JPH04140678A - Method for monitoring amount of remaining power of secondary cell - Google Patents

Abstract

PURPOSE:To enable usable remaining time to be calculated when using in the same state by dividing a value corresponding to an amount of remaining power which is detected by a value corresponding to an amount of consumed power which is integrated for a certain amount of time for obtaining the quotient. CONSTITUTION:An amount of discharge current which is consumed through a resistor from a secondary cell 1 is detected by a detection circuit of a current detection part 12, it is divided by the amount of basic power corresponding to a basic unit of count value of a counter which is located at a charging/discharging control part 8, and an integer part of the quotient is subtracted from the counted value. Also, the decimal part of the quotient is memorized and is subtracted from the counted value every time the accumulated value reaches 1. then, an analog value from a detection part 12 is A/D converted and is integrated for one minute for obtaining amount of discharge current for one minute and for converting it to current value again. When the remaining power at the current point is divided by the current value which is integrated for one minute, usable remaining time of the cell 1 can be calculated in units of minutes. Finally, a signal showing the integer part of the quotient is sent to an alarm/display part 9 as a usable remaining time (minute) and is displayed when continuing to use in the same state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for monitoring the remaining power level of a secondary battery.

[Conventional technology]

As a device for monitoring the remaining amount of power of a secondary battery such as a Ni-Cd battery, a device disclosed in Japanese Patent Application Laid-Open No. 59-28678 is known. In the device disclosed in the publication, the power consumed from the secondary battery is accumulated at predetermined intervals, and this cumulative value is subtracted from the value corresponding to the amount of electricity stored in the secondary battery to calculate the remaining power of the secondary battery. The remaining amount of power is displayed accordingly.

[Problem to be solved by the invention]

However, since such conventional devices display the remaining amount of power as it is, it is not possible to determine how much power can actually be used with the secondary battery, which is inconvenient for use.

Therefore, the present invention aims to solve the above-mentioned drawbacks.

[Means to solve the problem]

In order to achieve the above object, the method for monitoring the remaining power of a secondary battery according to the present invention includes the steps of: detecting the remaining power of the secondary battery; , a step of detecting the amount of power consumed from the secondary battery every predetermined time and integrating it for a certain period of time, and making a value corresponding to the accumulated amount of power consumption correspond to the detected remaining amount of power. The method includes the steps of dividing the value to obtain the quotient, and displaying the upper predetermined digits of the quotient as the remaining usable time of the secondary battery.

[Effect]

Since the present invention divides the accurately detected remaining power amount by the amount of power consumption, the quotient is the usable time if the device is continued to be used in the same state.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

FIG. 1 is a flowchart for explaining the present invention in detail, and FIG. 2 is a block diagram schematically showing the configuration of a portable laptop-type personal computer (hereinafter referred to as a personal computer) to which the present invention can be applied. 3 are block diagrams of the voltage detection section and current detection section shown in FIG. 2. Hereinafter, in order to facilitate understanding of the present invention, explanation will be given in order starting from FIG.

The personal computer shown in Figure 2 uses a rechargeable secondary battery 1 (rated voltage 9.6 V) such as a rechargeable Nt-Ccl battery as the main power source.
) inside it. The secondary battery 1 is connected to the DC/DCC/type converter 3 via a resistor 2, and the power stored in the secondary battery 1 is transferred to the main circuit unit 5 via the DC/DCC/type converter 3. supplied to

The power switch 7 of the personal computer is connected to the DC/DCC/type-ta 3, and when the power switch 7 is turned on, the DC/DCC/type-ta 3 is connected to the secondary battery 1.
The electric power stored in the main body circuit section 5 or the electric power supplied from the external power source 6 is adjusted to an appropriate voltage and supplied to the main circuit section 5. On the other hand, the secondary battery 1 is charged with power supplied from the external power supply 6 under predetermined conditions to be described later. Furthermore, external power supply 6
is not connected, and when the voltage between the terminals of the secondary battery 1 drops below a predetermined voltage, the power supply from the secondary battery 1 to the main circuit unit 5 is cut off, except for backup power. These operations of the DC/DC converter 3 are controlled by a charge/discharge control section 8 connected to the DC/DCC converter 3.

