd and NiMH batteries, Li-ion batteries can include features that provide protection against fault conditions both internal and external to the Li-ion battery. This prevents the cells in the lithium-ion battery pack from going bad and shortening the life of the battery pack. For example, if a fault condition such as a short circuit occurs inside or outside of a Li-ion battery pack, a fuse can be equipped to cut off the over-discharge current or over-charge current if the discharge current or the charge current becomes greater than a given current level .

Currently, protection circuits in battery packs such as Li-ion battery packs are primarily designed for low voltage portable electronic devices such as notebook personal computers and cellular phones, which require voltages typically on the order of 2 to 4V. Such devices are characterized by the use of battery packs consisting of cells (eg Li-ion, NiCd, NiMH cells) providing a maximum output voltage of approximately 4.2 volts per cell. For lithium-ion batteries, since lithium is a highly reactive species, care must be taken to prevent damage from electrical and mechanical stress.

Traditional protection circuits for these low-voltage battery packs monitor cell voltage to prevent overcharging or over-discharging a given cell, and monitor current to prevent the current from rising too high. Other protection circuits may include one or more temperature inputs that inhibit current flow until the battery pack cools down during charging or discharging. There are also protection circuits that can be designed to help maintain the balance of charge on the battery, these circuits are often called equalization circuits. A typical protection circuit can be connected to a given cell or group of cells in a battery pack to protect against these conditions. For example, conventional protection circuits may typically include a pair of MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or other semiconductors that prevent current from flowing in each direction.

However, for higher power electronic equipment such as cordless power tools, much higher voltages than those mentioned above are required. Therefore, higher power battery packs are being developed for cordless power tools. Such "high power" battery packs can provide higher voltage output than traditional NiCd and NiMH battery packs (and much higher power than traditional Li-ion battery packs for PCs and cellular phones), and are much lighter ( compared to conventional NiCd or NiMH battery packs used as power sources in conventional cordless power tools). These batteries are characterized in that the battery can exhibit much lower impedance characteristics than conventional NiCd, NiMH and/or even lower power Li-ion batteries.

Also, as these battery technologies continue to evolve, the introduction of lower impedance chemistries and structural forms to develop secondary batteries that generate much higher output voltages (eg, 18V and higher) may raise several additional protection concerns. A lower impedance battery pack also means that the battery pack can supply much higher currents to attached electronic components such as power tools. As the current flowing through a motor attached to a power tool increases, the demagnetizing magnetic potential (eg, armature turns of the motor x current (ampere-turns)) can increase significantly beyond the desired or design limits of the motor. Therefore, this undesired demagnetization may burn out the motor.

For example, a lower impedance power source can damage the tool's motor when the tool is in a stall condition. During motor stall, only the motor and battery impedance act to limit the current since the motor does not generate back EMF. The lower the impedance of the battery pack, the greater the current flow. Higher currents flowing through the motor will increase the likelihood of demagnetization of the permanent magnets within the tool motor.

In addition, starting the tool will generate additional starting current and cause the motor to demagnetize. Using a low-impedance power source in an existing power tool can also cause thermal overload, as the new battery may be designed to last longer and last longer than the original cordless tool system.

Therefore, different protection controls may be required to properly address potential fault conditions present in high powered battery packs suitable for use with existing cordless power tools, and power tools manufactured to incorporate these higher powered battery packs The processing line is used. Specifically, protection controls need to be developed to deal with conditions such as overcharge, overdischarge, overcurrent, excessive temperature, and cell imbalance that occur in one or more cells of a battery pack, such as a Li-ion or NiCd battery pack. to prevent internal or external damage to battery packs, accessory equipment such as chargers or tools, or users in the vicinity of battery packs connected to chargers or tools.

Contents of the invention

In a cordless power tool system including a battery pack, the exemplary embodiments of the present invention are directed to providing protection against fault conditions in a battery pack operatively attached to a power tool or charger so as to prevent damage to the battery Protection methods, arrangements and/or devices for internal or external damage caused by sets or accessory tools or chargers. These exemplary methods, circuits and devices address fault conditions in battery packs such as overcharge, overdischarge, overcurrent, overtemperature, and the like.

Description of drawings

A more complete understanding of exemplary embodiments of the present invention will be given by giving a detailed description with reference to the accompanying drawings, in which like numerals indicate like elements and which merely represent exemplary embodiments of the invention, Rather than being limited to the exemplary embodiments of the invention.

Figure 1 shows a partial block diagram of a protective structure according to an exemplary embodiment of the present invention;

Figure 2 shows a partial block diagram of a protective structure according to another exemplary embodiment of the present invention;

3A is a block diagram showing components and connections between an exemplary battery pack and an exemplary battery charger according to an exemplary embodiment of the present invention;

3B is a block diagram illustrating components and connections between an exemplary battery pack and an exemplary power tool according to an exemplary embodiment of the present invention;

FIG. 4 is a partial block diagram showing connections between a battery pack and a charger for overcharge protection according to an exemplary embodiment of the present invention;

5 is a partial block diagram illustrating connections between a battery pack and a charger for overcharge protection according to another exemplary embodiment of the present invention;

FIG. 6 is a graph showing the time-dependent voltage curve of the automatic cut-off of the over-discharge protection implemented by the protection circuit according to an exemplary embodiment of the present invention;

Fig. 7 is a voltage versus time curve representing a modified threshold value of over-discharge protection according to an exemplary embodiment of the present invention;

8A and 8B show an exemplary device for overcurrent protection according to an exemplary embodiment of the present invention;

Figure 9 shows a device providing over-temperature protection according to an exemplary embodiment of the present invention;

Fig. 10 shows the connection structure of the thermistor according to an exemplary embodiment of the present invention;

11 is a flowchart illustrating a method of alerting an operator of a power tool of an impending fault condition in a battery pack;

FIG. 12 is a block diagram showing an exemplary structure for determining SOC and changing the motor current switching frequency according to an exemplary embodiment of the present invention;

Figure 13A is an isometric view of a single layer cell;

Figures 13B and 13C illustrate a device providing protection against an overcharge condition according to an exemplary embodiment of the present invention;

14A and 14B illustrate a device providing protection against an overcharge condition according to another exemplary embodiment of the present invention;

15A and 15B illustrate a device providing protection against an overcharge condition according to another exemplary embodiment of the present invention;

16A and 16B represent a device providing protection against an overcharge condition according to another exemplary embodiment of the present invention; and

17-19 illustrate exemplary cordless power tools of a cordless power tool system in accordance with an exemplary embodiment of the present invention.

Detailed Description of Exemplary Embodiments

Referring now generally to the drawings, a system of cordless power tools constructed in accordance with the principles of exemplary embodiments of the present invention will be described. Exemplary cordless power tools for the system shown include, for example, circular saw 10 (FIG. 17), reciprocating saw 20 (FIG. 18), and drill 30 (19). Each of the tools 10, 20 and 30 may include a conventional DC (direct current) motor (not shown) adapted to be powered by a power source having a given rated voltage value. In an exemplary embodiment, tools 10, 20, and 30 may be powered by a detachable power supply having a rated voltage value of at least 18V. It will be apparent to one of ordinary skill in the art that the present invention is neither limited to the particular tool type shown nor to a particular voltage. In this regard, the principles of the invention are applicable to virtually any type of cordless power tool and to any supply voltage.

Continuing now with reference to the drawings, the detachable power supply may be embodied as a battery pack 40 . In the exemplary embodiment shown, the battery pack may be a rechargeable battery pack 40 . The battery pack 40 may include a plurality of batteries connected in series, and/or a plurality of series-connected battery strings, wherein the battery strings are connected in parallel with each other. For ease of describing an exemplary embodiment of the present invention, the battery pack 40 may be composed of cells comprising lithium-ion battery chemistry. Since the exemplary embodiment is intended for a cordless power tool environment, which requires a power source with a much higher voltage rating than traditional low voltage devices using lithium-ion battery technology, such as laptop computers and cellular telephones, the battery pack 40 The rated voltage value can be at least 18V.

However, in terms of the chemical composition of the individual cells, electrodes, and electrolytes of the battery pack 40, the battery pack 40 may, for example, be made of another lithium-based chemical composition such as lithium metal or lithium polymer, or such as nickel cadmium ( NiCd), nickel metal hydride (NiMH) and other chemistries such as lead-acid battery composition.

