JP3219731B2 - Rechargeable battery charging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging a secondary battery, and more particularly to a charging method for detecting a full charge by detecting .DELTA.V at which the battery voltage drops from a peak value.

[0002]

2. Description of the Related Art Nickel-cadmium batteries and nickel-cadmium batteries
When a secondary battery such as a hydrogen battery is charged with a constant current,
When fully charged, the battery voltage tends to drop from its peak value. A secondary battery exhibiting this property can detect full charge by detecting ΔV.

In the charging method for detecting full charge by detecting ΔV, it is difficult to determine the ΔV value for determining full charge. When the ΔV value is reduced, there is a feature that the secondary battery can be fully charged without overcharging. However,
Due to the influence of noise or the like, a secondary battery that is not actually fully charged is easily erroneously determined to be fully charged. Conversely, if the ΔV value is set to a large value, it is possible to reduce erroneous full charging, but there is a disadvantage that overcharging is likely to occur. This is because the secondary battery is fully charged and continuously charged until the voltage drops considerably.

Further, the discharged secondary battery is charged,
FIG. 1 may show a curve of the battery voltage when the charging of the battery proceeds. The battery voltage rises sharply at the beginning of charging and then falls. The voltage changes in this way because the internal resistance of the battery is large when charging is started. The internal resistance increases and decreases as the battery is charged. As described above, when the charging is started, the battery voltage decreases from the peak value, so that ΔV may be detected here to determine erroneously that the battery is fully charged. In order to prevent this adverse effect, a method has been developed in which charging is continuously continued for a certain period of time ignoring the detection of ΔV.

[0005]

The method of continuously charging the first predetermined time without detecting the battery ΔV has no problem when charging a sufficiently discharged secondary battery. However, when a fully charged secondary battery is charged, it is continuously charged for a certain period of time, so that there is a problem of overcharging. For this reason, the secondary batteries in all states cannot be fully charged in an ideal state.

[0006] Further, a method of detecting ΔV and performing full charge is also based on the magnitude of ΔV value for determining full charge, and erroneously determines that a secondary battery that is not fully charged is fully charged, or conversely. The problem of overcharging by further charging a fully charged secondary battery cannot be eliminated. In order to reduce such defects, for example, a method has been developed for detecting the slope of a curve in which the battery voltage changes in addition to the battery voltage ΔV. In this charging method, it is determined that the battery is fully charged when the gradient in which the voltage changes becomes greater than the set state, and when the battery voltage subsequently drops by ΔV. This method can accurately detect full charge as compared to the method of detecting only ΔV. However, this method also cannot detect the full charge accurately enough to satisfy all the secondary batteries. This is because the curve in which the voltage increases varies depending on the battery.

[0007] The present invention has been developed to solve such disadvantages of the conventional charging method. An important object of the present invention is to provide a charging method capable of preventing overcharge of a secondary battery and accurately detecting full charge.

[0008]

According to the method of charging a secondary battery of the present invention, the secondary battery 1 is charged by pulse charging,
Full charge is detected by detecting ΔV at which the battery voltage drops from the peak voltage. Furthermore, the charging method according to claim 1 of the present invention detects both the ON voltage of the secondary battery 1 being charged and the OFF voltage during which charging is suspended, and the charging ΔV at which the ON voltage drops from the peak value. And the pause ΔV at which the off-voltage drops from the peak value, and detects that either the charge ΔV or the pause ΔV becomes larger than the set value, thereby detecting full charge. Further, the charging method according to the present invention provides a secondary battery
1 until the set time elapses after charging starts.
Ignore full charge detection with electricity ΔV and fully charge only with pause ΔV
Is detected .

According to a second aspect of the present invention, there is provided a method for charging a rechargeable battery, comprising the steps of:
The V value is switched at a rate at which the voltage of the off-state voltage increases.
When the rising slope of the off-state voltage is larger than the off-setting slope, the charging ΔV value is set to be small.

