JPH09322420A - Charge time calculation method and battery pack - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To accurately obtain the charging time of a secondary battery. For example, when a secondary battery such as a lithium ion battery is charged with a constant current and a constant voltage, the internal resistance of the secondary battery is R, the charging voltage is V _chg, and the charging current is I _chg.
, And the remaining capacity when the open voltage of the secondary battery is x is C (x), the first time T _chg1 charged with a constant current is expressed by the formula T _chg1 = (C (V _chg -RI _chg ) -C (v _st )) / I
Calculated according to _chg . Also, the second time T _chg2 of charging with a constant voltage is the open voltage v (t) of the secondary battery.
It is calculated by approximating (t is time) by the formula v (t) = V _full × k × e ^{−1 / t} . In addition, k represents a coefficient corresponding to the characteristics of the secondary battery, V _full represents a full charge voltage of the secondary battery, and e ^{−1 / t} represents an exponential function.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a charging time calculation method and a battery pack. In particular, the present invention relates to a charging time calculation method and a battery pack that can accurately obtain the charging time until the charging of the secondary battery is completed.

[0002]

2. Description of the Related Art Recently, for example, a microcomputer (microcomputer) for monitoring a battery is built in, and the state of the secondary battery (for example, voltage of the secondary battery, charging / discharging current, remaining capacity (2
(Remaining capacity of the next battery), etc.) and exchange data (communication) with a charger or load such as a computer, smart battery (Smart Battery)
(Duracell (Intel) (proposed by Intel)) or intelligent battery such as a battery pack has been realized.

When such a battery pack is used, the state of the secondary battery transmitted from the battery pack can be notified to the user on the charger or the load side. Further, in the battery pack, for example, when the secondary battery is charged, the charging time until the charging is completed is transmitted to the charger, and the charger displays the charging time transmitted from the battery pack. And then
It is also possible to notify the user.

[0004]

By the way, in a smart battery (intelligent battery), a charging time is required based on, for example, a current integration method. That is, the charging time can be obtained by integrating the discharge current that has flowed from the time of full charge to time and dividing the resulting capacity (hereinafter, appropriately referred to as free capacity) by the charging current. Has been done.

Therefore, there is a problem that it is difficult to obtain an accurate charging time.

That is, the secondary battery is slightly discharged even if it is left unused without using it. Then, a slight discharge current due to this discharge causes an error in the free space, and as a result, there is a problem that it is difficult to obtain an accurate charging time.

Therefore, there is a method of providing a highly accurate current detection circuit capable of detecting such a small discharge current and calculating the empty capacity in consideration of the discharge current. The detection circuit is expensive, which increases the cost of the battery pack.

Further, in order to obtain an accurate charging time, there is a method of completely discharging the secondary battery before charging when charging, but this requires time. .

The present invention has been made in view of such a situation, and makes it possible to easily obtain an accurate charging time.

[0010]

According to a first aspect of the present invention, there is provided a charging time calculation method, wherein a first time during which a secondary battery is charged with a constant current is set to an open voltage and a secondary battery during constant current charging. Based on the voltage drop due to the internal resistance, 2
The second time during which the secondary battery is charged at a constant voltage is obtained based on the voltage drop due to the internal resistance.

The charging time calculation method according to claim 7 is 2
The first time for which the secondary battery is charged with a constant current is determined based on the open voltage and the voltage drop due to the internal resistance of the secondary battery during constant current charging, and the second time for which the secondary battery is pulse charged is determined. The time is obtained based on the duty ratio of the charging current.

A method for calculating a charging time according to claim 11 is
Based on the open voltage, the secondary battery obtains the first time during which the same discharge current as the charging current can be kept flowing, and the first time and the fully charged secondary battery are
The charging time is obtained from the second time during which the same discharging current as the charging current can be kept flowing.

The battery pack according to claim 15 is 2
A first time calculating means for determining a first time for which the secondary battery is charged with a constant current based on an open voltage and a voltage drop due to an internal resistance of the secondary battery during constant current charging, and a constant time for the secondary battery. A second time detecting means for determining a second time for charging with a voltage based on a voltage drop due to an internal resistance.

The battery pack according to claim 16 is 2
First time calculating means for obtaining a first time for which the secondary battery is charged with a constant current based on an open voltage and a voltage drop due to an internal resistance of the secondary battery during constant current charging, and a pulse for the secondary battery A second time calculating means for obtaining the second time to be charged based on the duty ratio of the charging current.

A battery pack according to a seventeenth aspect of the present invention is a battery pack according to the first aspect, further comprising first time calculating means for obtaining a first time during which the secondary battery can continue to flow the same discharge current as the charging current based on the open voltage. , A first time, and a charging time calculation means for calculating a charging time from a second time in which the secondary battery in a fully charged state can continue to flow the same discharge current as the charging current. And

In the charging time calculation method according to claim 1 and the battery pack according to claim 15, the first time when the secondary battery is charged with a constant current is an open voltage,
And the second time during which the secondary battery is charged at a constant voltage is calculated based on the voltage drop due to the internal resistance of the secondary battery during constant current charging, and the second time is calculated based on the voltage drop due to the internal resistance. Has been done.

In the charging time calculation method according to claim 7 and the battery pack according to claim 16, the first time when the secondary battery is charged with a constant current is an open voltage,
And the second time during which the secondary battery is pulse charged is determined based on the voltage drop due to the internal resistance of the secondary battery during constant current charging, and is determined based on the duty ratio of the charging current. There is.

According to the eleventh aspect of the charging time calculation method and the seventeenth aspect of the battery pack, based on the open voltage, the secondary battery can keep flowing the same discharging current as the charging current. 1 time is required, the first time, and the fully charged rechargeable battery,
The charging time is calculated from the second time during which the same discharging current as the charging current can be kept flowing.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but before that, in order to clarify the correspondence between each means of the invention described in the claims and the following embodiments. The features of the present invention are described as follows by adding a corresponding embodiment (however, an example) in parentheses after each means.

