JPH0420884A - Method for monitoring residual amount of electric power of secondary battery - Google Patents

Abstract

PURPOSE:To perform accurate monitoring by performing subtraction or addition for the value of a counter in correspondence with the residual amount of a secondary battery, and setting the specified value in corresponce with the value of the counter when the fully charged state of the secondary battery is detected based on the voltage across the terminals. CONSTITUTION:When the residual amount of the power of a secondary battery is monitored, the value of a counter which is provided in a charging/discharging control part 8 is made to correspond to the residual amount of the power of the battery 1. When the power is consumed from the battery 1, the value of the counter corresponding to the amount of the discharge at every specified time is subtracted from the value of the counter. When the battery 1 is charged, the specified value corresponding to the amount of the charge for every specified time is added to the value of the counter. The maximum charged capacity of the battery 1 is known beforehand by the specifications of the battery 1. Therefore, when the battery 1 is fully charged, the power corresponding to the maximum charged capacity is built up in the battery 1. Therefore, when the fully charged state is detected based on the fluctuation of the voltage across the terminal of the battery 1 by a -DELTAV method, the value corresponding to the maximum built-up voltage is set for the value of the counter as the specified value corresponding to the full charge. Thus, the value of the counter can be made to correspond to the residual amount of the power.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention monitors the remaining power of a secondary battery such as a Ni-Cd battery based on a counter value corresponding to the remaining power of the secondary battery. Regarding how to.

[Conventional technology]

A device disclosed in Japanese Patent Application Laid-Open No. 61-209371 is a device that monitors the remaining power of a secondary battery such as an N1-Cd battery based on a counter value corresponding to the remaining power of the secondary battery. Is it publicly known? In the device shown in the publication, the amount of charge to the secondary battery and the amount of discharge from the secondary battery are added and subtracted to accumulate, and when the voltage between the terminals of the secondary battery falls below a predetermined voltage, , the cumulative value will be reset.

[Invention or problem to be solved]

However, since the voltage between the terminals of the secondary battery fluctuates depending on the temperature of the secondary battery, etc., there is a difference in the timing of resetting the cumulative value due to fluctuations in the temperature of the secondary battery, and the remaining power of the secondary battery and the cumulative There was a problem that the remaining power of the secondary battery could not be accurately monitored due to errors occurring between the values.

Furthermore, such conventional devices do not take into account that the storage capacity of the secondary battery decreases depending on the degree of use thereof. For this reason, the usage period of the secondary battery may become longer,
If the frequency of use increases, an error will occur between the remaining power level of the secondary battery and the cumulative value.

Therefore, in view of the above-mentioned circumstances, an object of the present invention is to provide a method for monitoring the remaining power of a secondary battery, which can accurately monitor the remaining power of the secondary battery.

[Means to solve the problem]

In order to achieve the above object, in the method for monitoring the remaining power of a secondary battery according to the present invention, the power consumption and charging power of the secondary battery are detected, and values corresponding to these are set as the remaining power of the secondary battery. The remaining power of the secondary battery is monitored based on the counter value by subtracting or adding from the corresponding counter value, and when the fully charged state of the secondary battery is detected based on the voltage across the terminals, A predetermined value corresponding to full charge is set as the value.

Further, the predetermined value corresponding to full charge is changed depending on the degree of use of the secondary battery.

[Effect]

This allows the counter value to accurately correspond to the remaining amount of power in the secondary battery.

〔Example〕

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

FIG. 1 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 is applied, and FIG.
Although the block diagram of the voltage detection section and the current detection section shown in the figure and FIG. 3 are flowcharts for explaining the present invention in detail, in order to facilitate understanding of the present invention, the explanation will be explained in order from FIG. 1. That's it.

The personal computer shown in Figure 1 uses a rechargeable secondary battery 1 (rated voltage 9.6V) such as a Ni-Cd battery as the main power source.
is provided inside. The secondary battery 1 is connected to a DC/DCC/type controller 3 via a resistor 2.
The electric power stored in is supplied to the main circuit section 5 via the DC/DCC/type controller 3. In addition, an external power source 6 such as an AC adapter or an additional battery can be connected to the DC/DCC/type-ta 3, and power from the external power source 6 can also be connected to the DC/D
It is supplied to the main body circuit section 5 via the CC/type controller 3. The main circuit section 5 is a central part of the personal computer, which includes a CPU 9, a ROM, a RAM, data input means such as a keyboard, a liquid crystal display section, and the like.

