Battery pack for electric bicycle and electric bicycle equipped with this battery pack

Abstract

The present invention limits a voltage increase caused by a charging current from a drive motor, prevents battery deterioration caused by voltage increases, and ensures a sufficient level of safety.　This battery pack is equipped with: a rechargeable battery (1); a charging FET (3) which has a parallel diode (7) connected in series with the battery (1); and a control circuit (2) for controlling so as to turn the charging FET (3) on and off. The control circuit (2) is equipped with a distinguishing circuit (5) for distinguishing between a bicycle set state and a charger connection state, and a storage unit (6) for storing the full charge voltage of the battery (1). The control circuit (2) turns the charging FET (3) to the off state while in a state where the distinguishing circuit (5) detects the bicycle set state, and stops charging the battery (1) by switching the charging FET (3) to the off state upon detecting that the battery voltage charged by the charger is higher than the full charge voltage.

Description

[Technical Field]

[0001] The present invention relates to a battery pack that supplies power to a traction motor of an electric bicycle, and an electric bicycle equipped with this battery pack. [Background technology]

[0002] Electric bicycles equipped with a traction motor that drives the wheels can travel easily by supplying power from a battery to the traction motor. One such electric bicycle has been developed that is equipped with a circuit that charges the battery pack by regenerative braking when braking (see Patent Document 1).

[0003] The electric bicycle described in Patent Document 1 ensures that the battery has sufficient charge capacity to decelerate the bicycle smoothly using regenerative braking. A battery that has sufficient charge capacity can be charged using regenerative braking until it is fully charged, allowing the bicycle to be ridden smoothly down a long slope, for example, using regenerative braking. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-103871 Summary of the Invention [Problem to be solved by the invention]

[0005] The method of charging the battery while leaving some charge capacity has the disadvantage that the battery is not fully charged, thereby reducing the battery's mileage. Furthermore, because bicycles are used in a variety of riding conditions, the current charging the battery from the traction motor fluctuates greatly, and there are times when a large current is used to charge the battery. When a battery is charged with a large current, the voltage rises suddenly, causing various problems that can be detrimental to the battery.

[0006] The present invention was developed with the aim of further eliminating the above-mentioned drawbacks, and one of the objects of the present invention is to provide a battery pack for an electric bicycle that limits the rise in voltage due to the charging current from the traction motor, prevents battery deterioration caused by the voltage rise, and ensures sufficient safety, as well as an electric bicycle equipped with this battery pack. [Means for solving the problem]

[0007] A battery pack according to a first aspect of the present invention comprises a rechargeable battery, a charging FET with a parallel diode connected in series with the battery, and a control circuit that controls the charging FET on and off. The control circuit comprises a discrimination circuit and a memory unit, the discrimination circuit distinguishing between a bicycle-mounted state and a charger-connected state, and the memory unit stores the battery's full-charge voltage. When the battery pack is mounted on the bicycle and the discrimination circuit detects the bicycle-mounted state, the control circuit turns the charging FET off to prevent the battery from being charged by the traction motor's electromotive force. When the battery pack is connected to a charger and the discrimination circuit detects the charger-connected state, the control circuit turns the charging FET off to stop charging if the battery voltage being charged by the charger exceeds the full-charge voltage.

[0008] A battery pack according to a second aspect of the present invention comprises a rechargeable battery, a charging FET with a parallel diode connected in series with the battery, and a control circuit that controls the charging FET on and off. The control circuit has a discrimination circuit and a memory unit. The discrimination circuit distinguishes between a bicycle-set state (in which the battery pack is set on a bicycle) and a charger-connected state (in which the battery pack is connected to a charger), and the memory unit stores the battery's full charge voltage and a threshold voltage set lower than the full charge voltage. When the discrimination circuit detects the bicycle-set state and the battery voltage is higher than the threshold voltage, the control circuit turns the charging FET off to prevent charging by the electromotive force of the traction motor from exceeding the full charge voltage. When the battery voltage is lower than the threshold voltage, charging by the electromotive force of the traction motor can be prevented from exceeding the full charge voltage, so the charging FET is turned on to allow charging current. When the battery pack is connected to a charger, the discrimination circuit detects the charger-connected state and switches the FET off to stop battery charging if the voltage of the battery being charged exceeds the full charge voltage.

