JP2010141987A - Method and device for charging battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of connection terminals of a battery pack and a charging device. <P>SOLUTION: In a charging method, the battery pack having a plurality of secondary batteries connected in series is charged. When the battery whose voltage is not more than a prescribed voltage or reaches maximum charging voltage exists for one or above, an alarm signal is monitored to be output. When charging is started, the charging is performed with maximum charging current. Whenever the alarm signal is detected, a charging current is reduced stepwise after a prescribed time elapses. If the alarm signal is detected when the charging current is the lowest charging current, the charging is stopped. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery pack charging method and a charging device, and more particularly to a battery pack charging method and a charging device having an alarm signal.

  As a conventional method for charging a lithium ion secondary battery, constant current-constant voltage charging is generally used. This is because when the battery voltage reaches the maximum charge voltage when the battery voltage reaches the maximum charge voltage, it switches to constant voltage charge that applies the maximum charge voltage to the battery, and the charge current falls below a predetermined current value. This is a method of completing charging.

  However, in the above-described method, the constant current-constant voltage charging always detects the voltage and charging current of the secondary battery to be charged, and controls the charging state according to the detection result, so that the circuit becomes complicated. Further, in charging a lithium ion secondary battery, there is a restriction that the voltage of the lithium ion secondary battery must not be increased beyond the maximum charging voltage. This is because when an excessive voltage is applied to the lithium ion secondary battery, metallic lithium is deposited on the negative electrode, which may cause an internal short circuit.

  For this reason, when charging a plurality of lithium ion secondary batteries at the same time, the voltage of each secondary battery must be detected and controlled so as not to exceed the maximum charging voltage.

Patent Document 1 discloses a charging device for charging a battery composed of a plurality of secondary battery cells. This charging device sequentially increases the charging current step by step until the voltage of any of the secondary battery cells reaches a predetermined voltage. Then, when the voltage of any of the secondary battery cells reaches a predetermined voltage, the charging current is controlled to decrease sequentially.
JP 2001-186686 A

  However, when charging a battery pack containing a plurality of lithium ion secondary batteries, it is necessary to transmit voltage information of each battery from the battery pack to the charging device side, and the connection terminals of the battery pack and the charging device increase. There is a problem.

  In addition, the battery voltage may be reduced to around 0 V in the battery pack, and dangerous defective batteries may be mixed when charged. In such a case, the conventional battery charger cannot detect the defective battery, and the defective battery is charged until the normal battery is fully charged.

  The present invention has been made in consideration of the above-described circumstances, and a first object thereof is to reduce the number of connection terminals between the battery pack and the charging device.

  A second object of the present invention is to make it possible to prevent the battery voltage from rising above the maximum charge voltage with a simple circuit configuration and to charge the battery to a state close to full charge.

  Furthermore, a third object of the present invention is to perform charging quickly or stop charging when defective batteries are mixed.

  In order to solve the above-mentioned problem, the charging method of the present invention is a charging method for charging a battery pack having one or a plurality of secondary batteries connected in series, and there is one or more batteries that have reached the maximum charging voltage. Is monitored to output an alarm signal, charging is performed at the maximum charging current at the start of charging, and each time the alarm signal is detected, the charging current is decreased step by step after a predetermined time elapses. When the alarm signal is detected when is the minimum charging current, charging is stopped.

  In addition to the above-described configuration, the charging method of the present invention monitors to output an alarm signal when there is one or more batteries having a battery voltage equal to or lower than a predetermined voltage at the start of charging. It can be configured to prohibit charging when it is detected.

  Furthermore, in addition to the above configuration, the charging method of the present invention can be configured to reduce the charging current to ½ of the immediately preceding charging current every time an alarm signal is detected.

  The charging device of the present invention detects a battery voltage of each secondary battery and outputs a voltage detection result in the battery pack charging device for charging a battery pack having one or a plurality of secondary batteries connected in series. Voltage detection means, alarm signal output means for outputting an alarm signal when there is one or more batteries that have reached the maximum charging voltage based on the output of the voltage detection means, and a charging power supply for supplying a charging current to the battery pack; Control means for controlling the charging power supply in accordance with an output from the alarm signal output means, and the control means decreases the charging current stepwise after a predetermined time every time the alarm signal is detected. It is characterized by making it.

  The control means may be configured to stop charging when the alarm signal is detected when the charging current is the minimum charging current.

  The alarm signal output means outputs an alarm signal when there is one or more batteries having a battery voltage equal to or lower than a predetermined voltage based on the output of the voltage detection means, and the control means outputs the alarm signal at the start of charging. If a signal is detected, charging can be prohibited.

