JP2020054169A - Electrical machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent current from flowing from one battery pack to the other battery pack, suppress an increase in cell temperature of the battery pack, and increase battery life. An electric device that has two battery pack mounting portions and is connected in parallel to operate a working device by the battery pack, and allows a current in only one direction in a discharge path of a battery pack 100A and reverses the electric current. A first discharge cutoff unit (FET1, FET3) for cutting off a current in one direction is provided, and a second path for allowing a current in only one direction and blocking a current in the opposite direction is provided in the discharge path of the second battery pack 100B. Discharge interruption parts (FET2, FET4) were provided. The control unit 50 brings the current in the path of the higher voltage in the battery pack into the conducting state, and when the voltages of both battery packs become the same, brings the first and second discharge interruption units into the conducting state. [Selection diagram] FIG.

Description

  The present invention relates to an electric device that drives a load such as a motor and lighting using a battery pack as a power source, and more particularly to an improvement for efficiently using a plurality of mounted battery packs.

  Electric devices such as electric tools are driven by battery packs using secondary batteries such as lithium-ion batteries, and cordless electric devices are becoming more cordless. For example, in a hand-held power tool that drives a tip tool by a motor, a battery pack that can be mounted as a power source is used, and the motor is driven by electric energy stored in the battery pack. When the voltage of the battery pack is reduced by the discharge, the battery pack is detached from the power tool main body, charged using an external charging device, and mounted again on the power tool main body.

  Cordless power tools and electrical equipment require a certain amount of operation time and a certain amount of output. Higher capacity and higher voltage battery packs have been attempted as secondary battery performance has improved. . Also, with the development of electric equipment using a battery pack as a power source, battery packs of various voltages have been commercialized. Generally, the capacity of the battery pack is increased by increasing the capacity of the battery cells used or by connecting a plurality of cell sets or cells in parallel. Further, in Patent Literature 1, a plurality of battery packs can be mounted on one electric power tool to extend the operating time.

JP-A-2006-087724

  In a cordless electric device, in which a plurality of battery packs of the same voltage can be simultaneously mounted, a method of discharging battery packs one by one (switching method) and a method of connecting battery packs in parallel and discharging (parallel method) ) Are known. In the switching method, the operable time is increased by n times by the number (n) of the mounted battery packs. In the case of the parallel system, by discharging in parallel from the battery packs, it is possible to reduce the value of the current flowing through each battery pack in order to obtain the same output current, so that various advantages can be obtained. For example, a cell having a low rated current can be used, and the cost can be reduced. In addition, by supplying a larger current, a high-output device can be realized. The battery life can be extended by suppressing the temperature rise. Furthermore, by performing the parallel discharge, there is no sudden change in the output that occurs at the time of switching when discharging one by one, and the output of the electric device is continuously changed from the start of use of the battery pack to the end of use due to insufficient battery power. be able to. In this case, the user can use the electric device without feeling uncomfortable, and can naturally feel the consumption of the battery.

  On the other hand, when the battery packs are connected in parallel and discharged, simply connecting them in parallel may cause a phenomenon that current flows from one battery pack to the other battery pack. In particular, a large current exceeding the cell rating flows between battery packs having a large difference in the remaining capacity and a large difference in the battery voltage, resulting in deterioration and failure of the cell. In addition, when there is a battery pack in which cell imbalance occurs, that is, when a cell with reduced performance is included, it means that the battery pack is charged. There is a risk that the battery pack as a whole will be degraded or malfunction due to an overcharged state.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and an object of the present invention is to provide an electric device capable of operating for a long time with high output by connecting and discharging battery packs having the same rated voltage in parallel. Is to provide.
Another object of the present invention is to prevent a current from flowing from one battery pack to another battery pack when connecting a plurality of battery packs in parallel, suppress a rise in cell temperature of the battery pack, and extend the life of the battery. An object of the present invention is to provide an electric device that has been increased.
Still another object of the present invention is to provide an electric device in which a semiconductor switching element or a diode is inserted in a parallel connection circuit of a battery pack, and a stable operation is performed by detecting a failure of the semiconductor switching element or the diode at startup. To provide.
Still another object of the present invention is to provide an electric device in which a battery pack having a performance difference (for example, a voltage difference) can be used efficiently by switching between a parallel connection and a single connection of a plurality of connected battery packs. It is in.

The typical features of the invention disclosed in the present application will be described as follows.
According to one feature of the present invention, in an electric device having a plurality of battery pack mounting portions for mounting a battery pack and operating a working device by connecting the plurality of mounted battery packs in parallel, a first battery pack is provided. In the discharge path, a first discharge interrupting portion is provided to allow a current in only one direction and interrupt a current in the reverse direction, and to allow a current in only one direction in a discharge path of the second battery pack, A second discharge interrupter for interrupting the current in the direction was provided. In addition, a control unit is provided for controlling connection or cutoff of the first and second discharge cutoff units, and the control unit sets the current of the higher voltage path of the battery packs to a conduction state, and the voltage of both battery packs is reduced. When they became the same, the first and second discharge interrupting portions were made conductive. Each of the first and second discharge interrupting sections has a plurality of elements, and the elements include a switching element such as an FET that can control connection or interruption of a current path by a microcomputer.

  According to another feature of the present invention, the first and second discharge interrupting sections include a diode and a field effect transistor connected in series, or two field effect transistors connected in series. The two field-effect transistors connected in series each have a body diode and are connected so that the directions of the source and the drain are reversed. Further, switch means such as a trigger switch is provided in a path from the battery pack to the first and second discharge interrupting sections, and the operation or stop of the work equipment is switched by the switch means. When the trigger switch is turned on, the battery packs can be connected in parallel, and the control unit turns on the switching element in the first path and the switching element in the second path to establish parallel connection of the battery packs. Each of the battery packs has a function of outputting a discharge stop signal, and when the discharge stop signal is output, the control unit sets the discharge cutoff unit of the output path of the battery pack to a cutoff state and continues discharging the remaining battery packs. .

  According to still another feature of the present invention, in an electric device for operating a working device by connecting a plurality of battery packs in parallel, a trigger switch, a semiconductor switching device, and a reverse voltage protection device are provided in each of the connection paths of the plurality of battery packs. Are provided in series, and when the trigger switch is turned on, the control unit turns on the semiconductor switching element to establish a parallel connection circuit of the battery packs. Since the control unit controls the ON / OFF of the semiconductor switching element in this manner, the control unit can control the discharge start timings of the plurality of battery packs to be different depending on the voltage of the battery pack. For example, after the trigger switch is turned on, the control unit can control the semiconductor switching element by determining whether to perform single discharge or parallel discharge in accordance with the remaining amounts of the plurality of battery packs.

