JP2011211867A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack which an not be charged if a charger to be used does not have a required function.SOLUTION: A battery pack connected to a charger having a slow start function is normally charged when the battery pack is charged. If the battery pack is charged using a charger that has no slow start function, a charging circuit is forcedly shielded to prohibit charging with the battery pack.

Description

  The present invention relates to a battery pack used for an electric tool or the like, and more particularly to a battery pack incorporating a lithium ion battery.

  The charger for charging the battery pack is improved every day, and consideration is given so that the secondary battery built in the battery pack does not shorten its life. For example, Patent Document 1 proposes that a charger has a so-called slow start function that gradually increases a charging current in order to prevent an inrush current flowing in a secondary battery at the start of charging.

JP 2007-68264 A

  On the other hand, chargers that do not have the slow start function as described above are on the market. Many of these chargers are imitations and can normally charge a specific manufacturer's battery pack, but they do not have all the functions that are originally required for charging. For this reason, when a battery pack is charged with such an imitation charger, the battery pack is shortened.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a battery pack that cannot be charged unless the charger to be used has a predetermined function.

  A battery pack for achieving the above object is provided in a rechargeable secondary battery, a charging circuit formed when connected to a charger, a current detection unit for detecting a current flowing in the charging circuit, And a self-interrupting means for interrupting the current charging circuit when the current detected by the current detecting unit is equal to or higher than a predetermined level.

  The self-blocking means is preferably configured to block the charging circuit in response to an inrush current flowing from the charger to the secondary battery or from the secondary battery to the charger.

  Further, the blocking means is configured to block the charging circuit in response to an inrush current that flows from the charger to the secondary battery or from the secondary battery to the charger immediately after the start of charging. preferable.

  When charging the battery pack according to the present invention with a charger having a so-called slow start function, the battery pack connected to the charger performs regular charging, but the charger does not have a slow start function. When the battery pack according to the present invention is to be charged, the charging circuit is configured to be forcibly cut off and cannot be charged. For example, the battery pack can be prevented from being shortened. it can.

The circuit diagram when the battery pack by embodiment of this invention is connected to the charger. The circuit diagram when the conventional battery pack is connected to the charger. Explanatory drawing of operation | movement when charging the battery pack shown in FIG. 1 with the charger which has a slow start function. Operation | movement explanatory drawing at the time of trying to charge the battery pack shown in FIG. 1 with the charger which does not have a slow start function.

  Hereinafter, a battery pack according to an embodiment of the present invention will be described with reference to the accompanying drawings. In order to clarify the difference in configuration from the conventional battery pack, FIG. 2 showing the configuration of the conventional battery pack is also referred to as necessary.

  FIG. 1 shows a state in which the battery pack 1 according to the present embodiment is connected to the charger 6. The charger 6 has a built-in charge control unit 61, and the charge control unit 61 is operable by applying a reference voltage V via a resistor 62. The specific configuration of the charging control unit 61 differs depending on the charger. Here, the charging control unit 61 will be described separately as having a slow start function and not having the same function. When the battery pack according to the present embodiment is charged with the charger 6 having the slow start function, a normal charging operation can be performed, but when the charger 6 without the slow start function is intended to be charged The battery pack 1 itself is configured so as not to perform the charging operation.

  The slow start function changes the output voltage supplied from the charger to the battery pack before turning on the switch provided in the charging circuit, and the difference between the output voltage and the battery voltage falls within a predetermined range. The function of reducing the inrush current flowing transiently to the secondary battery in the battery pack by turning on the switch at the time. The configuration and operation of the charging control unit 61 having a slow start function are known as described in Patent Document 1, for example. Briefly describing the contents, the charging control unit 61 includes a battery voltage detecting circuit for detecting a battery voltage, a microcomputer (hereinafter referred to as “microcomputer”), a relay (switch) inserted in the charging circuit, A main component is a relay drive circuit for driving the relay and a voltage output circuit capable of changing an output voltage.

  When the battery pack 1 according to the present embodiment is connected to the charger 6 incorporating the charging control unit 61 having such a slow start function, the microcomputer detects the battery voltage via the charging positive terminal 162, and the microcomputer The output voltage of the voltage output circuit is changed according to the output from the output port of each of the output port and the second output port. For example, when both the first output port and the second output port are at L level, the output voltage from the voltage output circuit is the lowest, and when the first output port and the second output port are at L level and H level, respectively. The output voltage from the voltage output circuit is the second lowest, and when the first output port and the second output port are at the H level and the L level, respectively, the output voltage from the voltage output circuit is the third lowest. When the output voltage from the voltage output circuit is at the H level in both the first output port and the second output port, the output voltage from the voltage output circuit is set to be the highest.