  The control means can be configured to reduce the charging current to ½ of the immediately preceding charging current each time an alarm signal is detected.

  According to the present invention, since only three connection terminals with the charging device are required regardless of the number of secondary batteries in the battery pack, the number of terminals can be greatly reduced.

  In addition, when the alarm signal is detected, the charging current is gradually reduced until the alarm signal is no longer output, so the secondary battery can be charged to near full charge without charging more than the maximum charging voltage. Can do.

  Furthermore, charging can be stopped when defective batteries or the like are mixed.

  Furthermore, the charging device only needs to control the charging current, and voltage detection and current detection are no longer necessary, so that the configuration of the charging device can be greatly simplified. Further, since the charging current is decreased by ½, the charging current control circuit or the control method can be configured more easily.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram of a battery pack 10 and a charging device 20 of the present invention. The battery pack 10 includes secondary batteries B1 and B2, a protection circuit 11, a discharge control NMOS transistor M1, and a charge control NMOS transistor M2.

  The battery pack 10 also includes a positive terminal (T +) 121, a negative terminal (T−) 122, and an alarm signal output terminal (ALM) 123.

  On the other hand, the charging device 20 includes a charging power output terminal and an alarm signal input terminal, the power output terminal is connected to the positive terminal 121 and the negative terminal 122 of the battery pack 10, and the alarm signal input terminal is an alarm signal of the battery pack 10. The output terminal 123 is connected. The charging device 20 controls the charging current by a control circuit constituted by a built-in microcomputer or the like.

  The secondary batteries B1 and B2 are lithium ion secondary batteries and are connected in series. All of the positive terminals and the negative terminals of the secondary batteries B1 and B2 are input to the protection circuit 11. Further, the positive terminal of the secondary battery B1 is connected to the positive terminal T +, and the negative terminal of the secondary battery B2 is connected to one terminal of the discharge control NMOS transistor M1.

  The gate of the discharge control NMOS transistor M1 is connected to the output terminal Dout of the protection circuit 11. The other terminal of the discharge control NMOS transistor M1 is connected to one terminal of the charge control NMOS transistor M2. The other terminal of the charge control NMOS transistor M2 is connected to the negative terminal-. The gate of the NMOS transistor M2 is connected to the output terminal Cout of the protection circuit 11.

  The alarm signal output of the protection circuit 11 is connected to an alarm terminal (ALM) 123. The alarm signal becomes a high level when any of the secondary batteries B1 and B2 reaches the maximum charging voltage. The high level is also obtained when either of the secondary batteries B1 and B2 drops below a predetermined voltage close to 0V. The predetermined voltage close to 0V is a voltage for determining that the secondary battery is defective. In the case of a lithium ion secondary battery, it is set to around 1.0V.

  FIG. 2 is a block diagram showing an example of the battery pack 10 of the present invention.

  The battery pack 10 includes a secondary battery protection circuit 11 that protects the secondary battery from an abnormal state. This protection circuit 11 is integrated as a battery protection integrated circuit, and is housed in the battery pack 10 together with the lithium ion secondary batteries B1 and B2.

  The protection circuit 11 includes a microcomputer that controls on / off of a discharge control NMOS transistor M1 and a charge control NMOS transistor M2 that are semiconductor devices for controlling discharge of the secondary batteries B1 and B2. The control circuit 110 includes an overcharge detection circuit 111 and an overdischarge detection circuit 112 that detect battery voltages of the secondary batteries B1 and B2 and detect overcharge and overdischarge, respectively. Reference numeral 113 denotes a parasitic diode of the discharge control NMOS transistor M1, and 114 denotes a parasitic diode of the charge control NMOS transistor M2.

  At the time of charging, the overcharge detection circuit 111 of the battery pack 10 monitors the battery voltage so that the secondary batteries B1 and B2 are not overcharged. When the detected voltage is lower than the preset overcharge setting voltage, the overcharge detection circuit 111 notifies the control circuit 110 that it is in the normal state. In the normal state, the control circuit 110 gives an H (high) level signal to Cout, sets the gate of the charge control NMOS transistor M2 to H (high) level, turns on the charge control NMOS transistor M2, and energizes the charge current. .

  When the overcharge detection circuit 111 detects a battery voltage higher than the overcharge setting voltage, the overcharge voltage detection circuit 111 notifies the control circuit 110 that it is in an overcharge state. In the overcharge state, the control circuit 110 gives an L (low) level signal to Cout, sets the gate of the charge control NMOS transistor M2 to L (low) level, turns off the charge control NMOS transistor M2, and cuts off the charge current. Let

  Further, when any of the secondary batteries B1 and B2 reaches the maximum charge voltage, the overcharge detection circuit 111 notifies the control circuit 110 that the maximum charge voltage has been reached. In response to this notification, the control circuit 110 sets the alarm signal to the H (high) level.