FIG. 1 shows a partial block diagram of a protection structure according to an exemplary embodiment of the present invention. Figure 1 shows a portion of the battery circuit and specifically shows the respective protection device 102 for each cell 105 of a battery pack such as battery pack 40 in Figures 17-19. In FIG. 1, each protection circuit 102 is adapted to perform a current limiting function. In one example, protection circuit 102 may be embodied as a thermistor device, where the thermistor device is part of or contained within a battery.

A thermistor is a term used to describe a class of electronic components whose main characteristic is that their electrical resistance changes as their temperature changes, ie, 'Thermistors'. Thermistors can be further classified as 'positive temperature coefficient' devices (PTC devices) or 'negative temperature coefficient' devices (NTC devices). PTC devices are devices whose resistance value increases as their temperature increases. NTC devices are devices whose resistance value decreases as their temperature increases. NTC thermistors are typically made from proprietary formulations of transition metal oxide based ceramic materials.

In FIG. 1, the protection device 102 can be embodied as a PTC device, which can protect a string of cells from thermal overload. If one cell gets hot, the resistance of the PTC device in that cell increases, limiting current flow through the string. The disadvantage of this method of protecting the battery is that it requires a number of devices (in this example, PTCs) as protection devices 102 that perform the current limiting function.

FIG. 2 shows a partial block diagram of a protection structure according to another exemplary embodiment of the present invention. An alternative to using multiple protection devices 102 is for each battery to include a dedicated protection circuit 210 that detects one or more battery parameters in a battery pack like battery pack 40, for example. These parameters include, but are not limited to, current flowing through the battery pack, temperature, voltage, and impedance. The protection circuit 210 is operatively connected with a corresponding driving circuit 220 . Level shifting circuit 220 may be connected with a plurality of AND ("AND") gates (shown as block 230) to link protection circuit 210 with master device 240, which performs a current limiting or blocking function. If a protection circuit detects a problem, it can change from a high output state to a low output state. The AND gate ensures that the master device 240 is turned on only if the outputs of all protection circuits are at high level (OK). Additionally, it is conceivable that reverse logic circuits could be used with protection devices that normally output low and use NOR ("exclusive OR") gates instead. As shown in FIG. 2, the main device 240 may be embodied as a semiconductor device such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET). Thus, if the battery pack contains multiple cells 105 connected in series, an exemplary configuration can be envisioned as a set of protection circuits 210 (each battery to specify one).

As discussed above, the use of multiple dedicated protection circuits 210, for example, may require a corresponding level shifting circuit 220 as shown in FIG. 240. If monitoring each cell is excessive, then groups of cells or the entire battery pack can be monitored with a single protection circuit 210 and a single master 240 for current limiting or blocking.

3A is a block diagram illustrating components and connections between an exemplary battery pack and an exemplary battery charger in accordance with an exemplary embodiment of the present invention. FIG. 3A is merely an exemplary circuit configuration and is provided as a background to more clearly describe various protection methods, circuits, and devices according to exemplary embodiments.

Referring to FIG. 3A , the battery pack 100 may include a plurality of batteries 105 connected in series (six are shown for simplicity, the battery pack 100 may include more or less than six batteries, or may consist of series strings connected in parallel to each other in series). composed of battery strings). For ease of describing an exemplary embodiment of the battery pack 100, the battery pack 100 may be composed of batteries including lithium-ion battery chemistries. The voltage rating of the battery pack 100 may be at least 18V since the exemplary embodiments are intended for a cordless power tool environment, which requires a much higher voltage rating than conventional devices using lithium-ion battery technology.

Accordingly, the battery pack 100 in FIG. 3A (and in FIG. 3B ) is applicable to and/or designed for a cordless power tool system including at least a cordless power tool, a battery pack, and a charger. The battery pack 100 can be understood as a detachable power source for high power tool operation. In one example, battery pack 100 may have a rated voltage value of at least 18V and/or have a maximum power output of at least about 385W. However, it will be apparent to those of ordinary skill in the art that the present invention is neither necessarily limited to the specific tool types shown in FIGS. 17-19 nor to the specific voltage values and/or power outputs described above. Regulation.

As far as the chemical composition of the individual cells, electrodes, and electrolyte of the battery pack 100 is concerned, the battery pack 100 may further be composed of another lithium-based chemical composition such as lithium metal or lithium polymer, or such as nickel cadmium (NiCd ), nickel metal hydride (NiMH) and other chemistries such as lead-acid battery composition.

In FIG. 3A, seven wire ends are shown (Line Ends 1-7). However, since more or fewer terminals may be included depending on the desired information passing between the battery pack 100 or charger 150, or the parameters monitored by the battery pack 100 or charger 150, these exemplary embodiments do not Should be limited to this end-of-line configuration.

The battery pack 100 may also include a battery pack ID 110 connected to the output terminal (terminal 1) for identifying the battery pack 100 when inserted into the charger 150. The battery pack ID 110 may include, for example, model number, version, battery configuration, and battery type (chemistry) such as Li-ion, NiCd, or NiMH. The battery pack ID 110 can be embodied as one received from output 1 of the battery pack 100 through an asynchronous full-duplex communication system in the battery pack 100 as described in U.S. Patent No. 5,680,027 issued to Hiratsuka et al. or multiple communication codes. However, this is only an example, since the battery pack ID 110 can also be passed through an ID resistor, an LED display showing the identification data of the battery pack, serial data sent by agreement and detected by the tool/charger eg via terminal 2, and/or or materialize fields etc. in frames of data sent to the tool/charger via the air interface,

The battery pack 100 may further include one or more temperature sensors 120 . The temperature sensor 120 may be embodied as an NTC or PTC thermistor, a temperature detection integrated circuit, or a thermocouple. The temperature sensor 120 may communicate the temperature within the battery pack 100 to smart components in the battery pack 100 and/or via terminal 3 to smart components such as in the connected charger 150 . Since the function of such a temperature sensor is well known, a detailed description of the functional operation is omitted here for the sake of brevity. Electrical connections for charging and discharging are indicated as terminals 1 and 7 .

The battery electronic control unit 125 may be responsible for protecting the battery 105 from any fault conditions on the line caused by the user (via the charger 150, accessory tools, and/or due to user intervention). The battery electronic control unit 125 may be embodied in hardware or software as a digital microcontroller, a microprocessor, an analog circuit, a digital signal processor, or by one or more digital ICs such as application specific integrated circuits (ASICs), for example.

The discharge current and the charge current can be switched on or off using the semiconductor devices 130 a (discharge FET) and 130 b (charge FET) under the control of the battery electronic control unit 125 . The battery electronic control unit 125 may be powered by an internal power supply 135 as shown, and the semiconductor devices 130 a and 130 b may be linked through a drive circuit 140 .

The battery pack 100 may further include a current detector 145 that detects current and provides a signal to the battery electronic control unit 125 . The current detector 145 can be embodied as a well-known component that can provide a signal representative of the sensed current in the battery pack 100 to the battery electronic control unit 125 , current detectors such as shunt resistors, current transformers, and the like. The semiconductor device 130a may include a pull-down resistor 147 that functions to bypass the semiconductor device 130a when the device 130a is turned off and the battery pack 100 is in a sleep state.

The battery pack 100 may also include a voltage monitoring circuit 115 . The voltage monitoring circuit 115 may be embodied, for example, by any known voltage monitoring circuit, and may be configured to detect individual cell voltages and/or to detect the total battery pack voltage ('stack voltage') of the battery string 105, which will be representative of the individual cell or stack voltage The signal of is provided to the battery electronic control unit 125. As a variation, and instead of a single voltage monitoring circuit 115 configured to detect both individual cell and total stacked voltages, the battery pack 100 may include a voltage monitoring circuit as shown in FIG. A first voltage monitoring circuit (shown generally as 115A) and a second voltage monitoring circuit 115B that senses the total superimposed voltage of the battery 110 .

Referring back to, for example, FIG. 2 , the protection circuit 210 may include at least the battery electronic control unit 125, the current detector 145, the voltage monitoring circuit 115, and the temperature sensor 120, and optionally, may further include a battery pack ID 110 and a power supply such as a power supply 135. internal power supply. The driving circuit 140 may be similar to the driving circuit 220 in FIG. 2 , and the semiconductor devices 103 a and 130 b may individually or together represent a main device 240 with a current limiting/breaking function under the control of the protection circuit 210 .