[0009] A battery pack according to a third aspect of the present invention comprises a rechargeable battery, a charging FET with a parallel diode connected in series with the battery, and a control circuit that controls the charging FET on and off. The control circuit has a discrimination circuit and a memory unit, and the discrimination circuit distinguishes between a bicycle-set state (in which the battery pack is set on a bicycle) and a charger-connected state (in which the battery pack is connected to a charger), and the memory unit stores the battery's full-charge voltage and a threshold current for the load current supplied from the battery to the bicycle. When the discrimination circuit detects the bicycle-set state and the load current is less than the threshold current, the control circuit turns the charging FET off to prevent the battery from being charged by the electromotive force of the traction motor and its voltage from exceeding the full-charge voltage. When the load current is greater than the threshold current, the battery pack is in a discharging state, preventing the battery from being charged by the electromotive force of the traction motor and its voltage from exceeding the full-charge voltage. Therefore, the charge FET is turned on and the battery supplies current to the traction motor via the FET. Even when the charge FET is off, it can supply current to the traction motor via the parallel diode, but the parallel diode has a large voltage drop, resulting in significant power loss when a large current flows. When the load current supplied from the battery to the traction motor exceeds a threshold current, the control circuit switches the charge FET on and supplies the load current from the battery to the bicycle via the low-resistance charge FET. When a large current is supplied from the battery to the load traction motor, the charge FET has a smaller internal resistance in the on state than the parallel diode, resulting in a small voltage drop when a large current flows, allowing a large current to be supplied from the battery to the traction motor and minimizing power loss. When the battery pack is connected to a charger, the discrimination circuit detects the charger connection status, and when the voltage of the battery being charged exceeds the full charge voltage, it switches the FET off and stops charging the battery.

[0010] An electric bicycle according to one aspect of the present invention comprises any of the battery packs described above and a traction motor connected to the battery pack via a control converter, which supplies a charging current to the battery pack when the bicycle is regeneratively braking.

[0011] An electric bicycle according to another aspect of the present invention comprises any of the battery packs described above, a traction motor connected to the battery pack via a control converter, and a regenerative braking power generation mechanism that charges the battery pack using the electromotive force of the traction motor. [Effects of the Invention]

[0012] The battery pack for an electric bicycle of the present invention limits the rise in voltage caused by the charging current from the traction motor, preventing battery deterioration due to the voltage rise and ensuring sufficient safety. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a block diagram of a battery pack for an electric bicycle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The embodiment of the present invention may be specified by the following configurations. A battery pack for an electric bicycle according to a first embodiment of the present invention comprises a rechargeable battery, a charging FET with a parallel diode connected in series with the battery, and a control circuit that controls the charging FET on and off. The control circuit comprises a discrimination circuit that distinguishes between a bicycle-mounted state and a charger-connected state, and a memory unit that stores the battery's full charge voltage. When the discrimination circuit detects the bicycle-mounted state, the control circuit turns the charging FET off. When the discrimination circuit detects the charger-connected state, the control circuit detects that the battery voltage charged by the charger is higher than the full charge voltage, switching the charging FET off and ending battery charging.

[0015] In the above-described battery pack for an electric bicycle, the charge FET is turned off when the battery is set on the bicycle. Because the charge FET has a parallel diode such as a parasitic diode connected, it supplies power from the battery to the traction motor even when it is turned off. This battery pack is capable of supplying power to the traction motor when set on the bicycle, but prohibits the battery from being charged by the electromotive force of the traction motor. When set on the bicycle, the battery pack is charged by the electromotive force of the traction motor, and if the battery voltage exceeds the full charge voltage, battery deterioration will accelerate and safety will be reduced. A battery pack that keeps the charge FET turned off when set on the bicycle prohibits charging by the electromotive force of the traction motor when set on the bicycle. Therefore, when set on the bicycle, battery deterioration due to the electromotive force of the traction motor is prevented, ensuring safety.

