JPH07298511A - Method and circuit for charging secondary battery - Google Patents

Abstract

PURPOSE:To safely charge a secondary battery effectively in a short time with out decreasing its service life by a constitution wherein an accurate battery voltage is detected when a pulse current is not flowing during the pulse charging and the pulse current is reduced repetitively when the upper limit of charging current is reached. CONSTITUTION:A control circuit 2 charges a secondary battery 1 with a pulse current of a predetermined width fed from a DC power supply 13 and reduces the pulse current supply to the secondary battery 1 when the voltage thereof reaches an upper limit. When a battery 1 is set and the voltage thereof is between the upper and lower limits, a decision is made that the battery to be charged is a secondary battery which is then subjected to pulse charging with a predetermined width. If the battery voltage reaches the upper limit when the pulse charging is not performed. The charging current is reduced according to a function of time before the pulse charging is repeated. Consequently, the secondary battery can be charged efficiently and safely in a short time without loosing its service life.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a pulse current
The present invention relates to a charging method and a charging circuit for charging a secondary battery.

[0002]

2. Description of the Related Art Conventionally, as a method for rapidly charging a secondary battery,
Pulse charging as shown in FIG. 5 is performed. This pulse charging is a method in which a pulsed current of about 5 C (coulomb) is intermittently supplied to the battery for charging, and the charging is completed in, for example, about 15 minutes in the NiCd battery. Hereinafter, FIG. 5 will be briefly described.

FIG. 5 shows an explanatory view of the prior art. The horizontal axis represents the charging time, the left vertical axis represents the battery voltage (V) of the upper curve, and the right vertical axis represents the charging current (A) of the lower curve.
Represents

Next, the operation will be described. (1) The battery is charged at a duty T1 / T2 with a pulse current having a predetermined current value. Battery voltage rises gradually.

(2) The duty T1 / T2 is gradually reduced with time because charging becomes overcharged when the pulse current having the predetermined current value of (1) is charged.
Then, the charging is completed when a predetermined time has elapsed.

[0006]

According to the pulse charging method of FIG. 5 described above, a pulse current having a constant charging current value is applied to the battery and the duty T1 / T2 is gradually reduced to prevent overcharging. If this is done, charging will not be able to take place, so the duty T1 / T2 that normally causes overcharge
The battery is being rapidly charged at. As a result, the battery voltage may exceed the charging upper limit voltage Vu, which shortens the battery life. This does not shorten the life so much when using a water electrolyte as in a nickel-cadmium battery, but especially when using an organic solvent as a non-aqueous electrolyte such as a lithium battery, the tendency to shorten the life becomes remarkable. There was a problem that caused it.

The present invention solves these problems.
When the pulse current is not flowing during pulse charging, the accurate battery voltage is detected, and the pulse current is repeatedly reduced when the charging upper limit voltage Vu is reached, which is safe, efficient and short without shortening the battery life. Intended to be charged in time.

[0008]

[Means for Solving the Problems] Means for solving the problems will be described with reference to FIG. In FIG. 1, the secondary battery 1 is a battery to be pulse-charged.

The control circuit 2 supplies a pulse current of a predetermined width generated from a power source to the secondary battery 1 for charging, or when the secondary battery voltage reaches the charging upper limit voltage Vu, the secondary battery 1
It also reduces the pulse current supplied to.

The voltage detection circuit 12 detects the voltage V of the secondary battery 1 when the pulse current is not supplied.

[0011]

According to the present invention, as shown in FIG. 1, a pulse current of a predetermined width generated from a power source is supplied to the secondary battery 1 for charging, and when the pulse current is not supplied to the secondary battery 1. The detected voltage V of the secondary battery 1 is the charging upper limit voltage Vu.
Then, the pulse current supplied to the secondary battery 1 is repeatedly reduced to perform pulse charging.

Further, the control circuit 2 supplies the secondary battery 1 with a pulse current of a predetermined width generated from the power source to charge the secondary battery 1, and the voltage V of the secondary battery notified from the voltage detection circuit 12.
Is reduced to the charging upper limit voltage Vu, the reduction of the pulse current supplied to the secondary battery 1 is repeated.

