Charging control device and battery pack

Abstract

The present invention provides a charging control device and battery pack that can prevent false detection of charging abnormalities when nickel-cadmium batteries are replaced with nickel-metal hydride batteries. [Solution] The charging control device is a charging control device that controls charging when a second battery, which has different charging characteristics from the first battery, is charged by a charging circuit for charging the first battery, and comprises a charging control element that controls charging to the second battery, and a load through which current supplied from the charging circuit flows when charging of the second battery is stopped.

Description

Technical Field

[0001] The present disclosure relates to a charge control device and a battery pack for controlling the charging of a secondary battery.

Background Art

[0002] Conventionally, rechargeable secondary batteries have been widely used as power sources for operating various devices and the like. In particular, nickel-cadmium batteries have been widely used as secondary batteries suitable for high-output applications.

[0003] In recent years, nickel-metal hydride batteries with higher energy density, higher output, higher capacity, and longer life than nickel-cadmium batteries have emerged. Therefore, recently, the replacement of nickel-cadmium batteries with nickel-metal hydride batteries has been progressing.

[0004] When replacing a nickel-cadmium battery with a nickel-metal hydride battery, since the charging methods for both secondary batteries are different, usually, it is necessary to change the charging circuit for charging the secondary battery from the one for nickel-cadmium batteries to the one for nickel-metal hydride batteries. In contrast, Patent Document 1 discloses a charging device capable of charging regardless of the type of secondary battery.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when charging nickel-metal hydride batteries using a charging circuit designed for nickel-cadmium batteries, if the nickel-metal hydride battery reaches a fully charged state and charging is stopped, the bus voltage, which is the output voltage of the charging circuit, rises to the no-load voltage because the nickel-cadmium battery is being continuously charged. As a result, the charging circuit has the problem of falsely detecting a charging abnormality by detecting overvoltage.

[0007] The purpose of this disclosure is to provide a charging control device and battery pack that can prevent false detection of charging abnormalities when nickel-cadmium batteries are replaced with nickel-metal hydride batteries. [Means for solving the problem]

[0008] The charging control device relating to this disclosure is A charging control device that controls charging when a second battery, which has different charging characteristics from the first battery, is charged by a charging circuit for charging the first battery, A charge control element that controls charging of the second battery, When charging of the second battery is stopped, the load through which the current supplied from the charging circuit flows, It is equipped with.

[0009] Furthermore, the battery pack related to this disclosure is The above charging control device, The second battery described above, It is equipped with. [Effects of the Invention]

[0010] According to this disclosure, when a nickel-cadmium battery is replaced with a nickel-metal hydride battery, it is possible to prevent false detection of charging abnormalities. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing an example of the configuration of the charging system according to this embodiment. [Figure 2]Figure 2 is a block diagram illustrating the case of charging a nickel-metal hydride battery using a charging circuit designed for nickel-cadmium batteries. [Figure 3] Figure 3 is a schematic diagram illustrating an example of the arrangement of the charging control device according to this embodiment. [Modes for carrying out the invention]

[0012] Embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below, and can be modified in various ways without departing from the spirit of this disclosure. In addition, parts that are denoted by the same reference numerals in each drawing are the same or equivalent parts, and this is common throughout the entire specification.

[0013] [Configuration of charging system 100] Figure 1 is a block diagram showing an example of the configuration of a charging system 100 according to this embodiment. As shown in Figure 1, the charging system 100 comprises a charging control device 10, a charging circuit 20, and a secondary battery 30. The charging system 100 charges the secondary battery 30 connected to the charging circuit 20 via the charging control device 10.

[0014] (Charging circuit 20) The charging circuit 20 is a circuit for charging the secondary battery 30. More specifically, the charging circuit 20 is for charging a nickel-cadmium battery as the secondary battery 30. The charging circuit 20 has a DC-DC converter and a constant current circuit (not shown), etc., which convert an external voltage to a predetermined voltage and outputs a charging current to the secondary battery 30 based on the converted voltage. The output voltage from the charging circuit 20 is predetermined by a control unit (not shown). The nickel-cadmium battery corresponds to the "first battery" in this disclosure.

