JPH09331634A - Charge control equipment of secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly and fully charge all unit cells independently of irregularity of charge amount of the unit cells, by switching a current route bypassing the unit cells to a constant voltage detouring means and a constant current detouring means, on the basis of voltage difference obtained by a voltage difference operating means. SOLUTION: Initial voltages of unit cells after charge is stared are detected with a voltage difference operating means 22, and voltage difference ΔV between unit cells is calculated for each unit cell operated. On the basis of the voltage difference ΔV, the bypass route of a charging current is determined by a bypass route determining means 34. That is, in the initial stage of charging, a current is made to flow in a constant current bypassing means 26 so as to make currents flowing in the unit cells constant, and the voltage difference ΔV between unit cells is corrected to the utmost. Before it reaches full charge, the bypass route is changed from the constant current detouring means 26 to a constant voltage bypassing means 24, and charge is continued in older that the current flowing the unit cells become a constant voltage. Thereby, improving voltage difference correction capability, and charging the respective unit cells uniformly and fully.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for a secondary battery used as, for example, a battery of an electric vehicle, and more particularly to charging each cell battery when charging an assembled battery formed by connecting a plurality of cell batteries in series. The present invention relates to a secondary battery charge control device that suppresses variations.

[0002]

2. Description of the Related Art In addition to lead batteries, nickel-based batteries such as nickel-cadmium batteries and lithium-based batteries such as lithium-ion batteries are being adopted as storage batteries for electric vehicles. Therefore, an assembled battery formed by connecting a plurality of cell batteries in series is used. In this type of secondary battery, if the charge amount of each cell battery is non-uniform, a voltage drop occurs and the cruising range is shortened. It is desirable that the battery be fully charged uniformly.

For this reason, as shown in FIG. 9, when charging a plurality of lithium ion secondary batteries connected in series, the voltage detectors 101, B ₂ are charged to the batteries B ₁ , B ₂ , respectively.
2. Description of the Related Art It is known in the art to provide a relay 102 so as to cut off the charging power source when any one of the batteries B ₁ and B ₂ exceeds a design voltage when a constant current is supplied (for example, , Japanese Patent Laid-Open No. 4-331,425). As a result, overcharge is prevented, short circuit between the positive and negative electrodes of the battery and decomposition of the active material and electrolyte are suppressed, and the reliability of the battery is enhanced.

However, in this charge control device, the charging power source is shut off when the voltage of any one of the cell batteries B ₁ and B ₂ exceeds the design voltage. Therefore, if there is some variation in the amount of charge between the cell batteries B ₁ and B ₂ , overcharging can be prevented before the other batteries reach full charge, and overcharging can be prevented. It cannot be fully charged.

Therefore, in order to make the charging voltage of each battery to be fully charged uniformly, a plurality of batteries B ₁ , B connected in series are connected.
Constant voltage circuit 12 such as Zener diode for each ₂
1, 122 connected in parallel so that the charging voltage is evenly divided among the batteries (see, for example, JP-A-61-20
No. 6,179) is proposed. Figure 1
In the charging control apparatus shown in 0, the voltage from the charging power source is equally divided into cell batteries B _1, B _2, each cell batteries B _1,
When the voltage of B ₂ rises, the Zener diodes 121, 1
Since the current is bypassed to the 22 side, it is possible to prevent overcharging of the cell batteries and to make the charging voltage of each cell battery uniform and fully charged. The Zener diode 12
When one of 1, 122 operates, a timer 130 in which a fixed time is stored in advance is activated, and when the timer 130 times out, charging is terminated.

[0006]

However, in the latter charge control device, if the bypass capacity of the constant voltage circuits 121 and 122 is small, no more current is diverted, so the voltage variation of each cell battery exceeds the bypass capacity. If it is too large, there is a problem that a sufficient effect cannot be obtained.

The present invention has been made in view of the above problems of the prior art, and it is possible to fully charge all the cell batteries evenly regardless of the variation in the charged amount of the cell batteries. An object is to provide a battery charge control device.

[0008]

In order to achieve the above object, a charge control device for a secondary battery according to the present invention according to claim 1 is a charge for controlling an assembled battery composed of one or more cell batteries. Means, a voltage difference calculation means for detecting the voltage of each of the cell batteries to obtain a voltage difference, and a constant voltage provided in parallel with each of the cell batteries so that the current flowing through the cell battery becomes a constant voltage. Detour means, constant current detour means provided in parallel with each of the cell batteries so that the current flowing through the cell battery is a constant current, and the cell based on the voltage difference obtained by the voltage difference calculation means A bypass path determining means for switching a current path bypassing the battery to the constant voltage bypass means and the constant current bypass means;
The charging means is controlled by the constant voltage bypass means or the constant current bypass means.