[0016] A battery pack for an electric bicycle according to a second embodiment of the present invention comprises a rechargeable battery, a charging FET with a parallel diode connected in series with the battery, and a control circuit that controls the charging FET on and off. The control circuit comprises a discrimination circuit that distinguishes between a bicycle-mounted state and a charger-connected state, and a memory unit that stores the battery's full charge voltage as well as a threshold voltage set lower than the full charge voltage. When the discrimination circuit detects the bicycle-mounted state, the control circuit turns the charging FET off when the battery voltage is higher than the threshold voltage, and turns the charging FET on when the battery voltage is lower than the threshold voltage. When the discrimination circuit detects the charger-connected state, the control circuit detects that the battery voltage, resulting from charging by the charger, is higher than the full charge voltage, and switches the charging FET off to terminate battery charging.

[0017] When the above-described electric bicycle battery pack is installed on a bicycle, if the battery voltage is higher than a threshold voltage that is preset to be lower than the full-charge voltage, the charge FET is turned off, prohibiting charging using the electromotive force of the traction motor. Therefore, when the battery voltage is low, the battery is charged by the electromotive force of the traction motor, but in this state the battery voltage does not exceed the full-charge voltage, preventing battery degradation and ensuring safety. When the battery voltage is lower than the threshold voltage, the charge FET is turned on, allowing charging by the electromotive force of the traction motor, but the threshold voltage can be set to a voltage that allows charging by electromotive force but does not exceed the full-charge voltage. Therefore, even if the electromotive force of the traction motor charges the battery when the battery voltage is lower than the threshold voltage, the battery voltage does not exceed the full-charge voltage, preventing battery degradation and ensuring safety.

[0018] A battery pack for an electric bicycle according to a third embodiment of the present invention comprises a rechargeable battery, a charging FET with a parallel diode connected in series with the battery, and a control circuit that controls the charging FET on and off. The control circuit comprises a discrimination circuit that distinguishes between a bicycle-mounted state and a charger-connected state, and a memory unit that stores the battery's full charge voltage and a threshold load current. When the discrimination circuit detects the bicycle-mounted state, the control circuit turns the charging FET off when the load current is smaller than the threshold current, and turns the charging FET on when the load current is larger than the threshold current. When the discrimination circuit detects the charger-connected state, the control circuit detects that the battery voltage, resulting from charging by the charger, is higher than the full charge voltage, and switches the charging FET off to terminate battery charging.

[0019] In the above-described electric bicycle battery pack, when the bicycle is installed, the charge FET is controlled to the off state when the load current is smaller than the threshold current, but is controlled to the on state when the load current is larger than the threshold current. Because the charge FET is connected to a parallel diode, in the off state, power is supplied from the battery to the traction motor via the parallel diode. When the charge FET is off and power is supplied to the traction motor from the parallel diode, a voltage drop occurs across the parallel diode. The voltage drop across the parallel diode is larger than the voltage drop when the FET is on; a typical diode has a voltage drop of approximately 0.6 V. In contrast, the internal resistance of the FET in the on state is extremely small, at a few milliohms, and the voltage drop generated by current flow is smaller than that of the parallel diode. A parallel diode with a large voltage drop increases power loss proportional to the current, so when a large current is supplied from the battery to the traction motor, the power loss of the charge FET in the off state increases. In the above-described battery pack, the charge FET is controlled to the on state when the load current is larger than the threshold current, thereby reducing power loss across the charge FET when a large current is supplied from the battery to the traction motor.

[0020] In a battery pack for an electric bicycle according to a fourth embodiment of the present invention, the control circuit is equipped with an A / D converter that converts the battery voltage into a digital signal, and calculates the battery voltage by calculating the digital signal converted by the A / D converter.

[0021] In a battery pack for an electric bicycle according to a fifth embodiment of the present invention, the charging FET is a MOSFET with a parallel diode as a parasitic diode.

[0022] In a battery pack for an electric bicycle according to a sixth embodiment of the present invention, the rechargeable battery is a lithium-ion battery.

