JPH04242078A - Battery pack with residual capacity display - Google Patents

Abstract

PURPOSE:To prevent a damage by an overcharge and an overdischarge of a battery by adding and reducing the charging current and the discharging current to a secondary battery accumulatively at every specific time, and displaying the resultant residual capacity, in a battery pack with built-in secondary battery. CONSTITUTION:An A/D converter 3 outputs a binary number with mark, and the output is input to one side input terminal of a computing element 4, and the other side terminal of the computing element 4 is connected to a register 5 to store the operation result. The converting timing of the converter 3 and the storing timing to the register 5 are synchronized by a timer 6. And the value proportional to the charged power amount in the charging time is accumulated, while the value proportional to the value subtracting the discharge amount from the accumulated amount remains, in the register 5. The output of the register 5 is input to a display 7, where it is displayed as the battery residual capacity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack containing a secondary battery for use in portable terminals and the like.

0002

[Prior Art] A conventional battery pack incorporates only a secondary battery, and the state of charge or discharge of the battery,
That is, there is nothing that displays the remaining battery capacity at that point. Furthermore, even if we try to estimate the remaining capacity based on the battery voltage, the general discharge characteristics of secondary batteries are as shown in Figure 2.
Point B cannot be determined.

0003

[Problems to be Solved by the Invention] Therefore, conventional battery packs have a drawback in that it is impossible to determine how much remaining capacity is left before use, or how much remaining capacity is left during use. Furthermore, even though the battery had capacity remaining before use, charging was carried out without being able to determine it, resulting in damage to the secondary battery due to overcharging, and the battery could only be used for a shorter period of time than its original lifespan. This also caused a secondary problem.

0004

[Means for Solving the Problems] The present invention is a battery pack containing a secondary battery, which cumulatively adds the charging current flowing through the secondary battery at predetermined time intervals, and cumulatively subtracts the discharging current. The apparatus includes a calculation means and a display means for displaying the calculation result of the calculation means.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. 1 is a secondary battery, and 2 is a minute resistor inserted in series with the secondary battery 1. The AD converter 3 converts the voltage value generated across the resistor 2 into a digital value. Here, the value of resistor 2 is set smaller than the internal impedance of secondary battery 1. It is clear that the voltage value generated across this resistor 2 is proportional to the current flowing through the secondary battery 1. It is also clear that when charging the secondary battery 1, the battery flows from the top to the bottom in the diagram, and when discharging, the battery flows from the bottom to the top. The A-D converter 3 outputs a signed binary number, and is set to output a value with a + sign when charging and a value with a - sign when discharging, depending on the polarity of the input voltage. Further, the output of the A-D converter 3 is connected to one input terminal of the arithmetic unit 4, and the output of a register 5 for storing the result of the arithmetic unit 4 is connected to the other input terminal. Therefore, the next A-D conversion output is added to or subtracted from the previous calculation result. The timing of conversion by the AD converter 3 and the timing of storage in the register 5 must be synchronized, and a timing signal is output from the timer 6 to the register 5. Here, the interval measured by the timer 6 is set to an interval that can sufficiently follow changes in the charging current and discharging current. In addition, the register 5 is provided with a reset terminal R, so that when the battery is discharged to the final voltage,
Once the value of register 5 is reset to "0".

By adding such a circuit to the battery pack, a value proportional to the amount of electricity charged is stored in the register 5 when charging, and when discharging, the amount of discharged electricity is subtracted from the current amount of stored electricity. A value that is proportional to the value that remains will remain. The output of this register 5 is input to the display 7 and displayed as the remaining battery level. Further, as the display device 7, for example, a 7-segment type liquid crystal display (LCD) may be used, or a matrix type LCD may be used to display a bar graph.

[0008]

[Effects of the Invention] As explained above, the present invention has the effect that the remaining battery capacity is displayed on the battery pack, so that it can be seen at a glance. Another advantage is that it prevents damage to the battery due to charging without knowing that there is a remaining capacity.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing general discharge characteristics of a secondary battery.

[Explanation of symbols]

1 Secondary battery 2 Resistor 3 A-D converter 4 Arithmetic unit 5 Register 6. Timer 7 Display

Claims (1)

[Claims] 1. A battery pack containing a secondary battery, comprising a calculation means for cumulatively adding a charging current flowing through the secondary battery and cumulatively subtracting a discharging current at a predetermined time interval;
A battery pack with a remaining capacity display, comprising display means for displaying a calculation result by the calculation means.