JPH07143677A - Power supply - Google Patents

Abstract

PURPOSE:To easily make uniform electric currents to flow between each secondary battery by variably controlling the resistance values of variable resistors connected to second batteries having smaller internal resistances, better heavy load characteristics, and larger rated capacities than first secondary batteries have while the second batteries have the same nominal voltage as the first secondary batteries have at levels lower than the resistance values of fixed resistors connected to the first second batteries. CONSTITUTION:Batteries (A) 1, 2, 3, and 4 in each of which two first secondary batteries are connected in series and another battery (B) in which two second secondary batteries which have smaller internal resistances, better heavy load characteristics, and larger rated capacities than the first second batteries have, while the second secondary batteries have the same nominal voltages as the first secondary batteries have, are arranged are connected in parallel with each other. In case the total value of electric currents which flow from the batteries is, for example, <=1,000mA (1C) when electricity is discharged to an output device from the batteries (A) and (B), a controller 15 sets the resistance value of a variable resistor 11 at the same value as that of the batteries (A) 1, 2, 3, and 4, for example, 1mOMEGA by controlling the movement of a sliding piece 12. When the total value is larger than 1,000mA, the resistance value of the resistor 11 i.s reduced in steps front 0.9nOMEGA to 0.1nOMEGA through 0.6nOMEGA, 0.4nOMEGA, and 0.2nOMEGA.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and more particularly to a power supply device in which at least two types of secondary batteries having different discharge load characteristics are connected in parallel.

[0002]

2. Description of the Related Art Conventionally, a multi-cell parallel assembled battery using a plurality of secondary batteries in parallel as an assembled battery generally has an assembled battery structure in which a uniform current flows when the discharge load is changed. Each secondary battery is connected via a lead having a small resistance value. Therefore, the current varies within a range depending on the load. However, such an assembled battery structure has been established on the assumption that all batteries have a uniform discharge capacity and internal resistance.

In view of charge / discharge conditions, the multi-cell parallel assembled battery tends to have a large current in the secondary battery close to the output side in connection and a small current in the secondary battery cell far from the output side. Due to the difference in the internal resistance value of each secondary battery, the amount of current tends to vary depending on the resistance component of the secondary battery during charging and discharging with a large current.

In addition to such charging / discharging conditions, recently, when a multi-cell parallel assembled battery is used, it is not only continuously used under the same load condition but also during normal discharge load and in a short time. In general use, discharge conditions involving heavy load discharge, which is a combination of use under discharge load conditions in which a large current is passed, have been frequently performed.

[0005]

By the way, when charging and discharging the multi-cell parallel assembled battery under the above-mentioned charging and discharging conditions,
It is extremely difficult to control a uniform current to flow between the secondary batteries, and a difference in charge / discharge performance occurs.

When the above-mentioned multi-cell parallel assembled batteries are not continuously used under the same load condition as described above, the same load is applied to all the batteries, and a defect occurs in one battery. As a result, the entire assembled battery is affected, and the service life of the assembled battery is eventually shortened.

It is severe for a battery application to produce a large output in a short time, and all the batteries must have excellent performance under both light and heavy loads. This is because, in the case where multiple cells are used in parallel, if a defect occurs in one secondary battery, the burden is applied to the other batteries as a whole, resulting in an extremely large effect.

When the multi-cell parallel assembled battery, which is repeatedly charged and discharged under such charging and discharging load conditions and used in such a non-uniform state, is used as a power supply device, the difference between the batteries is rapidly increased. Therefore, there is a high possibility of reaching the end of life at an early stage, and there is a possibility that it will be extremely disadvantageous in practical use.

For this reason, various improvement methods for sufficiently maintaining the battery performance have been studied in the case of using a power supply device composed of a multi-cell parallel assembled battery under a use condition in which a heavy load discharge condition is large. For example, there is a method in which all the secondary batteries are discharged to the same state and then charged again. However, even if such a method is performed, it is only possible to make the battery voltage uniform by discharging under a light load discharge condition, and therefore it is not possible to improve the basic performance of each secondary battery. It is not possible to prevent the rapid deterioration of performance due to the discharge cycle.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to easily control the flow of a uniform current between the secondary batteries, and the charge / discharge performance between the secondary batteries. Does not cause a difference in battery performance and prevents a rapid decrease in performance due to charge / discharge cycles, and even if one secondary battery becomes defective, it does not affect the entire battery pack and the life of the battery pack It is an object of the present invention to provide a power supply device capable of extending the power supply.

