JP2001169471A - Secondary cell device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary cell device having charge-controlling functions capable of charging secondary cells efficiently up to full charging while suppressing the heat generation of the cells. SOLUTION: This device is provided with a secondary cell unit 1, a pulse- charge-controlling means (switch element 4) that controls the switching of a charging current to the cell unit to charge the secondary cells with pulses, and a cell-voltage monitoring part (sensing part 2) that detects a terminal voltage of the secondary cell unit. Another charge-controlling means (charge/ discharge control device 6) in particular is provided that drives the pulse-charge- controlling means to start the pulse-charge, when the charging voltage of the secondary cell unit exceeds a first set voltage that is set in accordance with the cell temperature of the cell unit during charging, and that stops the charging of the cell unit when the charging voltage of the cell unit reaches a second set voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery device having charge control means capable of efficiently charging a secondary battery body while suppressing heat generation of the secondary battery body.

[0002]

[Related Background Art] In non-aqueous solvent-based secondary batteries such as Li-ion batteries and Ni-MH batteries, if the battery voltage becomes too high during charging, the battery performance will be significantly degraded or the safety will deteriorate. Have problems such as damage to Therefore, conventionally, the charging voltage of the secondary battery (battery voltage)
The secondary battery is charged at a constant current while monitoring its charging voltage so that the battery voltage does not exceed a predetermined voltage, and the battery voltage of the secondary battery becomes a predetermined voltage value (for example, 4.2 V per battery cell). When it rises to the maximum, the battery is regarded as being in a fully charged state, charging is stopped, and overcharging is prevented.

[0003]

However, if the secondary battery is continuously charged with a constant current, the battery temperature rises due to the internal heat generated by this and the battery performance deteriorates. There is a problem that the battery cannot be fully charged. In addition, as the battery approaches a fully charged state, the temperature of the battery starts to rise rapidly, and the charging voltage also rises sharply with the temperature, so that the secondary battery is easily damaged. Therefore, various attempts have been made to control the charging while monitoring the rate of increase in the battery temperature. However, there is a problem that charging cannot be performed efficiently while suppressing a rise in battery temperature.

The present invention has been made in view of such circumstances, and has as its object to reduce heat generation of a secondary battery.
An object of the present invention is to provide a secondary battery device having a charge control function capable of efficiently charging the secondary battery and preventing overcharging thereof.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, a secondary battery device according to the present invention comprises: a secondary battery main body; and switching control of a charging current to the secondary battery main body, thereby controlling the secondary battery. Pulse charging control means for pulse charging;
A battery voltage monitoring unit that detects a terminal voltage of the secondary battery body, wherein the battery voltage monitoring unit is configured to control the charging voltage of the secondary battery body during charging. When the voltage exceeds a first set voltage set in accordance with the battery temperature of the secondary battery body, the pulse charge control means is driven to start pulse charging, and the charge voltage of the secondary battery body is changed to a second voltage. It is characterized by comprising a charge control means for stopping charging the secondary battery body when the set voltage is reached.

In a preferred aspect of the present invention, the first set voltage is set according to the battery temperature of the secondary battery body. Further, as set forth in claim 3, the charging control means stops the pulse charging when the open terminal voltage of the secondary battery main body at the time of pulse charging of the secondary battery main body reaches a third set voltage. When the terminal voltage of the secondary battery main body reaches the second set voltage during the subsequent charging of the secondary battery main body, the charging itself to the secondary battery main body is stopped.

[0007] The pulse charging control means may be configured as follows.
As described in (1), this is realized as a switch element that is interposed in series between the secondary battery main body and its charging power supply, and controls on and off.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a secondary battery device (battery pack) according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a secondary battery device (battery pack) according to this embodiment, where 1 is a secondary battery main body composed of a Li-ion battery, a Ni-MH battery or the like, and PS is this secondary battery main body 1 This is a charging power source used for charging the battery. The secondary battery device (battery pack) is mainly composed of the secondary battery main body 1, and further includes a sensing unit 2 for monitoring a terminal voltage of the secondary battery main body 1, a secondary battery main body 1 and a charging power supply P.
The switch elements 3 and 4 which are interposed in series with the S and control the charge and discharge thereof, a switch control unit 5 which is a drive circuit thereof, a charge and discharge management unit 6, and the like.

The secondary battery body 1 includes, for example, a plurality (four in this example) of unit cells (battery cells) 1a, 1b, 1c, 1
and the sensing unit 2 is configured to detect the terminal voltage Vb of each of these unit cells (battery cells) 1a, 1b, 1c, 1d. The switch elements 3 and 4 for charge / discharge control are, for example, field effect transistors (FETs). The field effect transistor (switch element) 3 having a source electrode connected to the positive electrode of the charging power supply PS is a secondary battery body 1. It has a role of controlling the discharge at the time of discharge. A field-effect transistor (switch element) 4 connected in series to the field-effect transistor (switch element) 3 and having its source electrode connected to the positive electrode of the secondary battery body 1 is charged when the secondary battery body 1 is charged. Play a role in controlling the

The field effect transistors (switch elements) 3 and 4 are turned on and off by the switch control section 5 under the control of the charge / discharge management section 6 as described later, and are selectively turned off to be turned off. The charge / discharge path of the secondary battery body 1 is cut off to stop (prohibit) charging or discharging. The charge control field-effect transistor (switch element) 4 intermittently interrupts the charging current at a predetermined cycle, particularly during charging of the secondary battery body 1, to suppress heat generation of the secondary battery body 1. It also functions as a switching element for pulse charging.

