Battery pack

Abstract

To enable adjustment of external device control by varying a temperature detection signal according to a battery characteristic in a battery back configured to detect and output a temperature.SOLUTION: A battery pack includes a first temperature detection circuit. The first temperature detection circuit includes a first current path from a first terminal to a second terminal, provides a temperature detection element and a first resistor on the first current path, and generates a temperature detection signal indicating a temperature of a battery corresponding to applying of a voltage across the first terminal and the second terminal through a resistor connected to a power supply line of a predetermined voltage. The battery pack also provides a second current path connected to the first current path in parallel, and a first switch provided on the second current path, a control circuit switches the first switch to on-state or off-state according to the state of the battery.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a battery pack having a temperature detection function.

Background Art

[0002] Patent Document 1 discloses a battery pack including a temperature detection circuit including a temperature detection element whose resistance value changes according to temperature, and a resistor connected in series or in parallel to the temperature detection element. In this battery pack, a power supply voltage is applied across both ends of the temperature detection circuit via a resistor, and the voltage across both ends of the temperature detection circuit is output to an external device as a temperature detection signal representing the temperature of the battery pack.

[0003] This external device is a charger that charges the battery in the battery pack, or an electric device that operates by receiving power supply from the battery. Then, these external devices detect the temperature of the battery by taking in the temperature detection signal from the battery pack, and control charging or discharging of the battery according to the detected battery temperature. For this reason, charging of the battery or discharging from the battery can be carried out within an appropriate temperature range that does not deteriorate the battery.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the battery pack described in Patent Document 1, the resistance value of the resistor connected in series or parallel to the temperature detection element in the temperature detection circuit is fixed. Therefore, although external devices can detect the battery temperature based on the temperature detection signal output from the battery pack and perform charging and discharging of the battery properly, there was a problem that the battery pack itself could not control the charging and discharging by the external device.

[0006] In other words, the performance of the batteries housed in a battery pack varies depending on the type of battery, and even at the same temperature, the optimal voltage and current values ​​for charging and discharging may differ. Therefore, depending on the battery pack, it may be desirable to stop charging or discharging at a temperature that reaches a set charging or discharging stop temperature on the external device side. However, since the above-mentioned battery pack is simply configured to output a temperature detection signal according to the temperature, it was not possible to control the charging and discharging control by the external device from the battery pack side according to the battery characteristics.

[0007] One aspect of this disclosure is to enable adjustment of charge / discharge control by external devices by changing the temperature detection signal according to the characteristics of the battery in a battery pack configured to detect and output the battery temperature. [Means for solving the problem]

[0008] One aspect of the present disclosure of a battery pack comprises a battery, a first power terminal, a second power terminal, a first temperature detection circuit, a first signal output terminal and a second signal output terminal, a second current path, a first switch, and a control circuit.

[0009] The battery has a positive terminal and a negative terminal and is rechargeable. The first power terminal has a first end connected to the positive terminal of the battery and a second end configured to be connected to the positive terminal of an external device. The second power terminal has a first end connected to the negative terminal of the battery and a second end configured to be connected to the negative terminal of an external device.

[0010] The first temperature detection circuit also has a first terminal, a second terminal, and a first current path from the first terminal to the second terminal. On this first current path, there is a temperature detection element configured to change its resistance value according to the battery temperature, and a first resistor connected to the temperature detection element. The first temperature detection circuit generates a temperature detection signal indicating the battery temperature in response to a voltage being applied between the first terminal and the second terminal via a resistor connected to a power supply line at a predetermined potential.

[0011] The first signal output terminal and the second signal output terminal are connected to the first and second terminals of the first temperature detection circuit, respectively, and output the temperature detection signal to an external device. The second current path is connected in parallel to the first current path of the first temperature detection circuit.

[0012] The first switch is located on the second current path and is configured to selectively switch between an ON state and an OFF state. When the first switch switches between an ON state and an OFF state, the second current path is either open or closed. 1st temperature The resistance value of the temperature detection circuit changes.

[0013] The control circuit is, The battery status is determined by obtaining at least one of the following: battery voltage, battery temperature, charging current to the battery, and discharge current from the battery, and then, according to the obtained battery status... Switch the first switch to the ON or OFF state. Therefore, according to the battery pack of this disclosure, the control circuit, depending on the state of the battery, First S By switching the switch on and off, 1st temperature By changing the resistance value of the degree detection circuit, 1st temperature This makes it possible to change the voltage value of the temperature detection signal output from the temperature detection circuit.

[0014] Therefore, external devices such as chargers that charge batteries or electrical equipment that operate using power supplied from batteries can detect the battery temperature from a temperature detection signal and adjust the control characteristics when controlling battery charging and discharging from the battery pack side.

[0015] Adjustments can be made from the battery pack side. PossibleExamples of charge / discharge control characteristics include, for example, the temperature at which charging / discharging of the battery is stopped, the switching temperature at which the charging current is reduced, and the like.

Brief Description of the Drawings

[0016] [Figure 1] It is a block diagram showing the configuration of the battery pack and the charger of the first embodiment. [Figure 2] It is an explanatory diagram showing the charging characteristics with respect to the battery temperature in the charger. [Figure 3] It is a flowchart showing the charge control executed by the charger. [Figure 4] It is an explanatory diagram showing the relationship between the resistance value of the first temperature detection circuit and the battery temperature. [Figure 5] It is an explanatory diagram showing the change in charge control accompanying the switching of the first switch. [Figure 6] It is a flowchart showing the switching control of the first switch. [Figure 7] It is an explanatory diagram showing the relationship between the resistance value of the first temperature detection circuit of the first modification example and the battery temperature. [Figure 8] It is an explanatory diagram showing the change in charge control accompanying the switching of the first switch of the first modification example. [Figure 9] It is a flowchart showing the switching control of the first switch of the first modification example. [Figure 10] It is a block diagram showing the configuration of the battery pack of the second embodiment. [Figure 11] It is an explanatory diagram showing the relationship between the resistance value of the first temperature detection circuit of the second embodiment and the battery temperature. [Figure 12] It is an explanatory diagram showing the change in charge control accompanying the switching of the first and second switches. [Figure 13] It is a flowchart showing the switching control of the first and second switches. [Figure 14] It is a flowchart showing the switching control of the first and second switches of the second modification example. [Figure 15]This is a block diagram showing the configuration of the battery pack according to the third embodiment. [Figure 16] This is an explanatory diagram showing the relationship between the resistance value of the first temperature detection circuit in the third embodiment and the battery temperature. [Figure 17] This is an explanatory diagram illustrating the change in charging control associated with the switching of the first switch in the third embodiment. [Figure 18] This is a flowchart illustrating the switching control of the first switch in the third embodiment. [Figure 19] This is a block diagram showing the configuration of a power tool connected to a battery pack in the third modified example. [Figure 20] This is a flowchart illustrating the switching control of the first switch in the third modified example. [Figure 21] This is a block diagram showing the configuration of a battery pack as an example. [Figure 22] This is an explanatory diagram illustrating the charging characteristics of a reference charger in relation to battery temperature. [Figure 23] This is a flowchart illustrating the switching control of a switch in a reference example. [Modes for carrying out the invention]

[0017] [Summary of Embodiments] In one embodiment, the battery pack may include a rechargeable battery having a positive electrode and a negative electrode. The battery pack may also include a first power terminal having a first end connected to the positive electrode and a second end configured to be connected to the positive terminal of an external device. The battery pack may also include a second power terminal having a first end connected to the negative electrode and a second end configured to be connected to the negative terminal of the external device.

[0018] In addition, / or, the battery pack may be provided with a first temperature detection circuit having a first terminal, a second terminal, and a first current path from the first terminal to the second terminal, the first current path comprising a temperature detection element configured to change its resistance value according to the temperature of the battery, and a first resistor connected to the temperature detection element.

[0019] This first temperature detection circuit may be configured to generate a temperature detection signal indicating the temperature of the battery in response to a voltage being applied between the first terminal and the second terminal via a resistor connected to a power supply line at a predetermined potential.

[0020] In addition, the battery pack may be provided with a first signal output terminal and a second signal output terminal, respectively, which are connected to the first terminal and the second terminal and configured to output the temperature detection signal to the external device.

[0021] In addition, / or, the battery pack may be provided with a second current path connected in parallel with the first current path. Furthermore, a first switch configured to selectively switch between an on state and an off state may be provided on this second current path.

[0022] In this case, the second current path is opened or closed depending on whether the first switch is switched to the ON state or the OFF state, 1st temperature The resistance value of the temperature detection circuit will start to change.

[0023] In addition, / or, the battery pack may be equipped with a control circuit configured to switch the first switch to the ON state or the OFF state depending on the state of the battery.

[0024] In this case, the control circuit will respond according to the battery status. First S By switching the switch on and off, 1st temperature By changing the resistance value of the degree detection circuit, 1st temperatureThis makes it possible to change the voltage value of the temperature detection signal output from the temperature detection circuit.

[0025] In addition, / or, the battery pack may be provided with a second temperature detection circuit configured to detect the temperature of the battery, separate from the first temperature detection circuit. In this case, the control circuit may be configured to switch the first switch to the ON state or the OFF state according to the temperature detected by the second temperature detection circuit and / or the voltage of the battery.

[0026] In this way, the control characteristics related to battery charging and discharging by external devices can be changed according to the temperature and voltage of the battery within the battery pack. As a result, charging and discharging of the battery can be performed appropriately, and battery degradation can be suppressed.

[0027] In addition, the temperature sensing element may be connected in series with the first resistor, and the second current path may be connected in parallel with the first resistor. Furthermore, the temperature sensing element may have a negative temperature characteristic, where its resistance decreases as the temperature increases. The external device may also be a charger.

[0028] In this case, the sum of the resistance value of the temperature detection element and the resistance value of the first resistor when the temperature of the battery is at the first temperature may be set to a resistance value that generates the temperature detection signal that causes the charger to stop charging.

