JPH05121102A - Secondary battery pack - Google Patents

Abstract

PURPOSE:To compensate a voltage drop by adding a separated cell in a combination battery in compliance with a battery temperature change or terminal voltage change in a secondary battery pack wherein a plurality of secondary batteries such as an Ni-Cd battery are connected to each other in series. CONSTITUTION:The pack is provided with: a secondary battery combination cell 2 composed of a plurality of cells and used at all times; a secondary battery additional cell 3 which is a cell separated from the combination cell 2 and used additionally at the time of emergency; a temperature sensor 6 installed inside for measuring a battery surface temperature; a voltage drop comparator 4 for monitoring a voltage drop at the time of discharging under an ordinary temperature; and a temperature change comparator 5 for monitoring a temperature drop at the time of full charge. A voltage drop due to internal resistance increase at a low temperature in the temperature sensor 6 at the time of a low temperature and full charge is detected by the comparator 5 so as to add the additional cell 3 to the combination cell 2 for output. At the time of an ordinary temperature and discharge, a voltage drop in the combination cell 2 is detected by the comparator 4 so as to add the additional cell 3 to the combination cell 2 for output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery pack in which a plurality of secondary batteries such as Ni-cd batteries are connected in series. The secondary battery is a rechargeable dry battery, and the Ni-cd battery is a typical one, and is a battery used in communication terminals such as cordless telephones and mobile phones. This Ni-cd battery has a capacity of 1.2V voltage and 500mAH in one electronic cell, and can be connected in series to form a secondary battery pack of 4.8V voltage and 500mAH capacity. In addition, it is possible to form a secondary battery pack having different voltage values and capacities by changing the number of electronic cells and the cell capacity as necessary.

In recent years, communication devices used outdoors such as mobile phones have become widespread, and most of these power supplies use Ni-cd batteries. The internal resistance of this battery increases as the external temperature decreases, and it tends to be more difficult to supply power to communication devices than at room temperature. That is, the device may not function when used outdoors in winter. This is because the internal resistance of a secondary battery such as a Ni-cd battery increases when the battery temperature decreases, and a voltage drop occurs due to the internal resistance when a current is applied in this state. This causes malfunction of the device. Therefore, there is a need for a secondary battery pack that does not affect the operation of the device even when the external temperature decreases.

[0003]

2. Description of the Related Art As described above, in a secondary battery such as a Ni-cd battery, the internal resistance increases when the battery temperature decreases, and when a current is passed in this state, a voltage drop occurs due to the internal resistance. In order to solve this problem, conventionally, a method of previously separating one cell of the assembled battery and adding the separated cell when the voltage drops has been adopted. The problem here is the terminal voltage of the battery. When the temperature decreases, the terminal voltage (no-load voltage) of the battery tends to increase. Therefore, it is difficult to monitor the battery voltage and add a spare cell.

[0004]

In the conventional case, when the voltage of a secondary battery such as a Ni-cd battery is dropped, it is charged each time, or one cell separated when the voltage drops is added. There is a method, but this is not done by monitoring the battery voltage. Therefore, it was not possible to automatically adjust the voltage of the battery according to the change in temperature.

It is an object of the present invention to develop a battery pack that monitors a decrease in battery temperature in a battery pack and a decrease in terminal voltage due to discharge and automatically adds or removes one cell that has been separated. To do.

[0006]

FIG. 1 shows a principle configuration diagram of a secondary battery pack of the present invention. In the figure, 1 is a secondary battery pack, 2 is a secondary battery assembly cell, 3 is a secondary battery addition cell, 4 is a voltage drop comparator, 5 is a temperature change comparator, 6 is a temperature sensor, 7 is a zener diode. , 8 are field effect transistors (FETs), and 9 is a backflow prevention diode. + B and GND are battery output terminals, CHG1 and C
HG2 indicates a battery charging terminal together with GND.

The rechargeable battery pack 1 is a plastic pack containing a rechargeable battery assembly cell 2 that is always used, a rechargeable battery addition cell 3 that is additionally used in an emergency, and other measuring circuits. It consists of a thermistor and is installed inside so that the surface temperature of the battery can be measured. The voltage drop comparator 4 monitors the voltage drop during discharge at room temperature, and the temperature change comparator 5 monitors the voltage drop due to the temperature drop during full charge.

[0008]

When the battery is fully charged at room temperature, that is, when the battery is fully charged, the outputs of the voltage drop comparator 4 and the temperature change comparator 5 are in an open state, and the voltage of the secondary battery cell 2 is for preventing reverse current. The output voltage is supplied to the outside from the + B terminal and the GND terminal through the diode 9.

When the battery is fully charged at low temperature, that is, when the battery is fully charged, the temperature sensor 6 detects a decrease in external temperature, the internal resistance of the temperature sensor 6 increases, and the output of the temperature change comparator 5 is turned on. Then, the field effect transistor 8 is activated, the secondary battery addition cell 3 is added to the secondary battery assembly cell 2, and the + B terminal and G are added through the field effect transistor 8.
The output voltage is supplied from the ND terminal to the outside. Therefore, the voltage drop due to the increase in internal resistance at low temperature is compensated.