Referring to FIG. 3A , during discharging, the battery electronic control unit 125 may output a pulse width modulation (PWM) control signal to drive the driving circuit 140 . For example, it is common in the electronics industry to use pulsed semiconductors (pulse width modulators (PWMs)) to generate an average voltage proportional to the duty cycle. PWM is a modulation in which the pulse width varies with a certain characteristic of the modulating signal. Alternatively, pulse frequency modulation can be used to generate this average voltage. In each case, semiconductor devices 130a and 130b (which may be embodied as discharge FETs and charge FETs, respectively) can be switched between on and off states to generate an average voltage proportional to the duty cycle of the switching.

During discharge, drive circuit 140 level shifts the PWM output of battery electronic control unit 125 to drive the gate of semiconductor device 130a, cycling semiconductor device 130a between on and off depending on the detected condition. Since semiconductor device 130a is reverse biased, device 130b will only let current flow in the presence of a diode drop. If the current is 2OA and device 130b has a forward voltage of 0.6V, the power dissipation is only 12W. If this power consumption is satisfactory, battery electronics 125 may output a status signal to driver circuit 140, which instructs semiconductor device 130b to remain on during the PWM action on semiconductor device 130a. The power dissipated by device 130b will now be its on-state times the square of the current (I ² R _ON ). Today's MOSFETs typically have an on-state (R _ON ) of 10mΩ, so at 20A, the power dissipation is only 4W. The result is a controlled discharge and lower losses through the semiconductor device.

During discharge, a reverse logic circuit can be applied. Semiconductor device 130a is reverse biased with respect to the direction of current flow, and although conducting in the off state, device 130a should remain in the on state in order to minimize the amount of losses. The semiconductor device 130 b can control the charging current according to the information from the battery electronic control unit 125 via the driving circuit 140 . The layout of components including the driving circuit 140 is known in the art and will not be described here for the sake of brevity.

When the battery pack 100 is connected to the charger 150 , the charger electronic control unit 155 in the charger 150 can be powered from the internal power source 135 of the battery through terminals 1 and 6 . This is only an exemplary connection scheme, as other means of supplying power to the charger ECU 155 may be employed. The charger 150 can have its own power source or be derived directly from the battery voltage. The charger electronic control unit 155 may also be embodied in hardware or software as a digital microcontroller, a microprocessor, an analog circuit, a digital signal processor, or, for example, by one or more digital ICs such as application specific integrated circuits (ASICs). change. Battery and charger data and control information can be exchanged over the serial data path on terminals 4 and 5. The charger ECU 155 can drive the power controller 160 with a set voltage and a set current, and transmit the required voltage and current from the power source 165 to the battery pack 100 through terminals 1 and 7 .

3B is a block diagram illustrating components and connections between an exemplary battery pack and an exemplary power tool in accordance with an exemplary embodiment of the present invention. FIG. 3B is merely an exemplary circuit configuration and is provided as a background to more clearly describe various protection methods, circuits, and devices according to exemplary embodiments. The battery pack and tool configuration of FIG. 3B is applicable to the exemplary cordless power tools in any of FIGS. 17-19 and equivalents. In Fig. 3B, a 'smart' power tool 170 is represented, it being understood that the battery pack 100 is also suitable for powering 'dumb' power tools, i.e. power tools without intelligent devices such as microprocessors or microelectronic control components powered by.

Referring to FIG. 3B , power tool 170 may be powered from internal battery power source 135 via terminals 1 and 6 . The tool 170 may include a mechanical switch 175 that pushes the terminal 7 to a high level when the semiconductor device 130a (discharge FET) is turned off. If the semiconductor device 130a is kept off while the battery pack 100 is in the sleep state, the voltage on the terminal 7 is at a low level due to the pull-down resistor 147 . This resistor should have a relatively high resistance because it functions to bypass semiconductor device 130a. With this pull-down resistor 147 in place and the semiconductor device 130a in the OFF state, the voltage on terminal 7 remains low until switch 175 in tool 170 is activated. As a result, the voltage at the power terminal 7 rises immediately, and the signal via the power terminal 7 can be used to wake up the battery pack 100 from the sleep mode of operation. Tool 170 may include a tool electronic control unit 180 . The tool electronic control unit 180 may also be embodied in hardware or software as a digital microcontroller, a microprocessor, an analog circuit, a digital signal processor, or by one or more digital ICs such as an Application Specific Integrated Circuit (ASIC), for example .

Tool ECU 180 is programmable to read the trigger position of trigger 181 and report the trigger position to battery ECU 125 via the serial data path on terminals 4 and 5 . Based on the trigger position data, the BECU 125 can vary the PWM duty cycle through the semiconductor device 130 a to obtain the desired motor speed of the tool motor 190 . While the semiconductor device 130a is turned off, the diode 195 in the tool 170 can recirculate the residual motor induced current to prevent voltage spikes therein. The forward/reverse switch 185 is commonly used in cordless tools and will not be described here.

A fool's kit (not shown) may simply contain a trigger 181 configured as a potentiometer and connected to one of terminals 1, 4 or 5, and to terminal 6. The battery electronics control unit 125 can recognize the presence or absence of serial data communication and carry out an analog evaluation of the voltage on terminals 4 or 5 . According to the analysis result, the battery electronic control unit 125 can send a PWM control signal through the drive circuit 140 to make the semiconductor device 130a switch according to the required duty cycle, so as to generate a predetermined motor speed. There can also be more foolish tools as on/off tools. These tools are only required to be connected to terminals 1 and 7 for operation.

overcharge protection

There are two basic types of battery chargers for recharging battery packs: trickle chargers and fast chargers. Trickle chargers are much less expensive than fast chargers; however, trickle chargers take about 1/2 day to recharge the battery pack. A fast charger can recharge the battery pack in about an hour. An overcharge fault condition may occur due to some fault condition or system failure in the charger or battery pack. Typically, a protection circuit in a battery pack can detect an overcharge fault condition by monitoring the voltage across the battery pack. During charging, the voltage reaches a certain threshold. The charger therefore considers the battery pack to be 'fully charged' and terminates the charging current. If the charger is locked on due to a component failure, it is preferable to enable the battery pack to disable the charging current with its own semiconductor device such as the charging FET (semiconductor device 130b) under the control of the battery electronic control unit 125 flow past.

Overcharge control can be provided using a charge lock-on detection circuit (also known as a 'hardware watchdog circuit') between the battery pack and charger. Generally speaking, if the charger is locked on and pulsed If data (for example, clock pulses from the battery pack to the charger via the appropriate serial data path) ceases, then the hardware watchdog can automatically shut off current flow.

Traditional hardware watchdog circuits are usually located in the charger. This circuit monitors the charge current and looks for a 10ms current disconnect reset pulse in the charge current. In a typical charging situation, a microprocessor in the charger (eg, the charger electronic control unit 155) can generate this reset pulse using the charging control line I _CTRL . In abnormal conditions (for example, the charger microprocessor has fully locked the current on the on state or the charger power supply has completely locked the current on the on state), the hardware watchdog circuit will suspend operation and use the charge FET Disconnect the charging circuit. However, in conventional configurations, it is still possible to overcharge the battery pack if the microprocessor in the charger continues to generate reset pulses without ever terminating fast charging (eg, due to inappropriate microprocessor behavior).

FIG. 4 is a partial block diagram showing connections between an overcharge protected battery pack and a charger according to an exemplary embodiment of the present invention. In FIG. 4, seven terminals and six batteries are shown for convenience. It goes without saying that more or fewer terminals and batteries can also be represented in exemplary embodiments.

In FIG. 4 , the battery pack 100 includes at least a battery electronic control unit 125 , a semiconductor device 130 b (for example, a charging control FET) and a temperature sensor 120 . The temperature sensor 120 may, for example, be embodied as an internal NTC thermistor. The charger 150 may include at least a charger electronic control circuit 155, a charge FET 157, and a hardware watchdog circuit 158.

The battery electronic control unit 125 may receive the battery temperature value from an internal NTC thermistor and may communicate this information to the charger electronic control circuit 155 via the serial data path on terminals 3 and/or 4 . In case of extreme battery temperature due to an overcharge condition, the battery electronic control unit 125 sends a PWM control signal or pulse through the drive circuit 140 to turn off the semiconductor device 130b, the charging current can be terminated. Alternatively, this control signal may be sent via the serial data path on terminals 3 and/or 4 to the charger electronic control circuit 155 to turn off the charging FET 157 in the charger 150. However, in the event of two points of failure in the battery pack 100 - a short circuit semiconductor device 130b (charge control FET) and improper unit behavior in one of the battery electronic control unit 125 or charger electronic control circuit 155, it is still possible The battery pack 100 is overcharged.

