JP2005322592A - Charging method of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the charging time of a secondary battery. <P>SOLUTION: A resistance value r of the internal resistance of a secondary battery 4 being charged is measured, and then the secondary battery 4 is charged at constant current I, and charge is finished when voltage V between terminals of the secondary battery 4 reaches voltage Vf+r×I obtained by adding voltage r×I obtained by multiplying the resistance value r by the constant current I to full charge voltage Vf. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charging method for a secondary battery suitable for charging a secondary battery such as a lithium ion battery or a lithium polymer battery used in a portable device or the like.

  Conventional charging of secondary batteries such as lithium ion batteries and lithium polymer batteries used in portable devices such as mobile phones and laptop computers is shown in FIGS. 4A and 4B in consideration of deterioration and safety of the secondary batteries. Thus, the so-called constant voltage charging is performed at a constant current I until the voltage V between the terminals of the secondary battery reaches the full charge voltage (specified voltage) Vf, and then at a constant voltage of the specified voltage Vf. A current constant voltage charging method (see Patent Document 1) is used.

  This is because the voltage V between the terminals of the secondary battery when the constant current is charged with the constant current I is equal to the original voltage (internal voltage) Vo of the secondary battery and the internal resistance of the secondary battery. The voltage drop r · I due to the resistance value r is added.

For this reason, even if the voltage V between the terminals of the secondary battery becomes the full charge voltage (specified voltage) Vf during constant current charging, the original voltage (internal voltage) Vo of the secondary battery is Vo = Vf−r · I
The secondary battery is a voltage lower than the fully charged voltage Vf by a voltage drop r · I due to the resistance value r of the internal resistance, and is charged at a constant voltage with the specified voltage Vf to make this a fully charged voltage. Was fully charged.
JP-A-6-325794

  By the way, secondary batteries such as lithium ion batteries and lithium polymer batteries are batteries having a high energy density, and are charged at a constant voltage up to a full charge voltage Vf with a very high accuracy in order to make full use of their characteristics. .

  Therefore, it is necessary to make the original voltage (internal voltage) Vo of the secondary battery as close as possible to the fully charged voltage (specified voltage) Vf (r · I is set to “0” as much as possible). A very large amount of time is spent in the region (if the charging current decreases, the increase (charging) of the original voltage (internal voltage) Vo also slows down accordingly), and the charging time is long.

  In addition, if the charging time of the secondary battery is long, it is often forced to use in a state where it is not fully charged, the usable time of the portable device is shortened, and charging / discharging is only that much. There is a disadvantage that the secondary battery needs to be frequently operated and the deterioration of the secondary battery is promoted.

  In view of this point, an object of the present invention is to shorten the charging time of a secondary battery.

  The secondary battery charging method of the present invention measures the resistance value of the internal resistance of the secondary battery to be charged, and then charges the secondary battery with a constant current I. The charging is terminated when the voltage Vf + r · I is obtained by adding the voltage r · I obtained by multiplying the constant current I by the resistance value r of the internal resistance to the full charge voltage Vf of the secondary battery. .

  According to the present invention, the secondary battery is charged with the constant current I, and the voltage across the secondary battery is obtained by multiplying the full charge voltage Vf of the secondary battery by the resistance r of the internal resistance and the constant current I. Since charging ends when the voltage Vf + r · I is obtained by adding the voltage r · I, the original voltage (internal voltage) Vo of the secondary battery becomes the fully charged voltage Vf at the end of the charging.

  In the present invention, since constant voltage charging is not performed only by constant current charging with a relatively large constant current I, the charging time can be shortened.

  Hereinafter, an example of the best mode for carrying out the method for charging a secondary battery of the present invention will be described with reference to the drawings.

  FIG. 1 shows a charging apparatus according to the present embodiment. In FIG. 1, reference numeral 1 denotes a charging control circuit composed of a microcomputer for controlling charging of the charging apparatus. Reference numeral 2 denotes a DC power supply for charging. The positive electrode of the DC power supply 2 is connected to the input side of the constant current circuit 3.

  The output side of the constant current circuit 3 is connected to the positive electrode of the secondary battery 4 to be charged, and the negative electrode of the secondary battery 4 is connected to the negative electrode of the DC power source 2.