[0023] An electric bicycle according to a seventh embodiment of the present invention comprises a battery pack as described above, a traction motor connected to the battery pack via a control converter, and a regenerative braking charging mechanism that charges the battery pack using the electromotive force of the traction motor.

[0024] The present invention will be described in detail below with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "upper," "lower," and other terms including these terms) will be used as necessary. However, the use of these terms is intended to facilitate understanding of the invention with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention. Furthermore, parts that appear with the same reference numerals in multiple drawings indicate the same or equivalent parts or components. Furthermore, the embodiments shown below are specific examples of the technical concept of the present invention and are not intended to limit the present invention thereto. Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described below are intended as examples and are not intended to limit the scope of the present invention thereto. Furthermore, the content described in one embodiment or example can also be applied to other embodiments or examples. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity of explanation.

[0025] (Embodiment 1) The battery pack 100 for an electric bicycle shown in the block diagram of Figure 1 comprises a rechargeable battery 1, a charging FET 3 with a parallel diode 7 connected in series with the battery 1, and a control circuit 2 that controls the on / off of the charging FET 3. The block diagram also shows a bicycle 20 to which the battery pack 100 is connected, and a charger 30 that charges the battery pack 100. When attached to the bicycle 20, the battery pack 100 supplies power to a traction motor 21 that propels the bicycle 20, and when connected to the charger 30, the battery pack 100 is removed from the bicycle 20 and connected to the charger 30. When attached to the bicycle 20, the battery pack 100 supplies power to the traction motor 21, providing driving force to the bicycle 20.

[0026] The battery pack 100 in Figure 1 is equipped with a charge FET 3 and a discharge FET 4 that controls the discharge of the battery 1. The charge FET 3 and discharge FET 4 are controlled to be turned on and off by a control circuit 2. The control circuit 2 is equipped with a discrimination circuit 5 and a memory unit 6. The discrimination circuit 5 distinguishes between a bicycle set state in which the battery pack 100 is set on a bicycle 20 and a charger connected state in which the battery pack is connected to a charger 30. The memory unit 6 is, for example, a semiconductor memory, and stores the full charge voltage at which the battery 1, whose voltage rises during charging, is detected as being fully charged and charging is stopped.

[0027] The charge FET 3 and discharge FET 4 are MOSFETs with a parasitic diode connected as the parallel diode 7. However, the charge FET 3 and discharge FET 4 can be FETs without a parasitic diode connected in parallel with a separate high-current diode, or a high-current diode can be connected in parallel with the parasitic diode. Diodes with excellent high-current characteristics are used to enable a large current to be supplied from the battery 1 to the traction motor 21. Diodes with a small voltage drop are particularly suitable. However, in a battery pack in which the charge FET 3 is turned on to supply a large current from the FET to the traction motor 21 when a large current is being supplied from the battery 1 to the traction motor 21, the parallel diode 7 does not necessarily require high-current characteristics because a large current is supplied from the FET to the traction motor. The battery pack 100 shown in Figure 1 uses N-channel FETs for both the charge FET 3 and the discharge FET 4. However, P-channel FETs may also be used for the charge FET and the discharge FET.

[0028] The discrimination circuit 5 shown in the block diagram of FIG. 1 is connected to the bicycle 20 via a connection terminal 12. The bicycle-side connection terminal 22 is connected to an earth line 24 via a resistor 23. The battery pack 100 connects the connection terminal 12 to a power source 14 via a pull-up resistor 13, and the discrimination circuit 5 detects the voltage at the connection terminal 12 to distinguish between a bicycle-set state and a charger-connected state. When the battery pack 100 is connected to the bicycle 20, the voltage at the connection terminal 12 is lower than the power supply voltage divided by the pull-up resistor 13 and the bicycle-side resistor 23, and when the battery pack 100 is connected to the charger 30, the connection terminal 12 is not connected to the earth line 24, so the voltage at the connection terminal 12 becomes the power supply voltage. Therefore, the discrimination circuit 5 determines that a state in which the voltage at the connection terminal 12 is lower than the power supply voltage as a bicycle-set state, Power supply voltage In this case, it is determined that the charger is connected.