In the charge control device for a secondary battery according to the first aspect of the present invention, when charging is first started and a charging current is supplied to each cell battery, the voltage of the cell battery starts to rise. The voltage difference between the cell batteries is calculated by the detection by the calculation means. Specifically, the charging current is I (A), the cell battery voltage difference is ΔV (V), and the cell battery charge amount difference is ΔQ.
(C), where the cell battery capacity is C (Ah), and the time difference Δt (h) from the voltage of any one of the cell batteries reaching a predetermined value to the voltage of all cell batteries reaching the predetermined value ,

The relationship of ΔV = ΔQ / C = I · Δt / C (1) holds. Here, since the charging current I and the battery capacity C are known, the voltage difference ΔV can be obtained by detecting the time difference Δt.

Next, based on this voltage difference ΔV, the bypass route of the charging current is determined by the bypass route determining means. For example, when the voltage difference ΔV between the cell batteries is small, it is considered that the capacity of the detour path will not exceed the capacity even if the capacity of the bypass path is slightly small. Divert the current to the detour means. As a result, a current corresponding to the voltage of the cell battery is divided into each cell battery, and each cell battery can be uniformly and fully charged. On the other hand, when the voltage difference ΔV between the cell batteries is large and the current is bypassed to the constant voltage bypass means, the bypass current may exceed the capacity. Therefore, in the initial stage of charging, the constant current bypass means detours the current so that the current flowing through the cell battery is a constant current, and the voltage difference between the cell batteries is corrected as much as possible. Then, before reaching full charge, the detour path is switched from the constant current detouring means up to that point to the constant voltage detouring means, and charging is continued so that the current flowing through the cell battery becomes a constant voltage. As described above, when the voltage difference between the cell batteries is large, the voltage difference is corrected by diverting the current to the constant current bypass means, so even if the constant voltage bypass means is switched to, the constant voltage bypass means is switched. It takes a long time to reach the bypass capacity, and as a result, the voltage difference correction capability is improved, and each cell battery can be uniformly and fully charged.

Further, in the secondary battery charge control device according to the second aspect, the detour timing to the constant voltage detouring means or the constant current detouring means is based on the voltage difference obtained by the voltage difference computing means. It is characterized by being controlled.

In the charge control device for a secondary battery according to the present invention, the constant voltage detouring means diverts the current so that the current flowing through the cell battery becomes a constant voltage, or the current flowing through the cell battery becomes a constant current. The detour timing of whether or not to detour the current to the constant current detouring means is changed and controlled by the voltage difference. For example, when the variation in the voltage difference is large, if the threshold voltage value of the detour timing in each cell battery is set to be lower than the full charge voltage, the cell battery with a smaller charge capacity is sufficiently charged accordingly. It will be. Therefore, as compared with the charge control device for the secondary battery according to claim 1,
The detour time of the constant voltage detouring means and the constant current detouring means becomes long, and the cell battery can be more fully charged to a uniform level.

According to a third aspect of the present invention, there is provided a secondary battery charge control device, wherein a battery temperature detecting means for detecting respective temperatures of the cell batteries, a voltage difference obtained by the voltage difference calculating means and the battery temperature detecting means. The constant voltage bypass means further comprising: a bypass time determining means for determining a bypass time of a current flowing through the constant voltage bypass means based on the battery temperature detected by; and a timer for setting a bypass time from the bypass time determining means. Means, the constant current bypass means, or the timer controls the charging means.

Further, in the charge control device for the secondary battery according to claim 4, the voltage difference ΔV (V) is the charge current I
(A), the capacity of the cell battery is C (Ah), and the time difference from the voltage of any one of the cell batteries reaching the predetermined value to the voltage of all the cell batteries reaching the predetermined value is Δt.
In the case of (h), it is characterized by being calculated by ΔV = I · Δt / C.

Further, in the charging control device for the secondary battery according to claim 5, the charging current is I during the detour time tb (h).
(A), the capacity of the cell battery is C (Ah), the voltage difference obtained by the voltage difference calculation means is ΔV (V), and the cell temperature of the cell battery determined based on the battery temperature detected by the battery temperature detection means. When the internal resistance is r (mΩ), it is characterized by being determined by tb = (ΔV−rI) · C / I.

In the secondary battery charge control device according to the third aspect of the invention, in addition to the control of the charging means by the constant voltage bypass means or the constant current bypass means, based on the voltage difference between the cell batteries and the battery temperature of the cell batteries. The charging means is also controlled by the detour time.

That is, the time tb for detouring to the constant voltage detouring means takes into consideration the voltage difference ΔV obtained by the above equation (1) and the battery temperature detected by the battery temperature detecting means. Although the internal resistance r of the battery decreases as the battery temperature T increases,
The relationship between the battery temperature T and the internal resistance r of the battery is stored in advance in the detour time determining means, and the internal resistance r of the battery corresponding to the battery temperature T detected by the battery temperature detecting means is quoted from the map. , The voltage value rI which is the product of the internal resistance r and the charging current I is used as a correction value. Here, between the voltage V, the current I, the battery capacity C, and the energization time t, t =
Since there is a relationship of V · C / I, if ΔV is corrected by rI,

(2) tb = (ΔV−rI) C / I (2) Therefore, as in the charge control device for the secondary battery according to the fifth aspect, the detour time tb to the constant voltage detour means is determined by the detour time determination means using the equation (2).