  The constant current circuit 3 is controlled by the charge control circuit 1 to output or not output current, and at the time of measuring the internal resistance of the secondary battery 4, it outputs a measurement current im. Control is performed to output a constant current I having a predetermined magnitude for charging.

  In FIG. 1, reference numeral 5 denotes a voltage detection circuit for detecting the voltage V between the terminals of the secondary battery 4. The detection voltage V detected by the voltage detection circuit 5 is supplied to the charge control circuit 1 and supplied to the memory 6. .

  The operation when charging the secondary battery 4 according to this example will be described with reference to the flowchart of FIG.

  First, it is determined whether or not the secondary battery 4 to be charged is connected (step S1). When the secondary battery 4 is connected, it is determined whether or not the secondary battery 4 is defective (step S2).

  When the connected secondary battery 4 is not defective, the voltage detection circuit 5 detects (measures) the initial voltage V1 of the secondary battery 4 to be charged (step S3), and stores the initial voltage V1 in the memory 6 To do.

  Next, the constant current circuit 3 passes the measurement current im of the resistance value r of the internal resistance of the secondary battery 4 to the secondary battery 4 (step S4). The voltage V2 between the terminals of the secondary battery 4 when the measurement current im is supplied is measured by the voltage detection circuit 5 (step S5), and the measurement voltage V2 is stored in the memory 6.

At this time, V2 = im × r + V1
Is established. From this equation, the charging control circuit 1 calculates the resistance value r of the internal resistance of the secondary battery 4 (step S6).
r = (V2-V1) / im

  Next, the charging end voltage VS is determined (step S7). A voltage drop r · I due to the internal resistance is obtained by multiplying the full charge voltage Vf of the secondary battery 4 by the resistance value r of the internal resistance of the secondary battery 4 and the constant current I when the charge end voltage VS is charged. The added voltage Vf + r · I. This charge end voltage VS = Vf + r · I is stored in the memory 6.

  Thereafter, the constant current circuit 3 is controlled to output a constant charging current I, and constant current charging is performed with the constant current I as shown in FIGS. 3A and 3B (step S8). During the constant current charging, the voltage detection circuit 5 always observes the voltage V between the terminals of the secondary battery 4 and determines whether or not the voltage V between the terminals has reached the charging end voltage VS = Vf + r · I ( Step S9).

  When the inter-terminal voltage V of the secondary battery 4 obtained in the voltage detection circuit 5 becomes the charge end voltage VS = Vf + r · I, the charge control circuit 1 sends a charge end signal to the constant current circuit 3 to The current circuit 3 stops the output of the constant current I and ends the charging.

  According to this example, the secondary battery 4 is charged with a constant current I, and the voltage V between the terminals of the secondary battery 4 is changed to the full charge voltage Vf of the secondary battery 4 to the resistance value r of the internal resistance. Since charging ends when the voltage Vf + r · I obtained by adding the voltage r · I multiplied by I is reached, the original voltage (internal voltage) Vo of the secondary battery 4 is the fully charged voltage Vf at the end of the charging. It becomes.

  In this example, since constant voltage charging is not performed only by constant current charging with a relatively large constant current I, the charging time can be shortened.

  According to this example, since the charging time is relatively short, the battery can be always fully charged and used, the usable time of the portable device becomes longer, and the number of times of charging / discharging can be reduced accordingly. There is a benefit that can extend the life of the.

  Of course, the present invention is not limited to the above-described examples, and various other configurations can be adopted without departing from the gist of the present invention.

It is a block diagram which shows the example of a charging device. It is a flowchart with which description of the example of the best form for implementing the charging method of the secondary battery of this invention is provided. It is a diagram with which it uses for description of this invention. It is a diagram with which it uses for conventional description.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Charge control circuit, 2 ... DC power supply, 3 ... Constant current circuit, 4 ... Secondary battery, 5 ... Voltage detection circuit, 6 ... Memory

Claims (1)

The resistance value r of the internal resistance of the secondary battery to be charged is measured, and then the secondary battery is charged with a constant current I.
When the inter-terminal voltage of the secondary battery becomes a voltage Vf + r · I obtained by adding the voltage r · I obtained by multiplying the resistance r of the internal resistance to the constant current I to the full charge voltage Vf of the secondary battery. A method for charging a secondary battery, characterized in that charging is terminated.

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