[0029] Furthermore, the control circuit switches the first switch to the ON state when the temperature of the battery exceeds the first temperature, and when the temperature of the battery is less than or equal to the first temperature, First S The switch may be configured to switch to the off state.

[0030] In this way, when the battery temperature falls below the first temperature, 1st temperatureBy increasing the resistance value of the temperature detection circuit, it becomes possible to stop charging by the charger. In addition, or the above 1st temperature The temperature detection circuit may include a second resistor and a second switch configured to selectively switch between an on state and an off state. The second switch may also be configured to connect the second resistor in parallel with the first resistor when it is switched to the on state.

[0031] In this case, when the temperature of the battery is at a second temperature higher than the first temperature and the second switch is in the ON state, the combined resistance value of the temperature detection element, the first resistor, and the second resistor may be set to a resistance value that generates the temperature detection signal that reduces the charging current and / or charging voltage for the charger.

[0032] In addition, / or, the control circuit may be configured to switch the first switch to the ON state and the second switch to the OFF state when the battery temperature exceeds the second temperature, and to switch the second switch to the ON state and then to the OFF state when the battery temperature falls below the second temperature.

[0033] In this way, when the battery temperature falls below the second temperature, 1st temperature By increasing the resistance value of the temperature detection circuit, the charging current and / or charging voltage from the charger to the battery can be reduced based on the temperature detection signal. Therefore, when the battery temperature falls below the second temperature, the charging rate by the charger can be reduced, thereby suppressing battery degradation due to charging.

[0034] In addition, if the external device is a charger and the temperature sensing element has a negative temperature characteristic, the sum of the resistance value of the temperature sensing element and the resistance value of the first resistor when the battery temperature is at the third temperature may be set to a resistance value that generates the temperature detection signal that reduces the charging current and / or charging voltage for the charger.

[0035] In this case, the control circuit, when the temperature of the battery exceeds the third temperature, First S When the switch is turned ON and the battery temperature is below the third temperature, First S The switch may be configured to toggle to the off state.

[0036] In this way, when the battery temperature falls below the third temperature, 1st temperature By increasing the resistance value of the temperature detection circuit, the charging current and / or charging voltage from the charger to the battery can be reduced based on the temperature detection signal. Therefore, when the battery temperature falls below the third temperature, the charging rate by the charger can be reduced, thereby suppressing battery degradation due to charging.

[0037] In addition, or, when the first switch is ON, the battery pack, via the second current path, 1st current The circuit may also include a third resistor connected in parallel to the series circuit of the temperature sensing element and the first resistor on the path.

[0038] In this case, if the external device is a charger and the temperature sensing element has a negative temperature characteristic, the combined resistance value of the temperature sensing element, the first resistor, and the third resistor when the battery temperature is the fourth temperature and the first switch is in the ON state may be set to a resistance value that generates the temperature detection signal for the charger to reduce the charging current and / or charging voltage when the battery is at a high temperature.

[0039] Furthermore, when the temperature of the battery is below the fourth temperature, the control circuit First S Switch the switch to the off state, and if the temperature of the battery exceeds the fourth temperature, First SThe switch may be configured to reduce the charging rate from the charger to the battery when the battery temperature exceeds the fourth temperature.

[0040] [Specific exemplary embodiments] Exemplary embodiments of this disclosure are described below with reference to the drawings. [First Embodiment] As shown in Figure 1, the battery pack 10 of this embodiment includes a battery 16 and can detachably connect to a charger 50 as an external device. When the charger 50 is connected, the battery pack 10 can charge the battery 16 from the charger 50.

[0041] Furthermore, the battery pack 10 can be detachably connected not only to the charger 50, but also to electrical equipment that operates by receiving power from the battery pack 10, such as the power tool 80 (see Figure 19), which will be described later. When connected to electrical equipment, the battery pack 10 functions as a power supply device that supplies DC power from the battery 16 to the electrical equipment.

[0042] The battery pack 10 is equipped with a first power terminal 21, a second power terminal 22, first and second voltage output terminals 23 and 24, and a signal output terminal 25, which are terminals that connect mechanically and electrically to external devices such as a charger 50 or a power tool 80 when the battery pack 10 is attached to an external device.

[0043] On the other hand, the charger 50 is equipped with a positive terminal 51, a negative terminal 52, first and second voltage input terminals 53 and 54, and a signal input terminal 55. When the battery pack 10 is attached to the charger 50, the first power terminal 21 and the positive terminal 51, and the second power terminal 22 and the negative terminal 52 become electrically conductive. Similarly, the first voltage output terminal 23 and the first voltage input terminal 53, the second voltage output terminal 24 and the second voltage input terminal 54, and the signal output terminal 25 and the signal input terminal 55 also become electrically conductive.

[0044] In addition to the battery 16, the battery pack 10 includes a power supply circuit 18, a control circuit 30, a cell voltage detection circuit 32, a second temperature detection circuit 34, a current detection circuit 36, an external device connection detection circuit 38, and a first temperature detection circuit 40.

[0045] The battery 16 is, for example, a lithium-ion battery and has a plurality of battery cells connected in series. In this embodiment, the battery 16 comprises a first cell 11, a second cell 12, and a third cell 13 connected in series from the negative terminal to the positive terminal of the battery 16. Each of the cells 11 to 13 has the same temperature characteristics and the same electrical characteristics.

[0046] The positive terminal of battery 16 (i.e., the positive terminal of the third cell 13) is connected to the first terminal of the first power terminal 21, whose second terminal is connected to the positive terminal 51 of charger 50. The positive terminal of battery 16 is also connected to the power supply circuit 18 and the cell voltage detection circuit 32.

[0047] The negative terminal of battery 16 (i.e., the negative terminal of the first cell 11) is connected to the first terminal of the second power terminal 22, whose second terminal is connected to the negative terminal 52 of charger 50. The negative terminal of battery 16 is also connected to the power supply circuit 18 and the cell voltage detection circuit 32.

[0048] Therefore, discharge from the battery 16 to the electrical equipment is performed via the first power terminal 21 and the second power terminal 22, and charging from the charger 50 to the battery 16 is also performed via the first power terminal 21 and the second power terminal 22.

[0049] Furthermore, the positive terminal of the first cell 11 is connected to the first voltage output terminal 23 and the cell voltage detection circuit 32 via a resistor 26, and the positive terminal of the second cell 12 is connected to the second voltage output terminal 24 via a resistor 27.

[0050] Therefore, a first voltage signal indicating the cell voltage of the first cell 11 is output from the first voltage output terminal 23, and a second voltage signal indicating the cell voltage of the second cell 12 is output from the second voltage output terminal 24.

[0051] The power supply circuit 18 generates a power supply voltage (constant DC voltage) Vcc for the control circuit 30 and other devices from the DC power supplied from the battery 16. The cell voltage detection circuit 32 detects the voltage across the battery 16 (i.e., the battery voltage) and the voltage across each of the cells 11 to 13 (i.e., the cell voltage).

[0052] The second temperature detection circuit 34 is provided to detect the temperature of the battery 16 (hereinafter referred to as "battery temperature"). The second temperature detection circuit 34 comprises, for example, a series circuit of a thermistor, which is a temperature detection element, and a resistor, with one end connected to the control circuit 30 and the other end connected to ground at the same potential as the negative terminal of the battery 16.

[0053] Since the control circuit 30 operates in response to the power supply voltage Vcc generated by the power supply circuit 18, the negative terminal of the control circuit 30 is also connected to the ground of the battery pack 10. For this reason, the control circuit 30 receives a voltage signal representing the battery temperature from the second temperature detection circuit 34.

[0054] Next, the current detection circuit 36 ​​is located on the current path that connects the negative terminal of the battery 16 to the second power terminal 22 and carries the charge / discharge current, and detects the charge / discharge current flowing through this current path. The detection result from the current detection circuit 36 ​​is then input to the control circuit 30 as a current detection signal.

[0055] The first temperature detection circuit 40 includes a first terminal 40A, a second terminal 40B, a first current path 40C, a second current path 40D, a temperature detection element 42, an intermediate resistor 43, and a first resistor 44.

[0056] The first current path 40C connects the first terminal 40A and the second terminal 40B. The temperature sensing element 42 and the first resistor 44 are arranged in series on the first current path 40C such that the temperature sensing element 42 is on the side of the first terminal 40A. An intermediate resistor 43 is provided between the temperature sensing element 42 and the first resistor 44 in the first current path 40C.

[0057] In other words, the first terminal 40A is connected to the temperature sensing element 42, and the second terminal 40B is connected to the first resistor 44. Also, the first terminal 40A is connected to the signal output terminal 25, and the second terminal 40B is connected to the second power supply terminal 22.

[0058] The second current path 40D is connected in parallel with the first resistor 44. A first switch SW1 is provided on the second current path 40D. The first switch SW1 is composed of a semiconductor switch such as an FET.

[0059] When the first switch SW1 is in the off state, the second current path 40D is interrupted. Therefore, the resistance value Rs between the first terminal 40A and the second terminal 40B (i.e., the resistance value Rs of the first temperature detection circuit 40) is the sum of the resistance value Rm of the temperature detection element 42, the resistance value Ra of the intermediate resistor 43, and the resistance value R1 of the first resistor 44, resulting in the resistance value "Rm + Ra + R1".

[0060] In contrast, when the first switch SW1 is ON, the second current path 40D conducts, so the resistance value Rs of the first temperature detection circuit 40 becomes the resistance value "Rm + Ra", which is the sum of the resistance value Rm of the temperature detection element 42 and the resistance value Ra of the intermediate resistor 43.

[0061] On the other hand, external devices connected to the battery pack 10, such as the charger 50 shown in Figure 1, are equipped with a detection signal input circuit 57 configured to apply the internal power supply voltage Vdd to the signal input terminal 55 via a pull-up resistor 58.

[0062] Therefore, when the battery pack 10 is connected to an external device, a voltage is applied to the first temperature detection circuit 40 via a resistor (such as a pull-up resistor 58) from the power line of the external device, which has a potential higher than the ground potential by the power supply voltage Vdd.