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/DCC/type converter 3 are controlled by a charge/discharge control section 8 connected to the DC/DCC/type converter 3.

The charge/discharge control unit 8 includes, for example, a 4-bit CPU, ROM, R
AM, counter, buffer memory, -ΔV detection circuit 8a
It is composed of etc. Then, in the charge/discharge control section 8,
AC adapter detection section 10, voltage detection section 11. Detection signals are input from the current detection section 12, the Hatteriro detection section 13, and the shutdown detection section 15, respectively. The AC adapter detection unit 10 is, for example, a voltage detector that detects whether the potential of the external power connection terminal 16 of the DC/DCC/type adapter 3 is equal to or higher than a predetermined potential. is higher than a predetermined potential (for example, 4■), it is determined that the AC adapter is connected to the DC/DCC/type controller 3, and a detection signal to that effect is sent to the charge/discharge control unit 8. Apply pressure. The voltage detection unit 11 monitors the voltage between the terminals of the secondary battery 1 during charging and outputs a detection signal corresponding to the voltage between the terminals of the secondary battery 1 to the charge/discharge control unit 8 . The current detection unit 12 detects the consumption current consumed by the secondary battery 1, and outputs a detection signal corresponding to the consumption current to the charge/discharge control unit 8. Battery low detection section 1
3 detects that the voltage of the secondary battery 1 has decreased to the required voltage required for the operation of the main body circuit section 5, and outputs a detection signal to that effect to the charge/discharge control section 8. The shutdown detection section 15 detects that the voltage of the secondary battery l has decreased to a point where the operation of the DC/DC converter 3 cannot be guaranteed, and outputs a detection signal to that effect to the charge/discharge control section 8. Based on these detection signals, the charge/discharge control unit 8 controls the DC
A command signal regarding charging and discharging of the secondary battery 1 is output to the /DC converter 3 to control charging and discharging of the secondary battery 1.

Furthermore, the charge/discharge control section 8 monitors the remaining power level 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 is output from the charge/discharge control unit 8 to the alarm/display unit 19, and a signal corresponding to the remaining power level of the secondary battery 1 is output from the light emitting diode (
Displayed by LED) etc.

Note that the charge/discharge control circuit 8 is manually supplied with a detection signal corresponding to the voltage between the terminals of the secondary battery 1 obtained from a voltage monitoring means (not shown), and is also supplied with power for driving by the regulator 17.
A reference voltage (4, 5 V) for A/D conversion is also supplied from a regulator 17 via a reference voltage source 18.

FIG. 2 shows a block diagram of the voltage detection section 11 and the current detection section 12. The voltage detection unit 11 includes a voltage detection circuit 11a connected to the resistor 2, a switch means 11b connected to the voltage detection circuit 11a, and a switch means 11. The impedance conversion circuit 11c is connected to the voltage detection circuit 11a via the voltage detection circuit 11a, and the level conversion circuit 11d is connected to the impedance conversion circuit 11c. The output from the level conversion circuit 11d is input to the charge/discharge control section 8, and a ΔV detection circuit 8a in the charge/discharge control section 8 determines whether the voltage between the terminals of the secondary battery 1 after full charge has decreased (-ΔV). Detected. The current detection unit 12 also includes a current detection circuit 12a connected to the resistor 2, a switch means 12b connected to the current detection circuit 12a, and an impedance converter connected to the current detection circuit 12a via the switch means 12b. The switch means 11-b and 12b are controlled by the charge/discharge circuit 8. Both the switch means 11-b and 12b are connected to the external power supply 6. When the power switch 7 of the personal computer body is turned off, both are turned off.

This prevents power from leaking from the built-in secondary battery 1 through the voltage detection section 11 and the current detection section 12.

The secondary battery 1 is charged by switching between quick charging performed with a constant charging current of 1 or 2 A and trickle charging performed with a constant charging current of 70 mA.