The charge / discharge management unit 6 is composed of, for example, a microcomputer or an ASIC in a dedicated circuit. The charge / discharge management unit 6 manages the cells 1a, 1b, 1c, 1d of the secondary battery body 1 detected by the sensing unit 2. The terminal voltage Vb is monitored to control the charging / discharging of the secondary battery body 1 by the switch elements 3 and 4 and to perform functions such as managing the remaining battery level. Further, the charge / discharge management unit 6 detects the battery temperature T of the secondary battery main body 1 via a temperature sensor 7 such as a thermistor provided near the secondary battery main body 1. Based on the detected battery temperature T, for example, a rate of increase in battery temperature during charging is determined, and a management voltage and the like necessary for charge / discharge control are set.

The control voltage is, for example, a charging voltage V of the secondary battery body 1 during charging (a terminal voltage CV during charging; Cl
osed Voltage) is a first set voltage V1 (pulse charging start voltage) for determining whether or not the rechargeable battery main body 1 has reached a voltage suitable for starting pulse charging while suppressing heat generation of the secondary battery main body 1. The second set voltage V2 (charge stop voltage) for determining whether or not the voltage at which the charging of the secondary battery body 1 should be stopped has been reached. Furthermore, it is determined whether or not the open terminal voltage of the secondary battery body 1 during pulse charging (terminal voltage OV when the switching elements 3 and 4 are off) reaches a voltage at which the pulse charging should be stopped. Third to do
The set voltage V3 (pulse charge stop voltage) is set in the same manner.

Incidentally, the pulse charging start voltage V1 is:
The secondary battery main body 1 (the single cell 1
a, 1b, 1c, 1d), for example, a voltage value at which rapid heat generation starts at, for example, 0.5 ° C./sec is determined by an experiment or the like, and a battery temperature derived based on the measured data and a rapid heat generation start voltage From the relationship, it is sufficient to set V1 = aT + b (where a and b are coefficients). The coefficients a and b are set in consideration of the charging current. The second set voltage V2 is set as a charge prohibition voltage (allowable maximum charge voltage) according to the battery characteristics of the secondary battery body 1.

In this case, the condition for starting pulse charging is determined from the charging voltage of the secondary battery body 1, and the condition for stopping pulse charging is determined from the open terminal voltage of the secondary battery body 1. The third set voltage V3 is set, for example, equal to the first set voltage V1. However, it goes without saying that the third set voltage V3 may be set separately from the first set voltage V1 according to the battery characteristics.

The charge / discharge management unit 6 having the first to third set voltages V1, V2, V3 set in this way.
Controls the charging of the secondary battery body 1 in accordance with, for example, the procedure shown in FIG. That is, the charge / discharge control unit 6 determines whether or not the secondary battery body 1 is being charged based on the direction of the charge / discharge current [Step S1]. Execute control. When the battery is not being charged, the charge / discharge control unit 6 executes other processes such as discharge control for the secondary battery body 1 and management of the remaining battery level (step S2).

During charging of the main body 1 of the secondary battery, the charging / discharging control section 6 detects the charging voltage V (terminal voltage CV during charging) of the main body 1 of the secondary battery via the sensing section 2. Then, it is always determined whether or not the charging voltage V exceeds the first set voltage V1 (step S3). When the charging voltage V exceeds the first set voltage V1, if the secondary battery main body 1 is continuously charged with a constant current as it is, pulse charging is started on the assumption that the battery temperature T may suddenly increase. [Step S4]. This pulse charging is performed by turning on / off the charging control switch element (FET) 4 at a predetermined cycle via the switch control unit 5 to interrupt (switch) the charging current. . As a result, the terminal voltage V of the secondary battery body 1 becomes
As schematically shown in FIG. 3, the charge voltage CV and the open terminal voltage OV gradually increase as the switching element 4 is turned on and off, as schematically shown in FIG. The secondary battery main body 1 is efficiently charged while the heat generation of the secondary battery main body 1 is suppressed by the switching of the charging current.

When the rechargeable battery body 1 is pulse-charged in this manner, the charge / discharge control unit 6 controls the sensing unit 2
Terminal voltage OV of the secondary battery body 1 detected through the
, And it is always determined whether or not the open terminal voltage OV has reached the above-described third set voltage V3 [Step S5]. And the open terminal voltage OV is equal to the third set voltage V3.
Is reached, it is determined that the secondary battery main body 1 has almost reached the full charge, and the above-described pulse charging is stopped [Step S
6]. By stopping the pulse charging, the secondary battery body 1 is charged again with a constant current.

