JPH03183330A - Charger - Google Patents

Abstract

PURPOSE:To accurately determine charging degree of a battery to be charged by obtaining the electromotive force of the battery based on a voltage between terminals of the battery to be charged if charging currents of different levels are selectively supplied, and comparing it with latched data. CONSTITUTION:An operation controller 18 first sets a charging circuit 14 to an operating state, supplies a charging current I2 to a battery 10, and measures a voltage V2 between the terminals of the battery 10 at that time by a voltage measuring circuit 12. Then, the discharging current of the circuit 14 is set to I1 for short time necessary for stably measuring the voltage, and a voltage V1 between the terminals of the battery 10 at that time is measured. The controller 18 calculates an electromotive force V of the battery 10 from the currents I1, I2 and the voltages V1, V2. The obtained force V is compared in the table of a memory 24, corresponding data of A, B, C is read, transferred to and displayed by a display unit 20.

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 specifically how long it will take to complete charging while the battery is being charged, and it is not possible to know specifically how long the battery can be used while it is still being charged. It was not possible to obtain specific information such as whether the battery was fully charged or not.

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

[Means for Solving the Problems] The charging device according to the present invention has a charging device that charges the electricity to be charged when charging currents of different levels are selectively supplied. Voltage detecting means for determining the electromotive force of this battery based on the voltage between the terminals of the battery, and data holding means for storing data on the charging/discharging characteristics of the electromotive force of the battery to be charged, It is characterized in that the state of charge of the battery is determined by referring to the data held by the means.

[Function] By means of the above means, the degree of charge of the battery to be charged can be accurately determined and a corresponding quantitative display can be obtained.

[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 is a current switching circuit that instructs switching of the charging current generated by the charging circuit 14; 18 is a current switching circuit that operates the charging circuit 14 and operates through the current switching circuit 16; Operation 1i! is made up of a microcomputer that controls the selection of the charging current and determines the degree of charge of the battery 10 from the output of the voltage measurement circuit 12! The I control circuit 20 is a display device that displays the calculation results of the calculation control circuit 18 and the control status. Also, 22
24 is an instruction switch that instructs the arithmetic and control circuit 18 to measure the degree of charge of the battery 10, and 24 is a memory that stores characteristic data such as charging and discharging characteristics of the battery 10.

The arithmetic control circuit 22 controls the charging circuit 14 via the current switching circuit 16, and selects two types of charging currents, 1 and 1, as shown in FIG. , 12 to charge the battery 10. These two types of charging current 1. , r*, the voltage across the terminals of the battery 10 is measured by the voltage measurement circuit 12, and the electromotive force (open circuit voltage) of the battery is calculated from the measurement results. That is, if the internal resistance of the battery 10 is R1, the electromotive force is V, the voltage between the terminals of the battery 10 when the charging current is I is Vl, and the voltage between the terminals of the battery 10 when the charging current is I2 is v2, then R= (VI V2) / (12II)v
=v, +zl + R =V2+12·R = (12V+LV2)/(It L).

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 T. 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 T is the time required to fully charge a battery that has been discharged to V 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 0-T until full charge,
C is data indicating the time T, ~O until the lowest working voltage V is reached. For example, the electromotive force of a car battery is V.

According to FIG. 2, the usable time is TITO (minutes). This state can be considered as T,/T,x 100(%) being used, which corresponds to the variable A in memory 28.
To A. It is stored in memory. From now on, TFXT
It is predicted that the battery will be fully charged in Q/Tl+ (minutes).

Table 1 FIG. 5 shows an operation flowchart of the arithmetic control circuit 18. First, the arithmetic control circuit 18 puts the charging circuit 14 into the operating state (Sl), and supplies the charging current (2) to the battery 10 (S1).
Sl), the voltage between the terminals of the battery 10 (2) at that time is measured by the voltage measuring circuit 12 (S3).

Next, the charging current of the charging circuit 14 is set to h for an extremely short time necessary for stable voltage measurement (S4), and the voltage V between the terminals of the battery 10 at that time is measured (S5).

The arithmetic control circuit 18 controls the charging current 1. , r, and S3.
Calculate the electromotive force V of the battery 10 by substituting the voltage across the terminals measured in step 5 and L into the above formula.S6) The obtained electromotive force V
is applied to the table in the memory 24 (Table 1), and the corresponding data of A, B, and C are read out (S7), transferred to the display device 24, and displayed (S8).

If the value is less than 100, it is not fully charged, so the output of the charging circuit 14 should be changed to a large charging current 2 to continue charging (5IO), and after charging for a predetermined time (Sll)
, or in response to the operation of the switch 22 (S12), the process returns to S2 and the measurement is performed. Furthermore, if the voltage between the terminals of the battery being charged decreases (S13), in order to finish charging, the electromotive force value V at full charge is substituted for the electromotive force variable V, and the process returns to S7 (S17). , A equal to 100 in memory 28
Read from

If A is equal to 100 in S9, the charging circuit 14 is stopped (S15) because the charging is full, 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 18 is simplified, although the accuracy is slightly lower than when using the electromotive force.

[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 state of charge such as the degree of charge/discharge of the battery, the time required for full charge, and the usable time. Become.

[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, FIG. 4 is a waveform diagram of charging current and voltage between terminals of the battery 10, and FIG. The figure is an operation flowchart of the arithmetic control circuit 18. IO=Battery 12: Voltage measurement circuit 14: Charging circuit 16: Current switching circuit 18: Arithmetic control circuit 20:
Display device 22: Switch 24: Memory diagram

Claims (1)

[Claims] Voltage detection means for determining the electromotive force of the battery to be charged based on the voltage between the terminals of the battery when charging currents of different levels are selectively supplied, and data on the charging and discharging characteristics of the electromotive force of the battery to be charged. 1. A charging device comprising: a data holding means for storing a battery, and determining the degree of charge of the battery by referring to the detected electromotive force and data held by the data holding means.