[0063] Therefore, external devices such as the charger 50 can supply current to the first temperature detection circuit 40 of the battery pack 10 via a resistor (such as a pull-up resistor 58), and obtain a temperature detection signal whose voltage changes according to the resistance value Rs of the first temperature detection circuit 40.

[0064] Thus, the voltage value Vs of the temperature detection signal output from the first temperature detection circuit 40 to the charger 50 is the voltage value obtained by dividing the power supply voltage Vdd by the pull-up resistor 58 and the first temperature detection circuit 40. Therefore, if the resistance value of the pull-up resistor 58 is R0, the voltage value Vs of the temperature detection signal is "Vs = Vdd × Rs / R0 + Rs".

[0065] Since the resistance value Rs of the first temperature detection circuit 40 is greater when the first switch SW1 is in the off state than when the first switch SW is in the on state, the voltage value Vs of the temperature detection signal increases when the first switch SW1 is switched from the on state to the off state.

[0066] On the other hand, the first temperature detection circuit 40 is equipped with an NTC thermistor having a negative temperature characteristic as the temperature detection element 42. Therefore, the resistance value Rm of the temperature detection element 42, or in other words, the resistance value Rs of the first temperature detection circuit 40, decreases as the battery temperature increases.

[0067] Therefore, when the first switch SW1 is in the ON state, 1 switch SW1 When the circuit is switched to the off state, the resistance value Rs of the first temperature detection circuit 40, and consequently the voltage value Vs of the temperature detection signal, increases, and the battery temperature recognized by the external device decreases.

[0068] Next, the control circuit 30 includes a microcontroller (hereinafter referred to as "microcontroller") which contains a CPU, ROM, RAM, etc. The control circuit 30 acquires the battery status based on detection signals from the cell voltage detection circuit 32, the second temperature detection circuit 34, and the current detection circuit 36. Specifically In terms ofThe system acquires the battery voltage, including the cell voltage of each cell 11-13 of the battery 16, the battery temperature, the charging current when charging the battery 16, and the discharge current when discharging the battery 16.

[0069] Then, based on the acquired battery status, the control circuit 30 switches the battery temperature recognized by external devices such as the charger 50 by turning the first switch SW1 of the first temperature detection circuit 40 on or off.

[0070] In this embodiment, the control circuit 30 turns on the first switch SW1 when the battery temperature is above a predetermined temperature, and turns off the first switch SW1 according to predetermined switching conditions when the battery temperature is below the predetermined temperature. This switching reduces the battery temperature recognized by external devices. The switching operation of the first switch SW1 of the control circuit 30 will be described later.

[0071] Next, the external device connection detection circuit 38 detects that the battery pack 10 is connected to an external device when an external device such as a charger 50 is connected to the battery pack 10 and voltage is applied from the external device to the signal output terminal 25.

[0072] When the external device connection detection circuit 38 detects that the battery pack 10 is connected to an external device, it outputs a detection signal to the power supply circuit 18, causing the power supply circuit 18 to operate and generate the power supply voltage Vcc.

[0073] Therefore, the control circuit 30 operates by receiving power from the power supply circuit 18 when an external device such as a charger 50 is connected to the battery pack 10 and a voltage is applied from the external device to the signal output terminal 25.

[0074] In this embodiment, the first terminal 40A and the second terminal 40B of the first temperature detection circuit 40 are connected to the signal output terminal 25 and the second power supply terminal 22, respectively, and the resistance between these two signal output terminals 25 and 22 is set to a resistance value Rs corresponding to the battery temperature.

[0075] Therefore, the signal output terminal 25 corresponds to an example of the first signal output terminal described in "Summary of Embodiments," and the second power supply terminal 22 corresponds to an example of the second signal output terminal described in "Summary of Embodiments." In other words, in this embodiment, the second power supply terminal 22 functions as a common terminal for the negative terminal and the second signal output terminal described in "Summary of Embodiments."

[0076] However, the second terminal 40B may be connected to a second signal output terminal for temperature detection signal output, rather than to the second power supply terminal 22, and configured to output a temperature detection signal via the signal output terminal 25 and the second signal output terminal.

[0077] Next, as shown in Figure 1, the charger 50 includes, in addition to the detection signal input circuit 57 described above, a voltage detection circuit 56, a control circuit 60, a rectifier circuit 62, a charging switching power supply circuit 64, and a power supply circuit 66.

[0078] The voltage detection circuit 56 detects the battery voltage and the cell voltages of each cell 11 to 13 based on the voltage signals input from the battery pack 10 via the positive terminal 51, the first voltage input terminal 53, and the second voltage input terminal 54, and inputs these to the control circuit 60.

[0079] Furthermore, the detection signal input circuit 57 includes a filter 59 that inputs the voltage from the signal input terminal 55 to the control circuit 60, separate from the pull-up resistor 58. This filter 59 is a noise removal filter that removes noise components (for example, high-frequency components above a predetermined frequency) from the temperature detection signal input from the first temperature detection circuit 40 of the battery pack 10 when the battery pack 10 is connected to the charger 50.

[0080] Meanwhile, the rectifier circuit 62 rectifies the AC voltage (for example, 100V AC) input from an external AC power source (generally a commercial power source) and converts it to DC. The charging switching power supply circuit 64 has a switching regulator that steps down the voltage rectified by the rectifier circuit 62 to generate a charging voltage for charging the battery 16. The charging voltage generated by the charging switching power supply circuit 64 is then output to the battery pack 10 from the positive terminal 51.

[0081] Furthermore, the power supply circuit 66 steps down the voltage rectified by the rectifier circuit 62 to generate the power supply voltage (DC constant voltage) Vdd inside the charger 50. This generated power supply voltage Vdd is then supplied to the internal circuits of the charger 50, such as the control circuit 60 and the detection signal input circuit 57.

[0082] Furthermore, the control circuit 60, like the control circuit 30 of the battery pack 10, includes a microcontroller with a CPU, ROM, RAM, etc. Based on the input signal from the detection signal input circuit 57, the control circuit 60 detects that the battery pack 10 has been connected to the charger 50 and controls the charging switching power supply circuit 64.

[0083] Furthermore, the voltage detection circuit 56, the charging switching power supply circuit 64, the control circuit 60, and the negative terminal of the power supply circuit 66 are connected to ground at the same potential as the negative terminal 52. Next, the control circuit 60 detects the battery temperature based on the input signal from the detection signal input circuit 57, and controls the charging switching power supply circuit 64 according to a preset charging control pattern based on the detected battery temperature.

[0084] As shown in Figure 2, this charging control pattern is set to charge the battery 16 when the battery temperature is within the range of 0°C to 60°C, and to stop charging the battery 16 when the battery temperature is below 0°C or above 60°C. This is to ensure that charging of the battery 16 is carried out within the appropriate temperature range, and this control can suppress the degradation of the battery 16 due to charging.

[0085] Furthermore, the charging control pattern is configured to control the charging switching power supply circuit 64 so that the charging voltage (specifically, the cell voltage of each cell 11-13) is 4.2V and the charging current is 5A when the battery temperature is in the normal temperature range of 10°C to 45°C.

[0086] Furthermore, the charging control pattern is set so that the charging voltage and charging current are lower in the low-temperature range of 0°C to 10°C, or in the high-temperature range of 45°C to 60°C, compared to the normal temperature range.

[0087] Specifically, as shown in Figure 2, in the cold temperature range, the charging conditions are set so that the charging voltage is 4.1V and the charging current is 1.5A, and in the high temperature range, the charging conditions are set so that the charging voltage is 4.15V and the charging current is 3A.

[0088] Next, the charge control determination process executed in the control circuit 60 of the charger 50 will be described. This charge control determination process is executed in the control circuit 60 when the battery pack 10 is connected to the charger 50.

[0089] As shown in Figure 3, when this charge control determination process is started, first, in S110, the operating mode of the control circuit 60 is set to the charge standby mode, and then the process proceeds to S120. In S120, the cell voltage Vcel of the battery 16 is obtained from the voltage detection circuit 56, and the cell temperature Tcel of the battery 16 is obtained from the temperature detection signal input from the detection signal input circuit 57.

[0090] The cell voltage Vcel is the voltage of each cell 11 to 13 of the battery 16, but the battery voltage across both ends of the battery 16 can also be used. The cell temperature Tcel is the battery temperature obtained from the temperature detection signal input from the first temperature detection circuit 40.

[0091] Next, in S130, it is determined whether the cell voltage Vcel obtained in S120 is above a threshold for determining full charge, thereby determining whether the cell voltage Vcel has reached the charging range. If it is determined that the cell voltage Vcel has reached the charging range, it is determined that charging of the battery 16 is complete, and the process proceeds to S135, where the operating mode of the control circuit 60 is set to the charging complete mode.

[0092] Furthermore, when the operating mode of the control circuit 60 is set to the charging completion mode, it stops the charging control determination process until the battery pack 10 connected to the charger 50 is replaced, and when the battery pack 10 is replaced, it resumes the charging control determination process from S110.

[0093] Next, in S130, if it is determined that the cell voltage Vcel has not reached the charging range, the process proceeds to S140, where it is determined whether the cell temperature Tcel obtained in S120 is above 60°C or below 0°C, as set in Figure 2.

[0094] In S140, if the cell temperature Tcel is determined to be above 60°C or below 0°C, the battery 16 is outside the appropriate temperature range for charging, so the process proceeds to S120, and the system waits for the battery 16 to return to the appropriate temperature range.

[0095] Next, in S140, if it is determined that the battery 16 is within the appropriate temperature range from 0°C to 60°C, the process proceeds to S150, where the operating mode of the control circuit 60 is set to charging mode. Then, in the following S160, the output of the charging current from the charging switching power supply circuit 64 is enabled (turned on), and charging control by the charging switching power supply circuit 64 is started.

[0096] When in charging mode, the control circuit 60 monitors the cell temperature Tcel of the battery 16 based on the input signal from the detection signal input circuit 57, and instructs the charging switching power supply circuit 64 to control the charging voltage and charging current according to the charging control pattern shown in Figure 2.