In the method of charging a secondary battery according to a third aspect of the present invention, the voltage rising gradient of the ON voltage becomes larger than the ON setting gradient after a set time has elapsed since the charging of the secondary battery 1 was started. Until ignoring full detection at charging ΔV, pause Δ
Full charge is detected only with V. After the voltage rising gradient of the ON voltage becomes larger than the ON setting gradient, full charging is detected by detecting both the charging ΔV and the pause ΔV.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. However, the following examples illustrate a charging method of a secondary battery for embodying the technical idea of the present invention, and the present invention does not specify the charging method as follows.

Further, in this specification, in order to make it easier to understand the claims, the numbers corresponding to the members shown in the embodiments will be referred to as "claims" and "claims". In the column of “means”.
However, the members described in the claims are not limited to the members of the embodiments.

FIG. 2 shows a charging circuit used in the charging method of the present invention. The charging circuit shown in the figure includes a charging power supply 2, a pulse charging switching element 4A, 4B, 4C, 4D, a pulse charging switching element 4A, 4B, 4C, 4D and a control circuit 3 for controlling the charging power supply 2. Have.

The charging power supply 2 is a switching power supply,
A rectifier circuit 5 for rectifying a 00 volt alternating current;
A switching circuit 6 for switching a DC output from the battery, an AC switched by the switching circuit 6 is input to the primary side, and the input voltage is changed to the secondary battery 1.
, A rectifier circuit 8 composed of a diode that rectifies an alternating current output from the transformer 7 and converts the alternating current to a direct current, and controls an output voltage of the rectifier circuit 8 to control a duty ratio at which the switching circuit 6 switches. C
A V / CC control 9 and an insulating PC circuit 10 are provided.

The pulse charging switching elements 4A, 4B,
4C and 4D are switched on and off at a constant cycle, and pulse-charge the secondary battery 1 in order. The pulse charging switching elements 4A, 4B, 4C, 4D shown in the figure are composed of transistors and FETs. The transistor pulse charging switching elements 4A, 4B, 4C, 4D
The collectors are connected to each other and connected to the output side of the charging power supply 2. Pulse charging switching elements 4A, 4B, 4
The emitters of the transistors constituting C and 4D are:
On the positive side of the secondary battery 1, the base is connected to the control circuit 3.

A plurality of pulse charging switching elements 4A,
4B, 4C, and 4D, one of them is turned on and the other is turned off, and the secondary battery 1 is pulse-charged as shown in FIG. Pulse charging switching elements 4A, 4B, 4
C and 4D are sequentially turned on, and the secondary battery 1
Are pulse-charged in the order of B1, B2, B3, B4. The pulse charging switching elements 4A, 4B, 4C, and 4D connected to the fully charged secondary battery 1 are controlled to be turned off even when it is turned on.

The pulse charging switching elements 4A, 4B,
4C and 4D are switched on and off by an output signal from the control circuit 3. The pulse charging switching elements 4A, 4B, 4C, and 4D, which are transistors, are turned on when a base current flows from the control circuit 3 and turned off when the base current is cut off. The pulse charging switching element of the FET is controlled to be turned on when a voltage is applied to the gate, and turned off when no gate voltage is applied.

The control circuit 3 switches the four sets of pulse charging switching elements 4A, 4B, 4C, and 4D on and off to control the state in which the secondary battery 1 is pulse-charged. The control circuit 3 includes a microcomputer and an A / D converter that detects a battery voltage and converts an analog voltage into a digital voltage. The voltage of each secondary battery 1 (B1 to B4 in the figure) is input to the microcomputer from the A / D converter. The microcomputer calculates the input battery voltage and controls the pulse charging switching elements 4A, 4B, 4C, 4D. Further, the control circuit 3 has a built-in timer,
Pulse charging switching element 4 with timer and battery voltage
A, 4B, 4C, and 4D are controlled.

The control circuit 3 detects both the ON voltage of the secondary battery 1 being charged and the OFF voltage of which the charging is suspended, and the ON voltage of each secondary battery 1 drops from the peak value. Charge ΔV and rest ΔV at which off-voltage drops from the peak value
To detect both. When detecting that either the charge ΔV or the pause ΔV becomes larger than the set value, the control circuit 3
Determines that the secondary battery 1 has been fully charged, and determines that the charging power source 2 and the pulse charging switching elements 4A, 4B, 4C, 4
Control D.