[0029] When the battery pack 100 is installed on the bicycle 20, for example, during regenerative braking, the traction motor 21 may act as a generator to charge the battery pack 100. The battery pack 100's voltage increases as it is charged, and the voltage also increases when it is charged by the electromotive force of the traction motor 21. If the voltage of the battery pack 100 increases above a set value, the electrical characteristics will deteriorate and safety will be compromised. For example, lithium-ion batteries are preferred for use in the battery pack 100 because they are light, compact, and have a large charge / discharge capacity. Lithium-ion batteries are charged with a maximum voltage set to 4.1 V to 4.2 V, but if they are charged above this maximum voltage, both the electrical characteristics and safety will deteriorate.

[0030] When the discrimination circuit 5 detects that the bicycle is set in place, the control circuit 2 of the battery pack 100 in Figure 1 turns off the charge FET 3, prohibiting the battery 1 from being charged with electromotive force from the traction motor 21. When this battery pack 100 is set in place on the bicycle 20, the off-state charge FET 3 prohibits the electromotive force of the traction motor 21 from charging the battery 1, so the battery is not charged with electromotive force from the traction motor 21 of the bicycle 20. In this state, the voltage of the battery pack 100 does not rise, preventing the adverse effects of a rise in power supply voltage that could deteriorate the battery 1 or reduce the safety of the battery 1. The discharge FET 4 is a switching element that supplies power from the battery 1 to the traction motor 21, so when this switching element is off, power cannot be supplied from the battery 1 to the traction motor 21 via the FET. When set in the bicycle 20, it is essential that the battery pack 100 supply power from the battery 1 to the traction motor 21. When the charging FET 3 is in the off state, the battery pack 100 described above supplies power from the battery 1 to the traction motor 21 via the parallel diode 7. The parallel diode 7 is connected so that current flows in the reverse direction to the forward direction of the FET, and supplies current from the battery 1 to the traction motor 21 when the FET is in the off state. Therefore, when the battery pack 100 in Figure 1 is installed on the bicycle 20, it supplies power from the battery 1 to the traction motor 21, but prohibits the battery 1 from being charged by the electromotive force of the traction motor 21, preventing deterioration of the battery 1 and ensuring safety.

[0031] The control circuit 2 can keep the charge FET 3 off all the time when the battery pack 100 is installed on the bicycle 20, but it can also switch the charge FET 3 on and off based on the battery voltage to prevent deterioration and reduced safety due to an abnormal voltage rise in the battery 1 while supplying a large current from the battery 1 to the traction motor 21, thereby reducing power loss. This battery pack 100 stores a threshold voltage set lower than the full charge voltage in the memory unit 6 of the control circuit 2. The threshold voltage is set taking into account the time delay at which the control circuit 2 switches the charge FET 3 off.

[0032] The control circuit 2 compares the battery 1 voltage with a threshold voltage set lower than the full-charge voltage. If the battery 1 voltage exceeds the threshold voltage, the control circuit 2 switches the charging FET 3 to the OFF state. Therefore, in principle, the battery voltage will never exceed the threshold voltage. However, since the control circuit 2 detects the battery voltage, determines whether the detected voltage is higher than the threshold voltage, and switches the charging FET 3 to the OFF state if it determines that the detected voltage is higher than the threshold voltage, there is a time delay between the time when the battery 1 voltage exceeds the threshold voltage and the time when the charging FET 3 is switched to the OFF state. In particular, there is a time lag between the time when the A / D converter converts the detected analog signal of the battery voltage into a digital signal, the time when the converted digital signal is processed, the time when the battery voltage exceeds the threshold voltage, and the time when the charging FET 3 is switched to the OFF state. Furthermore, in order to detect the battery voltage with high accuracy and reduce errors due to noise, the battery pack 100 calculates the battery voltage by averaging multiple digital signals converted by the A / D converter at a specified sampling period, which causes a time lag in the detection of the battery voltage. The threshold voltage is set to, for example, a voltage 0.1V to 0.3V lower than the fully charged voltage of the battery 1 so that the battery 1 is not charged by the traction motor 21 and exceeds the threshold voltage during the time lag between detecting the battery voltage and switching the charging FET 3 to the off state.

