JPH09238430A - Charging controller for secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To charge all cells fully and uniformly regardless of variations in the charging values and temperatures of the cells. SOLUTION: If a charging current is denoted by I, the capacity of a cell is denoted by C, a time difference since the voltage of one of the cell batteries reaches a required value till the voltage of all the cell batteries reach the required value is denoted by Δt and the internal resistance of a battery is denoted by (r), the voltage difference ΔV of that cell battery is obtained by a formula: ΔV=I.Δt/C. The internal resistance (r) of the battery is obtained from a battery temperature detected by a temperature sensor Tn and a detouring time tb to a charging current detouring circuit is determined by a formula: tb=(ΔV-rI)C/I. The detouring time tb is set in a timer 40. If one of the conditions that (1) charging currents of all the cells Bn flow through charging current detouring means 20n and (2) the detouring time tb' set in the timer 40 passes is satisfied, the charging is discontinued.

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 desired that the battery be fully charged uniformly.

Therefore, when charging a plurality of lithium-ion secondary batteries connected in series, as shown in FIG. 6, the voltage detectors 101, ₁ are connected to the batteries B ₁ , B ₂ , respectively.
It is known in the art to provide 02 to output to the relay 110 so as to cut off the charging power source when any one of the batteries B ₁ and B ₂ exceeds the design voltage.
-331,425 reference). 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, when any one of the cell batteries B ₁ and B ₂ exceeds the design voltage, the charging power source is shut off. Therefore, variations in the charge amount between the cell batteries B ₁ and B ₂ occur. When the value is large, charging ends before the other batteries reach full charge, and overcharging can be prevented, but it is not suitable for an assembled battery in which each cell battery is desired to be fully charged uniformly.

On the other hand, in order to make the charging voltage of each battery uniform, a constant voltage circuit 121, 122 such as a Zener diode is connected in parallel to each of a plurality of batteries B ₁ , B ₂ connected in series, and the charging voltage is changed. It is also proposed to divide the battery into each battery evenly (see, for example, Japanese Patent Laid-Open No. 61-206,179). That is, as shown in FIG. 7, in the charge control device, 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, overcharging of the cell batteries can be prevented and the charging voltage of each cell battery can be made uniform. In addition, the Zener diodes 121 and 12
When one of the two operates, a timer 130 in which a fixed time is stored in advance is activated, and when the timer 130 times out, charging is finished.

[0006]

As described above, the conventional charging control is a system that terminates charging according to the two conditions of the voltage of each cell battery and the charging time. That is, when one of the cell batteries reaches the specified voltage or when the predetermined charging time is up, the charging operation is terminated regardless of the charged amount of the other cell battery.

Therefore, when the temperature of the cell battery rises and the internal resistance of the cell battery decreases, a large amount of current flows into the cell battery and the battery voltage rises sharply. Therefore, the charging of the uncharged cell battery will be terminated. It is also possible to shorten the charging time depending on the battery temperature, but depending on the variation in the charge amount of each cell battery, the charging time set by the timer is reached before all the cell batteries are fully charged, After all, an uncharged cell battery will remain.

The present invention has been made in view of the problems of the prior art as described above, and uniformly charges all the cell batteries regardless of variations in the charged amount of the cell batteries and the temperature of the cell batteries. An object of the present invention is to provide a charge control device for a secondary battery that can be used.

[0009]

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, charging current bypass means that is provided in parallel with each of the cell batteries and is capable of bypassing the current flowing through the cell batteries, and voltage difference calculation means that detects the voltage of each of the cell batteries and obtains a voltage difference. A current flowing through the charging current detouring means based on a battery temperature detecting means for detecting respective temperatures of the cell batteries, and a voltage difference obtained by the voltage difference calculating means and a battery temperature detected by the battery temperature detecting means. And a timer for setting the detour time from the detour time determining means, the current flowing through the charging current detouring means or the timer. And controlling said charging means based on the detour time.