When the detour time is determined based on the voltage difference between the cell batteries and the battery temperature, this is set in the timer. Then, charging is stopped when the detour current flows in all the cell batteries in excess of the detour capacity of the constant voltage detour means, or when the detour time set by the timer elapses, whichever condition is satisfied. In the former case, signals are sent from the constant voltage bypass means to the charging means, and in the latter case, signals are sent from the timer to the charging means.

[0019]

According to the charge control device for a secondary battery of the present invention described in claim 1, the constant voltage bypass means is provided when the voltage difference between the cell batteries is small, and the constant current bypass means is provided when the voltage difference is large. By switching the charging current bypass path to the constant voltage bypass means and to the constant voltage bypass means, the bypass time can be lengthened, and as a result, even if the charge amount of the cell battery varies, it is not affected by these and always The cell battery can be fully charged. Further, even if the bypass capacity is small, the bypass time is long, so that the correction capability is improved and each cell battery can be fully charged.

According to the rechargeable battery charge control device of the second aspect, the detour time can be made longer than that of the rechargeable battery charge control device of the first aspect. Can be more fully charged.

According to the charge control device for the secondary battery described in claim 3, in addition to the effect according to the invention described in claim 1, it is possible to optimize the termination of charging according to the voltage of each cell battery and the termination of charging by the bypass time. Can be controlled.

According to the charge control device for a secondary battery of claim 4, in addition to the effect according to the invention of claim 3, all the cells are charged after the voltage of any one of the cell batteries reaches a predetermined value. The voltage difference of the cell battery can be obtained only by measuring the time difference until the voltage of the battery reaches the predetermined value.

Further, according to the charge control device for the secondary battery of the fifth aspect, in addition to the effect according to the invention of the third or fourth aspect, the detour time is determined while considering the temperature difference in the voltage difference. It is possible to fully charge each cell battery more accurately.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a charge control device for a secondary battery according to the present invention.
0, constant voltage bypass means 24, constant current bypass means 26, bypass path determination means 34, voltage difference calculation means 22, battery temperature detection means T, bypass time determination means 32, and timer 40.

The charging means 10 controls charging of an assembled battery composed of one or more cell batteries, and starts and stops charging. The constant voltage bypass means 24 is a charging current bypass circuit that is provided in parallel with each of the cell batteries and is configured so that the current flowing through the cell batteries has a constant voltage. On the other hand, the constant current bypass means 26 is a charging current bypass circuit that is provided in parallel with each of the cell batteries and configured so that the current flowing through the cell batteries becomes a constant current. The detour path determining means 34 determines whether the detour path of the charging current is the constant voltage detouring means 24 or the constant current detouring means 26, and is configured by, for example, a microcomputer.

The voltage difference calculating means 22 has a function of detecting the respective voltages of the cell batteries and a voltage difference ΔV between the cell batteries.
And the determined voltage difference is sent to the detour route determining means 34 and the detour time determining means 32 to determine the charging current detour route and the detour time tb described later. Be served. The battery temperature detecting means T is
It is composed of a temperature sensor and the like, and detects the temperature of each cell battery and sends the temperature information to the detour time determining means 32.

On the other hand, the detour time determining means 32 is composed of, for example, a microcomputer, and the constant voltage detouring means is determined by the voltage difference ΔV input from the voltage difference calculating means 22 and the battery temperature input from the battery temperature detecting means T. The bypass time tb of the current flowing through 24 is determined. The bypass time tb determined here is sent from the bypass time determining means 32 to the timer 40 and set. The timer 40 sends a command signal to the charging means 10 to stop the charging when the set detour time is up. In addition to stopping the charging by the timer 40, when all the cell batteries are fully charged while the constant current bypass means 26 is being used, and when the constant voltage bypass means 24 is being used, the constant voltage bypass means is used. When the bypass capacity of 24 is exceeded, a command signal is sent from the constant current bypass means 26 or the constant voltage bypass means 24 to the charging means 10 to stop charging.

The rechargeable battery charge control device of the present invention having such a function is preferably used for charging an assembled battery formed by connecting a plurality of cell batteries in series, such as a battery of an electric vehicle. . 2 is a block diagram showing an embodiment of a secondary battery charging control device of the present invention, FIG. 3 is a circuit diagram showing an electronic circuit example of a parallel circuit 20 _n of the same embodiment, and FIG. 4 is a microcomputer of the same embodiment. Time difference due to 30 Δ
It is a block diagram which shows the example of a digital circuit which calculates | requires t.