  ADVANTAGE OF THE INVENTION According to this invention, a high output and long-time operation | movement can be made possible by connecting and discharging the battery pack of the same rated voltage in parallel. In addition, when a plurality of battery packs are connected in parallel, current can be prevented from flowing from one battery pack to the other battery pack, so that a rise in cell temperature of the battery pack can be suppressed, and the life of the battery can be increased. . Even if a plurality of battery packs are connected in parallel, stable operation can be achieved. In a configuration in which battery packs are connected in parallel to prevent reverse voltage from the high-voltage battery pack side to the low-voltage battery pack side, a semiconductor switching element that switches on and off, and a semiconductor for reverse voltage prevention connected in series to the switching element Since the switching element or the diode is further provided, establishment and interruption of the parallel connection can be arbitrarily controlled by the control unit. In addition, since the semiconductor switching element with a body diode for preventing a reverse voltage can be switched between a conductive state and a non-conductive state, when it is expected that the body diode generates a large amount of heat, the body diode is turned off to suppress the heat generation of the body diode. It becomes possible. Furthermore, single connection is performed while the potential difference between the plurality of battery packs is large, and parallel connection is performed when the potential difference becomes equal to or less than the allowable value.Therefore, even when a battery pack having a large potential difference is mounted, the parallel connection operation is performed. It has become possible.

FIG. 2 is a perspective view of a power tool main body 1 to which a plurality of battery packs can be attached. FIG. 2 is a circuit diagram of the power tool main body 1 of FIG. 1. 2 is a flowchart illustrating a control procedure of a power input path using FETs 1 and 2 in the power tool main body 1 of FIG. 1. 4 is a flowchart showing a failure detection procedure in step 201 of FIG. FIG. 6 is a circuit diagram of a power tool main body 1A according to a second embodiment of the present invention. It is a flowchart which shows the control procedure of FET1-4 in the electric power tool main body 1A of FIG. 7 is a flowchart showing a control procedure of FETs 3 and 4 in step 300 of FIG. 7 is a flowchart showing another control procedure of the FETs 3 and 4 in step 300 of FIG. It is a flowchart which shows the determination procedure of the parallel discharge of the battery pack in the electric power tool main body 1A. It is a flow chart which shows another judging procedure of parallel discharge of a battery pack in electric power tool main part 1A. It is a figure for explaining the 1st discharge control of electric power tool main part 1A concerning a 2nd example of the present invention. It is a figure for explaining the 2nd discharge control of electric power tool main part 1A concerning a 2nd example of the present invention. It is a figure for explaining the 3rd discharge control of electric power tool main part 1A concerning a 2nd example of the present invention. It is a figure for explaining the 4th discharge control of electric power tool main part 1A concerning a 2nd example of the present invention. It is a figure for explaining the 5th discharge control of electric power tool main part 1A concerning a 2nd example of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same portions are denoted by the same reference numerals, and repeated description will be omitted. In this specification, a power tool that operates on a battery pack will be described as an example of an electric device.

  FIG. 1 is a perspective view of the power tool. The power tool includes a power tool main body 1 and two battery packs 100 (100A, 100B) mounted on the power tool main body, and drives a tip tool and work equipment (not shown) using a rotational driving force of a motor (not shown). The power tool main body 1 includes a housing 2 that is an outer frame that forms an outer shape. A handle portion 3 is formed in the housing 2, and a trigger switch 4 operated by an operator is provided near an upper end of the handle portion 3. A battery pack mounting portion 10 for mounting the battery pack 100 is formed below the handle portion 3. A tip tool mounting portion 9 is provided on the front side of the housing 2. In addition, a wind window 7 (intake port) for taking outside air into the housing 2 is provided at a rear portion of the housing 2. The wind window 7 may be an exhaust port for discharging the air inside the housing 2 to the outside.

  Two battery packs 100 (100A, 100B) can be mounted on the battery pack mounting section 10. In this specification, for convenience of description, one side is referred to as a battery pack A (100A), and the other side is referred to as a battery pack B (100B). Basically, the following description will be made assuming that both battery packs 100A and 100B have the same voltage and the same capacity. However, in this embodiment, battery packs having the same rated voltage and different battery capacities may be connected, or battery packs having different rated voltages and different rated capacities may be connected.

  The battery packs 100A and 100B are configured to be detachable from the power tool main body 1 by a rail mechanism (not shown) formed on the battery pack mounting portion 10. Five lithium-ion battery cells rated at 3.6 V are accommodated inside the battery pack 100, and supply a DC voltage of 18 V to the power tool body 1. A latch button 130 is formed on the upper part of the rear surface of the battery pack 100. When the battery pack 100 is mounted on the power tool main body 1, pressing the latch button 130 causes the latch claw of the latch mechanism and the power tool main body to move. 1 is released, and the battery pack 100 can be removed by relatively moving the battery pack 100 rearward. The two battery packs 100A and 100B that can be mounted can be separately mounted and removed from the battery pack mounting portion 10 in any order.

  FIG. 2 is a circuit diagram of the power tool of FIG. The power tool main body 1 operates at a rated voltage of 18 V, and a battery pack mounting portion 10 (see FIG. 1) is formed with terminal portions (not shown) for mounting two identical types of battery packs 100A and 100B. You. Inside the battery packs 100A and 100B, five cells 101 to 105 of a 3.6 V lithium ion secondary battery are connected in series to form one cell set 110, and the positive output of the cell set 110 is a positive terminal. 141, and the negative output of the cell set 110 is connected to the negative terminal 142. In the battery packs 100A and 100B, a control unit 120 for controlling charging and discharging of the cells 101 to 105 is provided. The control unit 120 can use a dedicated IC for monitoring the voltage between terminals of the battery cells 101 to 105, for example, a commercially available battery protection IC. Although one signal line 146 from the cell set 110 to the control unit 120 is shown here, it actually includes six wirings for transmitting potentials between the terminals 101 to 105.