  On the other hand, during discharge, the overdischarge detection circuit 112 of the battery pack 10 monitors the battery voltage so that the secondary batteries B1 and B2 are not overdischarged. It is monitored whether or not the detected voltage is equal to or lower than a preset overdischarge set voltage, that is, a predetermined voltage close to 0V. The predetermined voltage close to 0V is a voltage for determining that the secondary battery is defective. In the case of a lithium ion secondary battery, it is set to around 1.0V.

  When the detected voltage is higher than the preset overdischarge set voltage, the overdischarge detection circuit 112 notifies the control circuit 110 that it is in the normal state. In a normal state, the control circuit 110 gives a signal of H (high) level to Dout, sets the gate of the discharge control NMOS transistor M1 to H (high) level, turns on the discharge control NMOS transistor 113, and supplies a discharge current.

  When the overdischarge detection circuit 112 detects a battery voltage lower than the overdischarge set voltage, the overdischarge detection circuit 112 notifies the control circuit 110 that it is in an overdischarge state. In the overdischarge state, the control circuit 110 gives an L (low) level signal to Dout, sets the gate of the discharge control NMOS transistor M1 to L (low) level, turns off the discharge control NMOS transistor 113, and cuts the discharge current. .

  In addition, the control circuit 110 outputs a voltage alarm signal when it detects that either of the secondary batteries B1 and B2 has dropped below a predetermined voltage close to 0V from the overdischarge detection circuit 112 even at the start of charging. Set to H (high) level.

  As described above, the alarm signal is H when any of the secondary batteries B1 and B2 reaches the maximum charging voltage and when any of the secondary batteries B1 and B2 drops below a predetermined voltage close to 0V. (High) level.

  Next, the charging method of the present invention will be further described with reference to FIGS.

  FIG. 3 is a flowchart showing the charging method of the present invention. The charging method will be described based on this chart. In FIG. 3, Sn (n is an integer from 1 to 9) is a step number of each process.

  When the battery pack 10 is connected to the charging device 20 and charging is started, the charging device 20 first checks the presence or absence of an alarm signal in step S1. If an alarm signal is output, the process moves to step S8 and the charging is terminated. In other words, if the alarm signal is output before the charging current is applied, there is a secondary battery that is already fully charged or there is a mixture of defective batteries, so charging cannot be performed. It is.

  If no alarm signal is detected in step S1, the process proceeds to step S2 and charging is started with the maximum charging current.

  During charging, the presence or absence of an alarm signal is always checked in step S3. When an alarm signal is detected in step S3, the process proceeds to step S4. In step 4, a predetermined time is waited, and in step S5, the presence or absence of an alarm signal is confirmed again. If the alarm signal is not confirmed in step S5, the alarm signal confirmed in step S3 may be an erroneous signal due to noise or the like, so the process returns to step 3 to reconfirm the alarm signal. When the alarm signal is confirmed in step S5, the process proceeds to step S6.

  In step S6, the current charging current is checked. If it is not the minimum charging current, the process proceeds to step S7. In step S7, the charging current is set to a current value one step lower. In this embodiment, the current charging current is set to ½. When the charging current is lowered, the voltage of the battery pack 10 is lowered, so that the alarm signal disappears.

  After reducing the charging current in step S7, the process returns to step S3 to confirm the alarm signal. Thereafter, the processes from step S3 to step S7 are repeated. During the repetition, the charging current gradually decreases and becomes the minimum charging current. When the charging current is the minimum charging current in step S6, the process proceeds to step S9 and the charging is terminated.

  FIG. 4 is a timing chart showing the operation of the above flow. FIG. 4A shows a case where the alarm signal disappears whenever the charging current decreases, and FIG. 4B shows a case where the alarm signal continues to be output.

  First, the case of FIG. 4A will be described. In the initial stage of charging, charging is performed at the maximum charging current. Although the alarm signal becomes high level at time t1, the charging current does not change because it returns to low level after a predetermined time td.

  At time t2, the alarm signal becomes high level, and since the high level is maintained even after a predetermined time td has elapsed, the charging current is reduced to ½ of the maximum charging current. When the charging current decreases, the voltage of the battery pack 10 decreases, so that the alarm signal returns to the low level. The predetermined time td may be a time that allows the alarm signal and the noise to be distinguished from each other, and is set from several milliseconds to several tens of milliseconds.

  When the alarm signal is output again at time t3, the charging current is further halved. When an alarm signal is output at time t4, the alarm signal is further reduced by half to reach the minimum charging current. When an alarm signal is output at time t5 with this charging current, after a predetermined time td has elapsed, the charging current is set to 0 and charging is terminated.