[0015] In the charging circuit 20 according to this embodiment, the output voltage when charging of the secondary battery 30 is stopped, i.e., the output voltage under no load, will be equal to or greater than the assumed maximum voltage of the secondary battery 30.

[0016] (Secondary battery 30) The secondary battery 30 is composed of, for example, one or more secondary battery cells. When the secondary battery 30 is composed of a plurality of secondary battery cells, the secondary battery 30 is configured such that, for example, the secondary battery cells are connected in series. The secondary battery 30 is, for example, a nickel-hydrogen battery. The nickel-hydrogen battery has charging characteristics different from those of a nickel-cadmium battery and corresponds to the "second battery" of the present disclosure.

[0017] The secondary battery 30 is charged by a charging current supplied from the charging circuit 20 via the charge control device 10. In the present embodiment, the battery voltage of the secondary battery 30 is, for example, about 20 to 30V.

[0018] Also, in this example, one secondary battery 30 is provided, but the present invention is not limited to this, and two or more secondary batteries 30 may be provided. When a plurality of secondary batteries 30 are provided, the plurality of secondary batteries 30 are, for example, connected in parallel.

[0019] (Charge control device 10) The charge control device 10 controls the charging of the secondary battery 30 by the charging circuit 20. The charge control device 10 has a load 11, a switching element 12, and a charge control element 13.

[0020] The load 11 is connected in series with the switching element 12 and is connected between the positive terminal and the negative terminal of the charging circuit 20. When charging of the secondary battery 30 is stopped and the switching element 12 is in the ON state, power is consumed as the charging current flows from the charging circuit 20 through the load 11.

[0021] In the present embodiment, a resistance element is used as the load 11, for example. In this case, heat energy is generated as the charging current flows, and thereby the load 11 generates heat.

[0022] Alternatively, an LED (Light Emitting Diode) may be used as the load 11. In this case, light energy is generated when a charging current flows, causing the load 11 to emit light. By using an LED as the load 11, heat generation can be suppressed compared to when a resistive element is used as the load 11.

[0023] Furthermore, the load 11 is not limited to the examples described above; for example, a drive component such as a fan driven by the supplied current may be used.

[0024] The switching element 12 is connected between the positive and negative terminals of the charging circuit 20. The switching element 12 controls the current flowing to the load 11 so that when charging of the secondary battery 30 is stopped, charging current from the charging circuit 20 flows to the load 11.

[0025] In this embodiment, the switching element 12 performs a switching operation that turns ON or OFF depending on the state of the charge control element 13. When the switching element 12 is in the ON state, a charging current from the charging circuit 20 flows to the switching element 12 via the load 11.

[0026] In this embodiment, the switching element 12 is configured using a semiconductor element such as a transistor having a base (B) terminal, a collector (C) terminal, and an emitter (E) terminal. When the switching element 12 is a transistor, the collector terminal is connected to the load 11. The base terminal and emitter terminal are connected to the drain terminal and source terminal of the charge control element 13, respectively.

[0027] In this case, when a predetermined voltage is applied between the base terminal and the emitter terminal, current flows through the base terminal. Then, the switching element 12 turns ON, and current flows between the collector terminal and the emitter terminal. As a result, the charging current from the charging circuit 20 flows to the load 11.

[0028] The charge control element 13 is positioned on the current path between the charging circuit 20 and the secondary battery 30. Based on a switching signal supplied from a control unit (not shown), the charge control element 13 performs a switching operation to turn ON or OFF. This connects or disconnects the charging path.

[0029] In this embodiment, the charge control element 13 is configured using a semiconductor element such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) having a gate (G) terminal, a source (S) terminal, and a drain (D) terminal. When the charge control element 13 is a MOSFET, the source terminal and drain terminal are connected to the charging path connecting the charging circuit 20 and the secondary battery 30. The source terminal is connected to the emitter terminal of the switching element, and the drain terminal is connected to the base terminal of the switching element. The switching signal from the control unit is input to the gate terminal.

[0030] The charge control element 13 connects or disconnects the drain terminal and source terminal based on a switching signal input to the gate terminal. This connects or disconnects the charge path.

