JP2003232839A - Residual capacity operation method of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a residual capacity operation means of a secondary battery capable of operating accurately the residual capacity of the secondary battery. <P>SOLUTION: A discharge current integrated value detected by a discharge counter 6 becomes in the abnormally reduced state, when the secondary battery 10 is used in the low-temperature state or in the high-rate discharge state. If a learned capacity is updated by the discharge current integrated value, residual capacity operation can not be performed accurately, accordingly it is determined whether the learned capacity is to be updated or not by comparison with a charge current integrated value detected by a charge counter 5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery remaining capacity calculation method characterized by a learning capacity update method required for calculating the remaining capacity of a secondary battery.

[0002]

2. Description of the Related Art In an electronic device that operates using a secondary battery as a power source, a state where the residual capacity of the secondary battery is exhausted, that is, a so-called dead battery, causes the device to stop operating, and it is unlikely to hinder business. Absent. Therefore, a mobile phone, a portable personal computer, or the like is provided with a function of detecting and displaying the remaining capacity of the secondary battery, and issuing a warning when the battery is almost dead. In particular, battery exhaustion in a portable personal computer leads to data destruction, so a more accurate remaining capacity detection function is required.

The remaining capacity is displayed as a ratio of the discharge amount obtained by integrating the discharge current amount to the learning capacity, with the discharge current integrated value capable of discharging from the fully charged state of the secondary battery to a predetermined discharge end state as the learned capacity. It However, since the dischargeable capacity decreases when the environmental temperature decreases, it is necessary to consider the characteristic change of the secondary battery due to the battery temperature when the remaining capacity is detected.

In a relatively small secondary battery such as a nickel-cadmium secondary battery, a nickel-hydrogen secondary battery or a lithium-ion secondary battery, it is known that the internal resistance of the secondary battery increases as the battery temperature decreases. ing. This characteristic is that when the battery is discharged after being charged under the same charging conditions, the internal resistance of the secondary battery will differ depending on the battery temperature due to the environmental temperature even if the discharge rate is the same. Will be different. Further, when the battery temperature becomes extremely low, the internal resistance increases, so that the discharge current can hardly be extracted in the high rate discharge. In this state, even if the secondary battery has sufficient energy, it cannot be discharged at a low temperature, and a discharge current can be taken out when the battery temperature rises.

In the capacity calculation method for detecting the remaining capacity of the secondary battery having such characteristics, the amount of discharged electricity discharged from the fully charged state to the specific condition is stored as the learning capacity, regardless of the state. The amount of electricity charged in the secondary battery is calculated as the remaining capacity, and the remaining capacity is displayed as [remaining capacity / learning capacity × 100%]. The specific condition is that the discharge stop voltage is set low when the discharge rate is high or the battery temperature is low, and the discharge stop voltage is set high when the discharge rate is high or the battery temperature is high.

[0006]

However, when the battery temperature is low and the discharge rate is high, the capacity calculation means is clearly higher than the dischargeable electricity amount that the secondary battery has. Because it learns with a small value,
The function as the capacity calculation means cannot be fully exerted, the remaining capacity at the time of charging and discharging is not properly managed, and the displayed remaining capacity differs from the actual remaining capacity of the user. Problems such as obstacles to use management occur.

In order to solve the above problems, it is known that the following specifications are added to the learning capacity calculation function of the capacity calculation means. Determining Whether Learning can be Performed Based on Battery Temperature at the Time of Learning ... Learning is not permitted unless the battery temperature detected by the capacity calculating means at the time of learning is equal to or higher than a set temperature (for example, 25 ° C.). Determining whether learning can be performed based on the ratio of the new learning capacity value to the learning capacity ... [New learning capacity value> Current learning capacity value x
If set%], learning is prohibited. For example, the learning prohibited capacity in this case is 70%.

However, in the above solution, when the battery is discharged from the fully charged state to the learning-prohibited capacity close to 70% and then left in a low temperature environment and high rate discharge is performed, the secondary battery self-heats due to the high rate discharge. However, the internal resistance of the rechargeable battery has not fallen yet, so the discharge time cannot be sufficiently secured and the discharge inhibit voltage drops. It was

The object of the present invention is to eliminate the deficiency in the remaining capacity calculation due to the update of the learning capacity by the discharge current integrated value which is abnormally decreased due to the environmental temperature and deterioration of the secondary battery. It is to provide a method for calculating the remaining capacity of a battery.

[0010]

According to a first aspect of the present invention for achieving the above object, a cumulative current amount that can be discharged from a fully charged state to a predetermined discharge termination state is stored as a learning capacity,
The learning capacity is added or subtracted by an integrated value obtained by time-integrating the charging current or the discharging current to calculate the remaining capacity, and the discharge current integrated value obtained by integrating the discharge current from the fully charged state to the discharge end state is the learned capacity. A method for calculating the remaining capacity of a secondary battery that updates the learned capacity to the discharge current integrated value at the update timing when the amount becomes less than a predetermined amount, and integrates the charging current charged from the discharge end state to the full charge state. A value obtained by measuring a value and a discharge current integrated value discharged from a full charge state to a discharge end state, and multiplying the charge current integrated value by a preset learning implementation determination coefficient smaller than 1 at the update timing. Is larger than the discharge current integrated value, the update of the learning capacity is permitted.