[0097] Next, in S150 and S160, charging control by the charging switching power supply circuit 64 is started, and the process moves to S170, where, similar to S120 described above, the cell voltage Vcel and cell temperature Tcel of the battery 16 are obtained, and the process moves to S180.

[0098] In S180, similar to S140 described above, it is determined whether the cell temperature Tcel is 60°C or higher, or 0°C or lower. If S180 determines that the cell temperature Tcel is 60°C or higher, or 0°C or lower, it means that the cell temperature Tcel has fallen outside the appropriate temperature range during charging of the battery 16, so the process proceeds to S185, and the operating mode of the control circuit 60 is set to the charging completion mode.

[0099] As a result, similar to the execution of process S135 described above, the charging control determination process is stopped until the battery pack 10 connected to the charger 50 is replaced. Therefore, it is possible to prevent the battery 16 from being charged outside the appropriate temperature range and degrading the battery 16.

[0100] Next, in S180, if it is determined that the cell temperature Tcel is within the appropriate temperature range from 0°C to 60°C, the process proceeds to S190, where, similar to S130 described above, it is determined whether or not the cell voltage Vcel has reached the charging region.

[0101] Then, in S190, if it is determined that the cell voltage Vcel has reached the charging range, the process proceeds to S200, and the operating mode of the control circuit 60 is set to the charging completion mode. Also, in this case, since the battery 16 is fully charged by the charging switching power supply circuit 64, the process proceeds to S210, and the output of the charging current from the charging switching power supply circuit 64 is stopped (turned off).

[0102] Next, in the following S220, the system waits for the battery pack 10 to be disconnected from the charger 50 by determining whether the battery pack 10 has been disconnected from the charger 50. If it is determined in S220 that the battery pack 10 has been disconnected from the charger 50, the charging control determination process is terminated.

[0103] As described above, the charger 50 detects the cell temperature Tcel of the battery 16 in the battery pack 10 from the voltage value Vs of the temperature detection signal input from the signal input terminal 55, and controls the charging voltage and charging current according to the cell temperature Tcel.

[0104] In contrast, the first temperature detection circuit 40 of the battery pack 10 is configured such that the resistance-temperature characteristics when the first switch SW1 is ON, as shown by the solid line in Figure 4, correspond to the cell temperature detection characteristics of the charger 50.

[0105] Furthermore, the resistance value R1 of the first resistor 44 is set such that when the first switch SW1 is switched from the ON state to the OFF state, the resistance value Rs of the first temperature detection circuit 40 increases, and the resistance-temperature characteristic of the first temperature detection circuit 40 changes as shown by the dotted line in Figure 4.

[0106] Furthermore, when the first switch SW1 is in the off state, the resistance-temperature characteristics of the first temperature detection circuit 40 are set such that the resistance value Rs when the cell temperature is 10°C or less is greater than the resistance value at the lower limit temperature of the appropriate temperature range recognized by the charger 50: 0°C.

[0107] Next, as shown in Figure 5, the control circuit 30 of the battery pack 10 is configured to turn on the first switch SW1 when the cell temperature Tcel detected by the second temperature detection circuit 34 is 10°C or higher.

[0108] Furthermore, the control circuit 30 controls the cell temperature Tcel ga 1The system is configured to switch the first switch SW1 to the off state when the temperature is below 0°C and the cell voltage Vcel detected by the cell voltage detection circuit 32 is higher than 3.9V.

[0109] Therefore, in the region where the cell temperature Tcel of the battery 16 is lower than 10°C and the cell voltage Vcel detected by the cell voltage detection circuit 32 is higher than 3.9V, the charger 50 recognizes that the battery temperature is lower than 0°C and stops charging.

[0110] Therefore, according to the battery pack 10 of this embodiment, when the battery temperature is in the low temperature range of 0°C to 10°C, if the cell voltage Vcel is within the voltage range of 3.9V to 4.1V, charging by the charger 50 can be forcibly stopped. In this embodiment, the cell temperature Tcel of 10°C corresponds to an example of the first temperature described in "Summary of Embodiments".

[0111] Next, the switching control process for the first switch SW1, which is executed by the control circuit 30 of the battery pack 10 to switch the ON / OFF state of the first switch SW1, will be explained in accordance with the flowchart in Figure 6.

[0112] The switching control process shown in Figure 6 is executed in the control circuit 30 when the battery pack 10 is connected to an external device such as a charger 50. When this switching control process begins, first, in S310, the first switch SW1 is turned ON, and the process proceeds to S320. In S320, the cell voltage Vcel and cell temperature Tcel are detected via the cell voltage detection circuit 32 and the second temperature detection circuit 34. Then, in the following S330, it is determined whether or not charging current is being supplied from the charger 50 to the battery pack 10 based on the detection signal from the current detection circuit 36.

[0113] The current detection circuit 36 ​​is located on the current path between the negative terminal of the battery 16 and the second power supply terminal 22, and can also detect the discharge current from the battery 16. Therefore, in S330, it is determined whether or not a charging current is flowing based on the direction of the current detected by the current detection circuit 36.

[0114] If it is determined in S330 that no charging current is flowing, meaning that the battery 16 is not being charged from the charger 50, the process proceeds to S320, where the system waits for charging from the charger 50 to the battery 16 to begin.

[0115] On the other hand, if it is determined in S330 that a charging current is flowing, the process proceeds to S340, where it is determined whether the cell temperature Tcel detected in S320 is less than 10°C and whether the cell voltage Vcel detected in S320 exceeds 3.9V.

[0116] Then, if a positive result is obtained in S340, that is, if Tcel < 10°C and Vcel > 3.9V, the process proceeds to S350, where the first switch SW1 is switched to the OFF state and the switching control process ends.

[0117] Furthermore, if a negative result is obtained in S340, that is, if the cell temperature Tcel ≥ 10°C or Vcel ≤ 3.9V, the process proceeds to S320, and the processing from S320 onward is executed again.

[0118] As described above, in the battery pack 10 of this embodiment, the first switch SW1 is switched from the ON state to the OFF state when the switching conditions Tcel < 10°C and Vcel > 3.9V are met.

[0119] When the first switch SW1 is turned off, the battery temperature recognized by the charger 50 is lower than 0°C, as shown in Figures 4 and 5, so the charger 50 stops charging the battery 16.

[0120] Therefore, according to the battery pack 10 of this embodiment, under the switching conditions of Tcel < 10°C and Vcel > 3.9V, the charger 50 can forcibly stop charging control in response to battery temperature.

[0121] Therefore, according to the battery pack 10 of this embodiment, the control characteristics of the charger 50 when controlling the charging of the built-in battery 16 can be adjusted according to the characteristics of the built-in battery 16, and the deterioration of the battery 16 due to charging can be suppressed more effectively.

[0122] In this embodiment, the cell temperature Tcel and cell voltage Vcel are set as the switching conditions for switching the first switch SW1 from the ON state to the OFF state. However, it is also possible to set only the cell temperature Tcel or only the cell voltage Vcel as the switching conditions.

[0123] [First variation] In the first embodiment described above, when the cell temperature Tcel is less than 10°C and the cell voltage Vcel exceeds 3.9V, the first switch SW1 is switched from the ON state to the OFF state, thereby instructing the charger 50 to stop charging the battery 16.

[0124] In contrast, in this first modified example, as shown in Figure 7, when the cell temperature Tcel detected by the second temperature detection circuit 34 is within the temperature range of 10°C to 15°C, the first switch SW1 is turned off, and the cell temperature Tcel recognized by the charger 50 is switched to the low-temperature range.

[0125] As a result, as shown in Figure 8, when the cell temperature Tcel is within the temperature range of 10°C to 15°C, the charger 50 recognizes that the cell temperature Tcel is in the low-temperature range and reduces the charging voltage and charging current to the battery 16 compared to the normal temperature range.

[0126] Therefore, according to the first modified battery pack 10, even if the cell temperature Tcel is in the normal temperature range, if it falls below 15°C, the charger 50 can be instructed to reduce the charging voltage and charging current to perform charging of the battery 16 more slowly.

[0127] Therefore, in the first modified battery pack 10, the control characteristics when the charger 50 controls charging the battery 16 can be adjusted according to the characteristics of the built-in battery 16, and the same effects as in the first embodiment described above can be obtained.

[0128] In this first modified example, the control circuit 30 performs the switching control process in the procedure shown in Figure 9. In other words, in the switching control process of this first modified example, first, in S410, the first switch SW1 is turned ON, and then in S420, the cell temperature Tcel is detected via the second temperature detection circuit 34.

[0129] Then, in the following S430, similar to S330 above, it is determined whether or not charging current is being supplied from the charger 50 to the battery pack 10 based on the detection signal from the current detection circuit 36.

[0130] If it is determined in S430 that no charging current is flowing, then charging from charger 50 to battery 16 is not being performed, so the process proceeds to S420, and the system waits for charging from charger 50 to battery 16 to begin.

[0131] On the other hand, if it is determined in S430 that a charging current is flowing, the process proceeds to S440, where it is determined whether the cell temperature Tcel detected in S420 is within the voltage range of 10°C or more and less than 15°C.

[0132] Then, in S440, if the result is positive, that is, if 10°C ≤ Tcel < 15°C, then S 460 Then, switch the first switch SW1 to the OFF state. death, We will migrate to S420.

[0133] Furthermore, if a negative result is obtained in S440, that is, if Tcel < 10°C or Tcel ≥ 15°C, I switched to the S450. Turn the first switch SW1 to the ON state. death, We will migrate to S420.

[0134] Accordingly, according to this first modification, when the control circuit 30 performs the above switching control process, the first switch SW1 can be turned off when the cell temperature Tcel is in the range of 10°C to 15°C, thereby setting the cell temperature Tcel recognized by the charger 50 to the low temperature range. In this first modification, the cell temperature Tcel of 10°C to 15°C corresponds to an example of the third temperature described in "Summary of Embodiments".