As shown in FIG. 4, the pulse-charged secondary battery 1 changes its on-voltage and off-voltage. The on-voltage rises sharply at the beginning of charging. After that, it gradually decreases and then rises again to the peak voltage,
Thereafter, the voltage is reduced by ΔV to be fully charged. The off-voltage does not rise sharply when charging is started, but gradually rises and rises to a peak voltage, and further decreases by ΔV when further charging is performed.

The ON voltage rises to the peak voltage at the beginning of charging and then drops. This voltage change is similar to the ΔV drop of the ON voltage. If the control circuit 3 determines that the voltage change is a full charge due to the ΔV drop, the full charge cannot be accurately detected. To prevent this evil,
From the start of the charging of the secondary battery 1 to the lapse of the timer set time, the charging ΔV
Ignore full charge detection at. In this time zone, full charge is detected only by the pause ΔV. In FIG. 4, the set time of the timer is set to 10 minutes.

After the set time of the timer has elapsed, the full charge of the secondary battery 1 can be detected by the charge ΔV. In the charging method shown in FIG. 4, after the set time of the timer elapses after the charging of the secondary battery 1 is started, the ON voltage rises from the minimum value by a set voltage, or the voltage rise gradient of the ON voltage decreases. , Charging Δt until it becomes larger than the ON set gradient.
Full charge detection at V is ignored, and full charge is detected only at pause ΔV.

After the ON voltage rises from the minimum value to the set voltage, or after the voltage rise gradient becomes larger than the ON set gradient, full charge is detected by detecting both charging ΔV and pause ΔV. The figure shows that after the on-voltage drops to the minimum value,
When the voltage rises by 10 mV / cell from the minimum value, the detection of the full charge is started at the ON voltage charge ΔV. Instead of detecting that the on-voltage has risen from the minimum value, it is also possible to compare the rising gradient of the on-voltage with the on-set gradient and start full-charge detection based on the charging ΔV of the on-voltage.
At this time, the ON setting gradient is, for example, 10 mV / ce.
ll · sec.

After the voltage rise gradient of the ON voltage becomes larger than the ON set gradient, the control circuit 3 detects the charge ΔV to detect the full charge.
V is switched to a small value when the secondary battery 1 is almost fully charged. The charging ΔV value is switched at a rate at which the voltage of the off-state voltage increases. When the rising slope of the off-state voltage becomes larger than the off-setting slope, it is determined that the secondary battery 1 is almost fully charged, and the charging ΔV value is set to be small. The off set slope is
For example, it is set to 10 mV / cell, and the charging ΔV value becomes, for example, 40 mV / cell when the battery is almost fully charged.
Switching from cell to 20 mV / cell.

The microcomputer of the control circuit 3 charges the secondary battery 1 according to the flowchart of FIG. [Step of N = 1] As shown in FIG. 3, the control circuit 3 turns on and off the pulse charging switching elements 4A, 4B, 4C, and 4D in order to pulse-charge the secondary battery 1. The ON time of the pulse charging switching elements 4A, 4B, 4C, 4D is
For example, 0.5 seconds and the off time are set to 1.5 seconds. However, in the charging method of the present invention, the on-time is set to 0.1 to
It can be set in the range of 2 seconds. The off time is set to 3 to 10 times the on time. For example, a device that charges n secondary batteries 1 together sets the off time to (n−1) times the on time in order to pulse charge the secondary batteries 1 to be charged together in sequence.

[Step of N = 2] The control circuit 3 detects an off-voltage input from the A / D converter, detects a pause ΔV at which the off-voltage drops from the peak voltage, and sets this value to a set value. Some 20mV / cel
1 is determined. Rest ΔV is 20mV / ce
If it is larger than ll, it is determined that the battery is fully charged, the charging is stopped, and the full charge is displayed. The pulse charging switching element connected to the secondary battery 1 determined to be fully charged is not switched on, and only the pulse charging switching element connected to the secondary battery 1 that is not fully charged is switched on.
Fully charge all the secondary batteries 1 in order.

