JP2750539B2 - Rechargeable battery charge control method - Google Patents

Description

The present invention relates to a method for charging a secondary battery.

<Prior Art> Conventionally, as a method of charging a secondary battery such as a nickel-cadmium storage battery or a lead storage battery, a charging current is controlled by utilizing a characteristic that a terminal voltage of the secondary battery drops when fully charged. , -ΔV control charging method.

That is, in this charging method, as shown by a solid line in FIG. 4, the terminal voltage of the secondary battery is sequentially measured during charging, and the measured voltage value is increased as the measured voltage increases.
The charging current I, which is sequentially updated as the maximum voltage value and is finally indicated as a charge end at a time t when the voltage drops by a predetermined voltage ΔV from the largest maximum voltage value Vmax, is indicated by a chain line.
Is switched to a small current value corresponding to self-discharge. This charging method is used for quick charging, and the charging current I
Is set large, and in order to suppress overcharging, the predetermined voltage Δ
V must be reduced.

In such a charger using the charging method, the terminal voltage E of the secondary battery I is measured by the connector 2 as shown in FIG.
, And the current source 3 is controlled based on the measured voltage.

In this case, the measurement voltage V is as follows: V = E + e. Here, E is the actual terminal voltage of the secondary battery I,
e is the voltage due to the contact resistances r1 and r2 of the connector 2 (e = e1
+ E2 = I · r1 + I · r2).

<Problem to be Solved by the Invention> In such a charging method, if the contact resistance of the connector 2 changes during a charging period due to, for example, vibration or impact,
The above-described measured voltage V changes by Δe = I (Δr1 + Δr2). However, conventionally, no correction has been made for Δe, and therefore, for example, the measured voltage V
Falls to Δe, and when Δe is larger than the above-mentioned predetermined voltage ΔV used for determining the end of charging, it is erroneously determined that the charging has ended.

The present invention has been made in view of the above points,
The purpose is to correct the variation of the measured voltage during charging of the secondary battery that is not based on the change of the terminal voltage, that is, the change due to the change in the contact resistance of the connector, etc., and to prevent erroneous detection at the end of charging. And

<Means for Solving the Problems> In the present invention, the change in the terminal voltage of the secondary battery during charging is as small as about 0.0 several mV / sec / cell, whereas the contact resistance of the connector is small. Voltage change due to change Δe
For example, when a charging current of 1 A is flowing, a change of 1 mV at a change of 1 mΩ is considerably large, and therefore, a change of the measurement voltage at an appropriate time interval, for example, at an interval of about several seconds. Looking at it, it is possible to discriminate whether a change in the measured voltage is based on a change in the terminal voltage or a change in the contact resistance of the connector.

That is, in the present invention, the terminal voltage of the secondary battery during charging is sequentially measured at predetermined time intervals, and as the measured voltage increases, the maximum voltage value serving as a criterion for determining the end of charging is sequentially updated and updated. A charging control method for a secondary battery in which a charging current is controlled by setting a time point at which the voltage drops by a predetermined voltage from a maximum voltage value thereafter, and a change in a measurement voltage at each of the predetermined time intervals is measured. The change in voltage is sequentially compared with a predetermined identification voltage for identifying whether or not the change in the voltage is based on the change in the terminal voltage, and when the change in the measured voltage is equal to or greater than the identification voltage, the terminal voltage As a voltage change based on the change of the measured voltage, the maximum voltage value at that time is corrected depending on whether the measured voltage is in the rising period or the falling period, and in accordance with the change in the measured voltage. To have.

<Operation> According to the above configuration, it is determined whether or not the change in the measured voltage at each predetermined time interval is due to a change in the terminal voltage of the secondary battery, and a change in contact resistance or the like not based on the change in the terminal voltage. The maximum voltage value at that time,
Since the correction is performed, the charging end point can be detected more accurately than in the conventional example.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic structural view of a charger to which a method according to an embodiment of the present invention is applied.

1, reference numeral 1 denotes a secondary battery, and 4 denotes a charger for charging the secondary battery 1. The charger 4 measures a terminal voltage of the secondary battery 1 via a connector 2, and measures the measured voltage. Vn
And an A / D converter for converting the data into corresponding digital data, and a microcomputer 6 for detecting a charging end point based on the output of the A / D converter 5 as described later.
And a current source 3 whose charging current is controlled by the microcomputer 6.