That is, a battery pack according to a fifteenth aspect is a battery pack having a built-in secondary battery that is charged with a constant current and a constant voltage, and detecting means for detecting an open voltage of the secondary battery (for example, FIG. And the battery selector 10 shown in FIG. 9) and the first time for which the secondary battery is charged with a constant current,
First voltage calculation means (for example, processing step S2 of the program shown in FIG. 5) calculated based on the open voltage and the voltage drop due to the internal resistance of the secondary battery during constant current charging The second time to be charged at
Second time detection means (for example, processing step S3 of the program shown in FIG. 5) obtained based on the voltage drop due to the internal resistance is provided.

A battery pack according to a sixteenth aspect is a battery pack having a built-in secondary battery which is charged with a constant current until a full charge voltage is reached, and then the charging current is turned on / off to perform pulse charging. And a detection means for detecting the open voltage of the secondary battery (for example, the battery selector 10 shown in FIG. 1 and FIG. 9) and a first battery for charging the secondary battery with a constant current.
The first time calculating means (for example, the processing step S12 of the program shown in FIG. 7) for obtaining the time of 1) based on the open voltage and the voltage drop due to the internal resistance of the secondary battery during constant current charging, and the secondary Second, the battery is pulse charged
Is provided based on the duty ratio of the charging current (for example, the processing step S14 of the program shown in FIG. 7).

A battery pack according to a seventeenth aspect is a battery pack having a built-in secondary battery charged by a charging current supplied from the outside, and a detecting means (for example, a detecting means for detecting an open voltage of the secondary battery). Based on the battery selector 10 shown in FIG. 12) and the open voltage, a first time calculating means (for example, a first time calculating means for obtaining a first time during which the secondary battery can continue to flow the same discharging current as the charging current). , Processing step S23 of the program shown in FIG. 13),
Charging time calculating means for obtaining the charging time from the first time and the second time during which the secondary battery in the fully charged state can keep flowing the same discharging current as the charging current (for example, shown in FIG. 13). Program processing step S24, etc.).

Of course, this description does not mean that each means is limited to the above.

FIG. 1 shows a configuration example of a personal computer (personal computer) system to which the present invention is applied.
This personal computer system is composed of a personal computer (main body) and a battery pack attached to the personal computer, and the personal computer is, for example, a portable type.

The battery pack has the above-mentioned communication function (intelligent battery) and is attachable to and detachable from the personal computer. This battery pack has, for example, three lithium-ion type batteries (cells) E1 to E3 as secondary batteries, and these cells E1 to E3 are connected in series. And
The + terminal of the cell E1 is connected to the + terminal 2 of the pack (battery pack), and the-terminal of the cell E3 is the FET4 connected in series to the cells E1 to E3.
5 and a resistor 6 are connected to the GND terminal (ground terminal) 8 of the pack. Therefore, the discharge currents of the cells E1 to E3 (hereinafter, these are also collectively referred to as a secondary battery E as appropriate) flow through the + terminal 2 and the GND terminal 8 (for the load, the + terminal 2 and the GND terminal). The discharge current is supplied via 8), and the charging current for the secondary battery E also flows through the + terminal 2 and the GND terminal 8.

The microcomputer (microcomputer) 1 is
For example, a built-in CPU or the like is used to recognize the voltage of each of the cells E1 to E3 (the voltage between the + terminal and the − terminal of the cell) (hereinafter, appropriately referred to as cell voltage) based on the output of the amplifier 11. FET4, 5 corresponding to the cell voltage
The voltage applied to the gate (G) is controlled. Further, the microcomputer 1 recognizes the current (charging current and discharging current) flowing in the secondary battery E based on the output of the amplifier 7 and, even if it corresponds to the current, determines the voltage applied to the gates of the FETs 4 and 5. It is designed to be controlled.
That is, the microcomputer 1 thereby turns on / off (switches) the FETs 4 and 5 to prevent the battery pack from being overcharged and overdischarged.

The microcomputer 1 is also configured to calculate the capacity (remaining capacity) of the secondary battery E based on the cell voltage recognized as described above. Further, the microcomputer 1 is also configured to obtain (calculate) the charging time required to charge the secondary battery E by referring to various tables stored in the table storage unit 3. The microcomputer 1 is also connected to the communication terminal 9 of the pack, and communicates with the microcomputer 21 described later through the communication terminal 9 according to a predetermined communication procedure. That is, the microcomputer 1 performs a predetermined process according to the data (command) transmitted via the communication terminal 9, or the voltage of the secondary battery E (cells E1 to E3 connected in series). , The voltage between the positive terminal of the cell E1 and the negative terminal of the cell E3 (hereinafter referred to as battery voltage as appropriate), the cell voltage of each of the cells E1 to E3, the charge / discharge current, the remaining capacity of the secondary battery E, and the like. Secondary battery E
The information regarding the state (state information), the charging time required for charging the secondary battery E (cells E1 to E2), and other information are also output via the communication terminal 9.

The table storage unit 3 stores various tables as will be described later. The drain (D) of the FET (field effect transistor) 4 is connected to the negative terminal of the secondary battery E (the negative terminal of the cell E3), and the source (S) thereof is connected to the source of the FET 5. FET
The drain of 5 is connected to the GND terminal 8 via the resistor 6. A parasitic diode 4A is formed between the source and the drain of the FET 4 in the direction in which the discharge current of the secondary battery E flows (therefore, in the direction in which the charging current of the secondary battery E does not flow). There is. Further, in the FET 5, a parasitic diode 5A is formed between the source and the drain of the FET 5 in the direction in which the charging current of the secondary battery E flows (therefore, in the direction in which the discharging current of the secondary battery E does not flow). There is. Here, in the present embodiment, the FETs 4 and 5 are adapted to be turned on or off, respectively, when H or L level is applied to their gates.