[0033] The control circuit 2, which stores the threshold voltage in the memory unit 6, never turns off the charge FET 3 when the battery pack 100 is attached to the bicycle 20. When the discrimination circuit 5 detects that the bicycle is attached, the control circuit 2 turns off the charge FET 3 when the battery voltage is higher than the threshold voltage, but turns on when the battery voltage is lower than the threshold voltage. The charge FET 3 in the on state supplies power from the battery 1 to the traction motor 21 via the on-state FET, without going through the parallel diode 7. Although the voltage drop across the parallel diode 7 is large, the on-resistance of the on-state FET is extremely small, on the order of milliohms, so power loss in the charge FET 3 is extremely small, even when a large current is supplied from the battery 1 to the traction motor 21. Therefore, even when a large current is supplied from the battery pack 100 to the traction motor 21, power loss in the charge FET 3 is minimized, allowing power to be efficiently supplied from the battery 1 to the traction motor 21. Furthermore, the amount of heat generated by Joule heat in the charge FET 3 is reduced, minimizing temperature rise in the charge FET 3.

[0034] Furthermore, the charge FET3 is switched to the ON state only when the battery voltage is lower than a threshold voltage that is set to a voltage lower than the full charge voltage. Therefore, even if the electromotive force of the travel motor 21 charges the battery 1 while the charge FET3 is on and the battery voltage rises, the battery voltage will not rise to the full charge voltage within the time lag until the control circuit 2 detects the rise in battery voltage and switches the charge FET3 to the OFF state, preventing the battery voltage from exceeding the full charge voltage, which would cause deterioration and reduce safety.

[0035] The control circuit 2 described above switches the charge FET3 on when the battery voltage is lower than the threshold voltage, but the control circuit 2 can also switch the charge FET3 on only when the load current supplied from the battery 1 to the traction motor 21 exceeds the threshold current. This control circuit 2 stores the threshold current for the load current in the memory unit 6, and when the discrimination circuit 5 detects that the bicycle is set in a docked state, switches the charge FET3 off when the load current is lower than the threshold current, and switches the charge FET3 on when the load current is higher than the threshold current. This battery pack 100 does not switch the charge FET3 on when the load current supplied from the battery 1 to the bicycle 20 is lower than the threshold current, and switches the charge FET3 on only when a load current higher than the threshold current is supplied from the battery 1 to the bicycle 20. This reliably prevents the battery 1 voltage from exceeding the full charge voltage, while minimizing power loss in the charge FET3 and enabling efficient power supply from the battery 1 to the traction motor 21. A state in which the load current exceeds the threshold current is a discharging state in which power is supplied from the battery 1 to the traction motor 21, and the battery 1 is not charged by regenerative braking. Therefore, even if the charge FET3 is switched to the on state in this state, the battery 1 is charged by the electromotive force of the traction motor 21, and the battery voltage does not exceed the fully charged voltage, ensuring the safety of the battery 1. Furthermore, by switching the charge FET3 to the on state when the load current is greater than the threshold current, it is possible to reduce power loss in the charge FET3 when a large current is supplied from the battery 1 to the traction motor 21, and it is also possible to protect the charge FET3 by preventing a large current from flowing through the parallel diode.

[0036] When the battery pack 100 is disconnected from the bicycle 20 and connected to the charger 30, the discrimination circuit 5 detects the charger connection state, and when the battery voltage being charged by the charger 30 is lower than the full charge voltage, the charge FET3 is turned on to charge the battery 1, and when it detects that the voltage of the battery being charged is higher than the full charge voltage, the charge FET3 is switched off to end the charging of the battery 1.

[0037] The battery pack 100 described above is installed in a bicycle 20 and used as a power source to supply power to a traction motor 21 mounted on the bicycle 20. The electric bicycle 200 shown in FIG. 1 comprises a battery pack 100 and a control converter 25 connected between the battery pack 100 and the traction motor 21. The control converter 25 controls the power supplied from the battery pack 100 to the traction motor 21.