According to the above remaining capacity calculation method, when updating the learning capacity that is the basis of remaining capacity calculation, a value obtained by multiplying the discharge current integrated value by a preset learning execution determination coefficient greater than 1 is the charge current integrated value. Since the learning capacity is updated only when the value is larger than the value, the learning capacity is updated when the secondary battery is in a low temperature state or when there is a high rate discharge when the accumulated discharge current value is abnormally low. It can be prevented from being done. When the learning capacity is updated with an abnormally small discharge current integrated value, the remaining capacity calculation cannot be performed accurately. However, in such a case, the update of the learning capacity is not permitted, so there is no abnormality in the remaining capacity calculation. .

In the second invention of the present application, the accumulated amount of electric power that can be discharged from the fully charged state to a predetermined discharge termination state is stored as a learning capacity, and the accumulated value obtained by time-accumulating the charging current or the discharging current is preset. The remaining capacity is calculated by adding or subtracting the learning capacity with a value obtained by multiplying the constant voltage value by a constant voltage value, and the constant voltage value and the integrated value obtained by integrating the discharge current from the full charge state to the discharge end state. A method for calculating the remaining capacity of a secondary battery, which updates the learning capacity to the discharge power integrated value at an update timing when the multiplied discharge power integrated value becomes a predetermined amount or less than the learning capacity, and when the discharge end state is reached, The charging power integrated value charged up to the charging state and the discharging power integrated value discharged from the fully charged state to the discharge end state are measured, and at the update timing,
When the value obtained by multiplying the charging power integrated value by a preset learning execution determination coefficient smaller than 1 is larger than the charging power integrated value, updating of the learning capacity is not permitted.

According to the above remaining capacity calculation method, in the battery pack which manages the remaining capacity by integrating the amount of electric power, by adopting a constant voltage value as the voltage value of the secondary battery, The charge power integrated value can be calculated by multiplying the constant voltage value, and the discharge power integrated value can be calculated by multiplying the discharge current integrated value by the constant voltage value in the same manner. When the value obtained by multiplying the charging power integrated value by a preset learning implementation determination coefficient smaller than 1 is larger than the charging power integrated value, the discharge current integrated value is controlled by not allowing the update of the learning capacity. It is possible to prevent the learning capacity from being updated in a state where the number has abnormally decreased.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The embodiments described below are examples of embodying the present invention and do not limit the technical scope of the present invention.

FIG. 1 shows the structure of a battery pack to which the remaining capacity calculation method according to the present embodiment is applied, and the remaining capacity of the secondary battery 10 can be detected and displayed.

The charging counter 5 counts the amount of electricity charged in the secondary battery 10 when the charger 14 is connected to the input / output terminals 11 and 12 of the battery pack 15 and the battery pack 15 is in a charging state. The secondary battery until the full-charge detecting unit 3 detects the full-charged state of the secondary battery 10 by integrating the detection values of the charging current detected by the current detecting unit 1 and multiplying the charging efficiency by the charging efficiency. The charging current integrated value charged in 10 is stored. When the secondary battery 10 is a lithium ion secondary battery, the charging efficiency is almost 1
Since it is 00%, it is not necessary to multiply the charging efficiency. At this time, it is desirable that the charging efficiency and the discharging efficiency be set values that change depending on each current value, the environmental temperature, the charging capacity, and the like.

The charging current integrated value accumulated by the charging counter 5 from the predetermined discharge state to the full charge state is, for example, 0% after full charge without discharging.
It is not reset unless there is a specially set condition such as when the charging / discharging is performed more than the set number of times, and is held until the learning execution condition is satisfied.

The discharge counter 6 includes a battery pack 15
When the load 13 is connected to the input / output terminals 11 and 12 of the battery pack 15 and the battery pack 15 is in a discharged state, the amount of discharged electricity discharged from the secondary battery 10 is counted, and the discharge detected by the current detection means 1 is detected. The detected value of the current is integrated, and the amount of discharged electricity discharged from the secondary battery 10 is integrated and stored from the fully charged state until the voltage detection means 2 detects the discharge end voltage of the secondary battery 10.

Further, the charge counter 5 and the discharge counter 6 do not update the stored count value when charging or discharging reverses midway.

The remaining capacity calculating means 8 stores a discharge current amount which is expected to be able to discharge the fully charged secondary battery 10 as a learning capacity, and adds the learning capacity by the charging current integrated value by the charging counter 5. The learning capacity is subtracted from the discharge current integrated value by the discharge counter 6, and the calculated value is output to the display means 7 as the remaining capacity of the secondary battery 10.

The learning capacity is calculated from the full charge state to the predetermined discharge state with respect to the charge current integrated value accumulated by the charge counter 5 from the predetermined discharge state until the full charge state is detected. The update timing is rewritten when the discharge current integrated value integrated by the discharge counter 6 becomes large. When the learning capacity is updated, the remaining capacity calculating means 8 compares the charging current integrated value and the discharging current integrated value and executes the calculation of the following learning capacity update availability determination formula (1) or (2). To do. In the following equation, α is a learning implementation determination coefficient smaller than 1.