Further, in the charge control device for the secondary battery according to the second aspect, 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 charge control device for the secondary battery according to claim 3, 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 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 charging current is detected by the means, and when it becomes higher than a predetermined set value, the charging current is passed to the charging current bypass means. Further, when the charging current starts to flow to the charging current bypass means, a signal is sent to the bypass time determining means.

When this operation is performed for each cell battery, a time difference occurs in the signal sent from the charging current detouring means to the detour time determining means according to the voltage difference of each cell battery. The detour time determination means determines the detour time to the charging current detour means using this time difference.

That is, 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 a predetermined value is

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 as in the charge control device for the secondary battery according to the second aspect.

On the other hand, the time tb for bypassing to the charging current bypass means is determined by using the voltage difference ΔV obtained by the above equation (1). At this time, the battery temperature detected by the battery temperature detection means is determined. Consider. That is, as the battery temperature T increases, the internal resistance r of the battery decreases, but 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 detected by the battery temperature detecting means. The internal resistance r of the battery corresponding to the battery temperature T is quoted from the table, and the voltage value rI which is the product of the internal resistance r 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 = V · C /
Since there is a relation of I, when formulating to correct ΔV with rI,

(2) tb = (ΔV−rI) C / I (2) Therefore, as in the charge control device for the secondary battery according to the third aspect, the detour time determining unit determines the detour time tb to the charging current detouring unit by 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. In the former case, the charging is stopped when the charging current flows in the charging current bypass means in all the cell batteries or when the bypass time set by the timer elapses. Is from the charging current bypass means to the charging means, in the latter case from the timer to the charging means,
Send signals respectively.

[0017]

According to the charge control device for a secondary battery of the present invention as set forth in claim 1, the detour time is determined by the voltage difference between the cell batteries and the battery temperature. Even if there are variations, it will not be affected by these,
Each cell battery can always be fully charged. Further, it is possible to optimally control the end of charging according to the voltage of each cell battery and the end of charging according to the bypass time. In addition to this,
Even if the detour capacity is small, the detour time is determined to be the optimum value, so that each cell battery can be fully charged.

According to the charge control device for a secondary battery according to claim 2, in addition to the effect according to the invention according to claim 1, all the cells are operated 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 third aspect, in addition to the effect according to the invention of the first or second 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.

[0020]

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, charging current detouring means 24, voltage difference calculating means 22, battery temperature detecting means T, detouring time determining means 32, and timer 4.
0.

The charging means 10 controls charging of an assembled battery composed of one or more cell batteries, and starts and stops charging. The charging current bypass means 24 is a so-called charging current bypass circuit that is provided in parallel with each of the cell batteries and that can bypass the current flowing through the cell batteries.

The voltage difference calculating means 22 has a function of detecting the respective voltages of the cell batteries and a function of obtaining the voltage difference ΔV between the cell batteries, and the obtained voltage difference is the detour time determining means. 32, and a detour time tb described later.
Be used for the decision. The battery temperature detecting means T detects the temperature of each cell battery like a temperature sensor and sends the temperature information to the bypass time determining means 32.

The detour time determining means 32 is composed of, for example, a microcomputer, and uses the voltage difference ΔV input from the voltage difference calculating means 22 and the battery temperature input from the battery temperature detecting means T to charge current detouring means. The bypass time tb of the current flowing through 24 is determined. The detour time tb determined here is obtained from the detour time determining means 32 by the timer 40.
Sent 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 charging currents in all the cell batteries flow to the charging current bypass means 24, a command signal is sent from the charging current bypass means 24 to the charging means 10. And stop charging.

The secondary 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 one end (positive electrode end) 1a thereof has a charging voltage. 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 each of the 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.}
Has a voltage detection circuit 22a for detecting whether or not the voltage exceeds a predetermined voltage and sending this signal to the microcomputer 30, and a bypass circuit 24 for controlling the function of bypassing the charging current flowing through the battery pack. are doing.