The resistor 6 is a resistor having a minute resistance value for current detection, one end thereof is connected to the drain of the FET 5, and the other end thereof is connected to the GND terminal 8. The amplifier 7 detects the voltage drop (voltage) caused by the current (charging current and discharging current) flowing through the resistor 6 from the microcomputer 1
It is adjusted to a level that can be handled by and supplied to the microcomputer 1. The battery selector 10 is, for example, a multiplexer, and periodically selects each of the cells E1 to E3, detects the voltage (cell voltage) between the + terminal and the − terminal of the selected cell, and 11 is supplied. Like the amplifier 7, the amplifier 11 supplies the voltage (cell voltage) supplied from the battery selector 10.
Is adjusted (converted) to a level that can be handled by the microcomputer 1.
Then, the data is supplied to the microcomputer 1.

The battery pack includes the secondary battery E, the microcomputer 1, the + terminal 2, the table storage section 3, the FET 4, and the FET 4 described above.
5, a resistor 6, an amplifier 7, a GND terminal 8, a communication terminal 9, a battery selector 10, and an amplifier 11.

On the other hand, the personal computer comprises a microcomputer 21, a personal computer section 22, a charger 23, a + terminal 25, a communication terminal 26, and a GND terminal 27.

The microcomputer 21 is connected via the communication terminal 26 to
It is adapted to communicate with the microcomputer 1. That is, the microcomputer 21 is configured to, for example, transmit a predetermined command to the microcomputer 1 and receive the status information and other information transmitted from the microcomputer 1.
Further, the microcomputer 21 includes a personal computer section 22 and a charger 2.
The control of 3 is also performed.

The personal computer section 22 is a block having the original function of the personal computer, and operates by using the voltage and current supplied from the charger 23 or the voltage and current supplied from the battery pack as a power source.
The charger 23 is composed of, for example, a constant voltage source and a constant current source, supplies voltage and current as a power source to the personal computer section 22 under the control of the microcomputer 21, and charges a battery pack. It is designed to supply electric current.

The + terminal 25 is connected to the + terminal of the charger 23. The communication terminal 26 is connected to the microcomputer 21. The GND terminal 27 is connected to the-terminal of the charger 23.

The personal computer section 22 has a charger 23+
It is connected to the connection point with the terminal 25 and the connection point with the charger 23 and the-terminal 27. In addition, the + terminal 25, the communication terminal 26, or the GND terminal 27 has a battery pack
When properly attached to the personal computer, it is connected to the + terminal 2, the communication terminal 9 or the GND terminal 8, respectively.

Next, the operation will be described. When the personal computer section 22 operates using the battery pack as a power source, the + terminal of the secondary battery E (+ terminal of the cell E1), the + terminals 2 and 25, the personal computer section 22, the GND terminal 2
7, 8, resistor 6, FET5 (between drain and source), F
A discharge current flows through the path of ET4 (between the source and drain) and the-terminal of the secondary battery E (-terminal of the cell E3).

At this time, the microcomputer 1 uses the battery selection unit 10
Detects the cell voltage of each of the cells E1 to E3 periodically output by the amplifier 11 based on the output of the amplifier 11, and any one of the cell voltages of the cells E1 to E3 outputs a predetermined first reference voltage (cells E1 to E3). When E3 becomes smaller than the voltage that may cause an overdischarge state, the gate of FET5
The L level is applied to turn off the FET5.
Since the parasitic diode 5A of the FET 5 is connected in the direction in which the charging current flows, that is, the direction in which the discharging current does not flow, when the FET 5 is turned off, the discharging current is cut off. This prevents over-discharge.

The microcomputer 1 also detects the discharge current based on the output of the amplifier 7, which is the predetermined first value.
Even when the current exceeds the reference current (current that may cause the cells E1 to E3 to be in the over-discharged state), the FET 5 is turned off, and thereby the discharge current is cut off.

In this way, when the discharge current is cut off (immediately before being cut off), the microcomputer 21 controls the charger 23 to operate as a power source for the personal computer section 22 and to charge the battery pack with the charge current. To supply.
That is, in this case, the + terminal, the + terminal 25 of the charger 23,
2, the secondary battery E, the FET 4, the parasitic diode 5A, the resistor 6, the GND terminals 8 and 27, the charging current flows through the negative terminal of the charger 23, whereby charging of the secondary battery E is started. However, in this case, in the parasitic diode 5A, when a voltage of a certain level is applied to the gate in comparison with the source-drain of the FET 5 (the FET 5 (the same applies to the FET 4)), the ON resistance becomes a small value. Therefore, the voltage drop between the source and drain is very small), and a large voltage drop of about 0.6 to 0.8 V occurs, so that efficient charging cannot be performed.

Therefore, when the charging is started, the microcomputer 1 detects a voltage drop (for example, a voltage drop of about 1 V) caused by the charging, and when the voltage drop is detected,
F level is forcibly applied to the gate of FET5 and F
Turn on ET5. As a result, the charging current flows in the path of the + terminal of the charger 23, the + terminals 25 and 2, the secondary battery E, the FETs 4 and 5, the resistor 6, the GND terminals 8 and 27, and the-terminal of the charger 23, and the efficiency is improved. Charging is performed.

During charging, the microcomputer 1 detects the cell voltage as in the case of discharging, and the cell E
When any of the cell voltages of 1 to E3 becomes higher than a predetermined second reference voltage (voltage at which the cells E1 to E3 may be in an overcharged state), the gate of the FET4 is set to L level. Applied, which turns off FET4. Since the parasitic diode 4A of the FET 4 is connected in the direction in which the discharging current flows, that is, the direction in which the charging current does not flow, the charging current is cut off when the FET 4 is turned off. This prevents overcharging.

Note that the microcomputer 1 detects the charging current based on the output of the amplifier 7 as in the case of discharging, and this detects a predetermined second reference current (for example, the first reference current). When the current becomes larger than the same current), the FET 4 is turned off, so that the charging current is cut off.