  The control unit 120 monitors the voltage of the battery cells 101 to 105, and when any one of the battery cells 101 to 105 is in an overdischarge state, instructs the LD terminal 143 to stop the discharge in order to stop or limit the discharge. (Discharge stop signal 147). When the battery packs 100A and 100B are connected to an external charger instead of the power tool main body 1, the LD terminal 143 is used to send an instruction signal for stopping charging (a charging stop signal 147). Used. When charging is stopped, the control unit 120 monitors the voltage of the battery cells 101 to 105, and transmits a charge stop signal to the LD terminal 143 when any of the battery cells 101 to 105 is overcharged. The LS terminal 144 is a terminal for transmitting the output of the thermistor 145 to the power tool main body 1 or an external charger (not shown). Although the position of the thermistor 145 is not strictly shown in FIG. 2, a thermistor is disposed on the side of the object whose temperature is to be measured, for example, the battery cells 101 to 105, and a signal corresponding to the cell temperature is output from the LS terminal 144. You. The output signal of the thermistor 145 is not directly output to the power tool main body 1 side, but is output to the control unit 120, so that the control unit 120 generates a signal to the LS terminal 144. May be.

  The power tool main body 1 is provided with two sets of positive input terminals 41 and 46 and two sets of negative input terminals 42 and 47. Power from the positive input terminals 41 and 46 is transmitted to the motor 35 via the trigger switch 4. In the path from the positive input terminal 41 to the motor 35, a first pole 4a of the trigger switch 4 and a first discharge interrupter are provided. The first discharge interrupting unit is constituted by an FET (field effect transistor) 1 and a D (diode) 1. Similarly, a second pole 4b of the trigger switch 4 and a second discharge interrupting unit are provided in a path from the positive input terminal 46 to the motor 35. The second discharge interrupting unit is constituted by the FET2 and the diode D2. FET1 and FET2, which are one type of semiconductor switching element, are turned on (ON state) and turned off (ON state) by gate signals 53 and 54 from a microcomputer (hereinafter referred to as "microcomputer 50a") included in the control unit 50. OFF state) is switched. A body diode is provided between the drain and the source of each of the FET1 and the FET2, and the forward direction of the body diode is set to be opposite to the direction in which the main current (discharge current) flows. The diodes D1 and D2 are reverse voltage protection elements for preventing a reverse current flowing from a higher battery voltage to a lower battery voltage when the two battery packs 100A and 100B are connected in parallel.

  The trigger switch 4 is a two-circuit, one-contact (double-pole, single-throw) switch. When the trigger lever is pulled, the path from the positive input terminal 41 to the FET 1 and the path from the positive input terminal 46 to the FET 2 become independent. At the same time. The power tool main body 1 is further provided with two sets of LD terminals 43 and 48 and LS terminals 44 and 49, which are transmitted to the control unit 50 via signal lines 63 to 66.

  When at least one of the battery packs 100A and 100B is connected to the power tool main body 1 and the trigger switch 4 is first turned on, a power supply circuit (not shown) is activated to supply power to the control unit 50, thereby activating the microcomputer 50a. I do. Then, after checking whether the operation of the FET1 and the FET2 is normal, the microcomputer 50a turns on one or both of the FET1 and the FET2 using the gate signals 53 and 54. As a result, power is supplied to the motor 35, and the motor 35 starts. The negative terminal of the motor 35 is connected to the negative input terminals 42 and 47 via the switching element 36.

  The microcomputer 50a has a plurality of voltage signal lines for measuring a battery voltage in order to monitor the states of the battery pack 100 and the FETs 1 and 2. The voltage signal 51 of the battery pack 100A is used to measure the voltage on the output side of the trigger switch 4 (first pole 4a) and the input side of the FET 1 (voltage on the battery pack A side). Input to the converter. The voltage signal 52 of the battery pack 100B is used to measure the voltage on the output side of the trigger switch 4 (second pole 4b) and the input side of the FET 2 (voltage on the battery pack B side). Input to the converter. The microcomputer 50a outputs the gate signals 53 and 54 of the FETs 1 and 2, and the microcomputer 50a controls on / off of the FETs 1 and 2.

  The output voltage signal 55 on the battery pack 100A side is a signal line for measuring the voltage on the output side of the FET1, and the output voltage signal 56 on the battery pack 100B side is a signal line for measuring the voltage on the output side of the FET2. Both are input to the A / D converter of the microcomputer 50a. The microcomputer 50a can detect abnormality of the FET1, FET2, D1, and D2 by comparing the voltage signals (51, 52, 55, 56) (the detection procedure will be described later with reference to FIG. 4).

  The thermistor 38 is provided near the FET1, FET2, and the diodes D1, D2 on the circuit board, and detects the temperature of these elements. Only one thermistor 38 may be provided on the circuit board, or if it is desired to increase the accuracy, it may be provided corresponding to each. The microcomputer 50a can measure the temperature of the circuit board by A / D converting the circuit temperature signal 57 from the thermistor 38. If the temperature rise is high, the microcomputer 50a outputs one or both of the gate signals 53 and 54. By setting it to low, the power path on the FET1 side and / or the power path on the FET2 side can be cut off. In addition, as another usage of the FET1 and the FET2, the PWM control for limiting the output by repeating the ON and OFF of the gate signals 53 and 54 periodically may be performed instead of using only the cutoff.

  Before the motor 35 is connected to the positive terminal, the cathodes of the diodes D1 and D2 are short-circuited to establish a parallel connection circuit of the battery packs 100A and 100B. The motor 35 is a DC motor with a brush. However, an inverter circuit (not shown) may be further added to drive the brushless DC motor using the inverter circuit. The inverter circuit (not shown) may use a known circuit configuration including six FETs or IGBTs (insulated gate bipolar transistors), and can be controlled by the microcomputer 50a.

  A switching element 36 and a shunt resistor 37 are interposed in a power path from the negative terminal of the motor 35 to the negative input terminals 42 and 47. The switching element 36 can be composed of, for example, an FET, and is inserted to stop the rotation of the motor 35 according to an instruction from the microcomputer 50a. In the normal state, the turning on of the motor 35 is allowed by setting the gate signal 58 of the switching element 36 to high, but the control unit 50 automatically detects the end of the work and wants to control the stop of the motor 35. In this case, or when it is desired to stop the motor 35 due to occurrence of some abnormality (high temperature, overcurrent), the microcomputer 50a turns off the switching element 36 by turning the gate signal 58 low. Then, the rotation of the motor 35 is stopped or kept stopped irrespective of the operation of turning on the trigger switch 4 by the operator. The shunt resistor 37 is inserted to measure the value of the current flowing through the motor 35, and the voltage between both ends of the shunt resistor 37 is input to the microcomputer 50a via the signal line 59 (one in FIG. 1 but actually two). The microcomputer 50a can measure the measured value of the current flowing through the motor 35.

