JP3162506B2 - Rechargeable battery pack and its charging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rechargeable battery pack and a charging device therefor.

[0002]

2. Description of the Related Art A conventional rechargeable battery pack, particularly a rechargeable battery pack with an overcharge prevention function used for a cordless power tool, has a rechargeable battery and a thermostat built in the pack and has three terminals on the surface of the pack. Some are exposed. Here, the first terminal is connected to the positive electrode of the secondary battery, the second terminal is connected to the negative electrode, and the third terminal is connected to the negative electrode via a thermostat. According to this rechargeable battery pack, when the secondary battery is charged until it reaches full charge, the thermostat is turned off, and the third terminal is not grounded.

On the other hand, the side of the charging device for the rechargeable battery pack has a terminal contacting a third terminal, and while the terminal voltage is grounded, the switching element for turning on / off the charging current is turned on. In addition, a circuit that turns off the switching element when a voltage starts to be applied to the terminal voltage is incorporated. With this configuration, overcharge of the secondary battery is prevented.

[0004]

Normally, when a secondary battery is fully charged, the temperature of the secondary battery is about 40.degree. Therefore, a thermostat that turns on and off near this temperature is used. On the other hand 2
If the secondary battery is rapidly discharged, a higher temperature, for example, 6
It may be around 0 ° C. For that reason, a rapid discharge 6
When charging a rechargeable battery pack that has reached about 0 ° C., the thermostat is turned off, and a situation occurs in which charging current does not flow. That is, there is a problem that a battery that has been rapidly discharged cannot be recharged unless it is cooled to 40 ° C. or lower.

Applicants have attempted a technique utilizing a thermistor to recharge a rapidly discharged and heated battery pack without waiting for it to cool. That is, a thermistor is built in the battery pack, and the temperature is detected by the thermistor. If the temperature is equal to or lower than a predetermined value (which is higher than the temperature at which the thermostat is turned off), for example, It starts charging even if the thermostat is off. According to this, recharging can be performed without waiting for the rapidly discharged battery pack to cool. However, for this purpose, a fourth terminal connected to the thermistor must be added to the surface of the battery pack. However, in order to provide the fourth terminal on the surface of the battery pack, the shape must be changed from the shape of the conventional battery pack, and a new mold is required. Further, when four terminals are provided, the probability of any one of the terminals having a contact failure increases accordingly.

Accordingly, the present invention provides a new battery pack which enables recharged batteries without waiting for the rapidly discharged batteries to cool, and ensures stable contact without changing the external shape of the battery pack. In addition, a charging device for that purpose is proposed.

[0007]

According to the present invention, there is provided:
Built-in secondary battery and thermostat
Connected to the first and negative terminals connected to the south pole
Connects to the minus terminal via the second terminal and the thermostat
Rechargeable battery pack with a third terminal
The temperature at which the thermostat turns off from
At the above temperature, a thermistor having a positive characteristic in which the resistance value increases
A star is added to bypass the thermostat.
To create a rechargeable battery pack characterized by
Was. Here, the resistance value of the thermistor is
At a temperature higher than the temperature at which the
The current that flows through the
It is preferable that the resistance value is not more than the holding current. Also,
3. The rechargeable battery pack according to claim 1, further comprising a first operational amplifier and a second operational amplifier connected in parallel to the third terminal, wherein the first operational amplifier is inverted when the thermostat is turned off from on. However, the second operational amplifier has created a charging device characterized in that it reverses when the resistance value of the thermistor exceeds a predetermined value.

[0008]

According to the battery pack of the first aspect, only three terminals are required on the surface of the battery pack, and there is no need to change the shape of the battery pack from the conventional one. And since the thermistor is built-in, it is also possible to recharge a rapidly discharged battery before it is cooled. Ma
The resistance value of the thermistor is as defined in claim 2.
Thus, the conventional charging device can be used as it is. In this case, recharging before cooling after rapid discharge cannot be performed any more. According to the charging device of the third aspect , the three-terminal battery pack can perform charging and charging stop according to changes in the thermistor and the thermostat.

[0009]

Next, a first embodiment of the present invention will be described with reference to FIG. In the figure, reference numeral 10 denotes a circuit configuration of the charging device, and reference numeral 50 denotes a circuit configuration of the rechargeable battery pack. The charging device 10 is used by being connected to the commercial power supply 2, and includes a transformer 12.
, And rectified and smoothed by the rectifier 16 to obtain a charging current. The charging current is supplied to the first charging terminal 42 and the second charging terminal 4.
6. In this charging path, the switching element 36
Is inserted.