At this time, the pulse current value is decreased over time. Therefore, when the voltage V of the secondary battery is detected when the pulse current does not flow during pulse charging and the pulse current is reduced when the charging upper limit voltage Vu is reached, the secondary battery 1
The battery can be charged safely, efficiently and in a short time without shortening its life.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the construction and operation of an embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 1 shows a block diagram of an embodiment of the present invention.
In FIG. 1, a secondary battery 1 is a battery to be pulse-charged and has a non-aqueous electrolyte such as a lithium battery.
For example, the next battery.

The control circuit 2 supplies a pulse current of a predetermined width generated from the DC power supply 13 to the secondary battery 1 for charging, or when the secondary battery voltage reaches the charging upper limit voltage Vu, 2
The pulse current supplied to the secondary battery 1 is reduced, and is composed of 3 to 10.

The voltage control circuit 3 controls the voltage or current supplied from the DC power supply 13 to the secondary battery 1. The start / stop circuit 4 is a switch S
It controls the opening / closing of W10 and starts the timer 5.

The timer 5 is a total timer, which is activated when the switch SW10 is closed and the pulse charging of the secondary battery 1 is started, and limits the total time of the pulse charging.

The pulse generating circuit 6 generates a pulse signal corresponding to the pulse current supplied to the secondary battery 1. The current detection circuit 7 detects the charging current flowing in the secondary battery 1.

The OR circuit 8 calculates the OR logic of the pulse signal from the pulse generation circuit 6 and the signal from the current detection circuit 7 and the overcurrent signal detected by the resistance.

The amplifiers 9 and 10 amplify the voltage converted by the current flowing through the resistance. Switch S
W10 is a switch for supplying a pulse current to the secondary battery 1 or for stopping the supply.

The voltage detection circuit 12 detects the voltage V of the secondary battery 1 when the pulse current is not supplied. The DC power supply 13 is for generating a DC voltage for charging the secondary battery from an AC power supply (not shown).

Next, the operation of the configuration of FIG. 1 will be described in detail in the order shown in the flowchart of FIG. In FIG. 2, a battery is set in S1. This sets the secondary battery 1 at the right end of FIG. 1 to a state capable of pulse charging.

At S2, it is determined whether V> Vu. This is because the voltage detection circuit 12 of FIG. 1 measures the voltage V in a state where no pulse current flows in the secondary battery 1 set in S1,
The control circuit 2 that has received the notification of the voltage V compares it with a preset charging upper limit voltage Vu, and determines whether voltage V> charging upper limit voltage Vu. If YES, 2 set in S1
The voltage V of the secondary battery 1 in the non-pulse charged state was found to be higher than the charging upper limit voltage Vu, and it was found to be completely charged or another battery of a different type, so charging is stopped. If NO, the process proceeds to S3.

In S3, it is determined whether V <V1. This is because the voltage detection circuit 12 of FIG. 1 measures the voltage V in a state where no pulse current flows in the secondary battery 1 set in S1,
The control circuit 2 that has received the notification of the voltage V compares it with a preset charging lower limit voltage V1 and determines whether the voltage V <the charging lower limit voltage V1. If YES, 2 set in S1
It was found that the voltage V of the next battery 1 in the non-pulse-charged state was lower than the charging lower limit voltage V1, and it was found that the battery V had deteriorated performance or another battery of a different type, so charging is stopped. If NO, the process proceeds to S4.

In step S4, the total timer is activated. This is because the battery voltage V is between the charging upper limit voltage Vu and the charging lower limit voltage V1 due to YES in S2 and YES in S3, and it is found to be in the charging range. Therefore, a total timer (timer 5) for managing the entire charging time To start.

In step S5, I = Imax is initialized. This initializes the pulse charging current I to the maximum value Imax. In S6, it is determined whether t> tmax. This is because the current time t counted by the total timer is the maximum charging time tm.
It is determined whether it is larger than ax. If YES, the time t counted by the total timer is the maximum charging time tmax.
Since it has exceeded the limit, charging is completed. On the other hand, if NO, the process proceeds to S7.