After the charging is completed, the personal computer section 22 again
When the battery pack is operated with the power source, the FET 4 is turned off immediately after the charging is completed, and therefore the + terminal, the + terminal 2, 25 of the secondary battery E, the personal computer section 22, the GND terminals 27, 8 are connected. , The resistor 6, the FET 5, the parasitic diode 4A, and the negative terminal of the secondary battery E, the discharge current flows. However, in this case, the parasitic diode 4
In A, a large voltage drop occurs as in the above-mentioned parasitic diode 5A, so that efficient discharge cannot be performed.

Therefore, when the discharge is started, the microcomputer 1 causes, for example, a voltage drop (for example, 0.4
When a voltage drop of about V) is detected and the voltage drop is detected, the H level is forcibly applied to the gate of the FET4 to turn on the FET4. As a result, as described above, the + terminal, the + terminal 2, 25 of the secondary battery E, the personal computer section 22, the GND terminals 27, 8, the resistor 6, the FETs 5, 4, 2,
A discharge current flows through the path of the-terminal of the secondary battery E, and efficient discharge is performed.

When the battery pack is normally attached to the personal computer, the communication terminals 9 and 26 are connected between the microcomputers 1 and 21, including during charging and discharging as described above.
Communication is performed via. That is, for example, the microcomputer 21
However, when a command for inquiring the cell voltage of the cells E1 to E3, the remaining capacity, and the charging / discharging current is sent to the microcomputer 1, the microcomputer 1 detects (calculates) as described above in response to the command. The cell voltage, the remaining capacity, and the charging / discharging current are transmitted to the microcomputer 21.

Further, for example, the microcomputer 21 issues a command (Atrate Time to Full) for inquiring the charging time of the secondary battery E to the microcomputer 1 (for example, a code such as 0x05 (0x is a hexadecimal number following it). (Representing that there is)), the microcomputer 1 calculates the charging time while referring to the table storage unit 3 in response to the command, and sends it to the microcomputer 21.

Next, a method of calculating the charging time of such a secondary battery will be described. When the secondary battery is a lithium-ion battery as described above, the remaining capacity corresponds to the open voltage of the secondary battery in a one-to-one relationship, and therefore,
If the open voltage of the secondary battery is known, the remaining capacity can be known. Then, if the remaining capacity is known, the free capacity can be obtained by calculating "total capacity (= nominal battery capacity)"-"remaining capacity", and the free capacity is divided by the charging current ( The charging time can be determined by calculating "free space" / "charging current".

Therefore, first, when the secondary battery is charged with a constant current and a constant voltage, that is, until the battery voltage V (t) reaches the full charge voltage V _full as shown in FIG. I
_A method of calculating the charging time when charging with _chg and thereafter charging with constant voltage V _chg until the charging current I (t) becomes sufficiently small will be described.

In FIG. 2, time is represented by t, the charging current is I (t), and the battery voltage of the secondary battery (battery voltage when the charging current is flowing) is V (t). )
The open voltage of the secondary battery is v (t) (shown by a dotted line in the figure), the internal resistance of the secondary battery is R, and the full charge voltage of the secondary battery is V _full . Also,
In FIG. 2, V _chg represents the charging voltage output by the charger. Therefore, when charging is performed at a constant voltage, V
(T) = V _chg . Further, in FIG.
_chg represents a charging current when the secondary battery is charged with a constant current. Therefore, I (t) = I _chg when charging is performed with a constant current.

The full charge voltage V of the lithium ion battery
_Full is, for example, about 4.2 V, and charging voltage V _chg is a voltage somewhat higher than that (for example, about _4.25 V / cell).
It is said. The recommended value of the charging current I _chg is 1 C / cell or less. Here, C is an abbreviation for Charge, and 1C means that a current of 1000 mA (milliampere) is applied to a battery having a capacity of 1000 mAH (milliampere ower), for example.

In constant current constant voltage charging, I _chg ≤
When (V _chg -v (t)) / R, that is, while the open voltage v (t) of the secondary battery is V _chg -RI _chg or less, charging is performed by the charging current I _chg . Therefore, 2
The remaining capacity when the open voltage of the secondary battery is x is C
When expressed as (x), the open voltage v (t) of the secondary battery is V _chg from the time when the secondary battery is charged with a constant current, that is, from the start of charging (or the start of calculation of the charging time).
-Time (first time) T _chg1 before reaching RI _chg is
It can be calculated by the following formula.

T _chg1 = (C (V _chg −RI _chg ) −C (v _st )) / I _chg (1) Here, v _st represents the open voltage of the secondary battery at the start of charging.

As described above, the internal resistance R is _equal to the time T _chg1.
Voltage drop RI _chg when a current I _chg is flowing in
It can be _calculated from the open voltage v _st of the secondary battery.

Then, while the secondary battery is charged at a constant voltage, that is, the open voltage v (t) changes from V _chg -RI _chg to the full charge voltage V _full , the charging current I.
_{Since chg} can be expressed as (V _chg −v (t)) / R, the time (second time) T _chg2 required for this is the integration by the voltage v (t) expressed by the equation (2). Can be found at.

[0055]

[Equation 1] ... (2)

From equation (1) or (2), respectively, T
After _{obtaining chg1} or T _chg2 , the charging time T _chg can be obtained by the following equation.

T _chg = T _chg1 + T _chg2 (3)

By the way, in order to calculate the equation (2),
Open voltage v (t) of the secondary battery during constant voltage charging
Need to know. Therefore, here, the open voltage v
The (t), approximated by e.g. exponential function e ^x. That is, v
For example, (t) is approximated by the following equation.

V (t) = V _full × k × e ^{−1 / t} (4) However, k is a predetermined constant (hereinafter, appropriately referred to as a characteristic coefficient).

The characteristic coefficient k is determined based on the characteristics of the secondary battery. That is, by changing the characteristic coefficient k to, for example, k ₁ , k ₂ , k ₃ , ...
As shown in (a), various curves approximating v (t) can be obtained. Among these curves, the one whose shape best matches the characteristics of the secondary battery whose charge time is to be calculated. Is selected, and k that gives the curve is determined as the characteristic coefficient of the secondary battery. Specifically, for example, while charging the secondary battery, the open voltage of the secondary battery is actually measured, and the characteristic coefficient k that gives a curve that most closely approximates the measured change of the open voltage may be selected.