A constant voltage device 14 is connected to the transformer 12, and outputs a constant voltage Vcc. The microcomputer 20 and the operational amplifiers 30, 32 and 34 are used for controlling the switching element 36, and a constant voltage Vcc is supplied to them. The microcomputer 20 is a CP
The U22, the RAM 24, the ROM 26, and the I / O 28 are integrated into one chip. The first operational amplifier OP1 (34) compares the voltage of the third terminal 44 on the charging side with the set value V1 divided by the resistors R5 and R6, and inverts the output according to the magnitude. The second operational amplifier OP2 (32) compares the voltage of the third terminal 44 on the charging side with a set value V2 obtained by dividing the voltage by the resistors R3 and R4, and inverts the output according to the magnitude. The third operational amplifier OP3 (30) includes a charging-side first terminal 42 and a charging-side second terminal 46.
And the constant voltage Vcc divided by the resistors R7 and R8.
Are compared by resistors R1 and R2, and the output is inverted according to the magnitude of the voltage division. The third terminal 44 on the charging side is connected to a constant voltage Vcc via a diode 40.

The rechargeable battery pack 50 includes a rechargeable battery 5.
8 and a thermostat 62 are built in. A thermistor 60 is connected in parallel with the thermostat 62.
The thermostat 62 and the thermistor 60 are built in so that the temperature rises as the temperature of the secondary battery 58 rises.
On the surface of the battery pack 50, a pack-side first terminal 52,
The second terminal 56 and the third terminal 54 are fixed. The first terminal 52 is a positive terminal of the secondary battery 58, the second terminal 56 is a negative terminal, and the third terminal 54 is a thermostat 62.
Connected to the negative pole. When the battery pack 50 is set in the charging device 10, the first terminals 42 and 5
2, the second terminals 46 and 56 and the third terminals 44 and 54 are connected, respectively.

When the battery pack 50 is set in the charging device 10, the third terminal 44 on the charging side is connected to the thermostat 62.
Or grounded via a thermistor 60. The thermostat 62 has a temperature T when the secondary battery 58 is fully charged.
When the temperature rises to 1 (approximately 40 ° C. in the case of a normal secondary battery), it turns off from on. The thermistor 60 has a positive characteristic in which the resistance increases as the temperature rises. In particular, the resistance value largely changes before and after a high temperature T2 (usually about 60 ° C.) which significantly affects the durability of the secondary battery. .

As a result, the voltage of the charging-side third terminal 44 changes with temperature as shown in FIG. While the temperature is equal to or lower than T1, the thermostat 62 is conductive and grounded, and the voltage is zero. When the temperature exceeds T1, the thermostat 62 is turned off and the voltage increases. As the temperature further increases, the resistance of the thermistor 60 increases, and the voltage at the third terminal increases accordingly.

In FIG. 4, V1 represents one comparison voltage of the first operational amplifier OP1 (34). As a result, the output of the first operational amplifier OP1 (34) is low below T1 when the thermostat 62 is on, and goes high above T1 when the thermostat 62 is off. In the drawing, V2 indicates one comparison voltage of the second operational amplifier OP2 (32). As a result, the output of the second operational amplifier OP2 (32) is low when the battery temperature is equal to or lower than T2, and becomes high when the battery temperature is equal to or higher than T2.

A program for performing the processing shown in FIG. 2 is stored in the ROM 26 of the microcomputer 20. When the power is turned on in step S1, the output of the third operational amplifier OP3 (30) is input in step S2. Here the third
The operational amplifier OP (30) outputs a high voltage while the battery pack 50 is set (inserted) in the charging device 10, and outputs a low voltage while the battery pack 50 is not inserted. Therefore, in step S3, it is determined whether or not the battery pack 50 is inserted by determining whether the output of the third operational amplifier OP3 (30) is high or low. If not, the process of returning to step S2 is repeated, and the process waits until battery pack 50 is inserted.

When the battery pack 50 is inserted, the result of step S3 is YES, and then the output of the second operational amplifier OP2 (32) is fetched in step S4. Battery pack 50
Is equal to or greater than T2, the output of the second operational amplifier OP2 (32) is high, and if equal to or less than T2, the output is low. In step S5, the output of the second operational amplifier OP2 (32) is
It is determined whether it is 2 or more or less. If so, the process returns to step S4 and waits for the battery pack 50 to cool to T2 or less. When T2 or less, charging is started in the next step S6.