In S7, I = Imax · f (t) is set. This is a function f that decreases to Imax with time.
A value obtained by multiplying (t) is set as a charging current value I. That is, as shown in FIG. 3, a value obtained by multiplying Imax by a value obtained by substituting the current charging time t into the function f is set as the charging current value I. As a result, the charging current value I gradually decreases as the charging time t elapses, and as shown in FIG. 3, when the charging upper limit voltage Vu is reached, the charging current value I is set to a value slightly smaller than the charging upper limit voltage Vu. I try to repeat that.

In step S8, it is determined whether I <Imin. This determines whether the charging current value I is smaller than a predetermined lower limit charging current value Imin as shown in FIG. If YES, the charging is completed and the charging is finished. On the other hand, if NO, the process proceeds to S9.

In step S9, the circuit is closed and charging is started / restarted. This is determined to be within the charging time range and the charging current range by NO in S6, S7 and S8, so the switch SW10 in FIG. 1 is closed (closed).
Then, the secondary battery 1 is pulse-charged with the charging current I in a predetermined width as shown in FIG.

In S10, the circuit is opened and the voltage between the battery terminals is measured. This is when the switch SW10 in FIG. 1 is opened and the supply of the charging current I is stopped.
The voltage detection circuit 12 measures (detects) the voltage between the terminals of the secondary battery 1. As a result, the voltage between the terminals of the secondary battery 1 is detected in the state where the pulse current is not flowing.
The constant and more accurate voltage of the secondary battery 1 can always be detected without being affected by the magnitude of the charging current of the secondary battery 1.

In step S11, it is determined whether V <Vu. In the case of YES, it is determined that the current voltage of the secondary battery 1 is lower than the charging upper limit voltage V, so the process returns to S9 and the pulse charging is repeated. On the other hand, in the case of NO, the current voltage V of the secondary battery 1 is found to be equal to or higher than the charging upper limit voltage Vu, so the process returns to S6, and if within the charging time range, I is determined in S7.
= Imax × f (t), that is, the charging current value I is set to a slightly small value, and when the value I is within the charging range, S9 to S
Repeat 11

As described above, the secondary battery 1 is set, and 2
The voltage V of the secondary battery 1 is the charging upper limit voltage Vu and the charging lower limit voltage V
When it is within the range of 1, it is determined to be the secondary battery 1 to be charged,
Initially set to I = Imax, as shown in FIG. 3, pulse charging of a predetermined width is performed, and when the voltage V of the secondary battery when pulse charging is not performed reaches the charging upper limit voltage Vu, the charging current value I To a value that decreases as a function of time t, and again
Repeat pulse charging. Then, the charging is stopped when the charging current value I becomes equal to or lower than the charging lower limit current Imin. Further, the charging is stopped when the charging time t counted by the total timer value exceeds the charging maximum time tmax. As a result, the voltage of the secondary battery 1 does not exceed the charging upper limit voltage Vu during pulse charging, and thus the pulse charging can be efficiently performed in a short time without shortening the life of the secondary battery 1.

FIG. 3 is a diagram for explaining the operation of the present invention. Here, the horizontal axis represents charging time, the left vertical axis represents the battery voltage (V) of the upper curve, and the right vertical axis represents the charging current (A) of the lower curve.

Next, the operation will be described. (1) The secondary battery 1 is pulse-charged with a pulse current having a maximum current value Imax and a predetermined width. The voltage V of the secondary battery is detected at the pointed position in the section where the pulse charging is stopped.

(2) When the voltage V detected at the position marked with the point (1) exceeds the charging upper limit voltage Vu, that is, when the voltage V is, the charging is temporarily stopped. Then, the current charging time t is substituted into I = Imax × f (t) = Imax × exp (A · t), I is obtained as a value when it is slightly smaller than the charging upper limit voltage Vu, and the obtained charging current is obtained. Based on the value I
Pulse charging is repeated as in (1).