The charge/discharge control unit 8 is, for example, a 4-bit CPU or ROM.
%RAM, a counter, a buffer memory, a -ΔV detection circuit 83, and the like. The charge/discharge control section 8 receives detection signals from the AC adapter detection section 10, voltage detection section 11, current detection section 12, battery low detection section 13, and shutdown detection section 15, respectively. Based on these detection signals, the charge/discharge control section 8
A command signal regarding charging and discharging of the secondary battery 1 is output to the C/DCC/type controller 3 to control charging and discharging of the secondary battery 1. Further, the charge/discharge control section 8 monitors the remaining amount of power of the secondary battery 1 based on detection signals input from the voltage detection section 11 and the current detection section 12. Then, a signal corresponding to the remaining power level of the secondary battery 1 and a signal indicating the usable time are outputted from the charging/discharging control unit 8 to the alarm/display unit 19, and the remaining power level of the secondary battery 1 and a signal indicating the usable time are outputted from the control unit 8. The estimated usable time is displayed by a light emitting diode (LED) or the like.

The secondary battery 1 is charged by switching between quick charging performed with a constant charging current of 1.2A and trickle charging performed with a constant charging current of 70+aA.

When the secondary battery 1 becomes fully charged during charging, the voltage between the terminals of the secondary battery 1, which had been on the rise until then, decreases after being fully charged. The fully charged state of the battery 1 can be detected. Secondary battery 1
The voltage drop (-ΔV) after full charge is caused by the detected voltage from the voltage detecting section 11 being A/
The signal is converted into D and detected by the -Δ■ detection circuit 8a.

Whether or not a predetermined amount of power has been consumed from the secondary battery 1 can be detected by the current detection unit 12 . This is because when a current flows through the resistor 2, a potential difference proportional to the current flowing across the resistor 2 is generated. In this embodiment, the voltage detection section 1
In this case, the voltage detected by the secondary battery 1 drops to 12.9V or less, and the current detection unit 12
When it is detected that a current has flowed to the CC/type-ta 3 side, it is assumed that a predetermined amount of power has been consumed from the secondary battery.

Further, the amount of discharge consumed from the secondary battery 1 is detected as follows. Since the current from the secondary battery 1 always passes through the resistor 2, a potential difference is generated between both ends of the resistor 2 according to the consumed current value (discharge current value). This potential difference is sequentially detected by the current detection circuit 12a, and the detection result (analog value) is sent to the impedance conversion circuit 12c and the amplifier 12d.
The signal is sent to the charge/discharge control section 8 via the charge/discharge control section 8. The charge/discharge control unit 8 converts the analog data from the current detection unit 12 into digital data, samples this 3750 times every 16111 seconds, and calculates 0.016×3750-
Find the average value for 60 seconds. Then, the average value for the second 60 seconds is taken as the amount of discharge consumed from the secondary battery 1 in one minute.

Next, a description will be given of how the charge/discharge control unit 8 monitors the remaining power of the secondary battery 1.

The remaining amount of power of the secondary battery 1 is monitored based on the value of a counter included in the charge/discharge control section 8. That is, the counter value is made to correspond to the remaining amount of power of the secondary battery 1, and if power is being consumed from the secondary battery 1, a value corresponding to the amount of discharge for each predetermined time is subtracted from the counter value at predetermined intervals. However, when the secondary battery 1 is being charged, a constant value corresponding to the amount of charge for each constant time is added to the counter value at regular intervals. For example, when the maximum storage capacity of the secondary battery 1 is 6120 Asec, the counter value is set to 6120 in correspondence with the fully charged state of the secondary battery 1. If power is being consumed from the secondary battery 1, calculate the amount of power consumed from the secondary battery 1 every 1 second as described above, and calculate the value corresponding to the calculated discharge amount from the counter value for 1 second. Subtract each time. This subtraction is repeated while the power is being consumed from the secondary battery 1. In addition, as described above, charging of the secondary battery 1 is performed with a constant charging current, so while the secondary battery 1 is being charged, the
Add a constant value to the counter value every minute. For example, a constant value of 60 is added every minute during quick charging, and a constant value of 4 is added every minute during trickle charging. This constant value can be easily determined from the charging current and charging efficiency, and can also be determined experimentally. In this way, the current remaining amount of power in the secondary battery 1 can be accurately grasped from the counter value. Accurately grasping the remaining amount of power in this way is a prerequisite for accurately estimating the usable time, which will be described later.

The operation of monitoring the remaining power of the secondary battery 1 described above will be explained with reference to the flowchart shown in FIG.

In the illustrated flowchart, first, a determination is made as to whether the conditions required for charging (for example, whether the AC adapter is connected, etc.) are satisfied (step S1), and charging is performed. If the conditions for 2
The amount of discharge current (ampere amount) consumed through is sequentially detected (step 512). As described above, this amount of discharge current is detected by the current detection circuit 12a as a potential difference detected between both ends of the known resistor 20, and corresponds to the amount of power consumption.