In FIG. 3, point A indicates that step S6 was executed immediately without being affirmative in step S5, and point B indicates that step S5 became no while repeating steps S5 and S4. Is shown.

After charging is started in step S6, the output of the first operational amplifier OP1 (34) is input in step S7. Here, the output of the first operational amplifier OP1 (34) is high when the battery pack 50 is equal to or higher than T1, and is low when the battery pack 50 is equal to or lower than T1, so that in step S8, the output of the first operational amplifier OP1 (34) determines whether the battery pack 50 is equal to or higher than T1. Determine. T
If it is 1 or more, it is checked in steps S9 and S10 whether it is T2 or more. If T1 or more and T2 or more, step S1
In 3 stop charging. On the other hand, during T2 or less, step S7
Return to. FIG. 3C illustrates this case, where T is charged during charging.
Since it is equal to or more than 1 and equal to or less than T2, the process proceeds from step S8 to step S10, and the process of returning to step S7 is repeated. Then, at point D, step S10 becomes YES, and charging is stopped. In the case of E in FIG. 3, while step S8 is YES and step S10 is NO, step S8 becomes NO at point F. In this case, step S12 is executed, and step S13 is executed when the battery temperature that has dropped below T1 returns to T1.
In addition, as shown in H of FIG.
The charging is stopped when the answer is YES in step S12.

As is clear from the above processing and the description of FIG. 3, the battery pack is switched to T2 (for example, 60
(° C.) or more, charging is stopped in that state, so that the durability of the secondary battery is reduced, so that charging is stopped. And T
Charging is performed between 1 (for example, 40 ° C.) and T2, and charging is continued until T2 is reached. When the charging proceeds below T1 (H in FIG. 3 or between F and G in FIG. 3), the charging proceeds until T1. Therefore, recharging can be performed immediately after rapid discharge. Point G in FIG.
, Charging is stopped to prevent overcharging.

FIG. 5 shows a case where the battery pack 50 is mounted on a charging device 70 which has been widely used. In this case, when the power is turned on and the battery pack 50 is set in the charging device 70, a charging current flows through the capacitor C, the thyristor SCR is turned on, and charging is started. Then, when the temperature of the secondary battery 58 rises during charging and the thermostat 62 is turned off, charging is stopped. In the conventional battery pack, since the thermistor 60 is not inserted in parallel with the thermostat 62, the charging current is completely stopped when the thermostat 62 is turned off. In the case of the battery pack of the present embodiment, the thermostat 6 is connected because the thermistor 60 is connected in parallel.
Even if 2 is turned off, current continues to flow through the thermistor 60. However, in this case, the resistance value of the thermistor 60 is sufficiently high, and the current flowing through the thermistor 60 is a very small current equal to or less than the holding current of the thyristor SCR. Therefore, the thyristor SCR is turned off and charging is stopped.

In the circuit of FIG. 5, even if the battery pack 50 after being fully charged is cooled down while being attached to the charging device 70 and the thermostat 62 is turned on again, the capacitor C is already charged at that time. Thus, the thyristor SCR does not turn on again, and overcharging is prevented.
In this manner, the battery pack of this embodiment can be charged by the conventional charging device. However, in this case, charging cannot be started with the thermostat 62 opened.

Next, a second example of the charging device will be described with reference to FIG. In the figure, 82 is a transformer, 84 is a rectifier, 86 and 88.
Is a smoothing capacitor and a resistor. In this embodiment, the negative terminal of the first operational amplifier OP1 (104) is grounded via the capacitor 106. On the other hand, a third terminal 108 is connected to the plus terminal via a resistor R80. Due to the smoothing action of the capacitor 106, the voltage input to the negative terminal is momentarily delayed from the voltage of the positive terminal. Therefore, the output of the first operational amplifier OP1 (104) is high only for a moment when the thermostat 62 is turned off from on, and is low at other times. On the other hand, the plus terminal of the second operational amplifier OP2 (102) is connected to the third terminal 108 via the resistor R80. The set voltage V3 is input to the minus terminal. Therefore, while the thermostat 62 is on (that is, T1 or less) and the thermostat 62 is off but the resistance value of the thermistor 60 is low (that is, between T1 and T2), the second
The output of the operational amplifier OP2 (102) becomes low. However, when the resistance of the thermistor 60 increases (that is, when the resistance exceeds T2), the output of the second operational amplifier OP2 (102) becomes high.