The dashed arrowed line in FIG. 4 shows a hardware watchdog circuit 158 (hereinafter referred to as watchdog 158 ) having multiple reset inputs. In addition to monitoring the charge current reset pulse, watchdog 158 also monitors the serial communication clock pulse path (via terminal 3) as does the reset pulse. If one of these reset pulses does not occur, the watchdog will suspend operation and disconnect the charging current. In the case of two point failures in the battery pack 100 - a shorted charge control FET (e.g., device 130b) and improper unit behavior in either the battery electronic control unit 125 or the charger electronic control circuit 155, it is still possible to make the The battery pack 100 is overcharged.

In addition to monitoring the charge current reset pulse, watchdog 158 also directly monitors the battery pack temperature on temperature sensor 120 (eg, NTC thermistor) to detect an overcharge condition. In FIG. 4, shorting the battery charge control FET (semiconductor device 130b) and any fault in the battery electronic control unit 125 or charger electronic control circuit 155 does not affect the watchdog 158 monitoring the battery pack for detection and termination of an overcharge condition. temperature capability.

In addition to monitoring the charge current reset pulse, watchdog 158 also monitors the individual battery voltages using circuit 415A and terminal 6 to detect an overvoltage condition indicative of an overcharge condition. In FIG. 4, shorting the battery charging control FET (semiconductor device 130b) and any fault in the battery electronic control unit 125 or charger electronic control circuit 155 does not affect the watchdog 158 monitoring the individual batteries for the purpose of detecting and terminating an overcharge condition. voltage capability.

In addition to controlling the hardware watchdog, the voltage monitoring circuit 415A for monitoring the voltage of each battery can also directly control the charging FET 130b in the battery pack 100 through the driver circuit 140, and/or through the AND logic circuit (151) and terminal 6 directly controls the charging FET in the charger (157). This is shown by the dashed line between voltage monitoring circuit 415A and drive circuit 140 . This control allows circuit 415A to stop an overcharge condition caused by the overvoltage of the individual cells.

In addition to monitoring the charge current reset pulse, watchdog 158 also monitors the battery stack voltage using voltage monitoring circuit 415B and terminal 7 to detect an overvoltage condition indicative of an overcharge condition. In FIG. 4, shorting the battery charge control FET (semiconductor device 130b) and any fault in the battery electronic control unit 125 or charger electronic control circuit 155 does not affect the watchdog 158 monitoring the battery stack for detection and termination of an overcharge condition. voltage capability.

In addition to controlling the hardware watchdog, the voltage monitoring circuit 415B for monitoring the superimposed voltage of the battery can also directly control the charge FET (130b) in the battery through the driver circuit (140) (see optional dashed line 425), and/or through The AND logic circuit (151) and terminal (7) directly control the charge FET in the charger (157). This control makes it possible for the voltage monitoring circuit 415B to stop an overcharge condition caused by an overvoltage of the superimposed voltage of the entire battery.

5 is a partial block diagram illustrating a connection between a battery pack and a charger of an overcharge protected cordless power tool system according to another exemplary embodiment of the present invention. For clarity, FIG. 5 omits the voltage monitoring circuits 415A and 41B. It is understood that, similar to that shown in FIG. 'middle.

FIG. 5 is a hybrid of FIG. 4 and shows a watchdog 158' with multiple inputs. Watchdog 158' monitors the charge reset pulse, clock reset pulse, and NTC signal, battery voltage, and/or battery stack voltage to detect a charge lock-on condition. Even in the presence of a shorted charge control FET 130b in the battery pack 100 and inappropriate cell behavior in either the battery electronic control unit 125 or the charger electronic control circuit 155, the charge current can still be cut off and the NTC output can be reduced Share the desired number of terminals with clock pulse terminals. Thus, the exemplary hardware watchdog circuit in FIGS. 4 and 5 can prevent overcharging of the battery by monitoring the condition of both the battery pack 100 and the charger 150 . Even in the event of two point failures in one (or both) of the battery pack 100 and charger 150, such as a shorted battery charge FET and improper microprocessor behavior, the overcharge protection remains active.

Determination of the overcharge fault condition can also be done by other means. If a current detector in the battery pack (eg, current detector 145 ) is making accurate current measurements during discharge, then the battery electronic control unit 125 can make fuel measurements and put the extracted energy back where it came from. This measurement may or may not be used in conjunction with the voltage measurement by the protection circuit 210 in the battery pack 100 to detect an overcharge fault condition.

Over discharge protection

A variety of battery technologies can be harmed when discharged beyond the manufacturer's recommended values. According to an exemplary embodiment, a battery pack 100 such as that shown in FIG. 3A or 3B above may include circuitry that prevents current from flowing when the battery voltage drops below a given voltage threshold, and thus, the undervoltage lockout is turned off. The protection circuit 210 in the battery pack can detect the battery voltage and turn off the discharge FET (semiconductor device 130a) if the battery voltage drops below a given voltage level. The battery 105 is still susceptible to charging, but is no longer discharging. The threshold may be, for example, an absolute threshold set at the time of manufacture, or a threshold that may vary with the amount of a given factor.

FIG. 6 is a graph showing the voltage versus time for automatic cut-off by a protection circuit according to an exemplary embodiment of the present invention. To provide protection against an over-discharge fault condition in the battery pack of a cordless power tool system, if the voltage reaches a given threshold, the exemplary protection circuit 210 in FIGS. 3A-5 (like that shown in FIG. 2) and/or the battery electronics The control unit 125 can automatically cut off the current in the battery pack 100 .

A modification to the voltage threshold described above could be to combine the threshold with a portion of the discharge current to compensate for the impedance of the battery pack 100 . Basing the threshold on an absolute level and subtracting a fraction of the instantaneous current may provide an alternative to undervoltage lockout disconnect.

FIG. 7 is a graph illustrating a voltage versus time curve representing a modified threshold for over-discharge protection according to an exemplary embodiment of the present invention. To facilitate the description of FIG. 7 , the protection circuit 210 or the battery electronic control unit 125 of FIG. 2 may be configured to perform the following calculations and/or perform automatic cut-off. Figure 7 shows an example of a battery pack at 10% state of charge. By adding a portion of the discharge current to compensate for the impedance of the battery pack 100, the battery pack 100 remains above the given discharge threshold of 2.7V.

For example, if a 10A pulsed load is applied to the battery pack 100, the battery impedance causes the voltage to drop below the threshold momentarily, returning to its quiescent value when the current pulse is removed. Although the battery pack 100 still retains 10% charge, the protection circuit will interrupt the current flow. However, if the low voltage threshold is partially compensated by the current as described in the previous paragraph, the threshold will drop during periods of high current flow and no cut-off will occur. In other words, by subtracting a portion of the instantaneous discharge current to compensate for the battery pack impedance, the low-voltage threshold can be varied, thereby avoiding unnecessary automatic cut-offs.

Once the impedance of the battery pack is known, the portion of the low voltage threshold that is related to current can be calculated. Additional battery factors that may affect the low voltage threshold may include battery temperature, battery age, and rate of drop in battery voltage, among others.

overcurrent protection

8A and 8B illustrate exemplary devices that may be used for overcurrent protection in a battery pack according to an exemplary embodiment of the present invention. For simplicity, only a portion of the battery pack circuit is shown in FIGS. 8A and 8B. However, the devices in Figures 8A and 8B may be part of a battery pack 100 as shown in any of Figures 3A-5. Another mechanism by which batteries can be damaged is overcurrent. Various electronic switching methods may have the disadvantage that the electronic switch is prone to failure under short-circuit conditions. When this happens, the operator can overload the attachment tool's motor. For battery pack circuit designs that include discrete impedance branches, devices such as fuses or fusible links can be used to limit the maximum current through that circuit branch.

Since the basic function of fuses is to prevent short circuits, fuses are generally not designed to provide overload protection. However, dual-element (two-element) fuses or time-delay fuses can provide auxiliary motor overload protection, but since these fuses are non-renewable, they must be replaced when blown. Thus, such a fuse may represent a secondary fault and be intended, for example, to prevent further operation.

Thus, a simple fuse like the one shown in FIG. 8A can be designed to limit the current of the battery 105, but also cause permanent damage once its rating is exceeded. Other devices such as positive temperature coefficient (PTC) elements and resettable fuses can replace the fuse in FIG. 8A for overcurrent protection. As discussed above, PTC devices or elements are known as protective elements that control the current flow through the circuit to be protected because their resistance value increases as they give off heat under overcurrent conditions. For example, PTC thermistors have been used as overcurrent protection elements. When the circuit becomes overloaded, the conductive polymer of the PTC thermistor with PTC characteristics heats up and thermally expands to a large resistance value, thereby reducing the current of the circuit to a safe relatively small current level.

