JPH03180780A - charging device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a charging device for charging a secondary battery.

[Prior Art] Conventional chargers are equipped with a means for notifying the user when charging is complete, but this generally monitors the terminal voltage of the rechargeable battery being charged and waits until the terminal voltage reaches a predetermined level. When this value is reached, it is assumed that charging is complete and a predetermined display is displayed.

[Problems to be Solved by the Invention] However, in the conventional example, it is not possible to know the time until charging is completed during charging, and it is not possible to know how long the battery can be used while it is being charged. It was not possible to obtain specific information such as whether the capacity was reached or not.

An object of the present invention is to provide a charging device that can obtain such information.

[Means for Solving the Problems] A charging device according to the present invention includes a voltage measuring means for measuring an open circuit voltage of a battery to be charged, and a data storage device for storing data on charge/discharge characteristics of the open circuit voltage of a battery to be charged. and obtaining the charging/discharging state of the battery from the measured open circuit voltage and the data held by the data holding means.

[Operation] By means of the above-mentioned means, it is possible to accurately determine the degree of charging and discharging of the battery to be charged, and to obtain a corresponding quantitative indication.

[Example code] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention. 1
0 is the battery to be charged, 12 is a voltage measurement circuit that measures the voltage between the terminals of battery 10, and 14 is battery 1
16 and 18 are resistors for measuring the degree of charge of the battery 10, that is, the degree of charge; 20 is the output of the charging circuit 14; the resistor 16 or 18 is selectively connected to the battery 10; The switch 22 is an arithmetic control circuit consisting of a microcomputer that controls the operation of the charging circuit 14 and the switching of the switch 20 and determines the degree of charge of the battery 10 from the output of the voltage measurement circuit 12. The numeral 24 is the arithmetic result of the arithmetic control circuit 22. and a display device that displays the control status. Further, 26 is an instruction switch that instructs the arithmetic control circuit 22 to measure the degree of charge of the battery 10, and 28 is a memory that stores data on charging and discharging characteristics regarding the open circuit voltage of the battery 10 to be charged or measured.

When the arithmetic control circuit 22 charges the battery 10,
The switch 20 is connected to the a contact and the charging circuit 14 is activated. During charging, the switch 20 is connected to the B contact at predetermined time intervals, at time intervals corresponding to the voltage value between the terminals of the battery 10, at arbitrary time intervals, or in accordance with the operation of the switch 26. and C contact, and the voltage measuring circuit 12 measures the voltage between the terminals of the battery 10 at that time. The measured voltage of the voltage measurement circuit 12 is sent to the arithmetic control circuit 22.

The arithmetic control circuit 22 calculates the electromotive force V of the battery 10 from the inter-terminal voltage v1 when the resistor 16 is connected to the battery 10 and the inter-terminal voltage 2 when the resistor 18 is connected. Since the resistance value of resistor 16.18 is known,
The current is II.

If I2 is the internal resistance of the battery 10, and the electromotive force (open circuit voltage) is V, then R= (Vl-V2) / (I2-II)■=v1+
11.R=V2+I2.R.

The electromotive force V is a value that is not affected by external factors such as the internal resistance R and the resistance of the connecting lead wires, and by using the electromotive force, the degree of charge of the battery 10 can be accurately determined.

FIG. 2 shows the discharge characteristics when a predetermined load is connected to the Ni--Cd secondary battery.

The vertical axis is the electromotive force, and the horizontal axis is the elapsed time, and it can be seen that the electromotive force monotonically decreases as time passes.

Assuming that the lowest electromotive force that the equipment used can operate is V,
The usable time is I8. FIG. 3 shows charging characteristics when a Ni--Cd secondary battery is charged with a predetermined current. The vertical axis is the voltage between the terminals, and the horizontal axis is the time. When the battery is fully charged, the voltage between the terminals decreases a little, so it can be determined whether the battery is fully charged or not. Note that (1) T is the time required to fully charge a battery that has been discharged to 2 or less.

Table 1 is a table obtained by converting the discharge characteristics shown in FIG. 2 and the charging characteristics shown in FIG. 3 into data, and is stored in the memory 28. A in Table 1 is numerical data from 100 to O indicating the degree of charge,
B is data indicating the time from 0 to T until full charge,
C is data indicating the time T, ~0, until the lowest working voltage V is reached. For example, the electromotive force of a half-used battery is vo
Then, from Figure 2, the usable time is T, -T, (minutes)
It is. This state can be considered as T,/T,X 100 (%) being used, and this is stored in variable A of memory 28 as Ao. See you soon, Ty
It is predicted that the battery will be fully charged in XTo/TtC minutes).

Table 1 FIG. 4 shows an operation flowchart of the arithmetic control circuit 22. The arithmetic control circuit 22 first puts the charging circuit 14 into an operating state (Sl).Then, the switch 20 is connected to the b contact (Sl), and the voltage V between the terminals of the battery 10 due to the resistor 16 is
l is measured by the voltage measuring circuit 12 (S3). Next, the switch 20 is connected to the C contact (S4), and the voltage v1 between the terminals of the battery 10 due to the resistor 18 is measured by the voltage measuring circuit 12 (S5). Voltage Vl measured at S3 and S5
, V2 and its current 11.12 into the above formula to calculate the electromotive force V of the battery 10 (S6), the obtained electromotive force V
is applied to the table in the memory 28 (Table 1), the corresponding data of A, B, and C are read out (S7), transferred to the display device 24, and displayed (S8). If the value of A is less than 100, it is not fully charged, so switch 20
Connect it to the A contact and charge it, and after charging for a specified time (31
1, 12) or in response to the operation of the switch 26 (313
), return to SZ and take measurements. Furthermore, if the voltage across the terminals of the battery during charging decreases (S14), the electromotive force value V at full charge is assigned to the electromotive force variable V, the process returns to S7 (S17), and A equal to 100 is stored in the memory. 28.

If A is equal to 100 in S9, the charging circuit 14 is stopped (S16) because it is fully charged, and the process ends.

In the embodiment described above, the degree of charging and discharging is estimated based on the electromotive force of the battery, but it may of course be estimated based on the voltage between the terminals. When using the inter-terminal voltage, the operation of the arithmetic control circuit 22 is simplified, although the accuracy is slightly lower than when using the electromotive force. Instead of switching the two resistors 16, 18, the two resistance values may be obtained by partially shorting one resistor or the like.

[Effects of the Invention] As can be easily understood from the above explanation, according to the present invention, it is possible to accurately know the degree of charge and discharge of the battery, the time required for full light, etc., the usable time, etc. Furthermore, since the degree of charge is determined based on the open circuit voltage, variations among individual batteries can be reduced.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention, FIG. 2 is a discharge characteristic diagram, FIG. 3 is a charging characteristic diagram, and FIG. 4 is an operation flowchart of the arithmetic control circuit 22. 10: Battery 12: Voltage measurement circuit 14: Charging circuit 16, 18: Resistor 20: Switch 22: Arithmetic control circuit 24: Display device 26! Switch 28: Memory

Claims (1)

[Claims] Voltage measuring means for measuring the open circuit voltage of the battery to be charged;
A charging device comprising a data holding means for storing data on charging and discharging characteristics of an open circuit voltage of a battery to be charged, and obtaining a charging and discharging state of the battery from the measured open circuit voltage and data held by the data holding means. .