[0031] [Operation of Charging System 100] Next, the operation of the charging system 100 having the above configuration will be described. Here, the operation of the charging system 100 will be described when the secondary battery 30 is being charged and when the secondary battery 30 is fully charged and charging is stopped.

[0032] (When charging the secondary battery 30) The operation of the charging system 100 when charging the secondary battery 30 will now be described. In the charging system 100 according to this embodiment, when charging the secondary battery 30, first the secondary battery is connected to the charging circuit 20 via the charging control device 10.

[0033] When the secondary battery 30 is connected, a charging current is output from the charging circuit 20. The current output from the charging circuit 20 is supplied to the secondary battery 30 via the charging control device 10. This charges the secondary battery 30.

[0034] (When charging of secondary battery 30 stops) In this case, when charging a nickel-metal hydride battery using the nickel-cadmium battery charging circuit 20, the nickel-metal hydride battery, as the secondary battery 30, can be directly connected to the nickel-cadmium battery charging circuit 20 and charged, for example, as shown in Figure 2.

[0035] In this case, if a nickel-cadmium battery is left fully charged, an internal short circuit will occur, so it is necessary to continue charging even after it reaches full charge. Therefore, nickel-cadmium batteries are usually subjected to continuous charging, where charging continues even after they reach full charge.

[0036] In contrast, nickel-metal hydride batteries do not experience internal short circuits like nickel-cadmium batteries. Therefore, continuous charging of nickel-metal hydride batteries is not recommended because overcharging can accelerate battery degradation due to heat generation.

[0037] In this situation, if charging continues even after the nickel-metal hydride secondary battery 30 reaches a fully charged state, it will be overcharged, reducing its battery life. On the other hand, if charging of the secondary battery 30 stops when it is fully charged and the secondary battery 30 is removed, the output voltage of the charging circuit 20 rises above the no-load voltage, which is the expected maximum voltage of the secondary battery 30. As a result, an overvoltage is detected, leading to a false detection of a charging abnormality.

[0038] In contrast, in this embodiment, when charging is stopped, the charging control device 10 is used to connect a load 11 to the charging circuit 20 and to flow a charging current through the load 11 to lower the output voltage of the charging circuit 20 below the no-load voltage.

[0039] Specifically, in this embodiment, when the secondary battery 30 is fully charged, the charge control element 13 of the charge control device 10 is turned OFF. As a result, the charging path to the secondary battery 30 is blocked, and charging of the secondary battery 30 is stopped.

[0040] When the charge control element 13 is in the OFF state, the voltage between the drain terminal and source terminal of the charge control element 13 becomes "output voltage of the charging circuit 20 (no-load voltage) - battery voltage of the secondary battery 30". As a result, a voltage is applied between the base terminal and emitter terminal of the switching element 12, and current flows to the base terminal. Therefore, the switching element 12 turns ON. With the switching element 12 in the ON state, a charging current flows from the charging circuit 20 to the load 11.

[0041] At this point, the voltage between the base and emitter of the switching element 12 saturates at approximately +1V. As a result, the output voltage of the charging circuit 20 becomes approximately "battery voltage + 1V". Therefore, the output voltage of the charging circuit 20 decreases, and overcharge detection is avoided.

[0042] Thus, in this embodiment, when charging of the secondary battery 30 is stopped, a charging current from the charging circuit 20 flows to the load 11 of the charging control device 10. As a result, even if the secondary battery 30 is a nickel-metal hydride battery, the charging current from the charging circuit 20 continues to flow. Therefore, an increase in the output voltage of the charging circuit 20 is suppressed, preventing the detection of overvoltage and the false detection of a charging abnormality.

[0043] [Example of arrangement of the charging control device 10] Next, an example of the arrangement of the charging control device 10 will be described. Figure 3 is a schematic diagram illustrating an example of the arrangement of the charging control device 10 according to this embodiment.

[0044] As shown in Figure 3, the charging control device 10 is located separately from and connected to the battery pack 300. The battery pack 300 is formed integrally by connecting, for example, multiple secondary batteries 30 in series or parallel.