  Next, a control procedure of a power input path using the FETs 1 and 2 will be described with reference to FIG. The flow starting at step 200 is as follows. When at least one of the battery packs 100A and 100B is attached to the power tool body 1 and the microcomputer 50a is started, the microcomputer 50a executes a control program stored in the control unit 50 in advance. Done. Although the power supply circuit of the microcomputer 50a is not shown in the circuit diagram of FIG. 2, in the power tool main body 1 shown in FIG. 1, when the first trigger lever 4 is pulled, power is supplied to the power supply circuit and the microcomputer 50a Is activated and the microcomputer 50a is kept on by a power supply self-holding circuit (not shown) for a predetermined time (for example, several minutes to several tens of minutes) after the trigger lever 4 is returned. When a predetermined time elapses after the trigger lever 4 is returned, the microcomputer 50a shuts down the power supply by itself.

  When the microcomputer 50a is activated and the processing after step 200 is started, first, the microcomputer 50a detects whether or not the power control elements, ie, FET1, FET2, D1, and D2, have failed (step 201). ). The procedure of this failure detection will be described later with reference to FIG. Next, the microcomputer 50a determines whether any of the FETs 1 and 2 or the diodes D1 and D2 has failed from the detection result of Step 201 (Step 202). Here, when any of the failures is detected, the microcomputer 50a sets the gate signals 53 and 54 to the low state to turn off the FET1 and the FET2, cuts off the power input path, and further sets the gate signal 58 to the low level. By turning off the switching element 36 (see FIG. 2), the off state of the motor 35 is maintained (step 217). Thereafter, the power tool main body 1 in which the abnormality has occurred cannot be used because it cannot operate normally, and may be repaired by the manufacturer in some cases.

  If no failure is detected in step 202 (normal), the microcomputer 50a stops discharging from the battery pack 100A according to the state of the LD signal from the battery pack 100A transmitted via the LD terminal 43 (see FIG. 2). It is determined whether or not the permission is granted (step 203). If the permission is permitted, the temperature of the battery pack 100A is stopped using the temperature of the battery pack 100A input via the LS terminal 44 (FIG. 2). It is detected whether the temperature has to be high (step 204). When the battery temperature is in a normal range equal to or lower than a predetermined threshold, the microcomputer 50a measures the battery voltage of the battery pack 100A from the voltage signal 51, and determines a predetermined voltage value at which the voltage of the battery pack 100A must be stopped due to overdischarge. It is determined whether this is the case (step 205). When the battery voltage of the battery pack 100A is equal to or higher than a predetermined value, the microcomputer 50a sets the gate signal 53 (see FIG. 2) to a high state to turn on the FET 1 and to supply power from the battery pack 100A to the motor 35. Start supplying. In the case of NO in Steps 203 and 205 or in the case of YES in Step 204, the process proceeds to Step 207, where the microcomputer 50a keeps the FET 1 in the OFF state by setting the gate signal 53 (see FIG. 2) to the Low state (Step 207). ).

  Next, connection determination on the battery pack B side is performed in steps 208 to 212. These procedures are exactly the same as steps 203 to 207. Based on the state of the LD signal from the battery pack 100B transmitted via the LD terminal 48 (see FIG. 2), the microcomputer 50a determines whether discharging from the battery pack B is permitted (step 208). If not, it is detected whether the temperature of the battery pack 100B is high using the signal of the LS terminal 49 (FIG. 2) (step 209). If the battery temperature is normal, the microcomputer 50a determines whether the voltage of the battery pack 100B is overdischarged (Step 210). When the battery voltage of the battery pack 100B is equal to or higher than the predetermined value, the microcomputer 50a turns on the FET2 by turning on the gate signal 54 (see FIG. 2), thereby turning on the power from the battery pack 100B to the motor 35. Start supplying. In the case of NO in Steps 208 and 210 or in the case of YES in Step 209, the process proceeds to Step 212, where the microcomputer 50a keeps the FET 1 in the off state by setting the gate signal 54 (see FIG. 2) to the low state (Step 212). ).

  Next, the microcomputer 50a determines whether or not both the FET1 and the FET2 are in an off state from the states of the gate signals 53 and 54 of the FET1 and the FET2 (Step 213). Here, that both FET1 and FET2 are off means that both steps 207 and 212 have been executed. If both are not off, the microcomputer 50a determines from the output of the thermistor 38 whether or not the temperature (circuit temperature) of the circuit board on which the FET1, FET2, D1, and D2 are mounted is higher than an allowable value. (Step 214). Here, when the circuit temperature is equal to or lower than a predetermined value, the microcomputer 50a measures a current value from a voltage between both ends of the shunt resistor 37 (see FIG. 2), and determines whether the measured current value is within a predetermined allowable value. A determination is made (step 215). If the current value is within the allowable value, the microcomputer 50a sets the gate signal 58 of the switching element 36 to high to allow the motor 35 to start when the trigger switch 4 is pulled (step 216). ), And return to step 203.

  If any of steps 213 to 215 is YES, the microcomputer 50a sets the gate signal 58 (see FIG. 2) to a low state so that the motor 35 does not rotate, and the gate signals 53 and 54 (see FIG. 2). Is kept in a low state, the FET1 and the FET2 are turned off (step 218), and the process returns to the step 201.

  Next, the failure detection procedure in step 201 of FIG. 3 will be described with reference to the flowchart of FIG. In the failure detection step 201, it is checked whether each of the FET1, the FET2, and the diodes D1, D2 is operating normally, and these are executed by the microcomputer 50a. First, the microcomputer 50a determines from the output voltage signal 55 of the battery pack 100A (see FIG. 2) whether or not the output voltage of the FET1 is equal to or lower than a predetermined value, thereby determining whether or not the FET1 has a failure (step 221). At the time of this detection, although the trigger switch 4 is on but the FET 1 is still off, the output signal on the FET 1 side should be almost zero. Therefore, if the output voltage of the FET1 is equal to or higher than a certain level, there is an abnormality in the FET1, so the process proceeds to step 230, and the flow returns to the flowchart of FIG.