[0038] The traction motor 21 drives wheels (not shown) using power supplied from the battery pack 100. The traction motor 21 is connected to the battery pack 100 via a control converter 25, and the power supplied from the battery pack 100 is controlled by the control converter 25 to adjust the rotational torque of the wheels. The control converter 25 adjusts the power supplied to the traction motor 21 using the bicycle speed and the rotational torque of the pedals by the user as parameters. The control converter 25 controls the power supplied to the traction motor 21, for example, so that the torque with which the traction motor 21 rotates the wheels and the rotational torque of the pedals are in a predetermined ratio.

[0039] Bicycle 20, which uses regenerative braking with traveling motor 21, charges battery pack 100 with the power generated by traveling motor 21 to brake, so a charging current flows through battery pack 100 during regenerative braking. Because the charging current can cause damage to batteries 1 in battery pack 100, battery pack 100 has a built-in circuit that limits the charging current caused by regenerative braking of the bicycle. [Industrial Applicability]

[0040] The present invention is suitable for use as a battery pack that supplies power to the traction motor of an electric bicycle, and is particularly suitable for use in an electric bicycle equipped with a mechanism that charges the battery pack by regenerative braking during braking. [Explanation of symbols]

[0041] 100...Battery pack 200...Electric bicycle 1...Battery 2...Control circuit 3...Charging FET 4…Discharge FET 5…Discrimination circuit 6...Storage section 7...Parallel diode 12...Connection terminal 13...Pull-up resistor 14…Power supply 20...Bicycle 21...Traction motor 22...Connection terminal 23...Resistor 24...Earth line 25...Control converter 30…Charger

Claims

1. Rechargeable batteries and a charge FET having a parallel diode connected in series with the battery; a control circuit that controls the charging FET to be turned on and off; A battery pack for an electric bicycle, comprising: The control circuit a discrimination circuit that discriminates between a bicycle set state and a charger connection state; In addition to the battery's full charge voltage, a memory unit that stores a threshold voltage that is set lower than a full charge voltage, The control circuit When the discrimination circuit detects that the bicycle is set on the bicycle, When the battery voltage is higher than the threshold voltage, the charging FET is turned off. When the battery voltage is lower than the threshold voltage, the charging FET is turned on. When the determination circuit detects a charger connection state, Detects when the battery voltage becomes higher than the full charge voltage when charged by the charger, Switching the charge FET to an OFF state to terminate battery charging; A battery pack for an electric bicycle.

2. Rechargeable batteries and a charge FET having a parallel diode connected in series with the battery; a control circuit that controls the charging FET to be turned on and off; A battery pack for an electric bicycle, comprising: The control circuit a discrimination circuit that discriminates between a bicycle set state and a charger connection state; a memory unit that stores a full charge voltage of the battery and a threshold current of the load current; The control circuit When the discrimination circuit detects that the bicycle is set on the bicycle, When the load current is smaller than the threshold current, the charge FET is turned off; When the load current is greater than a threshold current, the charge FET is turned on; When the determination circuit detects a charger connection state, Detects when the battery voltage becomes higher than the full charge voltage when charged by the charger, Switching the charge FET to an OFF state to terminate battery charging; A battery pack for an electric bicycle.

3. 3. A battery pack for an electric bicycle according to claim 1 or 2, The control circuit an A / D converter for converting the battery voltage into a digital signal; The digital signal converted by the A / D converter is calculated, A battery pack for an electric bicycle, characterized in that the battery voltage is calculated.

4. 4. The battery pack for an electric bicycle according to claim 1, The charge FET is A battery pack for an electric bicycle, characterized in that the parallel diode is a MOSFET with a parasitic diode.

5. 5. The battery pack according to claim 1, A battery pack for an electric bicycle, wherein the rechargeable battery is a lithium ion battery.

6. A battery pack according to any one of claims 1 to 5; connected to the battery pack via a control converter, a traction motor that sends charging current to the battery pack when the bicycle is regeneratively braking; An electric bicycle comprising:

7. A battery pack according to any one of claims 1 to 5; a traction motor connected to the battery pack via a control converter; a regenerative braking and power generation mechanism that charges the battery pack with electromotive force of the traction motor; An electric bicycle comprising:

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