JP2002008734A - Detecting method for battery voltage and detecting device for battery voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detecting method and device of a battery voltage capable of judging whether voltage dispersion between cells is in an allowable range or not. SOLUTION: Voltage detecting parts 12a, 2b, 2c, 2d, etc., detect cell voltages of cells 1a, 1b, 1c, 1d, etc., and when the specified voltage is detected, a detected signal 'H' is transmitted, OR judgment and AND judgment of the detected signal 'H' are conducted with an OR judgment circuit 3a and an AND judgment circuit 3b of a logic circuit part 3. When the maximum voltage of the cells is detected when charging of a battery assembly, an OR signal FLG1 is transmitted to a high order ECU 4 from the OR judgment circuit 3a. When the minimum voltage of the cells is detected, an AND signal FLG2 is transmitted to the high order ECU 4 from the AND judgment circuit 3b. The high order ECU 4 measures the time elapsed from the FLG1 to the FLG2, and thereby, the dispersion of the cell voltages is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery voltage detecting method for detecting a variation in cell voltage in each cell constituting an assembled battery by a secondary battery, and more particularly, to an EV (Electric) method.
al Vehicle: Electric Vehicle and HEV (Hybrid Electri)
TECHNICAL FIELD The present invention relates to a battery voltage detection method and a battery voltage detection device for detecting a variation in cell voltage of a lithium ion (Li-ion) battery used in a cal vehicle (hybrid vehicle).

[0002]

2. Description of the Related Art In recent years, in EVs or HEVs,
Lithium ion batteries are preferred. this is,
Lithium-ion batteries have a relatively high electromotive force per cell, a high energy density, which makes them compact and lightweight, and a very wide operating temperature range of -55 ° C to 85 ° C. This is because the usability is good.

[0003] When a battery pack is composed of these secondary batteries, a method of detecting variations in cell voltage in each of these cells is to monitor the voltage values of all the cells while monitoring the A / D (analog / analog) of the microcomputer. There is known a method in which each cell voltage is measured by digital (digital) conversion processing, and a voltage difference between cells is compared by software processing to detect a variation in cell voltage.

[0004]

However, the method of measuring each cell voltage by the A / D conversion process of the microcomputer in the prior art requires a microcomputer for communicating the measured voltage value. There is a disadvantage that the cost of the apparatus is high. Further, in the case of cell voltage measurement by a microcomputer, when a load is connected to the battery, it is not possible to detect a variation in the cell voltage. Therefore, the cell voltage may be measured during the operation of the EV or the HEV, or the cell voltage may be abnormal. There was a problem that it was not possible to detect

The present invention has been made in view of the above circumstances, and has as its object to reduce the cost by eliminating the need for a microcomputer for communicating the measured voltage of the cell.
Provided are a battery voltage detection method and a battery voltage detection device which determine whether or not the cell voltage variation between cells is within an allowable range and perform equalization processing only when the cell voltage variation exceeds the allowable range. Is to do.

[0006]

In order to solve the above-mentioned problems, a battery voltage detecting method according to the present invention is a battery voltage detecting method for detecting a variation in remaining capacity of a cell in a power storage device including a plurality of cells. In the detection method, during charging or discharging, an elapsed time from the time when the cell voltage of any one cell exceeds a predetermined voltage to the time when the cell voltages of all the cells exceed the predetermined voltage (the embodiment) Then, cells 1a, 1
b, 1c, 1d,..., from the time when any of the cell voltages reaches a predetermined voltage to the time when the cell voltages of all the cells reach the predetermined voltage), and the elapsed time is measured. A predetermined time (in the embodiment, the variation is specified in advance according to the type of the battery, the ambient temperature, the charging current value, and the like. For example, the variation specified by the variation determination MAP shown in FIG. 4 using the charging current value and the ambient temperature as parameters. (Time) has been exceeded, and the voltage variation between the cells is determined.