[0011]

A power supply device according to the present invention has at least one or a plurality of first secondary batteries, and a small internal resistance while having the same nominal voltage as those of the first secondary batteries. Second with good load characteristics and large rated capacity
A secondary battery is connected in parallel to supply an output current to an output device, a fixed resistor is connected in series to the first secondary battery, and a fixed resistor is connected in series to the second secondary battery. A variable resistor is connected to the output device according to the detection value of the fluctuation output current detecting means for detecting the fluctuation of the output current flowing through the output device.
The problem is solved by variably controlling the variable resistance value of the variable resistor within a range of less than or equal to the resistance value of the fixed resistor and greater than 0.

In this case, the fluctuating output current detecting means is
It may be characterized in that the variation of the output current is directly detected.

Further, the fluctuation output current detecting means may detect a fluctuation of the current of the first secondary battery.

[0014]

In the range in which the resistance value of the variable resistor connected in series with the second secondary battery is less than the resistance value of the fixed resistor connected in series with the first secondary battery and is larger than 0, Since it is variably controlled according to the detection value from the output current detection means,
It is possible to easily control the flow of a uniform current between the cells, and to prevent a difference in charge / discharge performance between the cells, and prevent a rapid decrease in performance associated with a charge / discharge cycle.
Further, even if one cell becomes defective, it does not affect the entire assembled battery and the life of the assembled battery can be extended.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Three preferred embodiments (hereinafter, referred to as a first embodiment, a second embodiment and a third embodiment) of a power supply device according to the present invention will be described below.

First, in the first embodiment, as shown in FIG.
Batteries (A) 1, 2, 3 and 4 each having two first secondary batteries connected in series, and having the same nominal voltage as the first secondary battery but a small internal resistance and a heavy load characteristic. well,
A battery (B) 5 in which two second secondary batteries each having a large rated capacity are connected in series is connected in parallel to form batteries (A) 1, 2, 3 and 4 made of the first secondary battery. Are connected in series to fixed resistors 7, 8, 9 and 10, respectively, and a variable resistor 11 is connected to the battery (B) 5 composed of the second secondary battery to supply an output current to the output device 6. It is a device. Here, in batteries (A) 1, 2, 3 and 4, lithium cobalt composite oxide was used as the positive electrode active material, and carbon obtained by heat-treating petroleum pitch at 1000 ° C. in an oxygen atmosphere was used as the negative electrode active material. LiCoO ₂ / C rocking chair type non-aqueous electrolyte secondary battery with a diameter of 20 mm and a height of 50 mm is used as a single cell, and the battery capacity is 1000 mA.
h. Further, the battery (B) 5 is a LiCoO ₂ / C rocking chair type using a lithium cobalt composite oxide as a positive electrode active material and carbon obtained by heat-treating petroleum pitch as a negative electrode active material in an oxygen atmosphere at 1000 ° C. A non-aqueous electrolyte secondary battery with a diameter of 18 mm and a height of 65 mm is used as a single cell, and the battery capacity is 1050 mAh.
Is. The fixed resistors 7, 8, 9 and 10 are fixed resistors for current detection and have a resistance value smaller than the internal resistance of the first secondary battery and the second secondary battery, for example, 1 mΩ.
Is. Further, the variable resistance 11 sets the resistance value arbitrarily by, for example, 0.1 to 1 mΩ by controlling the movement of the sliding piece 12.

The movement control of the sliding piece 12 is performed by the controller 1.
It is done by 5. In addition, the control device 15 also controls the movement of the sliding piece 14, and controls the magnitude of the current supplied (discharged) to the output device 6 by making the resistance value of the variable resistor 13 variable. Further, the control device 15 is also a fluctuating current detecting means for detecting a fluctuation in the output current of the output device 6. The movement of the sliding piece 12 or 14 is controlled by the control device 15 according to the fluctuation of the output current detected by the control device 15. Further, the control device 15 includes an analog / digital (A / D) converter for converting a voltage value (analog value) generated at both ends of the fixed resistors 7, 8, 9 and 10 and the variable resistor 11 into a digital signal. 16 are connected.

The case of discharging the output device 6 in the first embodiment having the above-described structure will be described below. In the first embodiment, the current value flowing in the whole is 1000 mA.
When it is (1C) or less, the control device 15 sets the set value of the variable resistor 11 to the same value as the batteries (A) 1, 2, 3 and 4, that is, 1 mΩ. On the other hand, the current value is 1000 mA
If (1C) is exceeded, the control device 15 sets the set value of the variable resistor 11 to 0.8, 0.6, 0.4, 0.2,
It is gradually reduced to 0.1 mΩ.