  In the case of a lithium ion battery, since the nominal voltage per cell is 3.6V, for example, a battery set formed by connecting four cells has a nominal voltage of 14.4V. Here, when a battery pack including a 4-cell battery set is to be charged and the detected battery voltage is in the range of 10.6V to 14.7V, the second lowest voltage, for example, 12.6V Are output from the voltage output circuit, L level and H level signals are output from the first output port and the second output port of the microcomputer, respectively. Usually, both the first output port and the second output port are set to the H level, and the charger 6 outputs the highest voltage, for example, 16.8V. When the detected battery voltage is 12V, the first port output and the second port output are switched to L level and H level, respectively, and the output from the voltage output circuit is lowered from 16.8V to 12.6V. When the output from the voltage output circuit drops to 12.6 V, the microcomputer outputs a signal to the relay drive circuit via the output port to turn the relay from the OFF state to the ON state.

  Thereafter, both the first output port and the second output port are switched to the H level, and the output voltage from the voltage output circuit is increased from 12.6 V to 16.8 V that can be charged, for example. The relay has a slight time delay until the contact closes with respect to the actual signal, but this time delay is corrected, and a large inrush current flows transiently to the secondary battery as soon as the relay closes. Is suppressed. Since charging starts at a voltage close to the battery voltage of the secondary battery in this way, this is referred to as slow start.

  On the other hand, the charging control unit 61 of the charger 6 that does not have the slow start function does not include a configuration that variably controls at least the output voltage from the voltage output circuit stepwise or continuously. Therefore, if the conventional battery pack is charged by the charger 6 having no slow start function, an inrush current flows transiently in the initial stage of charging. Even when charging with the charger 6 having the slow start function, a current having a level higher than the steady current value flows immediately after the start of charging. The current level at this time has a slow start function under the same conditions. Compared to the level of inrush current that flows when charging with no charger, it is usually low.

  The configuration of the conventional battery pack 100 shown in FIG. 2 and the battery pack 1 according to the embodiment of the present invention shown in FIG. 1 are the same in the following points. The same reference numerals are assigned to the same components. The battery packs 1 and 100 shown in FIGS. 1 and 2 include a discharge positive terminal 161, a charge positive terminal 162, a battery voltage identification terminal 163, an overcurrent overdischarge output terminal 164, and a charge / discharge negative terminal 165. Connection terminals 16 are provided, and terminals corresponding to these terminals are also provided on the charger 6 side.

  Both battery packs 1 and 100 have a built-in battery set 12 in which a plurality of battery cells 121 are connected in series, and one end of each battery set 12 is connected to a discharge positive terminal 161 via a resistor 14. At the same time, it is connected to the charging positive terminal 162 via the resistor 15 and the P-type FET 134. The other end of the battery set 12 is connected to the charge / discharge negative terminal 165.

  Battery packs 1 and 100 incorporating a battery set 12 made of a lithium ion battery are mounted with a circuit board 13 for strictly monitoring charge and discharge and preventing overcurrent and overdischarge. A protection IC 131 and an N-type FET 133 are mounted on the circuit board 13, and the protection IC 131 is connected so as to detect overdischarge and overcurrent of each battery cell 121 and overdischarge and overcurrent of the battery set 12. ing. The output terminal of the protection IC 131 is connected to the gate of the FET 133. The FET 133 has a drain connected to the protection IC 131 and a source connected to the overcurrent overdischarge output terminal 164. When the protection IC 131 detects an overcurrent or overdischarge of any battery cell 121 or battery set 12, an H level detection output is applied to the gate of the FET 133 from the output terminal of the protection IC 131, and the FET 133 is turned on. As a result, an abnormal signal is input from the overcurrent overdischarge output terminal 164 to the charging control unit 61 of the charger 6, and the charger 6 stops charging in response to the abnormal signal.

  The battery voltage identification terminal 163 is connected so that voltage information of the battery set 12 is output.

  The battery pack 1 according to the present embodiment shown in FIG. 1 and the conventional battery pack 100 shown in FIG. 2 are structurally different in the following points.

  In the battery pack 1 according to the present embodiment, a FET 134 and a resistor 15 serving as self-blocking means are connected in series between the charging positive terminal 162 and the positive electrode of the battery set 12, and in parallel with the resistor 15. A charging current detection circuit 151 is connected. The output of the charging current detection circuit 151 is connected to the gate of the FET 134. The resistor 15, the charging current detection circuit 151, and the FET 134 constitute a charging current detection unit.

  Next, an operation when charging the battery pack according to the embodiment of the present invention in the case where the charging control unit 61 of the charger 6 has a slow start function will be described with reference to FIGS. 1 and 3.