After determining the characteristic coefficient k of the secondary battery, as shown in FIG. 3 (b), v (t) of the equation (4) given by the characteristic coefficient k is changed to various voltages v. ₁ , v ₂ ,
v _3, the time from the respective ... until the full charge voltage ^{_{V full t 1, t 2,}} t 3, determine the.., which, for example, as shown in FIG. 4, as previously tabulated (Such a table will be appropriately referred to as a charging time table hereinafter). This charging time table is V _chg -RI _chg
Are v ₁ , v ₂ , v ₃ , ..., And the open voltage v of each secondary battery when constant voltage charging is performed.
Time until (t) reaches full charge voltage V _full , that is, T
_{Since chg2} is represented, if V _chg −RI _chg is given, the time T _chg2 can be obtained by referring to this charging time table without calculating equation (4).

The given V _chg -RI _chg is the voltage v ₁ , v ₂ , v ₃ , ... Registered in the charging time table.
If it does not match any of the above, the V _chg −
The time T _chg2 corresponding to RI _{c hg} may be _obtained by, for example, performing linear interpolation using the registered value in the charging time table.

FIG. 5 is a flow chart for explaining the operation of the microcomputer 1 of FIG. 1 when the charging time is obtained as described above. The microcomputer 1 sends a command to inquire about the charging time (hereinafter, appropriately referred to as a charging time command),
When received from the microcomputer 21, in step S1,
The open voltage of each of the cells E1 to E3 is received from the battery selector 10 via the amplifier 11. That is, when the microcomputer 1 receives the charging time command before starting the charging (before receiving the charging current from the charger 23) (however, it is assumed that the discharging is not performed at this time). The output of the selector 10 is received as the open voltage of each of the cells E1 to E3. Also, microcomputer 1
Turns off FET4 once during charging,
The charging current is cut off, and in that state, the battery selector 10
The voltage output by the cell is received as the open voltage of each of the cells E1 to E3.

Then, in step S2, the microcomputer 1 calculates the time T _chg1 according to the equation (1) using the open voltage v _st received in step S1. That is, the table storage unit 3 stores a table in which the open voltage of the secondary battery is associated with the remaining capacity thereof (hereinafter, as appropriate,
The capacity table) is stored and the microcomputer 1
Referring to this capacity table, C in equation (1)
(V _chg −RI _chg ) and C (v _st ) are calculated (if necessary, for example, by performing linear interpolation). Then, the microcomputer 1 calculates the time T _chg1 by performing the calculation according to the equation (1).

Here, the charging voltage V _chg , the charging current I _chg , and the internal resistance R are required to calculate the equation (1). However, the charging voltage V _chg and the charging current I _chg are normally set in advance. Since it is determined and the internal resistance R can be measured in advance, the microcomputer 1 calculates the equation (1) based on the charging voltage V _chg and the charging current I _chg and the internal resistance R. ) Is calculated. However, the charging voltage V _chg and the charging current I _chg may be transmitted from the microcomputer 21 that controls the charger 23 to the microcomputer 1. The charging current I _chg is
Alternatively, the recognition may be performed based on the output of the amplifier 7.

When the battery pack has a plurality of cells such as cells E1 to E3 as in the embodiment of FIG. 1, the microcomputer 1 has the highest open voltage among them. It is designed to use things. In this way, the highest open voltage is used as a reference, and if the lowest open voltage is used as a reference,
This is because a cell having an open voltage higher than the open voltage may have a high voltage during charging, which is not preferable from the viewpoint of safety.

After calculating the time T _chg1 , the process proceeds to step S3, and the microcomputer 1 calculates the time T _chg2 as described above. That is, the table storage unit 3 stores the charging time table as shown in FIG.
Calculates the time T _chg2 corresponding to V _chg -RI _chg by referring to this charging time table (if necessary, for example, by performing linear interpolation). Alternatively, the microcomputer 1 may use the voltage v (t) given by the equation (4).
By executing the integration of the equation (2) using
_{Calculate chg2} . From the viewpoint of reducing the load on the microcomputer 1, it is desirable to calculate the time T _chg2 using a method using a charging time table.

Then, the microcomputer 1 proceeds to step S4 to calculate the charging time T _chg according to the equation (3),
For example, the processing is ended by transmitting it to the microcomputer 21.

The open voltage in the case where the secondary battery is a lithium ion battery corresponds to the remaining capacity thereof as described above. Therefore, by calculating the charging time according to such open voltage, the open voltage is accurately calculated. It is possible to obtain a proper charging time. That is, for example, even if a slight discharge current flows from the secondary battery, the decrease in the remaining capacity due to that appears in the open voltage, and the charging time is obtained based on this open voltage. Obtainable. Further, in order to obtain an accurate charging time, it is not necessary to completely discharge the secondary battery when charging, as in the case of the current integration method.

Next, as shown in FIG. 6, the secondary battery is charged with the battery voltage (voltage between the positive terminal and the negative terminal of the secondary battery).
Constant current I until V (t) reaches full charge voltage V _full
A method of calculating the charging time in the case of charging at (t) = I _chg and then performing pulse charging by turning on / off the charging current will be described. In FIG. 6, the open voltage v (t) of the secondary battery is not shown. FIG.
Then, in pulse charging, charging current I (t) = I _chg
Turns on for a period T _{1 and then} turns off for a period T ₂ ,
Again, the turning on for the period T ₁ is repeated. Then, during the period T ₂ in which the charging current I _chg is turned off, the battery voltage of the secondary battery (which is the battery voltage when the charging current is turned off is equal to the open voltage) is fully charged. When the voltage does not drop below V _full , pulse charging is terminated.

In this case, until the pulse charge is started, that is, until the battery voltage reaches (at first) the full charge voltage V _full , the same charge as in the constant current constant voltage charge is performed. Therefore, the time from the start of charging to the start of pulse charging (the time during which charging is performed at a constant current) (first time) T _chg1 can be calculated by the above equation (1). it can.