As described above, according to the first embodiment, the current value in the output device 6 is detected by the control device 15, and the resistance value of the variable resistor 11 is changed by this value, so that the current value flowing through the entire device is changed. Under a discharge condition of 1 C capacity or less, a uniform discharge current state is set for all batteries, and under a discharge load condition of 1 C capacity or more, the variable resistor 11 connected to the battery (B) 5 is used.
Can be changed so that a large preset current can flow only from the battery (B) 5.

Therefore, in the first embodiment, excessive concentration of current can be prevented at all times, and under heavy load conditions requiring a large current, a larger amount of current flows through the battery (B) 5 having a large capacity. Therefore, the occurrence of defective batteries can be prevented.

Now, the change of the discharge capacity with respect to the number of times of repeating the constant charge / discharge cycle in the first embodiment will be described. In this charge / discharge cycle, the discharge is first performed once with a discharge current of 3 A, then twice with a discharge current of 10 A,
Next, a cycle is performed in which a discharge current of 5 A is applied up to 2.5 V under each discharge condition, and all charging is performed with a current of 6 A for 3 hours to a final voltage of 4.20 V. At this time, the variable resistor 11 is set to 1 mΩ at 3 A, 0.4 mΩ at 10 A, and 1 mΩ at 5 A.
Set to Ω. 3 of the first embodiment under these charge / discharge conditions
The discharge capacity characteristic per battery (A) under the condition A is shown by a solid line in FIG.

FIG. 2 shows Comparative Example 1 and Comparative Example 2 for comparison. In Comparative Example 1, as shown in FIG.
Basically, the configuration is the same as that of the first embodiment, but the variable resistor (reference numeral 1 in FIG. 1 is connected to the battery (B) 5).
Instead of 1), a fixed resistance 17 of 1 mΩ was connected. The rest of the configuration is the same as that of the first embodiment, so its explanation is omitted.

The comparative example 1 shown in FIG. 3 was repeatedly subjected to a charge / discharge cycle test under the same conditions as in the first example, and the discharge capacity in each cycle was recorded. And the discharge capacity characteristics.

Further, the LiCoO ₂ / used in the first embodiment is used.
C Rocking chair Non-aqueous electrolyte secondary battery, diameter 2
1. A rechargeable battery with a height of 0 mm and a height of 50 mm is charged with a charging current of 1 A.
5 hours 4.20V final voltage, discharge current 0.5A 2.5
A case where the charge and discharge cycle in which the battery was discharged to the V cutoff voltage was repeated was set as Comparative Example 2, and the discharge capacity characteristics of one battery (A) thereof are shown in FIG.

The values of the discharge capacity for each cycle number of the first embodiment obtained from the characteristic diagram of FIG. 2 are shown as Comparative Example 1 and Comparative Example 2.
It is shown in Table 1 together with that.

[0026]

[Table 1]

As can be seen from this table, the first embodiment described above is several times better than Comparative Example 1 in which the resistance connected to the battery (B) 5 is a variable resistance so that the resistance is a fixed resistance. It is understood that the first embodiment has the discharge performance, and the first embodiment has substantially the same discharge performance as that of the comparative example 2 under the charging / discharging condition which is milder than the first embodiment.

That is, in the power supply device according to the first embodiment, it is possible to easily control the flow of a uniform current between the batteries, and to prevent a difference in charge / discharge performance between the cells. It is possible to prevent a rapid deterioration in performance associated with charge / discharge cycles, and further, even if one cell becomes defective, the entire assembled battery is not affected and the life of the assembled battery can be extended.

Next, a second embodiment will be described with reference to FIG. In FIG. 4, the same symbols are assigned to the same units as in FIG.

The second embodiment differs from the first embodiment whose configuration is shown in FIG. 1 above in that the resistance value of the variable resistor 11 is set only by the fluctuation of the output current of the output device 6. Is.

That is, in the second embodiment, the value of the variable resistor 11 is controlled to control the discharge according to the fluctuation of the current of the output device 6, and the discharge is controlled between the battery (A) and the battery (B). It is possible to prevent a rapid decrease in performance due to charge / discharge cycles without causing a difference in charge / discharge performance.

Next, a third embodiment will be described with reference to FIG. In FIG. 5 as well, the same symbols are assigned to the same units as in FIG.