Switching of the charging method is performed by the DC/DC converter 3 in response to a command signal from the charge/discharge control section 8. When the charge/discharge control unit 8 detects a fully charged state of the secondary battery 1 during rapid charging, it outputs a charging method switching signal to the DC/DC converter 3 to switch the charging method to trickle charging. Detection of full charge state is so-called -Δ
■Detected by method. In other words, when the secondary battery 1 becomes fully charged during charging, the voltage across the terminals of the secondary battery 1, which had been on the rise up until then, will drop after being fully charged regardless of the temperature of the secondary battery 1. By detecting the voltage drop after full charge, the fully charged state of the secondary battery 1 can be accurately detected. Voltage drop after full charge of secondary battery 1 (-ΔV
) is the detected voltage from the voltage detection section 11 described above, which is A/D converted inside the charge/discharge control section 8, and is then detected by the -ΔV detection circuit 8.
detected by a. As shown in FIG. 2, if a level conversion circuit 11d is provided before the charge/discharge control section 8, the voltage drop after the secondary battery 1 is fully charged is small compared to the voltage between its terminals. Even so, it is preferable because the voltage drop (-Δ■) after full charge can be detected more easily and accurately.

On the other hand, the charge/discharge control unit 8 changes the charging method to quick charging when it detects that a predetermined amount of power is consumed from the secondary battery 1 during trickle charging or that the secondary battery 1 is replaced. A charging method switching signal is output to the DC/DC converter 3 for switching. Whether 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 flowing current is generated across the resistor 20. In this embodiment, when the voltage detected by the voltage detection unit 11 drops to 12.9V or less, current flows from the current detection unit 12 or the secondary battery 1 to the inverter 3 side. If it is detected that a predetermined amount of power has been consumed from the secondary battery, it is assumed that a predetermined amount of power has been consumed from the secondary battery. In addition, whether or not the secondary battery 1 has been replaced can be detected from the detection signal of the voltage detection unit 11 that monitors the voltage between the terminals of the secondary battery if it is connected to the AC adapter or DC/DC converter 3. can do. That is, when the secondary battery 1 is removed, a charging voltage higher than the maximum voltage of the secondary battery 1 (for example, DC 15V) flows through the trickle charging circuit, and this charging voltage is directly detected by a voltage monitoring means (not shown). Therefore, by detecting this charging voltage, replacement of the secondary battery 1 can be detected. That is, by detecting a high voltage that would not have been detected if the secondary battery was connected, it is possible to detect that the secondary battery 1 has been removed and replaced. Further, when the AC adapter is not connected, if the secondary battery 1 is removed, the voltage between the terminals of the secondary battery 1 becomes 0, so that replacement of the secondary battery 1 is detected. Then, when the charge/discharge control unit 8 detects that either a predetermined amount of power is consumed from the secondary battery 1 or that the secondary battery 1 is replaced, the D
A charging method switching signal is output to the C/DC converter 3. In response to this switching signal, the charging method is switched from trickle charging to rapid charging.

Further, the amount of discharge consumed from the secondary battery 1 is detected as follows.

Since the power consumed from the secondary battery 1 always passes through the resistor 2, a potential difference is generated between both ends of the resistor 2 depending on the consumed current value (discharge current value) due to power consumption.

This potential difference is sequentially detected by the current detection circuit 12a,
The detection result (analog value) is sent to the charge/discharge control section 8 via the impedance conversion circuit 12 (and amplifier 12d).The charge/discharge control section 8 converts the analog data from the current detection section 12 into digital data. And this is 16
Sampled 64 times every m5ec, 0.016X64
- Find the average value for 1.024 seconds. And this 1.
This is the average value for 0.24 seconds or the amount of discharge consumed from the secondary battery 1 per second.

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

The remaining amount of power of the secondary battery 1 is monitored based on the counter value of a counter included in the charge/discharge control section 8. That is, the counter value is made to correspond to the remaining power level of the secondary battery 1,
If power is being consumed from the secondary battery 1, a value corresponding to the amount of discharge at each predetermined time is subtracted from the counter value, and if the secondary battery 1 is being charged, adds a constant value corresponding to the amount of charge per constant time to the counter value at regular intervals. For example, if the storage capacity of the secondary battery 1 is 6120Asec,
The counter value is set to 6120 corresponding to the fully charged state. Then, while power is being consumed from the secondary battery 1, the amount of discharge from the secondary battery 1 is reduced to 1 as described above.
The discharge amount is determined every second, and a value corresponding to the determined discharge amount is subtracted from the counter value every second. 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, a constant value is set to the counter value every minute. to add. For example, during quick charging, a constant value of 60 is added every minute, and during trickle charging, a constant value of 4 is added every minute. This constant value can be easily determined from the charging current and charging efficiency,
It is also possible to obtain it experimentally.