First, as shown in FIG. 2, the assembled battery to be charged is composed of a plurality of cell batteries B ₁ , B ₂ , ..., B _n connected in series, and the charging voltage is applied to one end (positive electrode end) 1 a thereof. The other end (negative electrode end) 1b is grounded via a relay 10 which is a charging means. These cell batteries B ₁ , B
_A constant current flows through ₂ , ..., _Bn by a variable constant current control circuit (not shown).

Parallel cells 20 ₁ , 20 ₂ , ..., 20 _n are connected in parallel to the respective cell batteries B ₁ , B ₂ , ..., B _n , and these parallel circuits 20 ₁ , 20 ₂ , … 、
20 _n are the cell batteries B ₁ , B ₂ , ..., B _n , _{respectively.}
Voltage detection circuit 22a that controls the function of sending out this signal to the microcomputer 30 and bypass circuits 24 and 26 that control the function of bypassing the charging current flowing in the battery pack. have. The bypass circuit includes a constant voltage bypass circuit 24 that bypasses the charging current so that the current flowing through the cell battery B _n becomes a constant voltage, and a charging current that causes the current flowing through the cell battery B _n to become a constant current. There is a constant current bypass circuit 26 that bypasses.

FIG. 3 is a circuit diagram showing an electronic circuit example of the parallel circuit 20 _n, are described by way of the parallel circuit 20 _n provided in one cell battery B _n as an example, all the other cells The parallel circuit of batteries is similarly configured. As shown in the figure, first, the voltage detection circuit 22 that controls the first function
a has a comparator 221a, and the + of this comparator 221a
Power supply terminals is connected to the positive terminal 1a of the cell batteries B _n - power supply terminal is connected to a negative electrode 1b of the cell batteries B _n. The voltage of the Zener diode 222a connected in parallel to the cell battery B _n is applied to the inverting input terminal (−) of the comparator 221a, while the non-inverting input terminal (+) of the comparator 221a is The voltage at the connection midpoint of the two resistors 223a and 224a connected between the + power supply terminal and the-power supply terminal is applied. The output terminal of the comparator 221a is connected to the transmission photocoupler P ₁ .

Therefore, charging is started and the cell battery B _n
Voltage of the Zener diode 22 increases.
Until the voltage exceeds a predetermined voltage value V ₀ determined by the ratio of the voltage of a and the resistances 223a and 224a, the comparator 221a.
Since the output terminal of continues to Lo, the photo coupler P for transmission
₁ is in the ON state, but when the voltage of the cell battery B _n exceeds the predetermined voltage value V ₀ , the output terminal of the comparator 221a becomes Hi.
Then, the transmission photocoupler P ₁ is turned off, and a signal is sent from the transmission photocoupler P ₁ to the time detection circuit 22b (see FIG. 4) described later. This judgment corresponds to step 10 shown in FIG.

Further, as another voltage detector circuit 22a, a comparator 225a, + supply terminal of the comparator 225a is is connected to the positive terminal 1a of the cell batteries B _n - power terminal cell battery B _n Is connected to the negative electrode end 1b. Further, the inverting input terminal (-) of the comparator 225a has a Zener diode 222a connected in parallel with the cell battery _Bn.
Meanwhile, the voltage at the connection midpoint of the two resistors 223a and 224a connected between the + power supply terminal and the − power supply terminal is received by the non-inverting input terminal (+) of the comparator 225a. Is applied via the photo coupler P ₂ . The output terminal of the comparator 225a is connected to the npn transistor 247 via the receiving photocoupler P ₄ and the resistor 242.
Connected to the base. Further, a transmission photocoupler P ₃ is mounted in parallel between the positive terminal 1a of the cell battery B _n and the output terminal of the comparator 225a.

Therefore, with the receiving photocoupler P ₂ in the conducting state, charging is started and the voltage of the cell battery B _n rises, and this voltage depends on the voltage of the Zener diode 22a and the ratio of the resistors 223a and 224a. The output terminal of the comparator 225a continues Lo until the predetermined voltage value that is determined is exceeded, so the transmission photocoupler P ₃ is in the ON state, but when the voltage of the cell battery B _n exceeds the predetermined voltage value, the comparator 221a output terminal becomes Hi, the transmission photo-coupler P ₃ is turned off the transmission photo-coupler P ₃
A signal is sent from the microcomputer to the microcomputer 30. This judgment corresponds to steps 18 and 28 shown in FIG.