Therefore, if a PTC device like the above is connected in series with the battery, the total battery impedance will increase with increasing current. If relatively low impedance is required and no single commercially available PTC device can provide the required low impedance and/or current capacity, then, for example, as shown in FIG. 8B, multiple PTCs can be connected in parallel with each other to share the current.

If separate charge and discharge paths or branches are envisioned in the battery pack, then a thermal fuse such as a PTC element can be placed on each current path. The advantage of this is that the charge path uses low current devices and the discharge path uses high current devices.

The close proximity of the fuse to the end of the line also provides the added benefit of isolating the downstream legs of the electronics from non-isolated chargers. If the battery pack 100 melts enough to expose the battery 105 and the electronic circuit, the fuse (which has been blown) close to the wire end will disconnect the exposed metal from the non-isolated charger output, thereby forming electrical isolation, possibly protecting the accessory. Electronic components in a charger (or tool). Therefore, placing the fuse (or PTC element) in FIG. 8A closer to the line terminals can provide additional overcurrent protection in the battery pack 100 .

Utilizing current sensing means (eg, current detector 145 of FIGS. 3A and 3B ) and semiconductor devices (eg, semiconductor devices 130a and 130b ) to stop current flow once an overcurrent threshold is reached may be a desirable method to prevent battery damage. For example, the current detector 145 may be adapted to sense battery pack current and generate a control signal based on the sensed current exceeding a given current limit or threshold. A semiconductor device (for example, semiconductor devices 130 a and 130 b ) having a current limiting or current breaking function may be directly connected to the current detector 145 . The semiconductor device may be adapted to limit or interrupt current flow based on a control signal received directly from the current detector 145 rather than from the battery electronic control unit 125 via the driver 140 .

It is also possible to combine current sensing with an averaging algorithm if momentary high current loads are acceptable but steady state high currents are not. The applicable current limit or threshold may also be variable and proportional to the temperature of the battery. The advantage of this is that if the battery is already hot, the maximum current drawn is not enough to overheat the internal battery chemistry.

over temperature protection

Some batteries may also be damaged by temperature extremes (extremely high or low temperature) or have decreased performance (ie, decreased voltage and/or current output) due to extreme temperatures. This is especially relevant for battery packs that contain lithium-ion battery chemistries. A battery temperature threshold can be set to shut off the battery pack before it cools below a desired or given temperature. Likewise, a battery temperature threshold can be set to shut off the battery pack before it rises above a desired or given temperature. These thresholds can also be based on set limits that depend in part on current, voltage, age, and rate of temperature rise or fall. As discussed above, one or more temperature sensors may be used to determine the state of the battery pack temperature.

Figure 9 shows a device providing over temperature protection according to an exemplary embodiment of the present invention. An over temperature fault condition in the battery can cause permanent damage. Accordingly, protection circuits configured to monitor absolute temperature can be used to protect against excessive temperature conditions. For the sake of brevity, Figure 9 shows only a part of the battery pack circuit. However, the device in Figure 9 could be part of a battery pack 100 as shown in any of Figures 3A-5.

As shown in FIG. 9 , the protection circuit 210 may be embodied as a thermal switch 910 that opens a high current contact 920 . These contacts may be located within an electrical circuit to stop any current flow in and out of the battery pack 100 until the temperature drops to an acceptable level. These devices can usually be set to break off at a predetermined temperature and are commonly found, for example, in coffee makers. Once the water in the coffee pot boils, the heating element temperature rises above 212°F. The temperature switch detects this temperature and turns off the temperature control switch. When the temperature of the battery pack (or cells) becomes too high, charging and/or discharging functions in the battery pack 100 are disabled.

Alternatively, a thermally controlled release mechanism may 'pop' the battery pack 100 out of the tool 170 or charger 150, and prevent it from being reinserted until the battery pack 100 has cooled. As will be seen in further detail below, this device is similar to an "eject timer" whose purpose is to provide a locking mechanism that confines the eject device within the battery pack 100 . Another device that provides protection against overtemperature fault conditions is the use in thermistors. A thermistor may be used in the battery pack 100 to monitor temperature conditions while maintaining complete electrical isolation of the thermistor from the battery 105 .

Currently, manufacturers can often include a thermistor in the battery pack to monitor the temperature of the core battery pack and terminate charging in the event of an over-temperature condition. These thermistors have a connection structure in which one end is externally connected to the terminal of the charger 150, and the other end is bound to the ground by a negative terminal lead in the battery pack.

In order for high power battery packs such as Li-ion battery packs to be suitable for use in conjunction with existing cordless power tools, and processing lines for power tools manufactured to use these high power battery packs, the above connection structure can be problematic , because this connection creates a potential on the charging path through the thermistor. If a small amount of current passes through the thermistor, it is possible to charge the battery pack outside the protection control and circuit provided in the battery pack 100 and the charger 150 . This could lead to inadvertent overcharging of the battery pack 100, a potentially dangerous condition.

FIG. 10 shows a connection structure of a thermistor according to an exemplary embodiment of the present invention. In FIG. 10, only the negative and positive terminals of the battery pack 100 are shown for clarity. For simplicity, Figure 10 shows only a portion of the battery circuit. However, the thermistor in FIG. 10 could be part of a battery pack 100 as shown in any of FIGS. 3A-5. The two leads (Th+ and Th-) of the thermistor can be brought out to separate terminals 2 and 3 outside the battery pack. These terminals may interface with temperature monitoring circuitry such as that of the charger electronic control unit 155 (not shown in FIG. 10 for clarity), eg, within the charger 150 . This allows the temperature of the battery pack 100 to be monitored while keeping the thermistor completely isolated from the charging path in the battery pack 100 . In doing so, there is no charging path through the thermistor and no potential for overcharging the battery pack 100 through the thermistor.

Audible/visual warning mechanism

It is desirable to provide some kind of warning to the operator of a cordless tool powered by an attached battery pack before cutting off battery power. Similar to the situation in which a fault condition occurs or is in progress, in the owner's car, before the engine is destroyed due to the fault condition (for example, piston damage caused by oil leakage), the car gauge can be detected for a given duration. A warning light is emitted to the vehicle owner on the board.

Both undervoltage and temperature limits can be used to cut off, ie, the battery pack 100 stops outputting current once a threshold is reached. However, before such a fault condition occurs (for example, reaching an undervoltage or overtemperature threshold), a warning mechanism in the battery pack or tool can warn the operator that the operator is approaching a battery that may automatically cut off power to the cells in the battery pack. The upcoming operating limit in the group. The warning mechanism may be audible (by means of a horn or buzzer) or may be visible eg with a desired lighting scheme like LEDs.

Audible and/or visual warning mechanisms may be incorporated into the existing circuitry in battery pack 100 or tool 170 . As discussed above, the battery pack 100, tool 170, or charger 150 in any of FIGS. 3A to 5 may be controlled by intelligent components in the battery pack, tool, charger, or the like. Intelligent components such as the battery electronic control unit 125 or the tool electronic control unit 180 may be configured to control warning mechanisms for various impending or occurred fault conditions. For example, separate audible or visual warnings may be provided to alert the operator of the tool to an over-discharge condition in the battery pack 100, an over-current condition in the battery pack 100, the motor 190 in the battery pack 100 or the accessory tool 170 An over-temperature condition in the battery pack 100 , and/or an under-voltage condition in the battery pack 100 caused by excessive current flowing from the battery pack 100 .

As discussed above, the warning mechanism prior to the impending automatic battery cutoff can be embodied in many different forms. The aforementioned audible warnings such as horns, buzzers, and speaker sounds are acceptable in some work environments, but may not be heard by the tool operator in loud environments. Visual cues such as specific lighting and gauges may also go unnoticed by tool operators in extremely dark or fairly bright work areas.

An alternative warning mechanism to alert the tool operator may be embodied with motor control of the tool motor. Typically, electronic circuitry in one of the tool or the battery pack can reduce the maximum power output capability of the battery pack and create a "foldback" condition. The operator can hear and feel this 'weakened' condition of the tool. Accordingly, operators may be prompted to back off and avoid impending fault conditions (eg, under voltage, over temperature, under temperature conditions, etc.).

Another method of alerting the user to an impending fault condition could be to vary the pulse width modulation (PWM) of the motor control to create a "chatter" effect in the speed of the motor. This gentle cyclical change in motor speed is chosen so that it does not negatively impact tool performance. This approach provides audible or tactile feedback to the user of an impending fault condition.