[0135] [Second Embodiment] The battery pack 10 of this second embodiment has the same basic configuration as the battery pack 10 of the first embodiment. The differences from the first embodiment are the configuration of the first temperature detection circuit 40 and the switching control processing performed by the control circuit 30. Therefore, in this second embodiment, these differences will be explained in detail, and other configurations will not be explained.

[0136] As shown in Figure 10, the first temperature detection circuit 40 of this embodiment includes a first terminal 40A, a second terminal 40B, a temperature detection element 42, and a first resistor 44. The temperature detection element 42 and the first resistor 44 are connected in series, and the first terminal 40A and the second terminal 40B are connected to both ends of this series circuit, respectively.

[0137] The first temperature detection circuit 40 is provided with two current paths connected in parallel to the first resistor 44, namely, a second current path 40D and a third current path 40E. A first switch SW1 is provided on the second current path 40D, similar to the first embodiment. A second resistor 46 and a second switch SW2 are provided on the third current path 40E. The first switch SW1 and the second switch SW2 are composed of semiconductor switches such as FETs.

[0138] When the first switch SW1 and the second switch SW2 are in the OFF state, 2nd, 3rd Current paths 40D and 40E are interrupted. As a result, the resistance Rs between the first terminal 40A and the second terminal 40B (in other words, the resistance Rs of the first temperature detection circuit 40) becomes the sum of the resistance Rm of the temperature detection element 42 and the resistance R1 of the first resistor 44, which is "Rm + R1".

[0139] In contrast, when the first switch SW1 is ON and the second switch SW2 is OFF, the second current path 40D conducts, so the resistance Rs of the first temperature detection circuit 40 becomes the resistance Rm of the temperature detection element 42. Therefore, the resistance Rs of the first temperature detection circuit 40 at this time is smaller than when the first switch SW1 and the second switch SW2 are OFF.

[0140] Furthermore, when the first switch SW1 is in the off state and the second switch SW2 is in the on state, the third current path 40E conducts, so the resistance value Rs of the first temperature detection circuit 40 becomes the combined resistance value of the temperature detection element 42, the first resistor 44, and the second resistor 46.

[0141] The combined resistance value is Rs = Rm + R1·R2 / (R1+R2), where R2 is the resistance value of the second resistor 46. Therefore, the resistance value Rs of the first temperature detection circuit 40 at this time is smaller than when the first switch SW1 and the second switch SW2 are in the off state, and larger than when the first switch SW1 is in the on state and the second switch SW2 is in the off state.

[0142] Therefore, as shown by the dotted line in Figure 11, the resistance-temperature characteristic of the first temperature detection circuit 40 (hereinafter referred to as the third resistance-temperature characteristic) when the first switch SW1 and the second switch SW2 are in the off state has the largest resistance value with respect to temperature.

[0143] Furthermore, when the first switch SW1 is in the off state and the second switch SW2 is in the on state, the resistance-temperature characteristic of the first temperature detection circuit 40 (hereinafter referred to as the second resistance-temperature characteristic) is smaller with respect to temperature compared to the third resistance-temperature characteristic, as shown by the dashed line in Figure 11.

[0144] Furthermore, the resistance-temperature characteristic of the first temperature detection circuit 40 when the first switch SW1 is in the ON state (hereinafter referred to as the first resistance-temperature characteristic) is as shown by the solid line in Figure 11. 2nd Switch S W2 Regardless of whether it is on or off, the resistance to temperature is minimized.

[0145] In contrast, the cell temperature detection characteristics in the charger 50 are set to correspond to the first resistance temperature characteristics when the first switch SW1 is in the ON state, as shown by the solid line in Figure 11. Therefore, similar to the first embodiment, when the first switch SW1 is switched from the ON state to the OFF state, the battery temperature recognized by the charger 50 decreases.

[0146] Furthermore, when the first switch SW1 is in the off state, and the second switch SW2 is also in the off state, the battery temperature recognized by the charger 50 is even lower compared to when the second switch SW2 is in the on state.

[0147] Furthermore, as shown in Figure 12, the charger 50 controls the charging voltage and charging current according to a charging control pattern similar to that of the first embodiment. The control circuit 30, in principle, when the battery temperature detected by the second temperature detection circuit 34 is within the charging temperature range of 0°C to 60°C corresponding to the charging control pattern, activates the first switch SW1 Turn it to ON, The second switch SW2 is configured to be in the OFF state.

[0148] Furthermore, if the battery temperature is within the temperature range of 10°C to 15°C and the cell voltage Vcel detected by the cell voltage detection circuit 32 exceeds 3.9V, the control circuit 30 switches the first switch SW1 to the OFF state and the second switch SW2 to the ON state.

[0149] As a result, when the battery temperature is within the 10°C to 15°C temperature range and the cell voltage Vcel detected by the cell voltage detection circuit 32 exceeds 3.9V, the resistance-temperature characteristic of the first temperature detection circuit 40 is switched to the second resistance-temperature characteristic. This second resistance-temperature characteristic is set so that when the battery temperature is within the 10°C to 15°C temperature range, the charger 50 recognizes that the battery temperature is in the low-temperature range of 0°C to 10°C.

[0150] Therefore, when the battery temperature is within the temperature range of 10°C to 15°C, and the cell voltage Vcel detected by the cell voltage detection circuit 32 exceeds 3.9V, the control circuit 30 switches the first switch SW1 to the off state and the second switch SW2 to the on state, causing the charger 50 to reduce the charging voltage and charging current to the battery 16.

[0151] Therefore, according to the battery pack 10 of this second embodiment, even if the cell temperature Tcel is in the normal temperature range, if it falls below 15°C and the cell voltage Vcel detected by the cell voltage detection circuit 32 exceeds 3.9V, the charger 50 can be instructed to reduce the charging voltage and charging current to perform charging of the battery 16 more slowly.

[0152] Furthermore, if the battery temperature is below 5°C and the cell voltage Vcel detected by the cell voltage detection circuit 32 exceeds 3.9V, the control circuit 30 switches both the first switch SW1 and the second switch SW2 to the off state. As a result, the resistance-temperature characteristic of the first temperature detection circuit 40 is switched to the third resistance-temperature characteristic.

[0153] This third resistance temperature characteristic is set so that when the battery temperature is below 5°C, the charger 50 recognizes that the battery temperature is in the charging stop temperature range below 0°C. Therefore, when the battery temperature is below 5°C and the cell voltage Vcel exceeds 3.9V, the charger 50 will stop charging the battery 16.

[0154] Therefore, according to the battery pack 10 of this second embodiment, even if the cell temperature Tcel is within the temperature range that the charger 50 recognizes as a low-temperature region, if it falls below 5°C, the charger 50 can be instructed to stop charging.

[0155] Therefore, according to the battery pack 10 of this second embodiment, the first Embodiments and one variant It can achieve the same effect as battery pack 10. In this second embodiment, the control circuit 30 performs the switching control process according to the procedure shown in Figure 13.

[0156] In other words, in the switching control process of this second embodiment, first, in S510, the first switch SW1 is turned ON and the second switch SW2 is turned OFF, and the process proceeds to S520. In S520, the cell voltage Vcel and cell temperature Tcel are detected via the cell voltage detection circuit 32 and the second temperature detection circuit 34. Then, in the subsequent S530, it is determined whether or not charging current is being supplied from the charger 50 to the battery pack 10 based on the detection signal from the current detection circuit 36.

[0157] If it is determined in S530 that no charging current is flowing, then charging from charger 50 to battery 16 is not taking place, so the process proceeds to S520, and the system waits for charging from charger 50 to battery 16 to begin.

[0158] Next, in S530, if it is determined that a charging current is flowing, the process proceeds to S540, where it is determined whether the cell temperature Tcel detected in S520 is within the range of 10°C to 15°C, and whether the cell voltage Vcel detected in S520 exceeds 3.9V.

[0159] Then, if the result in S540 is positive, that is, if 10°C ≤ Tcel < 15°C and Vcel > 3.9V, the process proceeds to S550, where the first switch SW1 is turned off and the second switch SW2 is turned on, and the process proceeds to S520.

[0160] In the S550, to prevent the first switch SW1 and the second switch SW2 from being turned off simultaneously, the second switch SW2 is switched to the ON position first, and then the first switch SW1 is switched to the OFF position.

[0161] Furthermore, if a negative result is obtained in S540, that is, if the cell temperature Tcel is outside the temperature range of 10°C to 15°C, or if the cell voltage Vcel is 3.9V or less, the process proceeds to S560.

[0162] Then, in S560, it is determined whether the cell temperature Tcel detected in S520 is less than 5°C and the cell voltage Vcel detected in S520 is greater than 3.9V. If the determination in S560 is positive, that is, if Tcel < 5°C and Vcel > 3.9V, the process proceeds to S570, where both the first switch SW1 and the second switch SW2 are switched to the OFF state, and the process proceeds to S520.

[0163] Furthermore, if S560 determines that it is negative, that is, if the cell temperature Tcel is 5° C and above If the above is true, or if the cell voltage Vcel is 3.9V or less, the process proceeds to S580. In S580, the first switch SW1 is switched to the ON state and the second switch SW2 is switched to the OFF state, and the process proceeds to S520. In this case as well, the first switch SW1 and the second switch SW2 are not switched to the OFF state simultaneously. Switch 1 After switching SW1 to the ON position, the second switch S W2 Switch it to the off state.

[0164] In this embodiment, a cell temperature Tcel of 5°C corresponds to an example of the first temperature described in "Summary of Embodiments," and a cell temperature Tcel of 10°C to 15°C corresponds to an example of the second temperature described in "Summary of Embodiments."

[0165] [Second variation] In the second embodiment described above, the switching control process shown in Figure 13, executed by the control circuit 30, is described as performing a switching determination for the first switch SW1 and the second switch SW2 in the determination processes of S540 and S560.

[0166] In contrast, in the switching control process of this second modified example, as shown in Figure 14, if it is determined in S530 that a charging current is flowing, the process proceeds to S532, where it is determined whether the cell temperature Tcel detected in S520 is 15°C or higher.