  Next, the microcomputer 50a determines from the output voltage signal 56 (see FIG. 2) of the battery pack 100B whether or not the output voltage of the FET 2 is equal to or lower than a predetermined value, thereby determining whether or not the FET 2 is faulty (Step 222). . If the output voltage of the FET2 is higher than the predetermined value, the process proceeds to step 230, where "there is an abnormality in the FET2" and the process returns to the flowchart of FIG. In step 222, if the output voltage of the FET2 is equal to or lower than the predetermined value, it means that both the FET1 and the FET2 are normal. Therefore, the microcomputer 50a turns on the FET1 by setting the gate signal 53 of the FET1 high. (Step 223). Here, that the FET1 is turned on means that a forward voltage is applied to the diode D1.

  Next, the microcomputer 50a determines whether the power of the battery pack 100A is applied to the anode of the diode D2 of the battery pack 100B using the output voltage signal 56 (see FIG. 2), specifically, the potential is equal to or less than a predetermined value. Is determined (step 224). Here, the fact that the output voltage signal 56 of the battery pack 100B is not substantially zero means that the diode D2 has failed and the reverse voltage prevention effect has been lost, so that the process proceeds to step 230. If the output voltage signal 56 is equal to or less than the predetermined value in step 224, the microcomputer 50a turns off the FET1 and turns on the FET2 (steps 225 and 226), and then detects the failure of the diode D1. The microcomputer 50a uses the output voltage signal 55 (see FIG. 2) to determine whether the power of the battery pack 100B is applied to the anode of the diode D1 or, specifically, whether the potential is equal to or lower than a predetermined value ( Step 227). Here, since the fact that the output voltage signal 55 of the battery pack 100A is not substantially zero means that the diode D1 has failed and the reverse voltage prevention effect has been lost, the process proceeds to step 230 (step 227). If the output voltage signal 55 is equal to or less than the predetermined value in step 227, the microcomputer 50a turns off the FET 2 (step 228), and returns to step 201 in the flowchart of FIG.

  As described above, according to the first embodiment, the parallel connection circuit is established after confirming that there is no failure in the FETs 1 and 2 and the diodes D1 and D2 when starting the electric device such as the power tool. In addition, a backflow phenomenon in which a current flows from one side of the battery pack to the other side can be effectively prevented. Even if the FET1 or the FET2 fails, the body diodes of the FET1 and the FET2 are connected so that the direction of the body diodes is opposite to the direction of the diodes D1 and D2. Can reliably be prevented from flowing.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a circuit diagram of a power tool main body 1A according to the second embodiment. The basic circuit configuration is the same as that of the first embodiment shown in FIG. 2, in which the first discharge interruption for allowing the current in only one direction and interrupting the current in the opposite direction is allowed in the discharge path of the battery pack 100A. (FET1, FET3), and a second discharge interrupter (FET2, FET4) that allows current in one direction and interrupts current in the opposite direction is provided in the discharge path of the second battery pack 100B. . The same portions are denoted by the same reference numerals, and the description thereof will not be repeated. A different point of the second embodiment is that FET3 and FET4 are provided instead of the diodes D1 and D2 shown in FIG. FET3 and FET4 are field effect transistors with a body diode, and the forward direction of the body diode is also reversed by reversing the direction of the source and drain of FET1 and FET3. As a result, current flowing in both directions can be blocked even when both FET1 and FET3 are off. Similarly, the direction of the source and the drain of the FET 2 and the FET 4 are reversed so that the forward direction of the body diode is also reversed. The FET 3 and the FET 4 can be turned on or off from the microcomputer 50 a by gate signals 61 and 62.

  Next, a control procedure of the FETs 1 to 4 in the power tool main body 1A will be described with reference to a flowchart of FIG. The basic flow is the same as that in FIG. 3, and the same steps are denoted by the same reference numerals, and the description thereof will not be repeated. The only difference is the portion indicated by the bold frame. In the failure detection step in step 201A, the failure of the FETs 3 and 4 is detected instead of the diodes D1 and D2, and the control of the FETs 3 and 4 after the steps 211 and 212 is performed. Step 300 is inserted. If an FET failure is detected in step 202, control to turn off the FETs 3 and 4 (portion of the thick frame 219a) is added in step 217A, and similarly, control to turn off the FETs 3 and 4 in step 218A ( That is, a thick frame 219b) has been added.

  The failure detection step 201A can be performed in exactly the same procedure as in FIG. In FIG. 4, if "D2 failure detection" is replaced with "FET4 failure detection" and "D1 failure detection" is replaced with "FET3 failure detection", the control itself is the same.

  In FIG. 6, after the on / off control of the FET 1 is completed in steps 203 to 207 and the on / off control of the FET 2 is completed in 208 to 212, the control of the FET 3 and the FET 4 is performed in a newly provided step 300. Here, there are two methods for controlling the FETs 3 and 4, as shown in FIGS.

  FIG. 7 shows a specific example of the control of FET3 and FET4 in step 300. This method uses body diodes of FET3 and FET4 when the battery packs 100A and 100B are connected in parallel. First, it is determined whether the voltage of the battery pack 100A is higher than the voltage of the battery pack 100B by a predetermined amount (α volt) or more (step 311). Here, when the potential difference is large, that is, when the voltage difference between the battery pack 100A and the battery pack 100B is equal to or more than the predetermined value α, the microcomputer 50a turns on the FET3, ends the processing in FIG. 7, and proceeds to step 213 in FIG. Return (step 316). When the step 316 is executed, the FET 3 side conducts, but the FET 4 remains off. When the voltage of the battery pack 100A is high, a current may flow from the battery pack A to the battery pack B side. However, the FET 4 remains off, and the FET 4 has a body diode as the diode D2 of FIG. Since the battery is in the same direction, it is possible to prevent a current from flowing from the battery pack 100A to the battery pack 100B.

  In step 311, if the potential difference is small, that is, if the voltage difference between the battery pack 100A and the battery pack 100B is less than the predetermined value α, the microcomputer 50a turns off the FET 3 (step 312), and then turns off the battery pack 100B. It is determined whether the voltage is higher than the voltage of battery pack 100A by a predetermined amount (α volt) or more (step 313). Here, when the potential difference is large, the microcomputer 50a turns on the FET 4 (step 315), and when the potential difference is small, the microcomputer 50a keeps the FET 4 off (step 314). When the processing in FIG. 7 is completed, the process proceeds to step 213 in FIG.