That is, according to the cell voltage measuring method by the battery voltage detecting method of the present invention, at the time of charging or discharging, after the cell voltage of any of the cells first exceeds a predetermined voltage, all the cells are charged. Since the variation of the cell voltage is determined by measuring the elapsed time until the cell voltage exceeds the predetermined voltage, the absolute amount of the variation of the cell voltage can be detected. Note that, at the time of discharging, which is opposite to the time of charging, the battery voltage decreases due to the decrease in the remaining capacity. Therefore, the same variation can be detected by detecting that the voltage has exceeded (below) the predetermined voltage.

Further, in the battery voltage detection method according to the present invention, the predetermined time is determined from a temperature of the power storage device and a current of the power storage device.

That is, according to the battery voltage detecting method,
With reference to a three-dimensional map (see FIG. 4) using the charging current value, the ambient temperature, and the variation determination time as parameters, an accurate variation time according to the surrounding situation is determined. Since the voltage variation between cells is determined based on the accurate variation time, the variation in remaining capacity between cells can be accurately determined.

Further, the battery voltage detecting device of the present invention is a battery voltage detecting device for detecting a variation in the remaining capacity of a cell in a power storage device composed of a plurality of cells, wherein the individual cell voltages are measured. Then, at the time when each cell voltage exceeds the predetermined voltage, a signal of a predetermined level (in the embodiment, when the voltage of each cell exceeds a set voltage of a predetermined value, the voltage detection unit outputs, "H" detection signal)
(In the embodiment, this cell voltage is determined by each of the voltage detectors 2a, 2b, 2c, 2d,...)
AND means for receiving the signals sent from the plurality of voltage detecting means, performing a logical OR operation, and outputting a logical OR signal (in the embodiment, a logical sum signal FLG1) according to the result (embodiment) Receiving the signals sent from the OR circuit 3a) and the plurality of voltage detecting means,
AND means (in the embodiment, a logical product determination circuit 3b) for performing a logical product operation and outputting a logical product signal (the logical product signal FLG2 in the embodiment) according to the result, and the logical sum signal and the logical product 4 is input, and the elapsed time from the time when the logical sum signal is received to the time when the logical product signal is received is the predetermined time (in the embodiment, the ambient temperature and the charging current value are shown in FIG. 4 as parameters. (A variation time specified by the variation determination MAP), and a determination unit (in the embodiment, the upper ECU 4) that determines the voltage variation between the cells.

That is, the battery voltage detecting device of the present invention performs a logical operation by using a plurality of voltage detecting means for detecting a cell voltage of each cell and a signal generated when each voltage detecting means detects a desired voltage. The system includes a logical operation unit for performing the operation, and a determination unit that measures a charging time of a cell based on a signal input from the logical operation unit and determines a voltage variation between cells. With such a system, the elapsed time from the time when any one of the cell voltages reaches the predetermined voltage to the time when all the cell voltages reach the predetermined voltage is derived, and the variation time is determined from the time difference, and the inter-cell time is determined. Can be determined.

As described above, the variation time at the time of charging / discharging in each cell is determined based on the interrelationship between the temperature of the secondary battery, the charging / discharging current, and the variation determination time. By judging the range of cell voltage variation, equalization processing for equalizing the cell voltage variation can be performed only when necessary.

In the battery voltage detecting method according to the present invention, it is preferable that each of the cells is a battery used for an electric vehicle or a hybrid vehicle, and each of the cells is a lithium ion battery. In other words, a lithium ion battery having a high electromotive force per cell and a high energy density is mounted on an electric vehicle or a hybrid vehicle to reduce the size and weight of the battery. Is detected, it is possible to detect a variation in the battery voltage when there is no trouble during driving. In addition, since cell equalization processing can be performed as needed, an extremely convenient electric vehicle can be realized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a battery voltage detecting method according to the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram for explaining an embodiment of a battery voltage detection method according to the present invention. That is, FIG.
In a lithium ion battery mounted on an EV or HEV, a configuration of a battery voltage detection method for detecting a variation of a cell battery constituting an assembled battery is shown. In the following description, a lithium ion battery is simply referred to as a battery.