The charging control method for the secondary battery according to the present embodiment includes the following:
Is basically the same as the -ΔV control charging method described above, which utilizes the characteristic that the terminal voltage of
In order to eliminate the influence of the change in the contact resistance of the connector 2, the following is performed.

That is, the terminal voltage of the secondary battery 1 during charging is
Paying attention to the fact that it does not change rapidly, the change in the measured voltage measured at a predetermined time interval is compared with a predetermined identification voltage, and when the change in the measured voltage is equal to or more than the identification voltage,
It is determined that the change is abrupt due to a change in the contact resistance of the connector 2 or the like which is not based on the change in the terminal voltage of the secondary battery 1, and as shown in FIG.
Vmax is corrected as follows.

FIG. 2 is an enlarged view showing a change in the measured voltage during the charging period, and corresponds to FIG. During the rising period of the measurement voltage, when the contact resistance of the connector 2 increases and the measurement voltage sharply increases, the second
As shown in FIG. 2A, the measured voltage value Vn is set to a maximum voltage value Vmax, and when the contact resistance decreases and the measured voltage drops sharply, as shown in FIG. ,
The decreased measured voltage value Vn is defined as the maximum voltage value Vmax.

Further, when the contact resistance of the connector 2 increases during the falling period of the measurement voltage and the measurement voltage rapidly increases, as shown in FIG.
Then, a voltage (Vn + Δv) obtained by adding a voltage drop Δv from the maximum voltage value up to that point to a new maximum voltage value Vmax, and when the contact resistance decreases and the measurement voltage suddenly decreases, As shown in FIG. 2 (D), a voltage (Vn + Δv) obtained by adding the voltage drop Δv from the maximum voltage value up to that time to the measured voltage Vn is added to the new maximum voltage value.
Vmax.

That is, conventionally, as the measured voltage increases, the measured voltage value Vn is sequentially updated as the maximum voltage value Vmax. For example, as shown in FIG. 2 (B), a measured voltage Vn lower than the previous voltage is set to the maximum voltage value Vmax, or as shown in FIGS. 2 (C) and 2 (D), The voltage (Vn + Δv) obtained by adding the voltage drop Δv from the maximum voltage value up to that point to the measurement voltage Vn is set as a new maximum voltage value Vmax, so that the influence of the change in the contact resistance of the connector 2 or the like is obtained. The maximum voltage value is corrected to eliminate it.

Thus, when there is a change in the measured voltage due to a change in the contact resistance or the like that is not based on the change in the terminal voltage of the secondary battery 1, depending on whether the measured voltage is in the rising period or the falling period, Further, since the maximum voltage value Vmax at that time is corrected according to the voltage change, it is possible to accurately detect the charging end point.

In the charger 4 of this embodiment, digital data corresponding to the measured voltage is given to the microcomputer 6 from the A / D converter 5, and the microcomputer 6 changes the measured voltage at predetermined time intervals and stores it in the memory 7. A comparison is made with a previously stored identification voltage. If the change in the measured voltage is equal to or greater than the identification voltage, the maximum voltage value Vmax is determined to be a voltage change due to a change in the contact resistance of the connector 2 that is not based on the terminal voltage change. Is performed as described above,
When the voltage is lower than the identification voltage, the maximum voltage value Vmax is sequentially updated to a larger value as in the related art, and when the measured voltage drops from the maximum voltage value Vmax by a predetermined voltage stored in the memory 7, It is determined that charging is complete and CPU 8
Controls the current source 3 to switch the charging current to a small current value corresponding to self-discharge.

 FIG. 3 is a flowchart for explaining the operation.

In FIG. 3, Vmax is the maximum voltage value as a criterion for determining the end of charging, Vn-1 is the previously measured voltage value, Vn is the current measured voltage value, and ΔV is a predetermined voltage for determining the end of charging. , Δvc is a predetermined identification voltage for identifying whether or not the terminal voltage is changed, S is a flag indicating whether the measured voltage is a rising period or a falling period, 1 is a rising period, 0 Indicates a descent period.

First, in step n1, each variable in the memory 7 is initialized and measurement is started. In step n2, the difference between the previous measured voltage value Vn-1 and the current measured voltage value Vn is determined by the identification voltage Δvc
It is determined whether or not the above is the case. If the voltage is equal to or higher than the identification voltage, it is determined that the voltage change is caused by the change in the contact resistance of the connector 2, and the process proceeds to Step n3.