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 non-inverting input terminal (+) of the comparator 221a, while the 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 pnp transistor 2 via the resistor 225a.
It is connected to the base of 26a.

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 pnp transistor 2 keeps Hi
26a is in the off state, but when the voltage of the cell battery B _n exceeds a predetermined voltage value V ₀ , the output terminal of the comparator 221a becomes Lo, a negative potential is given to the base of the pnp transistor 226a, and the pnp transistor 226a is discharged. Is turned on, which causes a current to flow from the collector to the emitter of the transistor 226a.

On the other hand, the collector of the pnp transistor 226a 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 227a. 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 243. Further, a photocoupler 228a is connected between the positive terminal of the cell battery B _n and the output terminal of the amplifier 241.

Therefore, when the pnp transistor 226a is turned on as described above, the current from the emitter turns on the npn transistor 243 via the output terminal of the amplifier 241. As a result, the photo coupler 228
When a is turned on, the optical signal is sent to the time detection circuit 22b.

[0031] 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 includes a bypass circuit 24 which controls a second function . That is, as shown in FIG. 3, the cell battery B _n
Between the positive electrode end 1a and the negative electrode end 1b, two consumption resistances 245 and 246 are connected in series with the npn transistor 243 interposed therebetween, and the resistor 227a on the emitter side of the pnp transistor 226a and the cell battery B _n are connected. A Zener diode 244 is connected in series with the negative electrode end 1b. A loop is formed so that the voltage on the emitter side of the npn transistor 243 is applied to the inverting input terminal (−) of the amplifier 241.

Therefore, as described above, the cell battery B
_When the voltage of _n exceeds the predetermined voltage V ₀ , the pnp transistor 2
When 26a is turned on and a current flows through the amplifier 241, np
Since the n-transistor 243 is turned on, the consumption resistance 24
A current will flow through 5,246. At this time, np
The emitter-side potential of the n-transistor 243 is the amplifier 24
The voltage applied to the inverting input terminal (-) of the amplifier 241 is equal to the voltage of the non-inverting input terminal (+), that is, the voltage of the Zener diode 244. As described above, the emitter of the npn transistor 243 and the inverting input terminal (-) of the amplifier 241 are
A negative loop is formed between them. This gives n
A constant current determined by the voltage of the Zener diode 244 flows through the pn transistor 243 and the consumption resistances 245 and 246, and the charging current that tries to flow to the cell battery B _n can be bypassed to the consumption resistances 245 and 246 side.

On the other hand, as shown in FIG. 4, each of the photocouplers 228 of the above-mentioned parallel circuits 20 ₁ , 20 ₂ , ..., 20 _n.
The outputs from a ₁ , 228a ₂ , ..., 228a _n are input to the time detection circuit 22b of the microcomputer 30, which is the voltage difference calculation means 22. This time detection circuit 22b
Are photocouplers 228a ₁ , 228a ₂ , ..., 228
AND circuit 221 to which the signals from a _n are respectively input
b and an OR circuit 222b, these AND circuits 22
The output terminal of 1b and the output terminal of the OR circuit 222b are connected to the clock 223b.

That is, any one photocoupler 22
When the signal from 8a _n is input, the signal is output from the output terminal of the OR circuit 222b to the clock 223b, while when the signals from all photocouplers 228a _n are input, the output terminals of the AND circuits 221b are output. The signal is output to the clock 223b, and the clock 22
In 3b, the time Δt from the input of the signal from the OR circuit 222b to the input of the signal from the AND circuit 221b is measured, and the result Δt is sent to the CPU of the voltage difference calculation means 22 in the microcomputer 30. Output.

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 obtained from the time difference Δt, and is used as one element for determining the time tb of the charging current flowing to the bypass circuit 24.