[0035] The above is a specific configuration of the voltage detection circuit 22a which controls a first function of the parallel circuit 20 _n, the parallel circuit 20 _n, the bypass circuit 24,2 governing a second function
6. That is, as shown in FIG. 3, two consumption resistors 245 and 248 are connected in series between the positive electrode end 1 a and the negative electrode end 1 b of the cell battery B _{n with} the npn transistor 247 interposed therebetween, and the transistor 247 is connected. Since the output terminal of the comparator 225a is connected to the base of, when the receiving photocouplers P ₂ and P ₄ are made conductive,
The transistor 247 is turned on via the resistor 242, which causes a current to flow through the consumption resistors 245 and 248. This constitutes the constant current bypass circuit 26.

On the other hand, the output terminal of the comparator 225a is connected to the npn transistor 249 via the receiving photocoupler P _5.
, The collector of the transistor 249 is connected to the positive terminal 1a of the cell battery B _n , and the emitter is applied to the non-inverting input terminal (+) of the amplifier 241 via the resistor 250. The + power supply terminal of the amplifier 241 is connected to the positive terminal 1a of the cell battery B _n , and-
The power supply terminal is connected to the negative terminal 1b of the cell battery B _n , and the output terminal of the amplifier 241 is np via a resistor 242.
It is connected to the base of the n-transistor 247. A consumption resistor 246 is provided in parallel with the consumption resistor 248 and is connected to the emitter side of the npn transistor 243. The base of the transistor 243 is connected to the positive terminal 1a of the cell battery B _n via the receiving photocoupler P _6.
, And the collector side is connected to the emitter side of the transistor 247.

Further, a Zener diode 244 is connected in series between the resistor 250 on the emitter side of the npn transistor 249 and the negative terminal 1b of the cell battery B _n . The inverting input terminal (-) of the amplifier 241 has n
A loop is formed so that the voltage on the emitter side of the pn transistor 243 is applied.

Therefore, when the receiving photocouplers P ₂ and P ₄ are in the conductive state and the voltage of the cell battery B _n exceeds the predetermined voltage, and the receiving photocouplers P ₅ and P ₆ are in the conducting state, the npn transistor 247 and Since the transistor 243 is turned on as well as the transistor 249 is turned on, a current flows through the consumption resistors 245, 246 and 248. At this time, since the emitter-side potential of the npn transistor 243 is applied to the inverting input terminal (−) of the amplifier 241, the voltage applied to the inverting input terminal (−) of the amplifier 241 is the non-inverting input terminal (+). ), That is, equal to the voltage of the Zener diode 244,
A negative loop is formed between the emitter of the npn transistor 243 and the inverting input terminal (−) of the amplifier 241. As a result, a constant current determined by the voltage of the Zener diode 244 flows through the npn transistors 247, 243 and the consumption resistances 245, 246, 248, and the cell battery B
consumption resistance of the charging current tends to flow to the _n 245,246
Can be bypassed to the side. This constitutes the constant voltage bypass circuit 24.

A Zener diode 252 and resistors 253 and 254 are connected in parallel with the consumption resistor 245. While the voltage of the Zener diode 252 is applied to the non-inverting input terminal (+) of the comparator 251, The voltage at the midpoint of connection between the two resistors 253 and 254 is applied to the inverting input terminal (-). Further, since the transmission photocoupler P7 is connected to the output terminal of the comparator 251, when the voltage across the consumption resistor 245 exceeds a predetermined voltage value determined by the ratio of the Zener diode 252 and the resistors 253, 254, the transmitter photocoupler P7 is transmitted. A signal is sent from the photocoupler P7 to the microcomputer 30. This determination corresponds to step 36 in the flowchart shown in FIG.

On the other hand, as shown in FIG. 4, the output from each transmission photocoupler P _{1 of} the parallel circuits 20 ₁ , 20 ₂ , ..., 20 _n described above is output from the microcomputer 30 which is the voltage difference calculating means 22. It is input to the time detection circuit 22b.
The time detection circuit 22b has an AND circuit 221b and an O circuit 221b to which signals from the transmission photocoupler P ₁ are input, respectively.
R circuit 222b, and the output terminal of these AND circuit 221b and the output terminal of OR circuit 222b are clock 2
23b.

That is, any one of the photo couplers P ₁
When signals from all photocouplers P ₁ are input, signals are output from the output terminal of the OR circuit 222b to the clock 223b.
A signal is output from the output terminal of the D circuit 221b to the clock 223b, and an OR signal is output from the clock 223b.
The time Δt from the input of the signal from the circuit 222b to the input of the signal from the AND circuit 221b is measured, and the result Δt is output to the CPU of the voltage difference calculation means 22 in the microcomputer 30.