At this time, when charging is completed, the battery voltage of the secondary battery drops by the amount of IR loss, that is, RI _chg (strictly speaking, it also drops by polarization, but its magnitude is the amount of IR loss. Since it is smaller than the above, it is ignored here, but this may be taken into consideration).
It can be considered that only I _{chg is} charged. That is, according to the pulse charging, the open voltage of the secondary battery is changed to V _full.
It can be considered that charging is performed from -RI _chg to V _full .

If v _pst = V _full −RI _chg is set,
The capacity increased by pulse charging is C (V _full ) −C
(V _pst ), and the duty ratio of the charging current I (t) during pulse charging, that is, T ₁ / (T ₁ + T
_{If 2} ) is set to η, the current value flowing by pulse charging is
Since it can be expressed as I _chg / η, the time during which pulse charging is performed (the time from when the battery voltage becomes V _full to the end of charging) (second time) T _chg2 is _calculated by the following equation. Can be found at.

T _chg2 = (C (V _full ) −C (v _pst )) / (I _chg / η) (5)

From equation (1) or (5), respectively, T
After _{obtaining chg1} or T _chg2 , the charging time T _chg can be obtained by the above equation (3).

FIG. 7 is a flow chart for explaining the operation of the microcomputer 1 of FIG. 1 when the charging time is obtained as described above. When the microcomputer 1 receives the charging time command from the microcomputer 21, the microcomputer 1 proceeds to step S11 or S1.
2, the same processing as in step S1 or S2 of FIG. 5 is performed, respectively.
Calculate _chg1 .

After the time T _chg1 is calculated, in step S13, the microcomputer 1 obtains the open voltage v _pst (= V _full −RI _chg ) when the pulse charging is started, and proceeds to step S14, where v _pst and v _pst The time T _chg2 is calculated from η according to the equation (5).

Here, since the charging current I (t) = I _chg is turned on / off by the microcomputer 1 controlling the FET 4, the duty ratio η can be recognized by the microcomputer 1.

When the duty ratio η (T ₁ and T ₂ ) is a fixed value, the fixed value may be used.
When the duty ratio η changes, that is, when T ₁ or T ₂ changes, it is possible to use, for example, an average value of the changing duty ratio η.

After calculating T _chg2 in step S14, the _process proceeds to step S15, and the microcomputer 1 performs the same process as in step S4 of FIG. 5 and ends the process.

Also in this case, since the charging time is calculated according to the open voltage of the secondary battery, the accurate charging time can be obtained.

By the way, the internal resistance R of the secondary battery changes with the environmental temperature T _a , for example, as shown in FIG. Also, during charging, the temperature T _t of the secondary battery itself changes, for example, as shown in FIG.
The internal resistance R also changes depending on this temperature T _t . Therefore, the resistance R is R as a function of temperature T _a and T _t.
It can be expressed as (T _a , T _t ), but in calculating the charging time, the internal resistance R considering the temperatures T _a and T _t is used.
_{(T a,} T _t) is better using, its accuracy can be further improved.

Therefore, FIG. 9 shows an example of the configuration of a personal computer system for calculating the charging time in consideration of the temperatures _Ta and _Tt . In the figure, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and description thereof will be omitted below as appropriate. That is, this personal computer system is configured similarly to the personal computer system of FIG. 1 except that the temperature sensor 31 and the temperature table storage unit 32 are newly provided.

In this personal computer system, the ambient temperature T _a is detected by the temperature sensor 31 and supplied to the microcomputer 1. Further, in the temperature table storage unit 32,
A table (hereinafter, appropriately referred to as a temperature table) in which the graph shown in FIG. 8B is made into a table is stored, and the microcomputer 1 has elapsed time t from the start of charging.
The temperature T _a which corresponds to the calculated by referring to the temperature table, based on the environmental temperature T _a received from the temperature T _a and the temperature sensor 31, and calculates the internal resistance _{R (T a, T t)} ( For example, a table in which R (T _a , T _t ) is associated with T _a and T _t is stored in the table storage unit 3, and by referring to the table, R (T _a , T _t) )
Is calculated). After that, the microcomputer 1 uses the internal resistance R ( _Ta , _Tt ) to calculate the charging time as described above.

In this case, the charging time can be obtained more accurately.

Next, for example, a lithium ion battery or the like
When the secondary battery is discharged with a predetermined constant current, its open voltage v (t) gradually decreases as shown in FIG. 10, for example. Now, the open voltage immediately before the secondary battery is over-discharged is V _emp (hereinafter, appropriately referred to as discharge end voltage), and the open voltage is the discharge end voltage V
_Assuming that the discharge of the secondary battery is terminated when _emp is reached, the discharge time T _B from when the open voltage becomes the full charge voltage V _full to the discharge end voltage V _emp can be measured in advance. it can. Similarly, the discharge time T _A from the predetermined voltage v (t) to the discharge end voltage V _emp can be measured in advance.
Therefore, the discharge time T required for the open voltage to reach the predetermined voltage v (t) from the full charge voltage V _full can be obtained by the following equation.

T = T _B −T _A (6)

Therefore, as shown in FIG. 11, if the discharge current is changed to various magnitudes and the discharge times T _A and T _B are measured and made into a table (such a table will be referred to below as appropriate). It is possible to easily obtain the discharge time T by referring to this time table).

By the way, a secondary battery such as a lithium ion battery has reversibility of charge and discharge. Therefore, the discharge time T
Is a rechargeable battery whose open voltage is v (t),
It is equal to the charging time to charge to full charge. Therefore, if the charging current and the open voltage at the start of charging are detected and the corresponding discharge time T is calculated by referring to the time table, that becomes the charging time. In the embodiment of FIGS. 1 and 9, It is also possible to use such a time table to obtain the charging time for a period in which the charging current is constant.