A third method of alerting the user to an impending fault condition could be to lower the PWM frequency to the audible frequency range and change the tone periodically. This provides an effective warning mechanism for the attention of the operator. At a minimum, the warning mechanism gives the operator a sense of warning, enabling them to complete the current job, but not continue to move on to another job without stopping or recharging the battery pack to eliminate or overcome the impending failure condition.

Any of the above warning mechanisms, whether used alone or in combination with another or more of the above warning alerts, has the potential to improve tool functionality and extend tool and/or battery pack life. The following detailed description is directed to the latter warning mechanism providing the above-mentioned chattering effect in the motor of a power tool depending on the state of charge in the battery pack.

PWM state-of-charge (SOC) indicator

The purpose of the PWM state-of-charge (SOC ) indicator is to alert the operator to an impending fault condition that may cause automatic battery-powered switching, causing the battery pack to 'fail'. This can be achieved by determining the SOC information directly in the motor control unit as part of the battery pack circuitry. Based on the SOC information, the motor control unit in the battery pack can vary the motor current switching frequency to create an audible and/or physically felt 'chatter effect' in the tool motor.

11 is a flowchart illustrating a method of alerting an operator of a power tool of an impending failure condition in a battery pack. Referring to FIG. 11, a motor control unit (not shown) in the battery pack may measure various battery pack parameters to determine state of charge (SOC) information in the battery pack at a given moment (S1110). The motor control unit may be embodied in hardware or software, for example as a digital microcontroller, microprocessor or analog circuit, and/or by a digital IC such as a digital signal processor or an application specific integrated circuit (ASIC). Based on the SOC information, the motor control unit determines a desired motor current switching frequency to affect the tool motor (S1120) in order to generate a vibrating effect to alert the operator (S1130).

There are many ways to evaluate, track and determine the SOC of a battery pack. For example, battery pack parameters measured by the motor control unit to determine SOC information may include battery pack voltage, charge (coulomb) counts (Ah _in −Ah _out ), total battery pack 100 impedance, and the like. Then, the motor control unit determines the motor current switching frequency according to the SOC information.

The motor current switching frequency of the tool 170 motor can be manipulated in a number of ways to alert the user. Therefore, adjusting the motor current switching frequency enables the tool's motor to communicate with the tool operator. The switching frequency can be selected within the audible frequency range so that the motor emits a noise that can be felt by the operator. Exemplary audible frequencies may be, for example, a constant frequency tone emitted by a tool motor, a variable frequency bell tone, or a series of complex multi-frequency tones that mimic the speaking voice of a tool operator. Additionally, the motor control unit may provide pulses to the motor to physically move or vibrate the tool in a manner that lets the operator know, for example, that the battery is dead, or that a fault condition is approaching requiring attention.

The method of pulse width modulating the motor to alert the operator of an impending fault condition such as a low SOC condition can also be used to communicate other fault conditions. For example, the motor current switching frequency may be adjusted to correspond to an over-temperature condition in the battery pack, an over-temperature condition in the tool motor, an over-current condition in the battery pack, and/or caused by excessive current draw from the battery pack The detected information about the undervoltage condition alerts the tool operator. Current, temperature and voltage are just exemplary measurable parameters that can be tracked for a given fault condition.

FIG. 12 is a block diagram showing an exemplary structure for determining SOC and changing a motor current switching frequency according to an exemplary embodiment of the present invention. Somewhat similar to FIG. 3B, FIG. 12 shows the electrical interface relationship between the battery pack 100' and the tool 170', but only certain components are shown for clarity.

Referring to Figure 12, IC1, R1 and Q1 contribute to the protection circuit and cell balancing functions as discussed above with reference to several other figures. IC1 may, for example, represent battery pack electronic control unit 125 in FIGS. 3A and 3B . DATA3 and DATA4 represent the serial data paths that carry serial data between IC1 and IC2; IC2 in Figure 12 could represent a motor control unit. For example, DATA3 may be dedicated to passing data and control signals between IC1 and IC2, and DATA4 is used to send clock pulses to synchronize IC1 with IC2, or vice versa.

Component REG is a voltage regulator that supplies VCC to digital devices IC2 and IC3. In FIG. 12, IC3 may represent the tool electronic control unit 180 as described, for example, in FIG. 3B, and DATA1 and DATA2 represent serial data paths that carry data and control signals between IC3 and IC2. SW1 represents the tool switch that sends current from the battery pack to power tool M1. Resistor R6 and potentiometer R7 form the tool's variable speed input. Each of IC1, IC2, and IC3 may be embodied in hardware or software, for example, as a digital microcontroller, microprocessor, or analog circuit, and/or through a digital IC such as a digital signal processor or an application-specific integrated circuit (ASIC). change.

The motor control unit IC2 drives the gates of Q5 and Q6 (which may be embodied as MOSFETs) in order to regulate the output voltage of the battery pack and thereby control the motor current supplying the motor M1 of the tool. IC2 can measure one of several battery pack parameters to determine SOC. For example, IC2 can monitor the battery pack output voltage across nodes N1 and N2, or perform fuel counting by monitoring the current across shunt resistor R5 and maintaining a time trace (via a suitable internal clock). Also, IC2 can monitor the battery pack impedance by subtracting the loaded pack output voltage (while current is flowing) from the unloaded pack voltage (recorded before current is flowing) and dividing the result by the current measurement made across R5 . Any of these measurable parameters can be used for SOC measurement. IC2 can then use this SOC information to determine the proper switching frequency, and control Q5 and Q6 to achieve that switching frequency.

Redundancy

The features described above are designed to prevent damage to the battery from overuse or malfunctioning components in any part of the control system in battery pack 100 , charger 150 , or tool 170 . By adding a redundant form of auxiliary, the battery is less likely to be damaged by the battery. For example, in FIG. 12, charger 150 and tool 170 may also monitor battery temperature and current flow through external terminals or communication lines. Battery voltage may also be monitored by charger 150 during charging. The battery voltage can also be verified by the tool during discharge.

Figures 13-16 generally represent various devices that provide overcharge protection in extreme conditions. In the event that an overcharge condition is not resolved by the watchdog circuits, other current sensing devices, and/or smart devices of FIGS. failure (multiple point failure in battery pack or charger). 13-16 illustrate potential secondary protection for battery pack 100 and/or charger 150 .

Figure 13A is an isometric view of a single layer battery in which a battery 1305 (similar to battery 105 in any of Figures 3A-5) contains tabs 1303 (also referred to as connectors) to connect to adjacent series cells. 13B and 13C illustrate a device providing protection against an overcharge condition according to an exemplary embodiment of the present invention.

The devices shown in Figures 13B and 13C can reduce the potential of cells containing Li-ion cell chemistries (or other cell chemistries) from rupture due to severe overcharge conditions in which other protection circuits in the battery pack do not participate. In general, the flaky Li-ion battery 1305 can exhibit severe swelling during the overcharging process. If the overcharging continues, this may cause one or more cells 1305 to rupture. Such a rupture could result in a fire and could cause serious damage to the battery pack 100 , the attached electronic device (charger 150 , tool 170 ), and/or the user of the battery pack 100 .

Therefore, battery packs can be designed to take advantage of this swelling phenomenon. 13B is a side view of the battery pack in a steady state or normal condition and shows tab welds 1306 or similar connection points for connecting adjacent cells 1305 in series between the positive and negative power terminals of the battery pack 100. As shown in Figure 13C, swelling of one or more given cells 1305 in the battery pack 100 may help prevent severe overcharge conditions from occurring. The expanding cell 1305 creates tension on its joints 1303 such that the two joints 1303 may separate at the joint weld 1306 . In this example, opening 1308 is formed in the circuit, thereby removing or interrupting the charging current to battery 130 and . Thus, as the cells 1305 expand, the tab connector 1303 is disengaged from the adjacent tab 1303 at the tab weld 1306 , breaking the electrical connection between the cells 1305 , thereby interrupting the flow of current in the battery pack 100 .

14A and 14B illustrate a device providing protection against overcharge conditions according to another exemplary embodiment of the present invention. FIG. 14A shows a side view of battery pack 100 in a steady state or normal condition, thereby illustrating another exemplary protective structure. In FIG. 14A, batteries 1305 may be arranged sequentially in a battery compartment (as generally shown by compartment side wall 1401a and compartment side wall 1401b), which may, for example, include an intermediate compartment wall 1401c. Insertion rods 1408 may be provided between the series cells 1305 and the middle box wall 1401c so as to extend into the groove 1409 through the walls 1401b and 1401c. In this example, the plunger may be constrained by a counter force provided by a spring 1410 to form a channel 1404 between the box side wall 1401b and the middle box wall 1401c. Lead wires (shown here as positive terminal wires or circuit traces) may pass through channel 1404 .