Before charging, each cell battery B ₁ , B ₂ ,
_If the amount of charge of B _n varies, the cell battery close to full charge reaches the predetermined voltage V ₀ immediately, while the cell battery close to empty charge reaches a predetermined voltage V ₀ for a considerable time. Therefore, the time required for the battery voltage of each of the cell batteries B ₁ , B ₂ , ..., B _n to reach the predetermined voltage V ₀ also varies accordingly. Therefore, the time difference Δ measured here
t is each of the cell batteries B ₁ , B ₂ , ..., Before starting charging.
It can be said that this is a parameter that potentially has a difference (variation) in the charging capacity of B _n . Therefore, in the present embodiment, the voltage difference ΔV between the cell batteries B ₁ , B ₂ , ..., B _n is calculated from the time difference Δt, and the constant voltage bypass circuit 24 or the constant current bypass circuit is used depending on the magnitude of the voltage difference ΔV. It is determined whether the circuit 26 is used. Further, this voltage difference ΔV is also one factor that determines the time tb of the charging current flowing to the constant voltage bypass circuit 24.

That is, as shown in FIG. 6, a predetermined value predetermined by the final charging current value is stored in the microcomputer 30, and the threshold voltage for determining the bypass route is selected. According to the predetermined voltage (threshold voltage) map shown in FIG. 6, when the final charging current is small,
The threshold voltage value is increased, and the charging current is diverted to the constant voltage bypass circuit 24 even if the voltage difference ΔV between the cell batteries is somewhat large. This is because when the final charging current is small, there is little risk of exceeding the bypass capacity even if constant voltage bypass is performed. Therefore, when the final charging current is large, the threshold voltage value is reduced so that even if the voltage difference ΔV is small, it is diverted to the constant current bypass circuit 26 to correct the voltage difference and then diverted to the constant voltage bypass circuit 24. To

Further, regarding the time tb of the charging current flowing to the constant voltage bypass circuit 24, the respective cell batteries B ₁ and B to be obtained are determined.
₂ , ..., B _n voltage difference ΔV (V), each cell battery B ₁ ,
When the difference between the charge amounts of B ₂ , ..., B _n is ΔQ (c) and the capacity of each cell battery B ₁ , B ₂ , ..., B _n is C (Ah),

## EQU00003 ## The relationship of .DELTA.V = .DELTA.Q / C is established, the charging current I (A) flowing through the battery pack, and the voltage of any one of the cell batteries reaches a predetermined value, and then all the cell batteries have a predetermined value. Difference Δt before reaching
Between (h) and the difference ΔQ in the charge amount of each cell battery,

Since there is a relation of ΔQ = I · Δt, the voltage difference Δ of each cell battery to be obtained
V is

[Expression 5] ΔV = I · Δt / C (1) Here, charging current I and battery capacity C
Is known, the voltage difference ΔV can be obtained from the equation (1) by detecting the time difference Δt by the time detection circuit 22b. This voltage difference ΔV is sent to the detour time determining means in the microcomputer 30.

By the way, as described above, the internal resistance of the battery fluctuates according to the battery temperature, and the internal resistance of the battery decreases when the battery temperature is high. In determining the time tb, the temperatures of the cell batteries B ₁ , B ₂ , ..., B _n are also taken into consideration.

[0046] That is, as shown in FIG. 2, each cell batteries B _1, B _2, ..., the B _n, the temperature sensors T ₁ is a battery temperature detecting unit, T _2, ..., T _n are respectively provided The output signals of these temperature sensors T ₁ , T ₂ , ..., T _n are sent to the detour time determining means 32 of the microcomputer 30. In the detour time determining means 32, a map showing the relationship between the battery internal temperature and the battery internal resistance is stored in the ROM or the like, and the battery internal resistance r is calculated from the map based on the temperature information from the temperature sensor T _n. Quote.

The detour time determining means 32 corrects the voltage difference ΔV using the internal resistance r quoted from the map. Specifically, the voltage value rI which is the product of the internal resistance r of the battery and the charging current I is used as the correction value. Here, between the voltage V, the current I, the battery capacity C, and the energization time t, t =
Since there is a relationship of V · C / I, if ΔV is corrected by rI,

Since tb = (ΔV−rI) C / I (2) and the charging current I and the battery capacity C are known,
The constant voltage bypass circuit 2 is obtained by substituting the voltage difference ΔV obtained by the voltage difference calculating means 22 and the internal resistance r obtained from the output from the temperature sensor T _n into the above equation (2).
The detour time tb to 4 is determined. This detour time tb
Indicates not only the variation in the charge amount of each cell battery B ₁ , B ₂ , ..., B _n before charging, but also the variation of each cell battery B ₁ , B ₂ ,
The control value takes into account the temperature fluctuation of B _n .

The detour time tb determined by the detour time determining means 32 is set in the timer 40 as shown in FIGS. As shown in FIG. 2, the timer 40 is connected to the relay 10 that starts / stops charging,
When the set detour time tb expires, a command signal is output to the relay 10 so as to cut off the charging current.
Further, even before the detour time tb set in the timer 40 is reached, when the voltage across the consumption resistor 245 detected by the transmission photocoupler P ₇ exceeds a predetermined value, the bypass capacity is exceeded and charging is performed. A command signal is output from the microcomputer 30 to the relay 10 in order to terminate the operation.