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 judgment is made as to whether or not the conditions required for charging are satisfied (for example, whether the charging power source is connected to an AC adapter or a DC/DC converter). If this condition is satisfied (step S1), a determination is made as to whether the various conditions required for rapid charging are also satisfied (step S2). Here, the conditions required for quick charging are ■
The power switch 7 of the main unit is in the off state, ■ The secondary battery 1 is connected to the DC/DC converter 3,
■Make sure that secondary battery 1 is not being rapidly charged.
■The four conditions are that the voltage between the terminals of the secondary battery 1 has decreased to 12.9V or less. If rapid charging is possible, rapid charging is performed with a constant charging current of 1.2A (step S3), and the counter value is set to a constant value (
60) is added (step S5). If a fully charged state is detected from fluctuations in the voltage between the terminals of the secondary battery 1 during rapid charging, the counter value is set to 6120 in correspondence with the fully charged state (step S6, step S7).
. In this way, by detecting the fully charged state of the secondary battery 1 and setting the value of 6120 in the counter corresponding to the fully charged state, the counter value can be made to accurately correspond to the remaining power level of the secondary battery 1. I can do it. The reason for this will be explained in detail later, since the operations in steps S6 and S7 are essential features of the present invention. By the way, in the illustrated flowchart, if the conditions for quick charging are not satisfied in step S2, trickle charging is performed with a constant heavy current of 70 mA (step S8), and a counter is activated every minute. A constant value (4) is added to the value (step 510). Further, in step S1, if the conditions for charging are not satisfied, it is further determined whether the power switch 7 is in the on state (step 511), and the power switch 7 is in the on state. In this case, the amount of discharge consumed from the secondary battery 1 through the resistor 2 is determined every second (step 512).

Then, a value corresponding to the discharge amount determined in step S12 is subtracted from the counter value (step 813). Then, the alarm/display unit 19 determines the remaining amount of power according to the counter value.
(Step 515).

Now, by executing step S6 and step S7 (the characteristic part of the present invention) in the above-mentioned flowchart,
The reason why the value of the counter can be made to accurately correspond to the remaining amount of power of the secondary battery 1 can be explained as follows.

That is, since the maximum storage capacity of the secondary battery 1 is known in advance based on the specifications of the secondary battery 1, if the secondary battery 1 is fully charged, the power corresponding to the maximum storage capacity will be transferred to the secondary battery 1. This means that it is stored in Therefore, when a fully charged state is detected based on fluctuations in the voltage between the terminals of the secondary battery 1 using the ~Δ■ method described above, a value corresponding to its maximum storage capacity is set as a predetermined value corresponding to full charge. By setting the counter value, it is possible to make the counter value correspond accurately to the remaining power level of the secondary battery 1.

Furthermore, when detecting the fully charged state of the secondary battery 1 using the -ΔV method, the fully charged state is accurately detected regardless of the temperature of the secondary battery 1. Therefore, it is possible to set the counter value to a value corresponding to the maximum storage capacity of the secondary battery when a fully charged state is detected, and to make the counter value correspond accurately to the remaining power level of the secondary battery 1. can. In the above example, each time a fully charged state is detected, 612 is displayed on the counter.
The value is set to 0. This makes it possible to prevent an error from increasing between the counter value and the remaining amount of power in the secondary battery 1 as the above-described additions and subtractions are repeated. By the way, the performance of the secondary battery 1 deteriorates depending on its degree of use, such as changes over time and the number of repeated charging and discharging, and its maximum storage capacity decreases. Therefore, in the present invention, the predetermined value set in the counter when it is detected that the secondary battery 1 is in a fully charged state is decreased in accordance with the degree of use of the secondary battery. As a result, the remaining amount of power of the secondary battery can be monitored in consideration of a decrease in the maximum storage capacity due to deterioration of the secondary battery 1. Specifically, a timer measures the elapsed time since the time when the secondary battery 1 was replaced, and a predetermined value (
On the upper side, 6120) is decreased according to 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 a 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.

By doing as described above, the remaining power level of the secondary battery 1 can be accurately monitored based on the counter value.

Then, a display command signal is output from the charge/discharge control section 8 to the alarm/display section 19 in accordance with the counter value corresponding to the remaining amount of power of the secondary battery 1. The remaining power level of the secondary battery 1 is displayed by causing LEDs of a number and color corresponding to the display command signal to emit light. Further, the alarm/display unit 19 has a buzzer that emits an alarm sound, and the battery low detection unit 13 detects the secondary battery 1.
When it is detected that the voltage has decreased below a predetermined voltage, an alarm sound is emitted every minute in response to an alarm command signal from the charge/discharge control section 8. This allows the user to recognize that the remaining power of the secondary battery 1 is low.