  Next, the case of FIG. 4B will be described. The alarm signal becomes high level during charging at the maximum charging current, and the alarm signal does not become low level even after the charging current is reduced to 1/2. Therefore, after a predetermined time td has elapsed, the charging current is reduced to 1/2. To do. Still, since the alarm signal does not fall to the low level, the charging current is further reduced to ½ after a predetermined time td. If the alarm signal does not go low as described above, the charging current is decreased every time the predetermined time td elapses, and the charging proceeds to the end of charging at a stretch. Therefore, a fully charged battery is charged for a long time to cause a problem. There is nothing. Further, the charging can be rapidly terminated even when the battery voltage is reduced to around 0 V due to disconnection in the battery pack 10 or internal short circuit of the battery during the charging.

  Although there is no timing chart, charging is not started when the alarm signal is at a high level before the maximum charging current is supplied to the battery pack 10, so that a fully charged battery pack or a defective battery is inadvertently charged. There is no need to charge the battery pack 10 that is mixed.

  In the above-described embodiment, the case where there are two secondary batteries in the battery pack 10 is shown, but there may be any number of secondary batteries. Since the number of batteries can be controlled by one alarm signal output terminal (ALM), the effect of the present invention increases as the number of batteries increases.

  In the timing chart, the charging current step is described in four stages, but any number of steps may be used as long as it is two or more stages.

  As described above, according to the present invention, the connection between the battery pack 10 and the charging device 20 can be made with only three connection terminals with the charging device 20 regardless of the number of secondary batteries in the battery pack 10. The number of terminals can be greatly reduced.

  In addition, when the alarm signal is detected, the charging current is gradually reduced until the alarm signal is no longer output, so the secondary battery can be charged to near full charge without charging more than the maximum charging voltage. Can do.

  Furthermore, when defective batteries or the like are mixed, charging can be stopped quickly.

  Furthermore, the charging device only needs to control the charging current, and voltage detection and current detection are no longer necessary, so that the configuration of the charging device 20 can be greatly simplified. Further, since the charging current is decreased by ½, the charging current control circuit or the control method can be configured more easily.

1 is a block diagram of a battery pack 10 and a charging device 20 of the present invention. It is a block diagram which shows an example of the battery pack 10 of this invention. It is a flowchart which shows the charging method of this invention. It is a timing chart which shows the charging method of this invention.

Explanation of symbols

  10 battery pack, 22 protection circuit, 20 charging device, B1, B2 lithium ion secondary battery, M1 discharge control NMOS transistor, M2 charge control NMOS transistor.

Claims (7)

In a charging method for charging a battery pack having one or a plurality of secondary batteries connected in series,
When there is one or more batteries that have reached the maximum charging voltage, monitoring is performed so that an alarm signal is output, charging is performed at the maximum charging current at the start of charging, and each time the alarm signal is detected, a predetermined time elapses. A method for charging a battery pack, wherein the charging current is decreased stepwise, and charging is stopped when the alarm signal is detected when the charging current is the minimum charging current.   When there is one or more batteries having a battery voltage equal to or lower than a predetermined voltage at the start of charging, monitoring is performed to output an alarm signal, and charging is prohibited when the alarm signal is detected. The battery pack charging method according to claim 1.   The method of charging a battery pack according to claim 1, wherein the charging current is reduced to ½ of the immediately preceding charging current every time an alarm signal is detected. In a battery pack charging device for charging a battery pack having one or a plurality of secondary batteries connected in series,
Voltage detection means for detecting the battery voltage of each secondary battery and outputting a voltage detection result; and an alarm for outputting an alarm signal when there is one or more batteries that have reached the maximum charge voltage based on the output of the voltage detection means A signal output unit; a charging power source that supplies a charging current to the battery pack; and a control unit that controls the charging power source in accordance with an output from the alarm signal output unit, wherein the control unit outputs the alarm signal. A charging device for a battery pack, wherein a charging current is reduced stepwise after a predetermined time elapses every time it is detected.   5. The battery pack charging device according to claim 4, wherein the control unit stops charging when the alarm signal is detected when a charging current is a minimum charging current. 6.   The alarm signal output means outputs an alarm signal when there is one or more batteries having a battery voltage equal to or lower than a predetermined voltage based on the output of the voltage detection means, and the control means outputs the alarm signal at the start of charging. 5. The battery pack charging device according to claim 4, wherein charging is prohibited when detected.   6. The battery pack charging device according to claim 4, wherein the control unit reduces the charging current to ½ of the immediately preceding charging current each time an alarm signal is detected.

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