In step n3, it is determined whether or not the flag S is 1, that is, whether it is a rising period or a falling period of the measured voltage. If it is a rising period, the process proceeds to step n4, and FIG. 2 (A) As described in (B), the current measured voltage value Vn is stored in the memory 7 as the maximum voltage value Vmax and the previous measured voltage value Vn-1, and the process proceeds to step n2.

When it is determined in step n3 that the period is the falling period of the measured voltage, the process proceeds to step n5, and FIG.
As described in (D), a voltage (Vn + Δv) obtained by adding a voltage drop Δv from the maximum voltage value up to that time to the current measurement voltage Vn is set as a new maximum voltage value Vmax, and The measured voltage value Vn is stored in the memory 7 as the previous measured voltage value Vn-1, and the process proceeds to step n2.

In step n2, when it is determined that the difference between the previous measured voltage value Vn-1 and the current measured voltage value Vn is not more than the identification voltage Δvc, the process is basically the same as the conventional one, and the process proceeds to step n6. It is determined whether or not the current measured voltage value Vn is greater than the maximum voltage value Vmax.If it is determined that the measured voltage value Vn is greater than the maximum voltage value Vmax, the process proceeds to step n7. Vn-1 is stored in the memory 7, and the process proceeds to step n2.

If it is determined in step n6 that the current measured voltage value Vn is not larger than the maximum voltage value Vmax,
n8, the current measured voltage value Vn is subtracted from the maximum voltage value Vmax to calculate a voltage drop Δv up to that point, and then the process proceeds to step n9, where the voltage drop Δv is used to determine the end of charging. It is determined whether the voltage is equal to or higher than a predetermined voltage ΔV,
When it is determined that the voltage is not equal to or higher than the predetermined voltage ΔV, the process proceeds to step n10, the current measured voltage value Vn is set to the previous measured voltage value Vn−1, the flag S is set to 0, and the process proceeds to step n2.

When it is determined in step n9 that the voltage drop Δv is equal to or higher than the predetermined voltage ΔV for determining the end of charging, the process proceeds to step n11 as charging is completed.
The current source 3 is controlled to change the charging current I, and the process ends.

As described above, in the charging control method of the present invention, the change in the measured voltage at each predetermined time interval is sequentially compared with the predetermined identification voltage, and when the change in the measured voltage is equal to or higher than the identification voltage, the connector 2 or the like is used. Assuming that the voltage change is based on the change in the contact resistance, the maximum voltage value at that time is corrected according to whether the measurement voltage is in the rising period or the falling period, and in accordance with the change in the measurement voltage. So
As a result, it is possible to prevent erroneous detection of the charging end point due to a change in the contact resistance of the connector 2 as in the conventional example.

Conventionally, when the connector 2 is momentarily interrupted during charging, the voltage of the current source 3 is higher than the terminal voltage, so the maximum voltage value Vmax is updated, and the measured voltage drops after the instantaneous interruption is restored. Therefore, it is erroneously determined that the charging is completed. However, in the method of the present invention, whether or not the change is the terminal voltage is identified, so that such erroneous detection is prevented.

<Effects of the Invention> As described above, according to the present invention, it is determined whether or not a change in the measured voltage at each predetermined time interval is due to a change in the terminal voltage of the secondary battery, and based on the change in the terminal voltage. If the change is due to a change in the contact resistance, the maximum voltage value at that time is corrected, so that the charging end point can be detected more accurately.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a charger to which the method of the present invention is applied,
2 is a diagram for explaining the correction of the maximum voltage value, FIG. 3 is a flowchart for explaining the operation, FIG. 4 is a diagram for explaining the -ΔV control charging method, and FIG. 5 is a conventional charging method. It is a figure for explaining a system. 1 ... secondary battery, 2 ... connector, 3 ... current source.

Claims (1)

(57) [Claims] 1. A terminal voltage of a secondary battery during charging is sequentially measured at predetermined time intervals, and as the measured voltage increases, a maximum voltage value serving as a criterion for judging completion of charging is sequentially updated. A method of controlling charging of a secondary battery in which charging is performed at a point in time when the voltage drops by a predetermined voltage from the maximum voltage value of the secondary battery, and a change in a measured voltage at each of the predetermined time intervals is determined by the measured voltage. Is sequentially compared with a predetermined identification voltage for identifying whether or not the change in the terminal voltage is based on the change in the terminal voltage.When the change in the measured voltage is equal to or higher than the identification voltage, Assuming that the voltage change is not based on the change, the maximum voltage value at that time is corrected depending on whether the measured voltage is in the rising period or the falling period, and in accordance with the change in the measured voltage. You Charging control method for a secondary battery.