Hereinafter, the process of indicating the current remaining power amount of the secondary battery 1 using a counter value will be explained based on steps S13 to S518. First, the discharge amount obtained in step S12 is divided by the basic power jl (I Asec ) corresponding to the basic unit of the counter value (step 31B), and the integer part of the quotient is subtracted from the counter value (step 515). . Also, step 3
The fractional part of the quotient obtained in step 13 is accumulated and stored in a buffer memory or the like (step 516). The cumulative value of the decimal part is 1
Each time the basic unit (1) is reached, the basic unit (1) is subtracted from the counter value (step S17.18). Note that at this time, 1 is also subtracted from the cumulative total value of the decimal part. In this way, the current remaining power amount is calculated, and the remaining power amount according to the counter value is displayed on the alarm/display unit 19 (step 520).

Next, a process of calculating the remaining usable time (estimated time) of the secondary battery 1 by integrating the amount of discharge current will be explained. First, the analog value from the current detection section 12 is A/D converted and integrated as digital data for 60 seconds to obtain the discharge amount for 9 minutes (step 521). Next, this integrated amount of discharge current is converted back into a current value (step 522).

Based on the current value accumulated for these 60 seconds, step S13~
By dividing the current remaining power amount determined in step 318 (step S2:3), the remaining usable time of the secondary battery 1 is calculated in minutes. Finally, a signal indicating the integer part, which is the quotient, is sent to the alarm/display unit 19 via serial communication as the remaining usable time (minutes) if continued use in the same condition, and is displayed on a CRT screen, etc. Step S
24).

For example, the value obtained by converting the integrated amount for 60 seconds into a current value or 50
0mA (=0.5A) and remaining power is 6000
Assuming that Asec, (= 100 All1n,), the available time is 200 minutes (-10010
, 5), the alarm/display section 19 displays, for example, "available time - 200 minutes".

Note that the present invention is not limited to the above embodiments.

For example, in the above-described embodiment, the integrated time is displayed in minutes, with one minute as the cumulative time, but the display is not limited to minutes. It may be in units of time or seconds.

In addition, if a power save mode is used that does not dim the backlight when the battery level is low, the usable time can be estimated by taking this into consideration.

Further, the performance of the secondary battery 1 deteriorates over time, the number of times of repeated charging and discharging, etc., and the performance deteriorates, and the maximum storage capacity decreases. Therefore, the predetermined value set in the counter when a fully charged state is detected is reduced in accordance with the degree of use of the secondary battery. This makes it possible to monitor the remaining amount of power of the secondary battery in consideration of the decrease in maximum storage capacity due to deterioration of the secondary battery 1. Specifically, a timer measures the elapsed time from the time when the secondary battery 1 was replaced,
Each time the fully charged state of the secondary battery 1 is detected, a predetermined value (6120 in the above example) set in the counter is decreased in accordance with the elapsed time measured by the timer. Furthermore, it is preferable to count the number of times the quick charge has been performed, and to decrease the predetermined value set in the counter at the time of full charge according to the elapsed time and the number of times the quick charge has been performed.

〔Effect of the invention〕

As described above, according to the present invention, the remaining power level of the secondary battery can be accurately monitored over time.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an operation for monitoring the remaining power of a secondary battery according to an embodiment of the present invention, FIG. 2 is a block diagram showing an information processing device to which the present invention can be applied, and FIG.
FIG. 2 is a block diagram of a voltage detection section and a current detection section that can be used in the information processing device shown in the figure. 1... Secondary battery, 2... Resistance, 3... DC/DC
converter, 5...main circuit section, 6...external power supply,
7... Power switch, 8... Charge/discharge control section, 8
a...-ΔV detection circuit, 10... AC adapter detection section, 11... Voltage detection section, lla... Voltage detection circuit, 11b... Switch means, 11C... Impedance conversion circuit, lld ...Level conversion circuit, 12...
Current detection section, 12a... Current detection circuit, 12b...
Switch means, 12c... impedance conversion circuit,
12d...Amplifier, 13...Battery low detection section, 15...Shutdown detection section, 16...External power supply connection terminal, 17...Regulator, 18...Reference voltage source, 19. ...Alarm/display section.

Claims (1)

[Claims] A method for monitoring the remaining amount of power of a secondary battery, which includes the steps of: detecting the remaining amount of power of the secondary battery; and detecting the amount of power consumed from the secondary battery at every predetermined time. the step of calculating the quotient by dividing the value corresponding to the detected remaining power amount by the value corresponding to the integrated power consumption amount, and calculating the upper value of the quotient. A method for monitoring remaining power of a secondary battery, comprising the step of: displaying up to a predetermined digit of the remaining usable time of the secondary battery.