That is, the cell batteries B ₁ , B ₂ ,
,, the voltage difference of B _n is 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 depending on 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.

[0038] 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 table indicating the relationship between the battery temperature and the internal resistance value of the battery is stored in the ROM or the like, and the temperature sensor T _{n is used.}
The internal resistance r of the battery is quoted from the table based on the temperature information from.

The detour time determining means 32 corrects the voltage difference ΔV using the internal resistance r quoted from the table. 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 detour time tb to the bypass circuit 24 is determined by substituting the voltage difference ΔV obtained by the voltage difference calculation means 22 and the internal resistance r obtained by the output from the temperature sensor T _n into the above equation (2). It The bypass time tb, each cell before charging battery B _1, B _2, ..., not only the variation in the charge amount of B _n, which each cell in the battery _{B 1, B 2, ...,} B n
It is a control value that takes into account the temperature fluctuations.

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, each cell battery B ₁ , B ₂ , ..., B _{n is} actually
When no charging current is flowing in the battery cell, that is, when all the charging currents in all the cell batteries B ₁ , B ₂ , ..., B _n are flowing in the bypass circuit 24, it is not necessary to continue charging, so charging is no longer necessary. A command signal is output from the microcomputer 30 to the relay 10 in order to end the.

Next, the specific operation will be described.

FIG. 5 is a flow chart showing the operation of this embodiment, in which a plurality of cell batteries B ₁ , B ₂ , ..., B _n are connected in series and a charging voltage is applied to the positive terminal 1a of these assembled batteries. When the charging current I is supplied (step 10), the charging current I flows through the cell batteries B ₁ , B ₂ , ..., B _n, and the voltage gradually rises. At this time, the voltage detection circuit 22a _n detects the voltage of each cell battery B _n and determines whether or not it has reached a predetermined voltage V ₀ (step 20). For the cell battery B _n whose battery voltage has not reached the predetermined voltage V ₀ , the charging current I continues to flow, but the predetermined voltage V _0.
With respect to the cell battery B _n that has reached, the charging current I is passed to the bypass circuit 24 (step 30), and it is determined whether the charging current has flowed to the bypass circuit 24 (step 40). For the cell battery B _{n in} which the charging current has flown to the bypass circuit 24, a signal to that effect is sent to the time detection circuit 22b.
To calculate the voltage difference ΔV, and then calculate the voltage difference ΔV
Is sent to the detour time determining means 32 (step 50).

The operations from step 20 to step 50 are performed by the voltage detection circuit 22a and the bypass circuit 24 in the parallel circuit 20 _n shown in FIG. That is, until the voltage of the cell battery B _n rises after charging is started and this voltage exceeds the predetermined voltage V ₀ , the comparator 221a
Since the output terminal of pnp transistor 2 keeps Hi
26a is in the off state, but when the voltage of the cell battery B _n exceeds the predetermined voltage V ₀ , the output terminal of the comparator 221a becomes Lo.
Then, a negative potential is applied to the base of the pnp transistor 226a and the pnp transistor 226a is turned on, which causes a current to flow from the collector to the emitter of the transistor 226a. As a result, it can be determined whether the voltage of the cell battery has exceeded the predetermined voltage (step 20).

The current from the emitter of the pnp transistor 226a is np through the output terminal of the amplifier 241.
The n-transistor 243 is turned on, and the emitter of the npn-transistor 243 and the inverting input terminal (-) of the amplifier 241 are turned on.
Since a negative loop is formed between them, a constant current flows through the npn transistor 243 and the consumption resistances 245, 246, and the charging current that is about to flow into the cell battery B _n is bypassed to the consumption resistances 245, 246 side. (Step 30).