Therefore, the charge / discharge control unit 6 again
The charging voltage CV of the secondary battery body 1 is monitored, and it is determined whether the charging voltage CV has reached the second set voltage V2 [Step S7]. The second set voltage V2 is a voltage set in consideration of a margin before the rechargeable battery main body 1 reaches a state in which the secondary battery main body goes out of control, and the charging voltage CV reaches the second set voltage V2. At this time, the charging / discharging control unit 6 determines that this state is the fully charged state of the main body 1 of the secondary battery, controls the switch element 4 to turn off, and prohibits (stops) the charging itself. [Step S8].

In the above description, the pulse charging is temporarily stopped, and then the charging of the secondary battery body 1 is controlled to be stopped. However, the pulse charging stopping control itself is executed as the charging stop. Is also possible. In this case, instead of comparing the open terminal voltage OV at the time of pulse charging with the third set voltage V3, the charge voltage V (terminal voltage CV) of the secondary battery body 1 is compared with the second set voltage V2. In comparison, it is of course possible to perform the charge stop control.

Thus, according to the secondary battery device having the function of controlling the charging of the secondary battery main body 1, when the secondary battery main body 1 is charged at a constant current,
Before the battery temperature T suddenly rises due to the heat generated by the secondary battery body 1 due to the continuous charging, the charging current is switched and the secondary battery body 1 is pulse-charged. 1 can effectively suppress a rise in battery temperature. And while suppressing the rise in battery temperature T,
The secondary battery body 1 can be charged efficiently. Therefore, according to the battery performance (battery capacity) of the secondary battery body 1, the secondary battery body 1 can be reliably charged until it is fully charged.

In particular, since the rechargeable battery main body 1 can be charged while suppressing heat generation, the rechargeable battery main body 1 does not run out of heat, and its safety can be sufficiently ensured. The effect can be achieved. Further, the rechargeable battery main body 1 can be pulse-charged only by switching the switch element 4 by effectively utilizing the switch element 4 for charge prohibition control provided in the secondary battery apparatus. There is also an effect that the cost does not increase.

The present invention is not limited to the above embodiment. For example, the charging control is performed by detecting the voltage between both ends of the secondary battery body 1 without individually detecting the terminal voltages of the plurality of cells 1a, 1b, 1c, 1d constituting the secondary battery body 1. Of course, it is possible. Further, the switching elements 3 and 4 are not necessarily interposed on the positive electrode side of the secondary battery main body 1 and may be interposed on the negative electrode side. In addition to the switch element 4 for charge prohibition control, a semiconductor switch element with a high switching speed dedicated to pulse charging can be interposed in the charge / discharge path of the secondary battery body 1.

Further, the ON / OFF driving cycle of the switch element for executing the pulse charging may be determined according to the battery specifications and the like, and the configuration itself of the secondary battery main body 1 is not particularly limited. Not done. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0024]

As described above, according to the present invention, the charging current is switched in accordance with the charging voltage of the secondary battery main body when the secondary battery main body is charged, whereby the secondary battery main body is pulse-charged. Therefore, it is possible to safely and reliably charge the secondary battery to its full charge while effectively preventing the heat of the secondary battery body. In addition, under the simple control, the secondary battery main body can be charged efficiently, and a great effect can be obtained in practical use.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a secondary battery device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a procedure of charge control in the secondary battery device according to the embodiment of the present invention.

FIG. 3 is a diagram schematically showing a change in charging voltage when the secondary battery body is charged by the charging control shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Secondary battery main body 2 Sensing part 3 Discharge control switch element 4 Charge control switch element 5 Switch control part 6 Charge / discharge control part 7 Temperature sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/48 H01M 10 / 48P H02J 7/04 H02J 7/04 F F term (Reference) 2G016 CA00 CB33 CC01 CC07 CC12 CC23 CD06 CF06 2G035 AA01 AB03 AC01 AD03 AD23 AD44 5G003 AA01 BA01 CA01 CA14 CB01 CC07 FA08 GA01 GC05 5H030 AA03 AA06 AS20 BB06 DD06 DD08 FF22 FF43

Claims (3)

[Claims] 1. A rechargeable battery main body, pulse charging control means for switching-controlling a charging current for the rechargeable battery main body to pulse-charge the rechargeable battery, and a battery for detecting a terminal voltage of the rechargeable battery main body. A voltage monitoring unit, wherein the battery voltage monitoring unit sets a charging voltage of the secondary battery body according to a battery temperature of the secondary battery body.
When the set voltage exceeds the set voltage, the pulse charge control means is driven to start pulse charge, and the charge voltage of the secondary battery body reaches a second set voltage set higher than the first set voltage. A secondary battery device comprising: a charging control unit that stops charging the secondary battery main body when the secondary battery main unit is turned off. 2. The charging control means stops the pulse charging when an open terminal voltage of the secondary battery main body reaches a third set voltage at the time of pulse charging of the secondary battery main body. 2. The secondary battery according to claim 1, wherein charging of the secondary battery main body is stopped when a terminal voltage of the secondary battery main body reaches the second set voltage during charging of the secondary battery main body. 3. apparatus. 3. The rechargeable battery according to claim 1, wherein the pulse charge control means controls on / off of a switch element interposed in series between the rechargeable battery main body and a charging power supply thereof. apparatus.