[0167] Then, in S532, if it is determined that the cell temperature Tcel is 15°C or higher, the process proceeds to S534, where the first switch SW1 is turned ON and the second switch SW2 is turned OFF, and the process proceeds to S520.

[0168] On the other hand, if it is determined in S532 that the cell temperature Tcel is less than 15°C, the process proceeds to S540, and the processing from S540 onward is executed in the same manner as the switching control process of the second embodiment shown in Figure 13.

[0169] According to this second modification, the switching control process performed by the control circuit 30 allows the first switch SW1 to be quickly switched to the ON state when the cell temperature Tcel is 15°C or higher, thereby returning the resistance-temperature characteristic of the first temperature detection circuit 40 to the first resistance-temperature characteristic.

[0170] [Third Embodiment] The battery pack 10 of this third embodiment has the same basic configuration as the battery pack 10 of the first and second embodiments. The differences from the first and second embodiments are the configuration of the first temperature detection circuit 40 and the switching control processing performed by the control circuit 30. Therefore, in this third embodiment, these differences will be explained in detail, and the explanation of other configurations will be omitted.

[0171] As shown in Figure 15, the first temperature detection circuit 40 of this embodiment includes a first terminal 40A, a second terminal 40B, a first current path 40C, a second current path 40D, a temperature detection element 42, a first resistor 44, and a third resistor 48.

[0172] The first current path 40C and the second current path 40D are connected in parallel to each other so as to connect the first terminal 40A and the second terminal 40B, respectively. A temperature sensing element 42 and a first resistor 44 are provided in series on the first current path 40C, and a third resistor 48 and a first switch SW1 are provided in series on the second current path 40D.

[0173] Therefore, when the first switch SW1 is in the off state, the second current path 40D is interrupted, and the resistance value Rs of the first temperature detection circuit 40 becomes the resistance value "Rm + R1", which is the sum of the resistance value Rm of the temperature detection element 42 and the resistance value R1 of the first resistor 44.

[0174] In contrast, when the first switch SW1 is ON, the second current path 40D conducts, so the resistance value Rs of the first temperature detection circuit 40 becomes the combined resistance value of the temperature detection element 42, the first resistor 44, and the third resistor 48.

[0175] The combined resistance value is Rs = R3·(Rm+R1) / (R3+Rm+R1), where R3 is the resistance value of the third resistor 48. Therefore, the resistance value Rs of the first temperature detection circuit 40 at this time is smaller than when the first switch SW1 is in the off state.

[0176] Therefore, as shown in Figure 16, the resistance-temperature characteristic of the first temperature detection circuit 40 when the first switch SW1 is ON is smaller than the resistance-temperature characteristic when the first switch SW1 is OFF.

[0177] On the other hand, the cell temperature detection characteristics in the charger 50 are set to correspond to the resistance-temperature characteristics when the first switch SW1 is in the off state, as shown by the solid line in Figure 16. Therefore, when the first switch SW1 is switched from the off state to the on state, the resistance value Rs of the first temperature detection circuit 40 decreases, and the battery temperature recognized by the charger 50 increases.

[0178] Furthermore, as shown in Figure 17, the charger 50 controls the charging voltage and charging current according to a charging control pattern similar to that of the first and second embodiments. In this third embodiment, the control circuit 30 of the battery pack 10 normally controls the first switch SW1 to the OFF state. The control circuit 30 also turns on the first switch SW1 when the battery temperature detected by the second temperature detection circuit 34 is within the temperature range of 40°C to 45°C. situation Switch to this.

[0179] As a result, when the battery temperature is within the range of 40°C to 45°C, the resistance-temperature characteristic of the first temperature detection circuit 40 is switched to a resistance-temperature characteristic shown by the dotted line in Figure 16, which has a small resistance value with respect to temperature.

[0180] This resistance-temperature characteristic is configured such that when the battery temperature is within the 40°C to 45°C temperature range, the charger 50 recognizes that the battery temperature is in the high-temperature range of 45°C to 60°C.

[0181] Therefore, when the battery temperature is within the temperature range of 40°C to 45°C, the control circuit 30 switches the first switch SW1 from the off state to the on state, causing the charger 50 to reduce the charging voltage and charging current to the battery 16.

[0182] Therefore, according to the battery pack 10 of this third embodiment, even if the cell temperature Tcel is in the normal temperature range, if it exceeds 40°C, the charger 50 can be instructed to reduce the charging voltage and charging current, thereby enabling slower charging of the battery 16.

[0183] Therefore, in the battery pack 10 of this embodiment, as with the battery pack 10 of the first and second embodiments described above, the control characteristics when the charger 50 controls charging the battery 16 can be adjusted according to the characteristics of the built-in battery 16.

[0184] In this third embodiment, the control circuit 30 performs the switching control process according to the procedure shown in Figure 18. In other words, in the switching control process of this third embodiment, first, in S610, the first switch SW1 is turned off, and the process proceeds to S620.

[0185] Next, in S620, the cell temperature Tcel is detected via the second temperature detection circuit 34, and in the following S630, it is determined whether or not charging current is being supplied from the charger 50 to the battery pack 10 based on the detection signal from the current detection circuit 36.

[0186] If S630 determines that no charging current is flowing, charging from charger 50 to battery 16 is not being performed, so the process moves to S620 and waits for charging from charger 50 to battery 16 to begin.

[0187] Next, in S630, if it is determined that charging current is flowing, the process proceeds to S640, where it is determined whether the cell temperature Tcel detected in S620 is within the range of 40°C to 45°C. If the determination in S640 is positive, that is, 40 °C≦Tcel< 45 If the temperature is °C, the program proceeds to S650, switches the first switch SW1 to the ON position, and then proceeds to S620.

[0188] Furthermore, if a negative result is obtained in S640, that is, if the cell temperature Tcel is 40 °C~ 45 If the temperature is outside the °C range, the process proceeds to S660. Then, in S660, the first switch SW1 is... off Switch to the current state and transition to S620.

[0189] In this embodiment, the cell temperature Tcel of 40°C to 45°C corresponds to an example of the fourth temperature described in "Summary of Embodiments". [Third variation] In the first to third embodiments described above, when the battery pack 10 is connected to the charger 50, the control characteristics of charging by the charger 50 can be adjusted by switching the on / off state of the first switch SW1 or the second switch SW2.

[0190] Alternatively, when the battery pack 10 is connected to an electrical device such as a power tool, the discharge characteristics from the battery pack 10 to the electrical device can be adjusted by switching the on / off state of the first switch SW1 or the second switch SW2.

[0191] Therefore, in this third modification, we will describe a case in which, when a power tool 80 is connected as an external device to the battery pack 10 of the third embodiment shown in Figure 15, the control circuit 30 switches the on / off state of the first switch SW1 to adjust the discharge characteristics to the external device.

[0192] The power tool 80 connected to the battery pack 10 is configured, for example, as shown in Figure 19. That is, the power tool 80 has a positive terminal 81, a negative terminal 82, and a signal input terminal 85. When the battery pack 10 is attached to the power tool 80, the first power terminal 21 and the positive terminal 81, the second power terminal 22 and the negative terminal 82, and the signal output terminal 25 and the signal input terminal 85 become electrically conductive.

[0193] The power tool 80 also includes a trigger switch 86, a motor 88, a power supply control switch 89, a control circuit 90, a voltage detection circuit 91, a detection signal input circuit 92, a switch detection circuit 95, a power supply circuit 96, and a switch control circuit 98.

[0194] The trigger switch 86 is located upstream of the motor 88 in the current path from the positive terminal 81 through the motor 88 to the negative terminal 72. A current control switch 89 is located downstream of the motor 88 in this current path. The trigger switch 86 is operated by the user of the power tool. The current control switch 89 is composed of a semiconductor switch, such as an FET.

[0195] When the battery pack 10 is connected to the power tool 80 and the trigger switch 86 is turned on, the voltage of the battery 16 (battery voltage) is input to the power supply circuit 96 and the switch detection circuit 95 via the trigger switch 86.

[0196] The power supply circuit 96 steps down the battery voltage to generate a power supply voltage (constant DC voltage) Vdd within the power tool 80. This generated power supply voltage Vdd is then supplied to the internal circuits of the power tool 80, such as the control circuit 90 and the detection signal input circuit 92. The switch detection circuit 95 detects the operating state of the trigger switch 86 when the battery voltage is input and outputs a signal indicating the detection result to the control circuit 90.

[0197] Next, the voltage detection circuit 91 is connected to the positive terminal 81. The voltage detection circuit 91 detects the battery voltage input from the battery pack 10 to the positive terminal 81 and outputs a signal indicating that battery voltage to the control circuit 90.

[0198] The detection signal input circuit 92, like the detection signal input circuit 57 of the charger 50, includes a pull-up resistor 93 as a second resistor and a filter 94. The pull-up resistor 93 receives a temperature detection signal from the first temperature detection circuit 40 in the battery pack 10 by applying the power supply voltage Vdd to the signal input terminal 85. 94 This removes noise components from the temperature detection signal and outputs it to the control circuit 90.

[0199] The control circuit 90, like the control circuit 30 of the battery pack 10, is equipped with a microcontroller including a CPU, ROM, RAM, etc. When the control circuit 90 detects that the trigger switch 86 has been turned on by an input signal from the switch detection circuit 95, it outputs a drive command to the switch control circuit 98 in order to rotate the motor 88 at a predetermined rotational speed.

[0200] A drive command is a command indicating the duty cycle. When a drive command is input from the control circuit 90, the switch control circuit 98 drives the motor 88 by turning the power supply control switch 89 on and off according to the duty cycle indicated by the drive command.

[0201] Furthermore, an input resistor 99 is provided in the output path of the drive signal from the switch control circuit 98 to the power supply control switch 89. Also, although the motor 88 is a brushed DC motor in this embodiment, this is merely one example.

[0202] When the motor 88 rotates, its rotational force drives tool elements (not shown), thereby enabling the power tool 80 to function. When the trigger switch 86 is turned off, the control circuit 90 stops outputting drive commands, which turns off the power supply control switch 89, and stops the motor 88.