Note that the present invention is not limited to the above-mentioned embodiments,
Various modifications are possible.

For example, in the embodiment described above, the fully charged state of the secondary battery 1 is detected by detecting the voltage drop (-ΔV) after the fully charged state, or the fully charged state of the secondary battery 1 is detected as follows. It is also possible to detect the In other words, in the above embodiment, rapid charging of the secondary battery 1 is performed with a constant charging current of 1.2 people, so if the maximum storage capacity and charging efficiency of the secondary battery are known, it is difficult to discharge the secondary battery 1. You can calculate the time it takes to fully charge from the off state. For example, 6120Asec (= 1700mAHour)
When rapidly charging a secondary battery with a maximum storage capacity of 130% with a charging efficiency of 65%,
After a few minutes of rapid charging, the battery will reach full charge. Therefore, the fully charged state can be detected by activating a timer from the time rapid charging is started and assuming that the secondary battery is fully charged when a predetermined period of time has elapsed. Furthermore, since the voltage between the terminals of the secondary battery 1 reaches its maximum in a fully charged state and exceeds a predetermined voltage value, the fully charged state can also be detected by monitoring the voltage value between the terminals of the secondary battery 1. For example, the voltage between the terminals of secondary battery 1 is 13.7V
In the above case, the charging/discharging control section 8 may be configured to detect this as a fully charged state of the secondary battery 1. Then, after the required charging time (130 minutes) has elapsed,
Even when the maximum voltage value (13.7V) of the secondary battery is detected, it is assumed that the secondary battery 1 has reached a fully charged state, and the charge/discharge control unit 8 instructs the DC/DC converter 3 to set the charging method. If a switching signal is output, it is possible to switch the charging method from quick charging to trickle charging in response to this switching signal.

Further, in the above-described embodiment, rapid charging is stopped in the following cases even if a fully charged state is not detected.

■When the power switch 7 of the main unit is turned on.

■When the AC adapter is not connected to the DC/DC converter 3.

(3) When the secondary battery 1 or the DC/DC converter 3 is not connected.

■When the voltage between the terminals of the secondary battery 1 drops abnormally (for example, when it becomes 9.6■ or less).

If any of these conditions ■ to ■ occur, the charging system or secondary battery is not in a state that allows rapid charging, or there is some kind of abnormality in the secondary battery. Since it is possible to determine whether the command signal from the charge/discharge control unit 8 to stop rapid charging or the DC/DC converter 3
is output, and depending on this, fast charging or stopping is performed. In this way, even if quick charging is stopped, trickle charging is always performed on the condition that the AC adapter is connected to the DC/DCC/type controller 3.

Note that if the conditions for starting quick charging are met, quick charging will be performed again.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to make the counter value correspond accurately to the remaining power amount of the secondary battery, so that the remaining power amount of the secondary battery can be accurately monitored.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an information processing device to which the present invention is applied, Fig. 2 is a block diagram of a voltage detection section and a current detection section, and Fig. 3 is a flowchart showing the operation of monitoring the remaining power of the secondary battery. It is. 1... Secondary battery, 2... Resistance, 3... DC/DC
converter, 5...main circuit section, 6...external power supply,
7...Power switch, 8...Charge/discharge control unit, 8a...-ΔV detection circuit, 1o...AC adapter detection unit, 11.Voltage detection unit, lla...Voltage detection circuit, 1
1b...Switch means, 11c...Impedance conversion circuit, 11d...Level conversion circuit, 12...
Current detection section, 12a... Current detection circuit, 12b Switch means, 12c... Impedance conversion circuit, 12
d...Amplifier, 13...Battery low detection section, 1
5... Shutdown detection unit, 16... External power supply connection terminal, 17... Regulator, 18-9. Reference voltage source, 19...Alarm/display section.

Claims (1)

[Claims] 1. Detect power consumption and charging power of the secondary battery, subtract or add values corresponding to these from a counter value corresponding to the remaining power of the secondary battery, and calculate the value of the counter value. A method for monitoring the remaining power level of the secondary battery based on the method, wherein when a fully charged state is detected from the voltage between terminals of the secondary battery, a predetermined value corresponding to full charge is set to the counter value. A method for monitoring the remaining power level of a secondary battery, characterized in that: 2. The method for monitoring the remaining power of a secondary battery according to claim 1, wherein the predetermined value corresponding to the fully charged state is changed depending on the degree of use of the secondary battery.