Next, in the case of using the time table, even if the secondary battery is charged by the variable charging current, the charging time by the variable charging current is adjusted to a certain degree of accuracy as follows. Can be found at. That is,
For example, by calculating a moving average value of variable charging current (hereinafter, appropriately referred to as moving average current) in a predetermined period after starting charging, and assuming that charging is performed at this moving average current, charging You can ask for time.

Here, the moving average value of the charging current in the predetermined period means that the charging current at the present time is the time when the time window corresponding to the predetermined period moves in the traveling direction of the time. The average value (already,
The value obtained by adding the charging current at the current time to the value obtained by subtracting the sum of the charging currents within the time window divided by the width of the time window) is divided by the width of the time window. Therefore, the current moving average value is calculated only by storing the total value of the currents used to calculate the previous moving average value, without storing each charging current in the time window. be able to. That is, the current moving average value is a value obtained by dividing the sum of the currents used to calculate the previous moving average value by the width of the time window (this is the previous moving average value). Can be calculated by subtracting, adding the charging current at the current time to the subtracted value, and dividing by the width of the time window.

This moving average value is equivalent to a value obtained by passing the charging current through a low-pass filter (RC filter) consisting of a resistor and a capacitor at a time constant of a time corresponding to the width of the time window.

After obtaining the moving average current, the charging time T corresponding to the moving average current and the open voltage at the start of charging may be calculated by referring to the time table.

FIG. 12 shows a configuration example of the personal computer system for calculating the charging time as described above. In the figure, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and the description thereof will be given below.
Omitted as appropriate. That is, this personal computer system is configured in the same manner as the personal computer system of FIG. 1 except that a moving average value calculation unit 41 that calculates a moving average value is newly provided. However, it is assumed that the table storage unit 3 stores the above-mentioned time table.

Next, the operation when the microcomputer 1 obtains the charging time by using the above-mentioned time table will be described with reference to the flowchart of FIG. Microcomputer 1
When receiving the charging time command from the microcomputer 21, in step S21, as in the case of step S1 of FIG. 5, the open voltage v _st is received. Then, in step S22, the microcomputer 1 causes the moving average value calculation unit 41 to transmit the moving average value of the charging current in a predetermined period, that is, the moving average current, and receives this.

Here, in the microcomputer 1, when the charging is started, the charging current is recognized, for example, every one second based on the output of the amplifier 7, and is supplied to the moving average value calculation section 41. The value calculation unit 41 is configured to calculate a moving average value of the charging current from the microcomputer 1 for one minute, for example.

That is, the moving average value calculation unit 41 uses the first 1
During the period, 60 current values supplied from the microcomputer 1 are added and stored in a built-in register (not shown).
Furthermore, the moving average value calculation unit 41 divides the value stored in the register by 60 (the number of samples of the current value added during 1 minute) corresponding to 1 minute, and the value obtained as a result is
Use the moving average value. Then, the moving average value calculation unit 41
When the 61st current value is supplied from the microcomputer 1, the value stored in the register is divided by 60,
That is, the previous moving average value is subtracted, and the subtracted value is
Add the current value of the second item. Furthermore, the moving average value calculation unit 4
The value 1 newly stores the added value in a built-in register, divides it by 60, and sets the division result as a moving average value (moving average current). Hereinafter, the moving average value calculation unit 41 performs the same processing each time it receives a current value (current current value) from the microcomputer 1.

Upon receiving the moving average current, the microcomputer 1 calculates the times T _A and T _B corresponding to the moving average current and the open voltage v _st in step S23 by referring to the time table. Then, the process proceeds to step S24, and the microcomputer 1 calculates the charging time T according to the equation (6) and transmits the charging time T to the microcomputer 21, for example, to end the process.

Also in the embodiment of FIG. 12, it is possible to determine the charging time in consideration of the temperatures _Ta and _Tt described above. Further, in the embodiment of FIG. 12, the moving average value of the charging current when the charging time command is received is used to obtain the charging time, but the charging time is the charging when the charging time command is received. It is also possible to obtain it by using the electric current itself.

As described above, the present invention can be mounted on a personal computer,
Although the case where the present invention is applied to a battery pack having a communication function has been described, the present invention can also be applied to a battery pack that can be attached to electronic devices other than a personal computer, for example. Further, it can be applied to a battery pack having no communication function.

In this example, the secondary batteries (cells E1 to E3) were lithium ion batteries, but
As the secondary battery, batteries other than lithium ion batteries can be used. However, the secondary battery needs to have a one-to-one correspondence between the remaining capacity and the battery voltage.

Further, in the present embodiment, the charging time is calculated in the battery pack, but the charging time may be calculated in the charger side, that is, in the personal computer in this case, for example.

[0103]

According to the charging time calculation method of the first aspect and the battery pack of the fifteenth aspect, the first time during which the secondary battery is charged with a constant current is the open voltage,
And the voltage drop due to the internal resistance of the secondary battery during constant current charging, and the second time during which the secondary battery is charged at a constant voltage is calculated based on the voltage drop due to the internal resistance. Therefore, the charging time can be accurately obtained.

According to the charging time calculation method of the seventh aspect and the battery pack of the sixteenth aspect, the first time when the secondary battery is charged with the constant current is the open voltage and the constant current charging time. Is obtained based on the voltage drop due to the internal resistance of the secondary battery, and the second time during which the secondary battery is pulse charged is obtained based on the duty ratio of the charging current. Therefore, the charging time can be accurately obtained.

According to the charging time calculating method of the eleventh aspect and the battery pack of the seventeenth aspect, the secondary battery can keep flowing the same discharging current as the charging current based on the open voltage. The first time is required,
The charging time is obtained from the first time and the second time during which the secondary battery in the fully charged state can continue to flow the same discharging current as the charging current. Therefore, for example, even when charging is performed with a variable charging current, the charging time can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of a personal computer system to which the present invention is applied.

FIG. 2 is a diagram showing changes with time in battery voltage and charging current when constant-current constant-voltage charging is performed.

FIG. 3 is a diagram showing an exponential function that approximates a voltage change of a secondary battery.