  As described above, in the control of FIG. 7, only the FET with the larger voltage is turned on among the FETs 3 and 4 in the path of the battery packs 100A and 100B, the smaller FET is kept off, and the FET on the turned off side. Are used for reverse current blocking. When the voltages of both battery packs are substantially equal, both of the body diodes are used for blocking reverse current by turning off both FET3 and FET4. In this way, the FETs 3 and 4 are used not only in a manner similar to the functions of the diodes D1 and D2, but also in a different manner by actively turning on the FETs 3 and 4.

  FIG. 8 is a flowchart showing another control procedure of the FETs 3 and 4 in Step 300 of FIG. Here, the microcomputer 50a finely switches between the parallel connection and the single connection of the two battery packs 100A and 100B using the FET3 and the FET4 in accordance with the battery voltage. First, in the control of the FETs 3 and 4 (Step 300A), it is determined whether or not the rotation of the motor 301 can be turned on, that is, whether or not the switching element 36 is on (Step 301). If the motor 35 cannot be turned on, the FET 3 and the FET 4 are also turned off, and the control process of the FET 3 and the FET 4 is ended (Step 305).

  If it is determined in step 301 that the rotation of the motor 301 can be turned on, the microcomputer 50a determines whether the battery packs 100A and 100B are to be discharged in parallel (step 302). The determination method will be described later with reference to FIGS. Next, the microcomputer 50a determines whether or not the result of the determination in step 302 is a parallel discharge (step 303). In the case of a parallel discharge, the microcomputer 50a sets the gate signals 61 and 62 high from the microcomputer 50a to thereby control both the FET3 and the FET4. Is turned on (step 304), and the process ends. If the parallel discharge is not performed in step 303, the processes in step 311 and subsequent steps are executed. However, since these processes are the same as those in the flowchart shown in FIG. 7 and are assigned the same step numbers, repeated description is omitted. .

  FIG. 9 is a flowchart showing the procedure for determining whether or not the battery packs can be discharged in parallel in step 302 of FIG. First, the microcomputer 50a determines whether or not the voltages of the battery pack 100A and the battery pack 100B are substantially equal (Step 321). Here, if the battery voltages are equal, parallel discharge is selected (step 322), and if they are not equal, non-parallel discharge is selected (step 323). What voltage difference is considered to be equal or not may be set in consideration of a potential difference such that current does not substantially flow from one battery pack to the other battery pack during parallel connection. As an alternative to the control of FIG. 9, instead of comparing the voltages of the battery pack 100A and the battery pack 100B in step 321, the decreasing slopes of both voltages are monitored, and if the slopes are substantially equal, the parallel discharge is selected. However, it is also possible to perform control such that non-parallel discharge is selected (step 323) when the inclinations are not equal.

  FIG. 10 is a flowchart showing another procedure for determining whether or not the battery packs can be discharged in parallel in step 302 of FIG. First, the microcomputer 50a determines whether there is a decrease in the voltage of the battery pack 100A (Step 331). If there is no decrease, non-parallel discharge is selected (step 334). If there is a decrease, the microcomputer 50a determines whether there is a decrease in the voltage of the battery pack 100B (step 332). If there is no decrease, non-parallel discharge is selected (step 334), and if there is a decrease, parallel discharge is selected (step 333). Here, both voltages of the battery packs 100A and 101B are decreasing, which means that both voltages are equal and a similar voltage decrease is occurring. In other words, this indicates that the reverse current does not flow from one battery pack to the other battery pack side, and the potential difference is such that current flows from each battery pack toward the load (motor).

Next, discharge control of the power tool main body (electric device main body) 1A according to the second embodiment will be described with reference to FIG. 11A is a timing chart of the operation procedure of the FETs 1 to 4, (B) and (C) are graphs showing the relationship between the battery voltage and the battery temperature of the battery packs 100A and 100B, and (D) is from the battery packs 100A and 100B. It is a graph which shows the combined output voltage supplied to a power tool main body (work equipment main body) side. The horizontal axis of each graph is the passage of time (unit: second), and the time axis is also displayed. Example of FIG. 11 shows a simple parallel discharge state has been widely used, the operator at time t ₁ is When you turn on the trigger switch 4, and start the microcomputer 50a that has been in sleep state After confirming that there is no failure in the FETs 1 to 4, the microcomputer 50a turns on all the FETs 1 to 4, thereby connecting the battery pack 100A and the battery pack 100B in a parallel connection state. When the battery packs 100A and 100B to be mounted are the same type of battery pack, the voltages decrease at an equal rate as the operation progresses, as in the voltages 550 and 570 shown in (B) and (C). Further, when discharging from the battery packs 100A and 100B, the temperature of the battery pack rises due to heat generation, and gradually rises, for example, to the temperatures 560 and 580 shown by dotted lines. Tool body output voltage supplied to the (working device body) side of the case is brought to such a voltage 590 (D), and gradually decreases until time t _{1 ~} time t _9. Although the voltage 590 decreases linearly in FIG. 11, the voltage 590 does not become linear because the voltage fluctuates according to the size of the load.

Battery pack 100A, 100B voltage of 550,570 reaches the discharge stop voltage at time _{t 9.} The discharge stop voltage may be a voltage instructed by the battery packs 100A and 100B to stop discharging, or may be a voltage indicated by the microcomputer 50a of the power tool main body 1A. At time _{t 9,} by the microcomputer 50a to the low gate signals to the FET1～4, battery pack 100A, the power supply from 100B is stopped. As described above, the discharge control shown in FIG. 11 is a discharge characteristic when the battery packs 100A and 100B having substantially the same remaining battery amount are connected in parallel.

FIG. 12 is a diagram showing another procedure of the discharge control of the power tool main body (electric device main body) 1A according to the second embodiment. The illustrated items are the same as those in FIG. In Figure 12, when the operator at time _{t 1} turns on the trigger switch 4, the microcomputer 50a by turning on the FET1～4, the battery pack 100A and the battery pack 100B and parallel connection state. Even if the battery packs 100A and 100B to be mounted are of the same type, both the battery packs 100A and 100B are not necessarily the same due to the state of the battery packs, especially the difference in the amount of charge and the degree of deterioration. Here, the voltage 551,571 was reduced in the same state until the time _t 1 ~t _5. However, the battery pack 100B shows an example in which the battery temperature 581 rises higher than the battery temperature 561 even with the same discharge amount due to the deterioration of the battery. In this case, the microcomputer 50a is battery temperature 581 at time _{t 5} is, detects that it has reached the battery holding upper-limit temperature, as shown by arrow 581a, in order to stop discharging of the battery pack 100B FET2 and the FET4 The gate signals 54 and 62 (the signals 521 and 541 in FIG. 12A) are turned off. Then, after time _{t 5} becomes the only discharge from the battery pack 100A side, at time _{t 7,} the voltage 551 of the battery pack 100A has reached the discharge stop voltage, the microcomputer 50a is FET1, FET 3 battery pack 100A turns off the To stop the discharge from. As described above, since two FETs are inserted in the discharge paths of the battery pack 100A and the battery pack 100B, switching between parallel connection and single connection (non-parallel connection) is easy.