(3) After the pulse charging is started in (2), when the voltage V detected at the pointed position exceeds the charging upper limit voltage Vu, that is, when the voltage V is, the charging is temporarily stopped. . Then, as in (2), I = Imax × f (t) = Imax × exp (A · t) is substituted, I is obtained as a value when it is slightly smaller than the charge upper limit voltage Vu, and the obtained charge is obtained. Based on the current value I
Repeat pulse charging.

(4) Then, when the obtained charging current value I becomes equal to or lower than the charging lower limit current value Imin, the charging is finished. Further, the obtained charging current value I is the charging lower limit current value Imi
Even when the charging time t does not become n or less, the charging is stopped when the charging time t exceeds a preset maximum charging time tmax.

As described above, as shown in FIG. 3, when the secondary battery 1 reaches the charging upper limit voltage Vu by repeating pulse charging with a predetermined width at the initial maximum current value Imax, the charging current I
By repeating the pulse charging again with a slight decrease, the charging upper limit voltage V of the secondary battery 1 at the time of pulse charging
It is possible to efficiently charge the secondary battery without exceeding u.

FIG. 4 shows an example of the pulse charging current of the present invention. Here, the horizontal axis represents the charging time (min) and the vertical axis represents the charging current (A). Here, the charging current I is represented by I = Imax · exp (−αt). For example, according to an experiment, a 350 mAh lithium ion battery is used as follows: Imax = 1.5 A, α = 0.03, Imin = 50 m
When A is set, the charging current value I is set with time (set in S7 of FIG. 2) as shown by the solid curve, and it is 3
I was able to charge 90% of the full charge in 0 minutes.

On the other hand, in the conventional constant voltage charging, only 70% of the full charge could be charged in 30 minutes. Also, the dotted line is 350
A mAh lithium-ion battery is Imax = 0.75A, α = 0.02, Imin = 50
A state in which the charging current value I in the case of mA is set (set in S7 of FIG. 2) with time is shown.

[0042]

As described above, according to the present invention,
A configuration is adopted in which the voltage V of the secondary battery is detected when the pulse current does not flow during pulse charging with a pulse current of a predetermined width, and the pulse current is reduced when the charging upper limit voltage Vu is reached. Therefore, the secondary battery 1 can be charged safely, efficiently and in a short time without shortening its life.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a flowchart explaining the operation of the present invention.

FIG. 3 is an operation explanatory diagram of the present invention.

FIG. 4 is an example of pulse charging current of the present invention.

FIG. 5 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 1: Secondary Battery 2: Control Circuit 3: Voltage Control Circuit 4: Start / Stop Circuit 5: Timer 6: Pulse Generation Circuit 7: Current Detection Circuit 8: OR Circuit 9, 11: Amplifier 10: Switch SW 12: Voltage Detection Circuit 13: DC power supply V: Voltage when pulse charging of secondary battery is not performed Vu: Charge upper limit voltage V1: Charge lower limit voltage Imax: Charge upper limit current Imin: Charge lower limit current tmax: Maximum charge time

Claims (3)

[Claims] 1. A pulse current of a predetermined width generated from a power supply
It is detected when the secondary battery (1) is supplied and charged and the pulse current is not supplied to the secondary battery (1).
A method of charging a secondary battery, characterized in that the pulse current supplied to the secondary battery (1) is repeatedly decreased when the secondary battery voltage reaches the charging upper limit voltage Vu. 2. A pulse current of a predetermined width generated from a power source
The secondary battery (1) is supplied and charged, and the pulse current supplied to the secondary battery (1) is reduced when the secondary battery voltage notified from the voltage detection circuit (12) reaches the charging upper limit voltage Vu. A control circuit (2) for repeating the operation and a voltage detection circuit (12) for detecting the voltage of the secondary battery (1) when the pulse current is not supplied from the control circuit (2) to the secondary battery. A charging circuit for a secondary battery, which is characterized by being provided. 3. The charging method for a secondary battery according to claim 1, or the charging circuit for a secondary battery according to claim 2, wherein the pulse current is decreased with time.