[0203] Furthermore, the control circuit 90 performs temperature protection control while the trigger switch 86 is turned on and the motor 88 is being driven, that is, while power is supplied from the battery 16 to the motor 88 and the motor 88 is being driven.

[0204] In other words, the control circuit 90 turns off the power supply control switch 89 when the voltage value Vs of the temperature detection signal input from the detection signal input circuit 92 falls below a preset motor stop voltage threshold, thereby forcibly stopping the discharge from the battery 16 to the motor 88.

[0205] Furthermore, the motor stop voltage threshold of the power tool 80 is set independently of the type of battery 16. In other words, the control circuit 90 of the power tool 80 performs temperature protection control based on the voltage value Vs of the temperature detection signal, without identifying the type of battery 16.

[0206] Furthermore, the control circuit 90 performs over-discharge protection control based on the battery voltage detected by the voltage detection circuit 91, regardless of the type of battery 16. 90 If the battery voltage falls below a predetermined voltage for over-discharge detection while the motor 88 is running, the system determines that the battery pack 10 is in an over-discharge state and performs over-discharge protection control by turning off the power supply control switch 89.

[0207] Meanwhile, when discharge from the battery 16 to the power tool 80 begins, the control circuit 30 of the battery pack 10 monitors the state of the battery 16, and when the state of the battery 16 reaches a preset over-discharge state, it switches the first switch SW1 from the off state to the on state.

[0208] In other words, in this third modified example, the control circuit 30 performs the switching control process in the procedure shown in Figure 20, for example. In the switching control process shown in Figure 20, first, in S710, the first switch SW1 is turned off, and the process proceeds to S720. In S720, the cell voltage Vcel is detected via the cell voltage detection circuit 32.

[0209] Next, in S730, based on the detection signal from the current detection circuit 36, it is determined whether or not a discharge current is flowing from the battery 16 to the external device. In other words, in S730, it is determined whether or not the motor 88 of the power tool 80 connected to the battery pack 10 is driven and a discharge current is flowing from the battery 16 to the motor 88.

[0210] If it is determined in S730 that no discharge current is flowing, the motor 88 of the power tool 80 is not being driven, so the process proceeds to S720 and waits for the motor 88 to start driving.

[0211] On the other hand, if it is determined in S730 that a discharge current is flowing, the process proceeds to S740, where it is determined whether the cell voltage Vcel detected in S720 is less than a preset voltage value for over-discharge detection, for example, 3V. If the cell voltage Vcel is 3V or higher, the process proceeds to S720. If the cell voltage Vcel is less than 3V, in S750, the first switch SW1 is switched to the ON state, and the switching control process ends.

[0212] In S750, when the first switch SW1 is turned ON, the resistance value Rs of the first temperature detection circuit 40, and consequently... temperature As the voltage value Vs of the detection signal decreases, the battery temperature recognized by the power tool 80 rises, and the discharge to the motor 88 is forcibly stopped.

[0213] Therefore, according to the battery pack 10 of this third modification, when a discharge current flows from the battery 16 to the power tool 80, even if the voltage and temperature recognized by the power tool 80 allow for continued discharge, the discharge can be forcibly stopped according to the characteristics of the built-in battery 16.

[0214] In other words, in this third modification, when the cell voltage Vs drops to a predetermined voltage during discharge from the battery 16, the control circuit 30 of the battery pack 10 forcibly stops the discharge from the battery 16. Therefore, even if the battery voltage is higher than the over-discharge detection threshold on the power tool 80 side, the battery pack 10 can perform over-discharge protection control according to the characteristics of the battery 16.

[0215] The control circuit 30 may also be configured to switch the first switch SW1 to the ON state and forcibly stop the discharge when the cell temperature Vcel or the discharge current value of the battery 16 exceeds a predetermined threshold.

[0216] [Reference example] According to the battery pack 10 described in the first to third embodiments and the first to third modified examples above, the resistance value Rs of the first temperature detection circuit 40 can be changed by switching the on / off state of the first switch SW1 and the second switch SW2 in the first temperature detection circuit 40.

[0217] By changing the resistance value Rs, the battery temperature (cell temperature Vcel) recognized by external devices such as the charger 50 and power tool 80 can be changed, and the protection function of the external device can be activated according to the characteristics of the battery 16 in the battery pack 10.

[0218] Therefore, even if the first temperature detection circuit 40 changes the resistance value Rs in accordance with the cell temperature Tcel detected by the second temperature detection circuit 34 or the cell voltage Vcel detected by the cell voltage detection circuit 32, it is still possible to activate the protection function by an external device.

[0219] Therefore, as a reference example of this disclosure, we will describe a battery pack 10 in which the first temperature detection circuit 40 is composed of four resistors 71, 72, 73, and 74 and three switches SW1, SW2, and SW3.

[0220] The battery pack 10 in this reference example has the same basic configuration as the battery pack 10 in the above embodiment. The differences from the above embodiment are the configuration of the first temperature detection circuit 40 and the switching control processing performed by the control circuit 30.

[0221] As shown in Figure 21, four resistors 71, 72, 73, and 74 are connected in parallel between the first terminal 40A and the second terminal 40B of the first temperature detection circuit 40. The ends of resistor 74 are directly connected to the first terminal 40A and the second terminal 40B via a current path. Switches SW1, SW2, and SW3 are provided on the current paths of resistors 71, 72, and 73, which are connected in parallel to resistor 74.

[0222] The resistance values ​​of resistors 71, 72, 73, and 74 are R1, R2, R3, and R4, and each resistance value R1 to R4 is set as follows. In other words, the resistance value R4 of resistor R4 is set such that when all three switches SW1 to SW3 are in the off state, the resistance value Rs of the first temperature detection circuit 40 is such that the temperature recognized by the charger 50 from the temperature detection signal is 5°C.

[0223] Furthermore, the resistance value R1 of resistor R1 is set such that when switch SW1 is ON and the other switches SW2 and SW3 are OFF, the resistance value Rs of the first temperature detection circuit 40 becomes 30°C, as recognized by the charger 50 from the temperature detection signal.

[0224] Furthermore, the resistance value R2 of resistor R2 is set such that when switch SW2 is ON and the other switches SW1 and SW3 are OFF, the resistance value Rs of the first temperature detection circuit 40 becomes 50°C, as recognized by the charger 50 from the temperature detection signal.

[0225] Furthermore, the resistance value R3 of resistor R3 is set such that when switch SW3 is ON and the other switches SW1 and SW2 are OFF, the resistance value Rs of the first temperature detection circuit 40 becomes 70°C, as recognized by the charger 50 from the temperature detection signal.

[0226] Switches SW1, SW2, and SW3 are composed of semiconductor switches such as FETs, and the control circuit 30 can individually switch the on / off state of each switch SW1, SW2, and SW3.

[0227] Next, the charger 50 connected to the battery pack 10 in this reference example is configured in the same way as described in the first embodiment, and the control circuit 60 performs charging control according to the charging control pattern shown in Figure 22, based on the battery temperature detected based on the temperature detection signal.

[0228] This charging control pattern is set to charge the battery 16 when the battery temperature is within the range of -5°C to 65°C, and to stop charging the battery 16 when the battery temperature is lower than -5°C or higher than 65°C.

[0229] Furthermore, the charging control pattern is configured to control the charging switching power supply circuit 64 so that the cell voltage Vcel of the battery 16 is 4.2V and the charging current is 5A when the battery temperature is in the normal temperature range of 5°C to 50°C.

[0230] Furthermore, the charging control pattern is set so that when the battery temperature is in the low temperature range of -5°C to 5°C, or in the high temperature range of 50°C to 65°C, the charging voltage and charging current are lower compared to the normal temperature range.

[0231] For example, in the cold temperature range, the charging conditions are set to a charging voltage of 4.1V and a charging current of 1.5A, while in the high temperature range, the charging conditions are set to a charging voltage of 4.15V and a charging current of 3A.

[0232] In the battery pack 10 of this reference example, when a charger 50 with the charging control pattern set as described above is connected, the control circuit 30 executes a switching control process in the procedure shown in Figure 23.

[0233] In other words, in the switching control process of this reference example, first, in S810, the cell temperature Tcel of the battery 16 is detected via the second temperature detection circuit 34, and the process proceeds to S820. Then, in S820, it is determined whether the cell temperature Tcel detected in S810 is below -5°C or above 65°C, which is the charging stop region.

[0234] In S820, if the cell temperature Tcel is determined to be in the charging stop range, the process moves to S830, where switch SW3 in the first temperature detection circuit 40 is turned ON, and the other switches SW1 and SW2 are turned OFF, before proceeding to S810. As a result, the resistance value Rs of the first temperature detection circuit 40 becomes 70°C, the temperature recognized by the charger 50 based on the temperature detection signal, and the charger 50 stops charging the battery 16.

[0235] Next, in S820, if it is determined that the cell temperature Tcel is not in the charging stop region, the process moves to S840, where it is determined whether the cell temperature Tcel is less than 5°C. In S840, if it is determined that the cell temperature Tcel is less than 5°C, the process moves to S850, where all three switches SW1 to SW3 in the first temperature detection circuit 40 are turned off, and the process moves to S810.

[0236] In other words, if S840 determines that the cell temperature Tcel is less than 5°C, then the cell temperature Tcel is in the low-temperature range of -5°C to 5°C. Therefore, in S850, the resistance value Rs of the first temperature detection circuit 40 is set so that the temperature recognized by the charger 50 becomes 5°C by turning off all three switches SW1 to SW3. As a result, the charger 50 recognizes that the cell temperature Tcel of the battery 16 is in the low-temperature range and performs charging control to the battery 16.

[0237] Next, in S840, if it is determined that the cell temperature Tcel is not less than 5°C, the process proceeds to S860 to determine whether the cell temperature Tcel is less than 50°C. Then, in S860, if it is determined that the cell temperature Tcel is less than 50°C, the process proceeds to S870, where switch SW1 in the first temperature detection circuit 40 is turned ON, and the other switches SW2 and SW3 are turned OFF, and the process proceeds to S810.