[0045] The charging control device 10 is formed by housing a charging control board 110, which has the functions of the charging control device 10 as described above, in a housing 120. The charging control board 110 is connected to the battery pack 300 via wiring. The charging control board 110 is also connected via wiring to a connector 400 for connecting to the charging circuit 20. In this example, the load 11 of the charging control device 10 is assumed to be a resistive element.

[0046] In this way, with the battery pack 300 (secondary battery 30) and the charging control device 10 connected, the connector 400 is connected to the charging circuit 20, thereby charging the secondary battery 30.

[0047] Then, when the secondary battery 30 is fully charged and charging is complete, the charging control device 10 generates heat as the charging current from the charging circuit 20 continues to flow to the load 11.

[0048] In this embodiment, since the charging control device 10 is formed separately from the secondary battery 30, the transfer of heat generated by the charging control device 10 to the secondary battery 30 is suppressed. Therefore, the heat generated by the charging control device 10 in the secondary battery 30 can be suppressed.

[0049] Although embodiments have been described above, this disclosure is not limited to the embodiments described above, and various modifications and applications are possible without departing from the gist of this disclosure. In the example described above, the charging control device 10 was described as being formed separately from the battery pack 300 (secondary battery 30), but this is not limited to this, and for example, the charging control device 10 may be formed integrally with the battery pack 300 (secondary battery 30).

[0050] By integrally forming the charging control device 10 and the secondary battery 30 in this way, even if the secondary battery 30 housed in the battery pack 300 is a nickel-metal hydride battery, the battery pack 300 can be charged without being aware of the type of secondary battery 30 during charging.

[0051] Furthermore, as in this embodiment, by forming the charge control device 10 separately from the battery pack 30, the effect of heat generation from the load 11 on the secondary battery 30 is reduced, and the lifespan of the secondary battery 30 can be extended. For this reason, it is more preferable that the charge control device 10 be formed separately from the battery pack 30.

[0052] Furthermore, although this embodiment describes the case where a nickel-cadmium battery is replaced with a nickel-metal hydride battery as an example, it is not limited to this, and the charging control device 10 can also be applied when a first battery having certain charging characteristics is replaced with a second battery having different charging characteristics from the first battery. [Explanation of symbols]

[0053] 100 Charging System 10 Charging control device 11 Load 12 Switching elements 13. Charging control element 20 Charging circuit 30 Secondary battery 110 Charging control board 120 cabinets 300 Battery Pack 400 connectors

Claims

1. A charging control device that controls charging when a second battery, which has different charging characteristics from the first battery, is charged by a charging circuit for charging the first battery, A charge control element that controls charging of the second battery, When charging of the second battery is stopped, the load through which the current supplied from the charging circuit flows, A charging control device equipped with the following features.

2. The charging control element further includes a switching element that controls the current flowing to the load so that current flows from the charging circuit to the load when the charging of the second battery is stopped by the charging control element. The charging control device according to claim 1.

3. The aforementioned switching element is A transistor having a base terminal, a collector terminal, and an emitter terminal, The load is connected to the collector terminal such that when a predetermined voltage is applied between the base terminal and the emitter terminal, causing current to flow to the base terminal, the current supplied from the charging circuit flows to the load. The aforementioned charge control element is A MOSFET having a gate terminal, a source terminal, and a drain terminal, The source terminal and the drain terminal are connected to the charging path that connects the charging circuit and the second battery. The emitter terminal of the switching element is connected to the source terminal. The base terminal of the switching element is connected to the drain terminal. A switching signal that controls the connection or disconnection of the charging path is supplied to the gate terminal by connecting or disconnecting the drain terminal and the source terminal. The charging control device according to claim 2.

4. A load is a resistive element that generates heat when current flows through it. The charging control device according to claim 1.

5. The load is a light-emitting diode that emits light when current flows through it. The charging control device according to claim 1.

6. A load is a drive component that is driven by the flow of electric current. The charging control device according to claim 1.

7. The charging control device according to claim 1, The aforementioned second battery, A battery pack equipped with these features.

8. The charging control device is Formed separately from the second battery, The battery pack according to claim 7.

9. The charging control device is Formed integrally with the second battery, The battery pack according to claim 7.

Images