Charge current integrated value × α <Discharge current integrated value (1) Charge current integrated value <Discharge capacity integrated value / α (2) Condition of formula (1) or (2) for determining whether or not the above learning capacity can be updated When is satisfied, the remaining capacity calculation calculation means 8 does not update the learning capacity as an abnormal decrease in the discharge current integrated value.

The abnormal decrease in the integrated value of the discharge current occurs when the battery pack 15 is placed in a low temperature environment and the secondary battery 10 becomes in a low temperature state to increase the internal resistance, or when high rate discharge is performed. If the internal resistance increases due to the low temperature state of the secondary battery 10, the integrated value of the discharge current until the discharge end voltage is detected by the voltage detection means 2 abnormally decreases. Further, in the high-rate discharge, the voltage drop due to the internal resistance becomes large, and similarly, the discharge current integrated value until the discharge end voltage is detected by the voltage detecting means 2 is abnormally reduced.

If the learning capacity is updated on the basis of the discharge current integrated value that has abnormally decreased due to the low temperature environment or high rate discharge as described above, the learning capacity is set to a smaller capacity than it actually is. Since the remaining capacity cannot be calculated, the learning capacity is not updated when the condition of the above-described learning capacity update availability determination equation (1) or (2) is satisfied, that is, when the discharge current integrated value is abnormally reduced. By doing so, it becomes possible to accurately calculate the remaining capacity.

Further, in a battery pack that manages the remaining capacity by accumulating the amount of electric power, similar control can be performed by adopting a certain constant voltage value as the secondary battery voltage value. That is, charging current integrated value × constant voltage value = charging power integrated value discharge current integrated value × constant voltage value = discharging power integrated value, so charging power integrated value × α <discharge power integrated value (3) charging power integrated value Value <cumulative discharge power value / α ... (4)

When the condition (3) or (4) for determining whether or not the learning capacity can be updated is satisfied, the remaining capacity calculating means 8 does not update the learning capacity in the same manner as the discharge current integrated value abnormally decreases.

Here, the constant voltage value can be set to, for example, about 10.8 V in the case of a battery pack formed by connecting three lithium ion secondary batteries in series.

The value of α is 0.8 <α <1.
It should be about 0.

[0029]

As described above, according to the present invention, the remaining capacity is calculated by updating the learning capacity by the discharge current integrated value which is abnormally decreased depending on the low temperature state of the secondary battery or the high rate discharge. The inaccuracy of is eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a battery pack according to an embodiment.

[Explanation of symbols]

1 Current detection means 2 Voltage detection means 3 Full charge detection means 4 Temperature detection means 5 charge counter 6 discharge counter 8 Remaining capacity calculation means

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G016 CB01 CB12 CB21 CB22 CB31                       CB32 CC02 CC03 CC04 CC06                       CC13 CC14 CC21 CC23 CC28                       CD02 CD03 CE00 CF06                 5G003 AA01 BA01 DA07 EA05 GC05                 5H030 AA04 AS11 AS14 FF41 FF42                       FF43 FF44

Claims (2)

[Claims] 1. A cumulative current amount that can be discharged from a fully charged state to a predetermined discharge termination state is stored as a learning capacity, and the learning capacity is added or subtracted by a cumulative value obtained by cumulatively integrating a charging current or a discharging current with time. The remaining capacity is calculated, and the learning capacity is updated to the discharge current integrated value at the update timing when the discharge current integrated value obtained by integrating the discharge current from the full charge state to the discharge end state becomes a predetermined amount or less than the learning capacity. A method for calculating the remaining capacity of a secondary battery, which measures a charging current integrated value charged from the discharge end state to a full charge state and a discharge current integrated value discharged from a full charge state to a discharge end state Then, at the update timing, when the value obtained by multiplying the charging current integrated value by a preset learning execution determination coefficient smaller than 1 is larger than the discharge current integrated value, learning is performed. Residual capacity calculation method of a secondary battery characterized in that it does not allow the amount of updating. 2. An integrated amount of electric power that can be discharged from a fully charged state to a predetermined discharge end state is stored as a learning capacity, and an integrated value obtained by time-integrating a charging current or a discharging current and a preset constant voltage value are stored. The remaining capacity is calculated by adding or subtracting the learning capacity by the multiplied value, and the discharge power integrated value obtained by multiplying the integrated value of the discharge current from the fully charged state to the discharge terminated state by the constant voltage value. Is a remaining capacity calculation method of the secondary battery that updates the learning capacity to the discharge power integrated value at an update timing when the value becomes less than the learning capacity by a predetermined amount, and is charged from the discharge end state to the full charge state. The integrated charging power value and the discharging power integrated value discharged from the fully charged state to the discharge end state are measured, and the charging power integrated value is preset to 1 at the update timing. Small when learning has been multiplied by the execution determination coefficient value is greater than the charge power accumulated value, the remaining capacity calculation method of a secondary battery characterized in that it does not allow updates of the learning capacity.