The third embodiment is different from the first embodiment whose configuration is shown in FIG. 1 above. It does not depend on the output current on the output device side, but can be changed by changing the current on the battery (A) side only. This is that the resistance value of the resistor 11 is variable.

That is, in the third embodiment, the value of the variable resistor 11 is controlled to control the discharge according to the fluctuation of the current on the battery (A) side, and even if one cell is defective, The entire battery is not affected and the life can be extended.

In the first, second and third embodiments, a battery having a diameter of 20 mm and a height of 50 mm is used as the battery (A), but the internal resistance of the battery at this time is about 40 mΩ. There is almost no effect because the connected resistor has a resistance value of 1 mΩ and is sufficiently small with respect to the internal resistance of the battery. Usually, it is an effective method to select 1/10 to 1/100 of the internal resistance of the battery as the value of this resistor.

On the other hand, it is effective that the variable resistance value can be variably set to 1/20 of the fixed resistance value. As a result, it becomes possible to measure the load current of each battery, monitor and shut off the flow of a large current concentrated in one battery by the control device, and limit the current to an appropriate value. Further, when the load device requires a predetermined set current value or more, the variable resistor is changed to a preset value so that the large current discharge can be used.

Further, in each of the above-mentioned embodiments, with respect to charging, the resistance value is made the same with a current of 1 C or less, but when the current exceeds 1 C due to some charger abnormality, the battery is charged. The connection on the circuit may be switched so that the group is disconnected from the charging circuit.

Further, in the first and second embodiments, as a method of setting the variable resistance, the current of the output device is detected by the control device, and the resistance value of the variable resistor is controlled by the current value at this time. However, by using the current value of the output device for switching the resistor, the variable resistor circuit is turned on and off. When the output is large, only 1/10 of the resistance is turned on, and when the output is small, May be set so that all resistors are turned on.

[0039]

The power supply device according to the present invention is at least
A single or a plurality of first secondary batteries and a second secondary battery having the same nominal voltage as those of the first secondary batteries but a small internal resistance, good heavy load characteristics, and a large rated capacity are connected in parallel. In the power supply device for supplying an output current to the output device, a fixed resistor is connected in series to the first secondary battery, and a variable resistor is connected in series to the second secondary battery,
The variable resistance value of the variable resistor is variably controlled within a range of less than or equal to the resistance value of the fixed resistor and greater than 0 in accordance with the detection value of the fluctuation output current detecting means for detecting the fluctuation of the output current flowing through the output device. Since it is characterized by that, it is possible to easily control the flow of a uniform current between each battery,
It does not cause a difference in charge / discharge performance between each battery, and can prevent a rapid decrease in performance due to charge / discharge cycles.
Even if an individual battery becomes defective, the life of the battery pack can be extended without affecting the entire battery pack.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of a power supply device according to the present invention.

FIG. 2 is a characteristic diagram of the discharge capacity with respect to the number of charge / discharge cycles of the first embodiment shown in FIG.

FIG. 3 is a circuit diagram of Comparative Example 1 used for comparison with the discharge capacity characteristic of the first embodiment in FIG.

FIG. 4 is a circuit diagram of a second embodiment of the power supply device according to the present invention.

FIG. 5 is a circuit diagram of a third embodiment of the power supply device according to the present invention.

[Explanation of symbols]

1, 2, 3, 4 ... Battery (A) 5 ... Battery (B) 6 ... Output device 7, 8, 9, 10 ... Fixed resistance 11, 13 ... Variable resistance 15 ... Control device 16 ... Analog / digital (A / D) converter

Claims (3)

[Claims] 1. At least one or a plurality of first secondary batteries, and a second secondary battery having the same nominal voltage as those of the first secondary batteries but small internal resistance, good heavy load characteristics, and large rated capacity. A secondary battery is connected in parallel to supply an output current to the output device, a fixed resistor is connected in series to the first secondary battery, and a fixed resistor is connected to the second secondary battery in series. A variable resistor is connected to the variable resistor, and the variable resistance value of the variable resistor is set to 0 or less than 0 of the fixed resistor according to the value detected by the variable output current detecting means for detecting the fluctuation of the output current flowing in the output device. A power supply device that is variably controlled within a large range. 2. The power supply device according to claim 1, wherein the fluctuating output current detecting means directly detects a fluctuation in the output current. 3. The fluctuating output current detecting means is the first
2. The power supply device according to claim 1, wherein a change in current of the secondary battery is detected.