[0238] In other words, if S860 determines that the cell temperature Tcel is less than 50°C, then the cell temperature Tcel is in the normal temperature range of 5°C to 50°C. Therefore, in S870, the resistance value Rs of the first temperature detection circuit 40 is set so that the temperature recognized by the charger 50 becomes 30°C by turning switch SW1 ON and turning the other switches SW2 and SW3 OFF. As a result, the charger 50 recognizes that the cell temperature Tcel of the battery 16 is in the normal temperature range and performs charging control to the battery 16.

[0239] Next, in S860, if it is determined that the cell temperature Tcel is not below 50°C, the process proceeds to S880, where switch SW2 in the first temperature detection circuit 40 is turned ON, and the other switches SW1 and SW3 are turned OFF.

[0240] In other words, if S860 determines that the cell temperature Tcel is not below 50°C, then the cell temperature Tcel is in the high-temperature range of 50°C to 65°C. Therefore, in S880, the resistance value Rs of the first temperature detection circuit 40 is set so that the temperature recognized by the charger 50 becomes 50°C by turning switch SW2 ON and turning the other switches SW1 and SW3 OFF. As a result, the charger 50 recognizes that the cell temperature Tcel of the battery 16 is in the high-temperature range and performs charging control to the battery 16.

[0241] As explained above, in the battery pack 10 of this reference example, the control circuit 30 sets the cell temperature Tcel recognized by the charger 50 by switching the resistance value Rs of the first temperature detection circuit 40 according to the cell temperature Tcel detected by the second temperature detection circuit 34.

[0242] Therefore, in the battery pack 10 of this reference example, similar to the battery pack 10 of the first to third embodiments described above, the control characteristics when the charger 50 controls charging and discharging the battery 16 can be adjusted according to the characteristics of the built-in battery 16. In addition, by switching the resistance value Rs of the first temperature detection circuit 40, the discharge current flowing from the battery 16 to external devices such as power tools 80 can also be adjusted.

[0243] In this example, the resistance value Rs of the first temperature detection circuit 40 is switched by turning on one of the three switches SW1 to SW3, but two or more switches may be turned on. In other words, the cell temperature Tcel recognized by the charger 50 can be arbitrarily set by switching the resistance value Rs of the first temperature detection circuit 40 by the combination of switches that are turned on.

[0244] [Other embodiments] Although embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above and can take various forms.

[0245] For example, the configuration of the first temperature detection circuit 40 provided in the battery pack 10 of the above embodiment is just one example, and the number of current paths, resistors, and switches in the first temperature detection circuit 40 can be changed as appropriate. For example, in the first temperature detection circuit 40 of the first embodiment shown in Figure 1, the intermediate resistor 43 is not necessarily required and may be omitted.

[0246] Furthermore, the first temperature detection circuit 40 was described as having a voltage applied via pull-up resistors 58 and 93 connected to a power line in an external device such as a charger 50 or a power tool 80, where the potential is higher than the ground potential by the power supply voltage Vdd.

[0247] However, the first temperature detection circuit 40 may also be configured to receive a voltage via a pull-up resistor from a power line within the battery pack 10, where the potential is higher than the ground potential by the power supply voltage Vcc. In other words, even in this configuration, the first temperature detection circuit 40 can still output a temperature detection signal to an external device.

[0248] Furthermore, in order to output a temperature detection signal from the first temperature detection circuit 40 to an external device, a voltage may be applied to the first temperature detection circuit 4 via a pull-down resistor connected to ground, which is the negative power line in the battery pack 10 or the external device.

[0249] In other words, the first terminal 40A of the first temperature detection circuit 40 is connected to a positive power line to which the power supply voltage Vcc or Vdd is applied in the battery pack 10 or external device, and the second terminal 40B is connected to ground via a resistor (pull-down resistor). The battery pack 10 is provided with a second signal output terminal connected to the second terminal 40B of the first temperature detection circuit 40.

[0250] Even with this configuration of the battery pack 10, external devices such as the charger 50 and power tools 80 can output the voltage between the second signal output terminal and the first signal output terminal, which is the signal output terminal 25, as a temperature detection signal.

[0251] Furthermore, the charging control patterns of the charger 50 described in each of the above embodiments, modified examples, or reference examples are merely examples, and the control patterns for charging voltage and charging current in relation to battery temperature (cell temperature Tcel) can be arbitrarily set.

[0252] In this case, the battery pack 10 should be configured so that the temperature recognized by the temperature detection signal from the first temperature detection circuit 40 when the charger 50 performs charging control according to the charging control pattern can be adjusted by the resistance value Rs of the first temperature detection circuit 40.

[0253] Furthermore, the functions of one component in the above embodiment may be distributed among multiple components, or the functions of multiple components may be integrated into one component. Also, at least a part of the configuration of the above embodiment may be replaced with a known configuration having a similar function. Also, a part of the configuration of the above embodiment may be omitted. Also, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of other above embodiments. Note that any aspect included in the technical concept specified solely by the wording described in "Summary of Embodiments" is an embodiment of the present disclosure. [Explanation of Symbols]

[0254] 10...Battery pack, 16...Battery, 21...First power terminal, 22...Second power terminal, 25...Signal output terminal, 30...Control circuit, 40...First temperature detection circuit, 40A...First terminal, 40B...Second terminal, 40C...First current path, 40D...Second current path, 42...Temperature detection element, 44...First resistor, SW1...First switch, SW2...Second switch.

Claims

1. A rechargeable battery having a positive electrode and a negative electrode, A first power terminal having a first end connected to the positive electrode and a second end configured to be connected to the positive terminal of an external device, A second power terminal having a first end connected to the negative electrode and a second end configured to be connected to the negative terminal of the external device, A first temperature detection circuit having a first terminal, a second terminal, and a first current path from the first terminal to the second terminal, wherein the first current path includes a temperature detection element configured to change its resistance value according to the temperature of the battery, and a first resistor connected to the temperature detection element, and is configured to generate a temperature detection signal indicating the temperature of the battery when a voltage is applied between the first terminal and the second terminal via a resistor connected to a power line of a predetermined potential, A first signal output terminal and a second signal output terminal are connected to the first terminal and the second terminal, respectively, and configured to output the temperature detection signal to the external device, A second current path connected in parallel to the first current path, A first switch provided on the second current path and configured to selectively switch between an ON state and an OFF state, wherein the second current path conducts or is interrupted in response to the first switch switching to the ON state or the OFF state, and the resistance value of the first temperature detection circuit changes. A control circuit is configured to acquire at least one of the following as the state of the battery: the voltage of the battery, the temperature of the battery, the charging current to the battery, and the discharge current from the battery, and to switch the first switch to the ON state or the OFF state according to the acquired state of the battery, Equipped with a battery pack.

2. A battery pack according to claim 1, A second temperature detection circuit, separate from the first temperature detection circuit, is provided, which is configured to detect the temperature of the battery. The control circuit is configured to switch the first switch to the ON state or the OFF state according to the temperature detected by the second temperature detection circuit and / or the voltage of the battery, in a battery pack.

3. A battery pack according to claim 1 or claim 2, The temperature sensing element is connected in series with the first resistor, The second current path is connected in parallel with the first resistor to a battery pack.

4. A battery pack according to claim 3, The aforementioned external device is a charger, The temperature sensing element has a negative temperature characteristic in which the resistance value of the temperature sensing element decreases as the temperature of the battery increases. The sum of the resistance value of the temperature detection element and the resistance value of the first resistor when the temperature of the battery is at the first temperature is set to a resistance value that generates the temperature detection signal that causes the charger to stop charging. The control circuit is configured to switch the first switch to the ON state when the temperature of the battery exceeds the first temperature, and to switch the first switch to the OFF state when the temperature of the battery is at or below the first temperature, in a battery pack.

5. A battery pack according to claim 4, The first temperature detection circuit is, The second resistor, A second switch configured to selectively switch between an ON state and an OFF state, wherein the ON state of the second switch is configured to connect the second resistor in parallel with the first resistor, A battery pack equipped with this feature.

6. A battery pack according to claim 5, When the temperature of the battery is at a second temperature higher than the first temperature, and the second switch is in the ON state, the combined resistance value of the temperature detection element, the first resistor, and the second resistor is set to a resistance value that generates the temperature detection signal that reduces the charging current and / or charging voltage for the charger. The control circuit is configured to switch the first switch to the ON state and the second switch to the OFF state when the temperature of the battery exceeds the second temperature, and to switch the second switch to the ON state and then to the OFF state when the temperature of the battery falls below the second temperature.

7. A battery pack according to claim 3, The aforementioned external device is a charger, The temperature sensing element has a negative temperature characteristic in which the resistance value of the temperature sensing element decreases as the temperature of the battery increases. When the temperature of the battery is at the third temperature, the sum of the resistance value of the temperature detection element and the resistance value of the first resistor is set to a resistance value that generates the temperature detection signal that reduces the charging current and / or charging voltage for the charger. The control circuit is configured to turn the first switch to the ON state when the battery temperature exceeds the third temperature, and to turn the first switch to the OFF state when the battery temperature is below the third temperature.

8. A battery pack according to claim 1 or claim 2, A battery pack comprising: a third resistor connected in parallel to the series circuit of the temperature sensing element and the first resistor on the first current path via the second current path when the first switch is in the ON state.

9. A battery pack according to claim 8, The aforementioned external device is a charger, The temperature sensing element has a negative temperature characteristic in which the resistance value of the temperature sensing element decreases as the temperature of the battery increases. When the temperature of the battery is at the fourth temperature and the first switch is in the ON state, the combined resistance value of the temperature detection element, the first resistor, and the third resistor is set to a resistance value that generates a temperature detection signal for the charger, which reduces the charging current and / or charging voltage when the battery is at a high temperature. The control circuit is configured to switch the first switch to the off state when the temperature of the battery is below the fourth temperature, and to switch the first switch to the on state when the temperature of the battery exceeds the fourth temperature, thereby reducing the charging rate from the charger to the battery.

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