Referring now to Figure 14B, Figure 14B shows a battery 1305 in an overcharged state. As the battery 1305 expands, the expansion force from the battery helps the plunger 1408 overcome the reactive spring pressure from the spring 1410 . Accordingly, the plunger 1408 enters the recess 1409, as generally shown at 1415, cutting the lead 1405, thereby interrupting the charging current to the cells 1405 of the battery pack. It should also be noted that the expanding battery 1305 also disengages the joint 1303 as generally shown at 1308 . Further redundancy is provided for cutting or destroying electrical connections within the battery pack. Thus, this protective feature prevents one or more cells in battery pack 100 from rupturing by interrupting the flow of electrical current.

15A and 15B illustrate a device providing protection against an overcharge condition according to another exemplary embodiment of the present invention. Figures 15A and 15B show a plunger designed to eject the battery pack from the charger.

Figure 15A is similar to Figure 14A, therefore, for the sake of brevity, only the differences are discussed. As shown in FIG. 15A , in steady state or normal operation, the plunger 1408 is biased against the reactive spring pressure of the spring 1410 so that the plunger 1408 rests against the charger case side wall 1501 . The side wall 1501 of the charger box is adjacent to the side wall 1040 b of the battery pack 100 . The battery pack lead 1405 and charger lead 1505 are operatively connected to contacts 1410 and 1510 .

Referring now to FIG. 15B, as the battery 1305 expands, the plunger 1408 overcomes the pressure of the spring 1410 causing the plunger 1408 to self-eject the battery pack 100 from the charger, see the gap between the charger case side wall 1501 and the battery pack side wall 1401b 1508. This action destroys contacts 1410 and 1510 . Thus, in the event of a severe overcharge condition, the expansion of the battery pack combined with the displacement of the plunger 1408 interrupts the charging current and prevents battery pack rupture by ejecting the battery pack from the charger. It should also be noted that the expanding battery 1305 also disengages the joint 1303 as generally shown at 1308 . Further redundancy is provided for cutting or destroying electrical connections within the battery pack. Thus, this protective feature prevents one or more cells in battery pack 100 from rupturing by interrupting the flow of electrical current.

16A and 16B illustrate a device providing protection against overcharge conditions according to another exemplary embodiment of the present invention. Figures 16A-B are similar in some respects to Figures 14A-14B, therefore, for the sake of brevity, only the differences are described.

In FIG. 16A , a charger lead or contact wire 1505 is connected to the battery pack leads at contacts 1405 and 1505 . Unlike FIG. 14A , the charger leads 1505 adjoin the inside surface of the charger case side wall 1501 . The plunger 1408 and spring 1410 are as described in Figure 14A. Referring now to FIG. 16B, FIG. 16B shows a battery 1305 in an overcharged state. As the battery 1305 expands, the expansion force from the battery helps the plunger 1408 overcome the reactive spring pressure from the spring 1410 . Accordingly, the plunger 1408 travels into the groove 1409, as generally shown at 1615, cutting the lead 1505, thereby interrupting the charging current to the cells 1405 of the battery pack. It should also be noted that expanding battery 1305 also ruptures joint 1303 as generally shown at 1308 . Further redundancy is provided for cutting or destroying electrical connections within the battery pack. Thus, this protective feature prevents one or more cells in battery pack 100 from rupturing by interrupting the flow of electrical current.

While exemplary embodiments of the invention have thus been described, it will be obvious that they may be varied in many ways. Such changes are not to be regarded as a departure from the spirit and scope of the exemplary embodiments of this invention, and all such modifications apparent to those of ordinary skill in the art are intended to be included within the scope of the appended claims.

Claims (49)

1. one kind provides protection in case the protection structure in the battery pack of fault state in battery pack, and battery pack is fit to the cordless power tool power supply and comprises a plurality of batteries, and this protection structure comprises:

A plurality of different protection devices, each battery contain the corresponding protection device that is fit to carry out current-limiting function.

2. structure according to claim 1, wherein, each protection device is embodied to thermistor.

3. structure according to claim 1, wherein,

Battery connect mutually form a string battery and

Each protection device is embodied to when its respective battery reaches fault state, and its resistance value increases positive temperature coefficient (PTC) device with the electric current of restricted passage entire cell string.

4. structure according to claim 1, wherein, battery pack is the lithium ion battery group.

5. structure according to claim 4, wherein, the lithium ion battery group has the load voltage value of 18V at least.

6. one kind is fit to the cordless power tool power supply and comprises the battery pack of a plurality of series-connected cells, and this battery pack comprises and being fit to according to the fault state restriction that detects in battery pack or the protection structure of interrupting the electric current in the battery pack.

7. battery pack according to claim 6, described structure further comprises:

At least one protective circuit is used to detect given battery pack parameter, to determine the fault state in one or more batteries and to generate control signal according to the indication of fault state; With

Main device contains and is fit to basis from the control signal restriction of protective circuit reception or the current limliting or the cutout function of interruptive current.

8. battery pack according to claim 6, described structure further comprises:

Temperature sensor is used to detect battery pack temperature to generate first signal;

Current detector is used to detect battery pack current to generate secondary signal; With

Battery control circuit is fit to receive described first and second signals to determine the fault state in the battery pack and to generate control signal.

9. battery pack according to claim 8, wherein,

The battery electron control unit with control signal send to the semiconductor device that operationally is attached thereto and

Semiconductor device has current limliting or the cutout function according to control signal restriction or interruptive current.

10. battery pack according to claim 6, described structure further comprises:

Current detector is used to detect battery pack current to generate control signal according to the overcurrent fault situation that detects; With

Have current limliting or cutout function and the semiconductor device that operationally is connected with current detector, this semiconductor device is fit to according to the control signal restriction or the interruptive current that receive from current detector.

11. wherein, if the battery pack current that detects surpasses given threshold value, there is the overcurrent fault situation in battery pack according to claim 10.

12. battery pack according to claim 11, wherein, current threshold is based on the temperature of battery.

13. battery pack according to claim 6, described structure further comprises:

Battery control circuit is configured to monitoring battery voltage, battery current and current temperature, so that generate control signal; With

Operationally be subjected to the semiconductor device of battery control circuit control, this semiconductor device is fit to according to control signal restriction or interruptive current.

14. battery pack according to claim 13, described structure further comprises:

Temperature sensor is used to detect battery temperature, so that detection signal is outputed to battery control circuit;

Current detector is used to detect battery current, so that detection signal is outputed to battery control circuit; With

Voltage monitoring circuit is used to detect one of each cell voltage of battery pack and total battery voltage, so that detection signal is outputed to battery control circuit.

15. battery pack according to claim 6, described structure further comprises:

At least one communication ends is used for that information is sent to attached external component and from attached external component detection information.

16. battery pack according to claim 6, described structure further comprises:

At least one protective circuit if be used for reaching given voltage threshold at the potential overdischarge fault state monitor battery pack voltage of battery pack and the voltage that is fit to monitor, automatically perform the electric current that cuts off in the battery pack and flows.

17. battery pack according to claim 6, described structure further comprises:

At least one protective circuit if be used for reaching given dynamic electric voltage threshold value at the potential overdischarge fault state monitor battery pack voltage of battery pack and the voltage that is fit to monitor, automatically perform the electric current that cuts off in the battery pack and flows,

Wherein, change the dynamic electric voltage threshold value, with the impedance of balancing battery group with avoid temporarily dropping to the wrong cut-out automatically that the electric current that causes below the threshold value flows because of the voltage that monitors by from the absolute threshold level, deducting a part of instantaneous discharge electric current.

18. battery pack according to claim 6, described structure further comprises:

Being placed to connects with the series-connected cell in the battery pack provides protection in case the single PTC device of overcurrent fault situation, total this PTC device is fit to increase its battery pack resistance value that raises with the electric current in the battery pack.

19. battery pack according to claim 6, described structure further comprises:

In battery pack, be placed to parallel with one another to form a plurality of PTC devices of PTC string in parallel; this parallel connection PTC string is placed with connect with series-connected cell provides protection in case the overcurrent fault situation, total this parallel connection PTC string is fit to increase its battery pack resistance value of rising with the electric current in the battery pack.