Further, at this time, since the photocoupler 228a is turned on, the optical signal is sent to the time detection circuit 22b, and it is judged whether or not the charging current has flown to the bypass circuit 24 (step 40) and the time detection. The output to the circuit 22b will be executed (step 50). The output to the time detection circuit 22b is the AND circuit 2 shown in FIG.
21b and the OR circuit 222b, the clock 22
In 3b, the time Δt from the input of the signal from the OR circuit 222b to the input of the signal from the AND circuit 221b is measured, and the result Δt is sent to the CPU of the voltage difference calculation means 22 in the microcomputer 30. Output. The voltage difference calculating means substitutes the time difference Δt into the above-mentioned formula (1) to obtain the cell battery voltage difference ΔV, and sends this to the detour time determining means 32 (step 50).

Next, the output signals from the temperature sensors T ₁ , T ₂ , ..., T _n are taken into the detour time determining means 32 of the microcomputer 30 (step 60). Then, the detour time tb to the bypass circuit 24 is determined by substituting the voltage difference ΔV obtained in step 50 and the internal resistance r of the battery determined from the battery temperature into the above-described equation (2) ( In step 70), this is set in the timer 40 (step 80).

Then, in step 90, it is judged whether or not all the charging currents in all the cell batteries B ₁ , B ₂ , ..., B _n are flowing in the bypass circuit 24. When all the charging currents are flowing in the bypass circuit 24, That is, when the charging current does not actually flow in each of the cell batteries B ₁ , B ₂ , ..., B _n, it is no longer necessary to continue the charging, so that the charging is completed regardless of the bypass time tb of the timer 40. In order to do so, a command signal is output from the microcomputer 30 to the relay 10 (step 110).

Further, all cell batteries B ₁ , B ₂ , ..., B
_{Even if} all the charging current does not flow to the bypass circuit 24 at _n , it is determined whether the detour time tb set in the timer 40 has expired (step 100),
When the time is up, a command signal is output to the relay 10 to cut off the charging current (step 110).

As described above, according to the secondary battery charge control device of the present embodiment, the detour time tb is determined by the voltage difference ΔV between the cell batteries B _n and the battery temperature T. Even if the temperature and the temperature vary, each cell battery B _n can be fully charged without being affected by them. 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 when the bypass capacity is small, the bypass time tb is determined to be the optimum value, so that each cell battery B _n can be fully charged.

The embodiments described above have been described in order to facilitate understanding of the present invention, and are not described to limit 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 configurations shown in FIGS. 2 and 3, and can be variously configured by analog circuits and / or digital circuits. 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 an embodiment of a charging current bypass means 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 circuit diagram showing a conventional charge control device for a secondary battery.

FIG. 7 is a circuit diagram showing a conventional secondary battery charging 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 ... Bypass circuit (charging current bypass means) 30 ... Microcomputer 32 ... Detour time determining means 40 ... Timer _Bn ... Cell battery _Tn ... Temperature sensor (battery temperature detecting means)

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H02J 7/10 H02J 7/10 HL

Claims (3)

[Claims] 1. A charging unit that controls charging of an assembled battery composed of one or more cell batteries, and a charging current bypass unit that is provided in parallel with each of the cell batteries and that can bypass a current flowing through the cell batteries. A voltage difference calculating means for detecting respective voltages of the cell batteries to obtain a voltage difference, a battery temperature detecting means for detecting respective temperatures of the cell batteries, and a voltage difference obtained by the voltage difference calculating means. A detour time determining means for determining a detour time of a current flowing through the charging current detouring means based on the battery temperature detected by the battery temperature detecting means, and a timer for setting a detour time from the detour time determining means, A charging control device for a secondary battery, which controls the charging means based on a current flowing through the charging current bypass means or a bypass time set by the timer. 2. 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 charge control device for a secondary battery according to claim 1, wherein when (h) is set, ΔV = I · Δt / C is calculated. 3. The detour time tb (h) is the charging current I (A), the capacity of the cell battery is C (Ah), the voltage difference obtained by the voltage difference calculating means is ΔV (V), 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 1 or 2
Secondary battery charge control device.