The pulse charging switching element connected to the fully charged secondary battery 1 is not switched on, but at this time, the other pulse charging switching elements are not switched on. Even after one of the secondary batteries 1 is fully charged, the control circuit 3 does not change the timing of switching on the pulse charging switching element, for example, as shown in FIG. When the secondary battery 1 is fully charged, the pulse charging switching element 4B connected to the secondary battery 1 is turned off as shown by a dashed line, and ch1, ch3,
The pulse charging switching elements 4A, 4C and 4D connected to the secondary battery 1 connected to ch4 are turned on and off at the same cycle.

[Step N = 3] If the pause ΔV is smaller than 20 mV / cell, the timer starts counting, and the steps N = 2 and N = 3 are looped until the set time of the timer elapses. . The set time of the timer is set to 10 minutes. However, the setting time of the timer is shorter than 10 minutes, and can be longer.

[Step N = 4] When the set time of the timer elapses, it is determined whether or not the on-voltage has risen by 10 mV / cell from the minimum value.

[Step of N = 5] When the ON voltage rises from the minimum value to 10 mV / cell or more, the charging ΔV of the ON voltage is set to 40 mV / cell, and whether the ON voltage has dropped by ΔV larger than the charging ΔV is determined. Is determined. When the charge ΔV becomes larger than 40 mV / cell, it is determined that the battery is fully charged.

[Step of N = 6] When the charging ΔV of the ON voltage is smaller than 40 mV / cell, or when the ON voltage is 10 mV / ce from the minimum value.
When it does not rise above 11, the pause ΔV is 10 mV / c.
It is determined whether or not the time when the cell becomes higher is shorter than the set time. In the flowchart of FIG.
The time T (n) required to increase mV / cell is the same as the time T (n) required previously to increase 10 mV / cell.
It is determined whether the value is shorter than 1 / 1.125 than -1). That is, in this step, it is determined whether or not the rising slope of the off-state voltage is larger than a predetermined off-setting slope. When the rising gradient of the ON voltage is smaller than the OFF setting gradient, the process loops to the step of N = 2.

[Step of N = 7] When the rising gradient of the ON voltage becomes larger than the OFF setting gradient, the charging ΔV is reset and the charging ΔV is reset from 40 mV / cell to 2
Switch to 0 mV / cell.

[Step N = 8] It is determined whether or not the off-voltage has dropped below the pause ΔV of 20 mV / cell, and if it has fallen below the pause ΔV, it is determined that the battery is fully charged.

[Step of N = 9] When the OFF voltage does not decrease by the pause ΔV, the ON voltage becomes
It is determined whether the charging voltage is lower than 20 mV / cell, which is the charging ΔV, and it is determined that the battery is fully charged when the ON voltage is lower than the charging ΔV.

[Step of N = 10] It is determined whether or not the time during which the off-state voltage increases by 10 mV / cell is longer than twice the previous time, in other words, whether or not the rising curve of the off-state voltage has become loose. When the off-voltage rise curve becomes gentle, it is determined that the battery is fully charged. When the off-voltage rise curve does not become loose, N =
Jump to step 8. It is also possible to omit the step of N = 10 and loop the steps of N = 9 and N = 8.

[0036]

The method for charging a secondary battery according to the present invention has the advantage that overcharge of the secondary battery can be prevented and full charge can be accurately detected. That is, the charging method of the present invention detects both the ON voltage of the secondary battery that is pulse-charging and the OFF voltage that suspends the charging, and also determines the charging ΔV at which the ON voltage drops from the peak value, This is because full charge is detected by detecting both the pause ΔV in which the voltage drops from the peak value and detecting that either the charge ΔV or the pause ΔV becomes larger than the set value. The charging method of the present invention for detecting full charge in this manner makes use of the battery characteristics of the ON voltage and the OFF voltage to more accurately charge the battery by comparing either the charging ΔV or the pause ΔV with a set value. Detects charging,
Features that can effectively prevent overcharging can be realized.