During the period T2 or less, that is, the first operational amplifier O
When the charge start switch 90 is once turned on while both the P1 (104) and the second operational amplifier OP2 (102) are low, both the transistor 96 and the thyristor 98 are turned on, and the exciting current starts flowing through the coil 94b of the relay 94. . As a result, the relay contact 94a turns on, and charging starts. On the other hand, if the temperature of the thermistor 60 is equal to or higher than T2, the second operational amplifier OP2 (10
2) Since the transistor outputs a high level, the transistor 100 is turned on and the transistor 96 is turned off, so that charging is not started.

When the thermostat 62 is turned off during charging, the negative terminal of the first operational amplifier OP1 (104) is grounded via the capacitor 106, so that the first operational amplifier OP1 (104) momentarily outputs high. Therefore, the transistor 100 is turned on, the transistor 96 is turned off, and the relay 94 is opened to stop charging. When the resistance value of the thermistor 60 becomes a value corresponding to a temperature equal to or higher than T2,
The second operational amplifier OP2 (102) is turned on, and the relay 94 is opened as described above.

Even after the full charge, the battery pack 50 continues to be set in the charging device 80. During this time, even if the battery pack is cooled and both the first operational amplifier OP1 and the second operational amplifier OP2 are turned on, at this time, the charging start switch 9
Unless 0 is pressed, the thyristor 98 does not turn on and recharging does not start. For this reason, overcharging is prevented. Thus, also in the second embodiment, the charging and the charging stop shown in FIG. 3 are executed.

As will be understood from the above, the rechargeable battery pack 50 of the present embodiment has a three-terminal outer shape, and can have exactly the same shape as a conventional battery pack. Therefore, the battery pack of the present invention can be manufactured by a conventional manufacturing apparatus. Further, the battery pack of this embodiment can be charged by a conventional charging device. In addition, since the battery pack 50 of the present embodiment has a built-in thermistor in addition to the thermostat, even if the thermostat is turned off, it is detected from the output of the thermistor whether or not the battery can still be charged. Can be charged without waiting for it to cool down.

[0027]

According to the present invention, a rechargeable battery pack whose temperature has risen due to rapid discharge can be recharged without waiting for cooling, so that continuous operation is possible with a small number of battery packs, and the The load can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a first embodiment of the present invention.

FIG. 2 is a processing procedure diagram of the first embodiment.

FIG. 3 is a diagram showing start and stop of charging according to the first embodiment;

FIG. 4 is a diagram showing a relationship between a third terminal voltage and a comparison value.

FIG. 5 is a diagram showing a circuit when the battery pack of the first embodiment is mounted on a conventional charger.

FIG. 6 is a diagram showing a circuit configuration of a second embodiment.

[Description of Signs] 34, 104 First operational amplifier OP1 32, 102 Second operational amplifier OP2 50 Battery pack 58 Secondary battery 60 Thermistor 62 Thermostat

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-89431 (JP, A) JP-A-4-117140 (JP, A) JP-A-4-340330 (JP, A) 47352 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/42-10/48 H02J ⁷ /00-7/36

Claims (3)

(57) [Claims] 1. A secondary battery and a thermostat are built in, and a first terminal connected to a positive terminal of the secondary battery, a second terminal connected to a negative terminal, and a negative terminal connected through the thermostat. And a third terminal on the surface of the rechargeable battery pack, the temperature of which is equal to or higher than the temperature at which the thermostat turns on and off.
A thermistor having a positive characteristic in which the resistance value increases.
A rechargeable battery pack characterized in that it is added so as to bypass a thermostat . 2. The rechargeable battery pack according to claim 1, wherein a resistance value of the thermistor is changed from a state in which the thermostat is turned on.
Current flowing through the thermistor at a temperature higher than the turning-off temperature
Is lower than the holding current of the switching element for charging current.
A rechargeable battery pack having a resistance value . 3. The charging device for a rechargeable battery pack according to claim 1, further comprising a first operational amplifier and a second operational amplifier connected in parallel to the third terminal, wherein the first operational amplifier is A charging device, wherein the thermostat is inverted when the thermostat is turned off from on, and the second operational amplifier is inverted when the resistance value of the thermistor exceeds a predetermined value.