When the voltage of the secondary battery assembly cell 2 drops due to long-time use of the battery at room temperature, the output of the voltage drop comparator 4 is turned on and the field effect transistor 8 is activated to activate the secondary battery addition cell. 3 is added to the secondary battery assembly cell 2,
An output voltage is supplied to the outside from the + B terminal and the GND terminal through the field effect transistor 8. Therefore, the voltage drop due to the discharge at room temperature is compensated.

When it is desired to charge the secondary battery unit cell 2, C
Connect a charger between the HG2 terminal and the GND terminal to charge the secondary battery additional cell 3 with the CHG1 terminal and the CHG terminal.
A charger can be connected between the two terminals to charge the batteries individually.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A circuit configuration diagram of an embodiment of the present invention is shown in FIG.
In the figure, 11 is a secondary battery pack, 12 is a 4.8V secondary battery assembly cell BAT2 consisting of four 1.2V battery cells, 13 is a secondary battery addition cell BAT1 consisting of one 1.2V battery cell, 14 is resistance
Voltage drop comparators COMP1 and 15 for comparing the reference voltage divided by R1 and Zener diode D2 with the voltage drop divided by resistors R2 and R3 are the reference voltage divided by resistors R4 and R5. Temperature change comparator COMP2 that compares the internal resistance of the temperature sensor with the voltage divided by resistance R6
Indicates.

Reference numeral 16 is a temperature sensor TH including a thermistor or the like.
Then, it is attached to the surface of one battery cell in the secondary battery assembly cell 11. 17 is a Zener diode D2 for applying a reference voltage to the negative terminal of the voltage drop comparator COMP1, 18 is a comparator CO
The field effect transistors Q1 and 19 that connect the source and drain terminals by receiving the Lo output of MP1 or the comparator COMP2 at the gate terminal are BA when the field effect transistor Q1 is open.
A diode that supplies T2 to the + B terminal and supplies the voltage of BAT1 + BAT2 to the + B terminal when the field effect transistor Q1 is on.

With the above circuit, CO
MP1 and COMP2 are opened, and the voltage of BAT2 is supplied to the outside through D1. At low temperature and full charge, temperature sensor TH detects temperature, COMP2 becomes Lo, Q1 turns on, BAT2 and BA
The added voltage of T1 is externally supplied through Q1 to compensate the voltage drop due to the increase of internal resistance at low temperature. If the voltage of BAT2 drops at normal temperature and discharge for a long time, the COMP
1 becomes Lo, Q1 turns on, and the added voltage of BAT2 and BAT1 is externally supplied through Q1 to compensate for the voltage drop due to discharge.

When charging BAT2 and BAT1, CHG2
Connect a 4.8V charger between the terminal and GND terminal
BAT1 can be charged by connecting a 1.2V charger between the CHG1 and CHG2 terminals.

[0016]

As described above, when one cell in the assembled battery is separated and usually one cell is separated, the battery is used when the temperature of the battery becomes low or the terminal voltage of the battery drops. , The voltage of the rechargeable battery pack can be automatically compensated by adding the separated cell, so the device can be used as it is even when the temperature of the mobile phone etc. is used outdoors in winter. It becomes possible.

Also, by automatically adding one battery cell, the battery can be used for a longer time than before without charging, and the charging timing can be extended. FIG. 3 shows a comparison between the battery usage time and the voltage drop. By using the additional voltage for one battery cell, the usage time can be extended by t hours as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram of the principle of the present invention.

FIG. 2 is a circuit configuration diagram of an embodiment.

[Figure 3] Comparison diagram of battery usage time and voltage drop

[Explanation of symbols]

 1,11 Secondary battery pack 2,12 Secondary battery assembly cell 3,13 Secondary battery addition cell 4,14 Voltage drop comparator 5,15 Temperature change comparator 6,16 Temperature sensor 7,17 Zener diode 8, 18 Field effect transistor 9,19 Reverse current prevention diode

Claims (2)

[Claims] 1. A rechargeable battery pack in which a plurality of rechargeable batteries are connected in series, wherein a rechargeable battery assembly cell (2) consisting of a plurality of battery cells that are always used and one of the assembly cells are separated. Cell (3) for secondary battery addition that is additionally used in an emergency, a temperature sensor (6) installed inside so that the surface temperature of the battery can be measured, and a voltage that monitors the voltage drop during discharge at room temperature It has a drop comparator (4) and a temperature change comparator (5) for monitoring the temperature drop at full charge, and at the time of low temperature and full charge, voltage drop due to an increase in internal resistance of the temperature sensor (6) at low temperature. Is detected by the temperature change comparator (5), the secondary battery addition cell (3) is added to the secondary battery assembly cell (2), and the result is output. 2. A voltage drop comparator (4) detects a voltage drop of a secondary battery assembly cell (2) due to long-term use at normal temperature and discharge, and the secondary battery assembly cell (2) is charged with a secondary battery. The secondary battery pack according to claim 1, wherein the additional cells (3) are added and output.