  When the battery pack 1 is connected to the charger 6 (S1), the battery pack 1 and the charger are connected via the charging positive terminal 162, the battery voltage identification terminal 163, the overcurrent / overdischarge output terminal 164, and the charging / discharging negative terminal 165. 6 is connected. Immediately after connecting the battery pack 1 to the charger 6, the charging current detection circuit 151 does not detect the charging current, and the FET 134 is off. Therefore, the charging current circuit including the route of the charging / discharging negative terminal 165, the battery set 12, the resistor 15, the FT 134, and the charging positive terminal 162 is open (S2).

  Next, the battery voltage is detected from the battery voltage identification terminal 163, and it is determined whether the detected battery voltage is lower or higher than the reference value (S4). In the case of a lithium ion battery having four cells, for example, the level of the detected battery voltage is determined in comparison with each of three different reference values. If the first reference value is 6.3V, the second reference value is 10.5V, the third reference value is 14.7V, and the battery voltage is less than or equal to the first reference value (0 to 6.3V) If the charging voltage is set to 4.2V and the battery voltage exceeds the first reference value and is equal to or lower than the second reference value (6.4V to 10.5V), the charging voltage is set to 8.4V. If the battery voltage exceeds the second reference value and is equal to or lower than the third reference value (10.6V to 14.7V), the charging voltage is set to 12.6V. Thus, after adjusting the voltage from the voltage output circuit included in the charge control unit 61 according to the battery voltage, the charging circuit is closed and charging is started (S6). When charging is started, the charging current or charging voltage is gradually increased, and thus charging is performed at a slow start (S7). When charging is started, the FET 134 is turned on by the charging current detection circuit 151.

  At this stage, it is determined whether or not an inrush current of a predetermined level or more is flowing through the battery set 14 (S8). Unless the charging current detection circuit 151 detects an inrush current of a predetermined level or higher (S8: NO), the charging current continues to flow and charging continues normally (S9). When the charging current detection circuit 151 determines that an inrush current of a predetermined level or more has flowed to the battery set 14 (S8: YES), an H level signal is applied from the charging current detection circuit 151 to the gate of the FET 134, and the FET 124 Turn off. Therefore, the charging current circuit is opened and charging is stopped (S10).

  Thus, when charging the battery pack 10 according to the present embodiment with the charger 6 having the slow start function, control is performed so that no inrush current is generated at the initial stage of charging, and normal charging is possible. is there. If it is determined that an inrush current has flowed, charging is not continued for safety (S10).

  Next, the operation when charging the battery pack according to the embodiment of the present invention in the case where the charging control unit 61 of the charger 6 does not have the slow start function will be described with reference to FIGS. 1 and 4.

  If the battery pack 1 is connected to the charger 6 (S100) and the battery voltage is low (S101: YES), since the charger control unit 61 does not have a slow start function, an inrush current flows through the battery pack 100. (S103). When the charging detection circuit 151 detects an inrush current of a predetermined level or higher (S104: YES), the FET 134 is turned off, so that the charging current circuit is opened (S106), and the battery pack 1 cannot be continuously charged ( S107). When the battery voltage detected at the start of charging is high (S101: NO, S102: NO) and when the level of the inrush current is lower than a predetermined level (S104: NO), the influence caused by the current flowing in the initial stage of charging is serious. Therefore, charging can be continued.

  As described above, when the battery pack 1 according to the present invention is charged with a charger having a slow start function, the battery pack connected to the charger performs normal charging, but has a slow start function. When the battery pack according to the present invention is to be charged with a charger that does not, the charging circuit formed by connecting the battery pack to the charger is forcibly cut off.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the battery set built in the battery pack is not limited to the four cell type, and the present invention can be applied regardless of the number of cells. Further, the specific method of the slow star is not limited to the one described in the above embodiment.

  The battery pack of the present invention can be used for battery-driven electric equipment, for example, an electric tool such as an electric drill.

DESCRIPTION OF SYMBOLS 1,100: Battery pack, 6: Charger, 13: Circuit board, 16: Connection terminal, 61: Charge control unit, 131: Protection IC, 134: FET, 151: Charge current detection circuit

Claims (3)

Rechargeable secondary battery,
Provided in a charging circuit formed when connected to a charger, a current detection unit for detecting a current flowing in the charging circuit;
When the current detected by the current detection unit is equal to or higher than a predetermined level, self-interrupting means for interrupting the charging circuit;
A battery pack comprising:   The self-cutoff means cuts off the charging circuit in response to an inrush current flowing from the charger to the secondary battery or from the secondary battery to the charger. Battery pack.   The self-cutoff means cuts off the charging circuit in response to an inrush current that flows from the charger to the secondary battery or from the secondary battery to the charger immediately after the start of charging. The battery pack according to 1.

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