Further, the method of charging a secondary battery according to the second aspect of the present invention has a feature that a full charge can be detected more accurately.
This is because this charging method switches the charging ΔV value that determines the full charge by detecting the ON voltage ΔV at a gradient in which the OFF voltage rises. This charging method is
When the rising slope of the off-state voltage is larger than the off-setting slope, it is determined that the secondary battery is almost fully charged, and the charging ΔV value is set small. Therefore, there is a feature that the full charge can be accurately detected and the overcharge can be reliably prevented.

Further, the method for charging a secondary battery according to the present invention comprises:
There is a feature that erroneous determination of full charge at the start of charging can be effectively prevented. This is because the charging method ignores the detection of the full charge at the charge ΔV and detects only the pause ΔV to detect the full charge until the set time elapses after the charging of the secondary battery is started. Because. According to this charging method, the voltage change at the first ON voltage at which charging is started is not erroneously determined as the fully charged charging ΔV. In this time zone, full charge is detected only by the off-state pause ΔV with a small voltage change, so that full charge can be accurately detected without erroneous determination.

Further, in the method of charging a secondary battery according to the third aspect of the present invention, after the set time elapses from the start of charging, the voltage rise gradient of the ON voltage becomes larger than the ON set gradient. , Ignoring full detection at charging ΔV, pause ΔV
Only when the full charge is detected, and after the voltage rising gradient of the ON voltage becomes larger than the ON setting gradient, the charging ΔV and the pause Δ
Since full charge is detected by detecting both V, it is possible to confirm that the erroneous determination of full charge at the start of charging has been avoided, and then a feature that the full charge can be accurately detected by the charge ΔV is realized. You.

[Brief description of the drawings]

FIG. 1 is a graph showing characteristics of a battery voltage when a secondary battery is charged.

FIG. 2 is a block diagram of a charging circuit used for a method of charging a secondary battery according to an embodiment of the present invention.

FIG. 3 is a diagram showing a state in which a pulse charging switching element of the charging circuit shown in FIG. 2 is controlled to be turned on and off.

FIG. 4 is a graph showing the characteristics of the ON voltage and the OFF voltage of the secondary battery charged by the charging method according to the embodiment of the present invention.

FIG. 5 is a flowchart illustrating a method for charging a secondary battery according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Secondary battery 2 ... Charging power supply 3 ... Control circuit 4A, 4B, 4C, 4D ... Pulse charging switching element 5 ... Rectifier circuit 6 ... Switching circuit 7 ... Transformer 8 ... Rectifier circuit 9 ... CV / CC control 10 ... Insulation PC circuit for

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02J ^7/ 00-7/10 H01M 10/44

Claims (3)

(57) [Claims] 1. A charging method for pulse charging a secondary battery (1), comprising detecting a full charge by detecting ΔV at which a battery voltage drops from a peak voltage. (1) detecting both the ON voltage and the OFF voltage at which charging is paused, and charging ΔV at which the ON voltage drops from the peak value, and pause ΔV at which the OFF voltage drops from the peak value.
Are detected, one of the charging ΔV and the rest ΔV is detected to be larger than a set value, a full charge is detected, and furthermore, a set time after starting charging of the secondary battery (1) is detected. But
Until elapse, the detection of full charge at charge ΔV is ignored, and
A method for charging a secondary battery, wherein a full charge is detected only by stopping ΔV . 2. The method for charging a secondary battery according to claim 1, wherein the charging ΔV value is set to be smaller when the rising slope of the off-state voltage is larger than the off-setting slope. 3. After a set time has elapsed from the start of charging of the secondary battery (1), the on-voltage rises from a minimum value to a set voltage, or the on-voltage rise gradient is an on-set gradient. Until it becomes larger, the full charge is detected only at the pause ΔV, ignoring the full detection at the charge ΔV, and after the voltage rising gradient of the ON voltage becomes larger than the ON setting gradient,
2. The method for charging a secondary battery according to claim 1 , wherein both the charge ΔV and the pause ΔV are detected to detect a full charge.