20. battery pack according to claim 6, described structure further comprises:

Be arranged in the battery of battery pack and at least one fuse between the line end, wherein, it is nearer that battery is compared to line end in the body position of fuse, thereby under the situation that occurs overcurrent fault in battery pack, the battery of battery pack is separated with link to each other charger or electric tool with associated electronics.

21. battery pack according to claim 6, wherein, this battery pack is the lithium ion battery group.

22. battery pack according to claim 6, wherein, the lithium ion battery group has the load voltage value of 18V at least.

Can listen alert mechanism 23. battery pack according to claim 6, described structure further comprise, be configured to being about in user's battery pack of indicating battery group and occur or the situation that broken down.

24. battery pack according to claim 6, described structure further comprises visual cautionary mechanism, is configured to being about in user's battery pack of indicating battery group and occurs or the situation that broken down.

25. the method for overvoltage protection is provided in the battery pack on being attached to cordless power tool or charger, and this battery pack operationally is attached on the charger to batteries charging interchangeablely, this method comprises:

Detect the overvoltage fault state in the battery pack; With

According to the charging current in fault state termination battery pack that detects or the charger.

26. method according to claim 25, wherein, this termination step comprises the control signal that generates in the battery pack, so that the semiconductor device in the battery pack of the electric current in the charge path of suitable restriction of disconnection or interruption battery pack.

27. method according to claim 25, wherein, this termination step further comprises:

Generate the control signal in the battery pack; With

Control signal is sent to charger, so that the semiconductor device in the battery pack of the electric current in the charge path of suitable restriction of disconnection or interruption battery pack, the electric current that stops in the battery pack is mobile.

28. the watchdog circuit of a charger, this charger operationally is attached on the battery pack to this batteries charging, this watchdog circuit flows with the electric current that stops in the battery pack at from one or more control signal monitor battery pack of battery pack or charger and the parameter in the charger.

29. watchdog circuit according to claim 28, wherein, described parameter comprise battery pack temperature, each cell voltage, cell stack voltage, from the charging current replacement pulse of battery pack, from the clock resetting pulse of battery pack and/or one or more from the discharging current replacement pulse of charger.

30. in the charger that is fit to batteries charging, the charger of cordless power tool systems and battery pack part, this charger comprises:

The charging current interrupt circuit is used for flowing with the electric current that stops in the battery pack at from the one or more control signal monitor battery pack of battery pack or charger and the parameter of charger.

31. charging current interrupt circuit according to claim 30, wherein, described parameter comprise battery pack temperature, each cell voltage, cell stack voltage, from the charging current replacement pulse of battery pack, from the clock resetting pulse of battery pack and/or one or more from the discharging current replacement pulse of charger.

32. one kind is fit to the cordless power tool power supply with by the battery pack of charger charging, this battery pack comprises a plurality of batteries, and this battery pack comprises:

According to the battery pack temperature that surpasses given temperature threshold or separately battery temperature stop the device of the excessive temperature situation in the battery pack.

33. battery pack according to claim 32, wherein, this device further comprises:

Thermal switch; With

A plurality of big current contact,

Wherein, when battery pack or battery temperature surpassed given threshold value, thermal switch was opened big current contact.

34. in the battery pack that operationally is attached on the charger, at the device that the excessive temperature protection is provided in battery pack between charge period, this battery pack is fit to the cordless power tool power supply, this device comprises:

Thermistor;

First thermistor lead-in wire that the positive terminal that thermistor and battery pack and charger are shared is connected; With

Second thermistor lead-in wire that the negative terminal that thermistor and battery pack and charger are shared is connected.

35. device according to claim 34, wherein, positive terminal that is connected with first and second lead-in wires and the handing-over of the temperature monitor circuit in negative terminal and the charger, thus the charge path in keeping thermistor and battery pack can the monitor battery pack temperature when isolating.

36. a battery pack, this battery pack operationally are attached on the cordless power tool motor power supply to electric tool, this battery pack comprises:

Motor control unit is used for determining at least one measurable parameter of battery pack that can the indication fault situation; With

The pair of transistor of communicating by letter with circuit for controlling motor, but this circuit for controlling motor is controlled the user that this offers one of visible or tactile feedback to transistor instrument.

37. in comprising the cordless power tool systems that is attached to the battery pack on the electric tool, provide listened to warning in the motor of electric tool with operating personnel's battery pack of reminding instrument or the method that is about to the situation of breaking down in the instrument, this method comprises interchangeablely:

Determine at least one measurable parameter in one of battery pack or instrument; With

But one of visible or tactile feedback are offered the user of instrument according at least one measurable parameter of determining.

38. according to the described method of claim 37, wherein, this provides step to comprise according at least one to determine parameter adjustment current of electric switching frequency, to produce the audible tone in the motor of instrument that warning tool operation personnel are about to the situation of breaking down.

39. according to the described method of claim 37, wherein, this provides step to comprise the required PWM duty ratio of adjusting at least one semiconductor device in the battery pack, to produce the vibrato that warning tool operation personnel are about to the motor speed of the situation of breaking down.

40. according to the described method of claim 39, wherein, this set-up procedure comprises minimizing PWM duty ratio, warns the user to be about to the instrument reduction as tool user is felt of the situation of breaking down to produce.

41. a battery pack that has additives for overcharge protection, this battery pack comprises:

Battery case;

Wherein a plurality of series-connected cells; With

The current interruptions mechanism of the electric current in the interruption battery that during the process of overcharging occurring, triggers according to the expansion of at least one battery.

42. according to the described battery pack of claim 41, wherein,

Battery strings is associated between the power end of battery pack and by joint connector and interconnects, and the joint connector of adjacent cell interconnects.

43. according to the described battery pack of claim 42, wherein, current interruptions mechanism is embodied to at least one joint connector of adjacent cell throws off at least one joint connector with the expansion battery of interruptive current.

44. according to the described battery pack of claim 41, wherein, current interruptions mechanism comprises:

Inserted link; With

Spring, inserted link is being constrained under the effect of the reaction force that spring provides between the sidewall of series-connected cell and battery case, the part that comprises inserted link stretches into the part in the groove that forms in the middle of the midfeather of battery box and lateral wall, groove comprises the lead-in wire that comes from battery pack that the battery with battery pack is electrically connected with charger

Wherein, the expansion of at least one battery helps inserted link to overcome spring pressure to cut off lead-in wire in the groove with interruptive current.

45. according to the described battery pack of claim 41, wherein, battery strings is associated between the power end of battery pack and by joint connector and interconnects, the joint connector of adjacent cell interconnects and current interruptions mechanism further comprises with at least one joint connector of adjacent cell and throws off at least one joint connector with at least one expansion battery of interruptive current.

46. according to the described battery pack of claim 41, wherein, current interruptions mechanism comprises:

Inserted link; With

Spring, inserted link is being constrained under the effect of the reaction force that spring provides between the sidewall of series-connected cell and battery case, and inserted link comprises that part stretches into the part in the groove, and groove runs through the sidewall of battery box and the sidewall of charger box extends,

Wherein, the charger that charger is electrically connected with the respective lead of battery pack lead-in wire along the charger box sidewall surfaces and on groove longitudinal extension and

Wherein, the expansion of at least one battery helps inserted link to overcome spring pressure to be breaking at the charger lead-in wire that extends on the groove with interruptive current.

47. according to the described battery pack of claim 46, wherein, battery strings is associated between the power end of battery pack and by joint connector and interconnects, the joint connector of adjacent cell interconnects and current interruptions mechanism further comprises with at least one joint connector of adjacent cell and throws off at least one joint connector with at least one expansion battery of interruptive current.

48. according to the described battery pack of claim 41, wherein, current interruptions mechanism comprises:

Inserted link; With

Spring, inserted link is being constrained under the effect of the reaction force that spring provides between the sidewall of series-connected cell and battery case, and inserted link comprises that part stretches into the part in the groove of battery box and charger box formation,

Wherein, the lead-in wire that comes from battery on contact interface, be electrically connected with the respective lead of charger and

Wherein, the expansion of at least one battery helps inserted link to overcome spring pressure to eject battery box from charger box, contact interface is split with interruptive current.

49. according to the described battery pack of claim 48, wherein, battery strings is associated between the power end of battery pack and by joint connector and interconnects, the joint connector of adjacent cell interconnects and current interruptions mechanism further comprises with at least one joint connector of adjacent cell and throws off at least one joint connector with at least one expansion battery of interruptive current.

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