FIG. 13 is a diagram showing a discharge control procedure of the electric device main body (electric device main body) 1A according to the third embodiment of the present invention, wherein (A) to (D) are the same items as FIG. In FIG. 13, the two voltages of the battery packs 100A and 100B are made equal by single connection before the parallel connection, and the parallel connection is performed after the voltages are made equal. Here is high voltage of the battery pack 100A of the front mounting shows an example voltage before attachment voltage pack 100B is low (eg not fully charged), the trigger switch is turned on at time t _1, The microcomputer 50a measures the voltages of the battery pack 100A and the battery pack 100B using the voltage signals 51 and 52, and connects only the battery pack having a higher voltage (the battery pack 100A in this example). That is, at time _{t 1,} the gate signal 53 and 61 to the FET1 and FET3 turn on (FIG. 13 (signal 512,532 of A)) as a high gate signal 54, 62 (FIG. 13 signal 522 of the (A), 542) to low to turn off the gate FETs 2 and 4. Consequently, until time _t 1 ~t _3, since only the output of the battery pack 100A is transmitted to the working device side, the corresponding portion of the output voltage 592 shown in (D) (arrow 592a) is the same as the arrow 552a Become. Also, until time _t 1 ~t ₃ As can be seen by the arrows 572a shown in FIG. 13 (C), the power of the battery pack 100B side is not consumed.

The microcomputer 50a continues to monitor the voltage of the battery pack 100A and 100B running, when the voltage 552 and the voltage 572 is equal at _{t 3,} the gate signals 54 and 62 (the signal in FIG. 13 (A) 522,542) By setting to high, the parallel connection of the battery pack 100A and the battery pack 100B is established. At this time, since there is no possibility that a current flows from the battery pack 100A to the battery pack 100B or in the reverse direction, it is possible to suppress heat generation in the FET3 and the FET4. Time _{t 3} or later, combined output voltage of the battery pack 100A and the battery pack 100B is reduced as shown by the arrow 592b. The progress of the voltage drop between the voltage 552 and the voltage 572 becomes the same as indicated by arrows 552b and 572b because they are connected in parallel. FIGS. 13B and 13C show examples of temperatures 562 and 582 of the battery packs 100A and 100B. Due to the large power consumption by the power tool main body 1, the single discharge of the battery pack 100A generates a large amount of heat by the discharge, and the temperature rises sharply as indicated by an arrow 562a. However, the time t ₃ after, the load per one battery pack by the parallel connection is reduced by half, the temperature rise as shown by the arrow 562b becomes gentle. When both the battery pack 100A, 100B reaches the discharge stop voltage at time _{t 8,} the microcomputer 50a is turned off in the low all the gate signal of FET1 to FET4.

FIG. 14 is a view for explaining the fourth discharge control of the power tool main body (electric device main body) 1A according to the second embodiment of the present invention. In this example, the two voltages of the battery packs 100A and 100B are equalized before the parallel connection, as in FIG. 13, and the parallel connection is performed after the voltages are equalized. Here, the voltage of the battery pack 100A before mounting is high and the voltage of the voltage pack B is low, but this is not due to the difference in the amount of charge, but to the difference in the type of battery pack. Here, an example is shown in which the rated voltage of battery pack 100A is 18V, and the rated voltage of battery pack 100B is 14.4V. When the trigger switch is turned on at time _{t 1,} the microcomputer 50a measures the voltage of the battery pack 100A and the battery pack 100B using the voltage signals 51 and 52, the battery pack 100A in voltage is high battery pack (in this example ) Alone is connected. That is, at time _{t 1,} the gate signal 53 and 61 the FET1 and FET3 as high (Figure 14 (signal 513,533 of A)) is turned on, the gate signal 54, 62 (FIG. 14 signal 523 of the (A), 543) to low to turn off the gate FETs 2 and 4. Consequently, until time _t 1 ~t _2, since only the output of the battery pack 100A is transmitted to the power tool body (work device body) side, that portion of the output voltage 593 shown in (D) (arrow 593a) is , 553a. Also, until time _t 1 ~t ₂ As can be seen by the arrows 573a in FIG. 14 (C) the power of the battery pack 100B side is not consumed.

The microcomputer 50a continues to monitor the voltage of the battery pack 100A and 100B running, when the voltage 552 and the voltage 572 is equal at _{t 2,} battery pack 100A by a gate signal 54, 62 to the high and the battery pack 100B Establish a parallel connection. Time _{t 2} later, the combined output voltage of the battery pack 100A and the battery pack 100B is reduced as shown by the arrow 593b. The progression of the voltage drop of the voltage 553 and the voltage 573 becomes the same because they are connected in parallel. Are not equal. The microcomputer 50a continues to monitor the voltage of each of the battery packs 100A and 100B running, in order to stop discharging of the battery pack 100A reaching the discharge stop voltage at time _{t 6,} the gate signal 53 and 61 to a low To turn off FET1 and FET3. Time _{t 6} after the order becomes a single discharge of the battery pack 100B, amount of discharge voltage 573 as shown by an arrow 573b in FIG. 14 (C) is increased. The microcomputer 50a, at time _{t 10} detects that the battery pack 100B has reached the discharge stop voltage may be turned off all FET1~FET4 by the gate signal 54 and 62 low.