As for the detour time tb set in the timer 40, an appropriate time corresponding to the final charging current value is previously verified as shown in FIG. It is also possible to store it in 30 and sequentially cite it.

Next, the specific operation will be described. FIG. 5 is a flow chart showing the operation of the present embodiment, in which a plurality of cell batteries B ₁ , B ₂ , ..., B _n are connected in series, a charging voltage is applied to the positive terminal 1a of these assembled batteries, and a charging current is applied. When I is supplied, the charging current I flows through each of the cell batteries B ₁ , B ₂ , ..., B _n, and the voltage gradually rises. At this time, the voltage detection circuit 22a _n (comparator 221a shown in FIG. 3) detects the voltage of each cell battery B _n and determines whether it has reached a predetermined voltage V ₀ (step 10). For cell batteries B _n the battery voltage has not reached this predetermined voltage V _0, but it continues to flow the charging current I, for the cell batteries B _n reaches a predetermined voltage V _0, that the transmission photocoupler P ₁ A signal to that effect is sent to the time detection circuit 22b, and the voltage difference Δ
V is calculated (step 12). This calculation is obtained by the above-mentioned formula (1).

Next, the voltage difference Δ found in step 12
It is determined whether V is larger or smaller than a predetermined value of the voltage difference quoted from the predetermined voltage map shown in FIG. 6 (step 14). When the voltage difference ΔV is larger than the predetermined value, that is, when the variation between the cell batteries is large and there is a high possibility that the bypass capacity will be exceeded in the constant voltage bypass, the process proceeds to step 16 and the constant current bypass command is sent. Specifically, in FIG. 3, receiving photocouplers P ₂ and P
A signal for conducting ₄ is sent from the microcomputer 30. As a result, the input line to the non-inverting input terminal of the comparator 225a is connected.
When the voltage value detected by 25a exceeds the full charge voltage, the transistor 247 is turned on in step 20, and a bypass current flows through the consumption resistors 245 and 248.

When all the cell batteries have reached full charge in step 22, the charging is terminated because no further charge is required, but in this step, one of the cell batteries has not reached full charge. In this case, the process proceeds to step 24 and the constant current bypass circuit 26 is applied to all the cell batteries.
Judge whether or not a current has flowed through. Specifically, the determination is made based on the output signal of the transmission photocoupler P ₃ .

If the result of determination in step 24 is that current is flowing in all constant current bypass circuits 26,
Although some cell batteries have not reached full charge, the variations at the beginning of charging have been corrected. Therefore, in step 26, the voltage is changed to the constant voltage bypass to uniformly charge all the cell batteries. That is, in step 30, FIG.
A signal for making the receiving photocouplers P ₅ and P ₆ conductive is sent from the microcomputer 30 to turn on the transistors 249 and 243. As a result, a current flows through the consumption resistors 245, 248 and 246.

In step 32, the detour time tb obtained from the above-mentioned voltage difference ΔV (or quoted from the timer time map shown in FIG. 7) is set in the timer 40, and the timer is set regardless of the charged state of the cell battery. Charging is completed by the time up of 40 (step 34). As a result, overcharge can be prevented and the life of the cell battery can be extended. Even before the detour time tb by the timer 40, in step 36, when the current flowing through the constant voltage bypass circuit 24 has exceeded the capacity, the charging is terminated. This judgment is made by the comparator 251 shown in FIG.
Then, a signal is sent from the transmission photocoupler P ₇ to the microcomputer 30.

On the other hand, when the voltage difference ΔV in step 14 is smaller than the predetermined value, that is, when the voltage variation between the cell batteries is small and the bypass capacity of the constant voltage bypass circuit 24 can suffice, the constant voltage bypass circuit is directly used. Divert 24 the charging current. Specifically, the receiving photocouplers P ₂ , P ₄ , P ₅ and P ₆ are made conductive, and it is determined in step 28 whether the cell battery voltage has reached the full charge voltage. This judgment is performed by the comparator 225a. When the output terminal of the comparator 225a becomes Lo, the transistor 247 is turned on. Therefore, the constant voltage bypass circuit 24
An electric current will flow through. The following operation is the same as that described above.

As described above, according to the charge control device for a secondary battery of the present embodiment, the bypass path of the charging current is determined by the voltage difference ΔV of each cell battery B _n , so that the charge amount of the cell battery varies. However, each cell battery B _n can always be fully charged while correcting these. Further, it is possible to optimally control the end of charging according to the voltage of each cell battery B _{n and} the end of charging according to the bypass time. In addition to this, even if the bypass capacity is small, the variation is corrected by using the constant current bypass circuit 26, so that there is no possibility of overcapacity, and each cell battery B _n can be fully charged.