FIG. 4 is a diagram showing a charging time table.

5 is a flowchart for explaining the processing of the microcomputer 1 of FIG.

FIG. 6 is a diagram showing changes over time in battery voltage and charging current when pulse charging is performed.

FIG. 7 is a flowchart for explaining the processing of the microcomputer 1 of FIG.

FIG. 8 is a diagram showing a relationship between internal resistance and temperature of a secondary battery.

FIG. 9 is a block diagram showing the configuration of a second embodiment of a personal computer system to which the present invention is applied.

FIG. 10 is a diagram showing a change with time of an open voltage when a secondary battery is discharged.

FIG. 11 is a diagram showing a change with time of the open voltage of the secondary battery when the discharge current is changed to various magnitudes.

FIG. 12 is a block diagram showing the configuration of a third embodiment of a personal computer system to which the present invention has been applied.

13 is a flowchart for explaining the processing of the microcomputer 1 of FIG.

[Explanation of symbols]

1 microcomputer, 3 table memory, 4, 5 FE
T, 6 resistance, 9 communication terminals, 10 battery selector,
21 microcomputer, 23 charger, 26 communication terminal,
31 temperature sensor, 32 temperature table storage unit,
41 Moving Average Calculation Unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naohisa Yamaki 325 Ganbara, Nakashinta-cho, Kami-gun, Miyagi Prefecture

Claims (17)

[Claims] 1. A charging time calculation method for calculating a charging time until the end of charging when a secondary battery is charged by constant current constant voltage charging, the open voltage of the secondary battery being detected, The first time for which the secondary battery is charged with a constant current is determined based on the open voltage and the voltage drop due to the internal resistance of the secondary battery during constant current charging, and the secondary battery is charged with a constant voltage. The charging time calculation method is characterized in that the second time is calculated based on the voltage drop due to the internal resistance, and the charging time is calculated from the first and second times. 2. The charging time calculation method according to claim 1, wherein the secondary battery has a one-to-one correspondence between the open voltage and the remaining capacity. 3. Based on an exponential function approximating a change in the open voltage of the secondary battery when charged at a constant voltage,
The charging time calculation method according to claim 1, wherein the second time is obtained. 4. The second time is obtained on the basis of a charging time table which is created based on the exponential function and which tabulates the time until the open voltage of the secondary battery reaches the full charge voltage. The charging time calculation method according to claim 3, wherein 5. The charging time calculation method according to claim 1, wherein the charging time is calculated in consideration of a change in the internal resistance due to an environmental temperature. 6. The charging time calculation method according to claim 1, wherein the charging time is calculated in consideration of a temperature change of the secondary battery. 7. A rechargeable battery is charged with a constant current until the voltage reaches a full charge voltage, and then the charge current is turned on / off to perform pulse charge, and a charge time until the end of charge is calculated. A charging time calculation method for detecting the open voltage of the secondary battery, the first time during which the secondary battery is charged with a constant current, the open voltage, and the secondary time during constant current charging. The second time during which the secondary battery is pulse-charged is obtained based on the voltage drop due to the internal resistance of the battery, and is obtained based on the duty ratio of the charging current. From the first and second times, A method for calculating a charging time, characterized by obtaining a charging time. 8. The charging time calculation method according to claim 7, wherein the secondary battery has a one-to-one correspondence between the open voltage and the remaining capacity. 9. The charging time calculation method according to claim 7, wherein the charging time is obtained in consideration of a change in the internal resistance due to an environmental temperature. 10. Considering the temperature change of the secondary battery,
The charging time calculation method according to claim 7, wherein the charging time is obtained. 11. A charging time calculation method for calculating a charging time until the end of charging when a charging current is supplied to a secondary battery, the method comprising: detecting an open voltage of the secondary battery; Based on the above, the secondary battery is capable of continuing to flow the same discharging current as the charging current.
Is calculated, and the charging time is calculated from the first time and the second time during which the secondary battery in a fully charged state can continue to flow the same discharge current as the charging current. Characteristic charging time calculation method. 12. The charging time calculation method according to claim 11, wherein the rechargeable battery has an open voltage and a remaining capacity in a one-to-one correspondence. 13. When the open voltage of the secondary battery is a predetermined voltage, the first time is based on a time table in which the time during which the secondary battery can keep flowing a predetermined discharge current is tabulated. The charging time calculation method according to claim 11, wherein the charging time is calculated. 14. The secondary battery during the first time period,
The charging time calculation method according to claim 11, wherein the charging time calculation method is a time during which the same discharging current as the moving average value of the charging current in a predetermined period can be kept flowing. 15. A battery pack having a built-in secondary battery that is charged with a constant current and a constant voltage, comprising: detecting means for detecting an open voltage of the secondary battery; and the secondary battery being charged with a constant current. A first time calculating means for obtaining the time of 1 on the basis of the open voltage and a voltage drop due to an internal resistance of the secondary battery during constant current charging; and a second time when the secondary battery is charged at a constant voltage. And a second time detecting means for determining the time of 1) based on the voltage drop due to the internal resistance. 16. A battery pack having a built-in secondary battery that is charged with a constant current until a full charge voltage is reached, and then is pulse-charged by turning on / off the charging current, wherein the secondary battery is open. A detecting unit for detecting a voltage, and a first time for charging the secondary battery with a constant current based on the open voltage and a voltage drop due to an internal resistance of the secondary battery during constant current charging. 1. A battery pack comprising: a time calculating unit of 1; and a second time calculating unit that obtains a second time in which the secondary battery is pulse-charged based on a duty ratio of the charging current. 17. A battery pack containing a secondary battery charged by a charging current supplied from the outside, said detecting means detecting an open voltage of said secondary battery, and said detecting means based on said open voltage. The first rechargeable battery is capable of continuously supplying the same discharge current as the charge current.
From the first time calculating means for obtaining the time of, the first time, and the second time in which the secondary battery in the fully charged state can keep flowing the same discharge current as the charging current, A battery pack comprising: a charging time calculating means for calculating the charging time.