FIG. 15 is a diagram for explaining the fifth discharge control of the power tool main body (electric device main body) 1A according to the second embodiment of the present invention. In this embodiment, since the on / off control of each of the FETs 1 to 4 can be controlled by the microcomputer 50a, it is easy to control such single switching discharge which has been widely used in the past. When the operator at time t ₁ turns on the trigger switch 4, the microcomputer 50a is the order determined in advance (for example, a battery pack 100A side is away, or higher of the battery voltage) in accordance with, the one battery pack side Make the path conductive. At time _{t 1} here, to turn on the FET1 and FET3 gate signal 53 and 61 (the signal in FIG. 15 (A) 514,534) as a high. FET2 and FET4 remain off. Consequently, until time _t 1 ~t ₄ becomes a single discharge of the battery pack 100A, composite voltage 594 is the same as the voltage 554.

At time _{t 4,} the voltage 554 of the battery pack 100A is lowered to the discharge stop voltage, the microcomputer 50a is an off-the FET1 and FET3 the gate signal 53 and 61 as a low, gate signals 54 and 62 (FIG. 15 (A) Signals 524 and 544) are turned high to turn on the gate FETs 2 and 4. Consequently, until time _t 4 _{~t 11} becomes a single discharge of the battery pack 100B, composite voltage 594 is the same as the voltage 574. At time _{t 11,} the voltage 574 of the battery pack 100B is lowered to the discharge stop voltage, the microcomputer 50a is turned off all FET1~FET4 by the gate signal 54 and 62 low.

  As described above, the control examples of the FETs 1 to 4 have been described with reference to FIGS. 11 to 15. In this embodiment, when the FETs 3 and 4 can be turned on in a parallel connection configuration using the FETs 3 and 4 with a body diode, That is, by turning on the FETs 3 and 4 in a state where there is no possibility that current flows from one battery pack to the other battery pack, heat generation in the FETs 3 and 4 can be suppressed. In particular, it is possible to prevent the body diode of the FET from generating heat with the energy of forward voltage × current. Further, since the on / off of the FETs 3 and 4 can be electrically controlled from the microcomputer 50a, the switching control between the parallel connection and the single connection of the battery packs can be performed at a high level.

  As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the electric device main body has been described as an example of the electric tool. However, the present invention is not limited to the electric tool, and may be realized by any electric device that operates using the battery packs 100A and 100B as a power supply. Also, the number of battery packs that can be mounted on the electric device body is two in the above example, but may be three or more, and an FET and a diode or two FETs may be provided in each power path. You can do it.

DESCRIPTION OF SYMBOLS 1, 1A Electric power tool main body 2 Housing 3 Handle part 4 Trigger switch 4a First pole 4b (of trigger switch) Second pole 7 Wind window 9 Tip tool mounting part 10 Battery pack mounting part 35 Motor 36 Switching element 37 Shunt resistor 38 Thermistor 41, 46 Positive input terminal 42, 47 Negative input terminal 43, 48 LD terminal 44, 49 LS terminal 50 Control unit 50a Microcomputer 51, 52 Voltage signal 53, 54 Gate signal 55, 56 Output voltage signal 57 Circuit temperature Signal 58 Gate signal 59 Signal line 61, 62 Gate signal 63-66 Signal line 100, 100A, 100B Battery pack 101-105 Battery cell 110 Cell group 120 Control unit 130 Latch button 141 Positive terminal 142 Negative terminal 143 LD terminal 144 LS terminal 145 sa Mister 146 Signal line 147 Charge / discharge stop signal 510-514 State of FET1 520-524 State of FET2 530-534 State of FET3 540-544 State of FET4 550-554 Voltage 560-564 (of battery pack A) (battery pack A) 570-574 Voltage (for battery pack B) 580-584 Temperature (for battery pack B) 590-594 Output voltage

Claims (10)

An electric device having a plurality of battery pack mounting portions for mounting a battery pack, and operating a working device by connecting the mounted plurality of battery packs in parallel,
In the discharge path of the first battery pack, a first discharge cutoff unit that allows current in only one direction and cuts off current in the opposite direction is provided,
In the discharge path of the second battery pack, a second discharge cutoff unit that allows a current in only one direction and blocks a current in the opposite direction is provided,
Providing a control unit for controlling connection or interruption of the first and second discharge interruption unit,
The control unit sets the current in the higher voltage path of the battery pack to a conductive state, and sets the first and second discharge interrupting units to a conductive state when the voltages of both battery packs become the same. Electrical equipment characterized by the following.   2. The device according to claim 1, wherein the first and second discharge interrupting units each include a plurality of elements, and the elements include a switching element that can control connection or interruption of a current path by a microcomputer. 3. Electrical equipment.   The electric device according to claim 1, wherein the first and second discharge interrupting units include a diode and a field-effect transistor connected in series, or two field-effect transistors connected in series. .   4. The electric device according to claim 3, wherein the two field-effect transistors connected in series each have a body diode, and are connected so that directions of a source and a drain are reversed. 5.   The switch according to any one of claims 1 to 4, wherein a switch is provided in a path from the battery pack to the first and second discharge interrupting units to switch operation or stop of the work equipment. Electrical equipment. When the switch is turned on, the battery packs can be connected in parallel,
The electric device according to claim 5, wherein the control unit establishes a parallel connection of the battery packs by turning on a switching element in a first path and a switching element in a second path. Each of the battery packs has a function of outputting a discharge stop signal,
7. The method according to claim 1, wherein, when the discharge stop signal is output, the control unit sets the discharge interrupting unit in an output path of the battery pack to an interrupted state to continue discharging the remaining battery packs. An electrical device according to any one of the preceding claims. An electric device having a plurality of battery pack mounting portions for mounting a battery pack, and operating a working device by connecting the mounted plurality of battery packs in parallel,
In each of the connection paths of the plurality of battery packs, a trigger switch, a semiconductor switching element and a reverse voltage protection element are provided in series,
When the trigger switch is turned on, the control unit turns on the semiconductor switching element to establish a parallel connection circuit of the battery packs. An electric device having a plurality of battery pack mounting portions for mounting a battery pack, and operating a working device by connecting the mounted plurality of battery packs in parallel,
A plurality of battery packs having different rated voltages can be connected at the same time,
In each of the connection paths of the plurality of battery packs, a semiconductor switching element and a reverse voltage protection element are provided in series,
An electric device, wherein the control unit that controls on / off of the semiconductor switching element controls the discharge start timing of the battery pack to be different according to the voltage of the battery pack. A two-pole trigger switch is provided in a path between the semiconductor switching element and the battery pack,
The controller, after the trigger switch is turned on, determines whether to perform single discharge or parallel discharge according to the remaining amount of the plurality of battery packs, and controls the semiconductor switching element. The electric device according to claim 9.

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