FIG. 8 is an electronic circuit diagram showing another embodiment of the secondary battery charge control device of the present invention, and is a diagram corresponding to FIG. In the present embodiment, the electronic resistor 226a is connected to the inverting input terminal (−) of the comparator 225a, and the resistance value changes by receiving a signal from the microcomputer 30. This is step 18 shown in FIG.
And 28, the threshold voltage value is appropriately changed, which means that the timing for starting the constant current bypass or the constant voltage bypass can be selected. For example, the full charge voltage is V ₂₁ (V), the charging current is I (A), the bypass capacity is Ib (A), the battery capacity is Q (Ah), the internal resistance of the battery is r (mΩ), and the charging time is t. ₂ (Hr), when the time from 0 to t ₂ is t ₃ (Hr), the voltage V ₄ of the highest voltage cell battery is V ₄ = V ₂₁ − (I−Ib) (t ₂ −t ₃ ) / Q + (I-
Since it is represented by Ib) r, the bypass is started by setting this voltage value V ₄ as a threshold value.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention. For example, the parallel circuit 20 _n of the present invention is not limited to the specific configuration shown in FIGS. 2 and 3 or 8 and can be variously configured by an analog circuit and / or a digital circuit. Further, the battery pack to be charged is made up of at least one cell battery, and the number and capacity thereof are not limited at all.

[Brief description of drawings]

FIG. 1 is a block diagram showing a charge control device for a secondary battery of the present invention.

FIG. 2 is a block diagram showing an embodiment of a secondary battery charge control device of the present invention.

FIG. 3 is a circuit diagram showing a parallel circuit shown in FIG.

FIG. 4 is a block diagram showing an embodiment of the microcomputer shown in FIGS. 2 and 3.

5 is a flowchart showing the operation of the embodiment shown in FIG.

FIG. 6 is a graph showing a predetermined voltage map.

FIG. 7 is a graph showing a timer time map.

FIG. 8 is a circuit diagram showing a parallel circuit according to another embodiment of the secondary battery charge control device of the present invention.

FIG. 9 is a circuit diagram showing a conventional secondary battery charge control device.

FIG. 10 is a circuit diagram showing a conventional secondary battery charge control device.

[Explanation of symbols]

10 ... Relay (charging means) 20 _n ... Parallel circuit 22a ... Voltage detection circuit (voltage difference calculation means) 22b ... Time detection circuit (voltage difference calculation means) 24 ... Constant voltage bypass circuit (constant voltage detour means) 26 ... Constant current Bypass circuit (constant current detouring means) 30 ... Microcomputer 32 ... Detouring time determining means 34 ... Detouring route determining means 40 ... Timer _Bn ... Cell battery _Tn ... Temperature sensor (battery temperature detecting means) _Pn ... Photocoupler

Claims (5)

[Claims] 1. A charging unit that controls charging of an assembled battery composed of one or more cell batteries, a voltage difference calculation unit that detects a voltage difference between each of the cell batteries and obtains a voltage difference, and a charging unit that flows through the cell battery. A constant voltage bypass means provided in parallel with each of the cell batteries so that the current becomes a constant voltage, and a constant voltage provided in parallel with each of the cell batteries so that the current flowing through the cell battery becomes a constant current. Current diversion means,
The constant voltage bypass means includes a bypass path determination means for switching a current path bypassing the cell battery to the constant voltage bypass means and the constant current bypass means based on the voltage difference obtained by the voltage difference calculation means. Alternatively, a charging control device for a secondary battery, wherein the charging means is controlled by the constant current bypass means. 2. The detouring timing to the constant voltage detouring means or the constant current detouring means is controlled on the basis of the voltage difference obtained by the voltage difference calculating means. Secondary battery charge control device. 3. The constant voltage bypass based on a battery temperature detecting means for detecting respective temperatures of the cell batteries, a voltage difference obtained by the voltage difference calculating means and a battery temperature detected by the battery temperature detecting means. Further comprising a detour time determining means for determining a detour time of a current flowing through the means, and a timer for setting a detour time from the detour time determining means,
The charge control device for a secondary battery according to claim 1 or 2, wherein the charging means is controlled by the constant voltage bypass means, the constant current bypass means, or the timer. 4. The voltage difference ΔV (V) is a charging current I
(A), the capacity of the cell battery is C (Ah), and the time difference from the voltage of any one of the cell batteries reaching the predetermined value to the voltage of all the cell batteries reaching the predetermined value is Δt.
The charging control device for a secondary battery according to claim 1, wherein when (h) is set, ΔV = I · Δt / C is calculated. 5. The detour time tb (h) is a charging current I (A), a capacity of the cell battery is C (Ah), a voltage difference obtained by the voltage difference calculating means is ΔV (V), and When the internal resistance of the cell battery determined based on the battery temperature detected by the battery temperature detecting means is r (mΩ), it is determined by tb = (ΔV−rI) · C / I. 2 according to claim 3 or 4
Secondary battery charge control device.