In FIG. 1, in order to obtain a desired voltage required for an EV or an HEV, an assembled battery includes N cells 1a, 1b, 1c, 1d.
.. Are connected in series. The battery voltage detection method of the present invention uses N voltage detection units 2a, 2b, 2c, 2 to detect the voltage of each of the cells 1a, 1b, 1c, 1d,.
d ... are connected between the cells. Further, the output signals of the voltage detectors 2a, 2b, 2c, 2d,... Are input to the logic circuit unit 3, and the logical sum judgment circuit 3a and the logical product judgment circuit 3b in the logic circuit unit 3 respectively perform the logical sum operation. The signal FLG1 is distinguished from the AND signal FLG2, and these signals are
(Electrical Control Unit). Then, the host ECU 4 is configured to determine the variation of the cell voltage of the battery.

More specifically, each of the voltage detectors 2a, 2
, b, 2c, 2d... respectively detect the cell voltage of each cell 1a, 1b, 1c, 1d.
For example, an "H" (High) detection signal is transmitted. Further, the detection signal "H" transmitted from each of the voltage detection units 2a, 2b, 2c, 2d,... Is input to the logic circuit unit 3, and the detection signal "H" is output by the OR judgment circuit 3a and the AND judgment circuit 3b. OR and AND judgments are performed.

That is, in the charging process, the first detection signal “H” is output from the voltage detection unit that has detected the highest cell voltage.
Is sent to the logic circuit unit 3, the logical sum judgment circuit 3 a
The logical sum is determined by the logical sum signal FLG1 from the logical sum determination circuit 3a of the logic circuit unit 3 to the host ECU 4.
Is transmitted. As a result, the host ECU 4
It is determined that the maximum voltage has been input from any one of 1a, 1b, 1c, 1d..., And time counting is started.

Further, in the charging process, when the last detection signal "H" is transmitted from the voltage detection unit which has detected the lowest cell voltage to the logic circuit unit 3, the logical product of all the detection signals "H" is determined. The logical product signal FLG2 is sent from the logical product determination circuit 3b of the logic circuit unit 3 to the host ECU 4.
Is transmitted. As a result, the host ECU 4
1a, 1b, 1c, 1d, etc., it is determined that the minimum voltage has been input, and the counting of time is terminated. The time from when the maximum voltage is input until the minimum voltage is input is determined. measure. Then, the host ECU 4 determines, based on the length of time from when the maximum voltage is input to when the minimum voltage is input,
It is determined whether the cell voltages of the cells 1a, 1b, 1c, 1d,...

FIG. 2 is a specific configuration diagram of a logic circuit in the logic circuit section 3 of FIG. 1, wherein (a) shows a logical sum judging circuit 3a and (b) shows a logical product judging circuit 3b. That is,
In the logical sum judging circuit 3a shown in FIG. 9A, the voltage detection signal "H" from each of the voltage detectors 2a, 2b, 2c, 2d. Therefore, when any one of the detection signals “H” is input, the output of the OR circuit 3a becomes “H” and the OR signal FLG1 is transmitted. In other words, this logic phenomenon charges the battery pack from a low voltage,
When the cell having the maximum voltage among the cells 1a, 1b, 1c, 1d,... Reaches the set voltage, the output of the OR judgment circuit 3a becomes "H".
Means that the logical sum signal FLG1 is transmitted.

In the AND circuit 3b shown in FIG. 2B, the voltage detection signal "H" from each of the voltage detectors 2a, 2b, 2c, 2d,... Is input by AND logic. Therefore, when all the inputs become the detection signals "H", the output of the AND circuit 3b becomes "H" and the AND signal FLG2 is transmitted. That is, this logic phenomenon occurs when the battery pack is charged from a low voltage, and when all the cells 1a, 1b, 1c, 1d ... reach the set voltage, the cell having the minimum voltage reaches the set voltage. Then, the output of the logical product judgment circuit 3b becomes "H", which means that the logical sum signal FLG2 is transmitted.

Next, the host ECU 4 measures the time required from receiving the logical sum signal FLG1 based on the maximum voltage of the cell to receiving the logical product signal FLG2 based on the minimum voltage of the cell. The process of performing the variation determination will be described.
FIG. 3 is a timing chart showing the transition of the cell voltage during charging and the time relationship between the logical sum signal and the logical product signal.
(A) is a timing waveform of an OR signal, (b) is a timing waveform of an AND signal, and (c) is a waveform of a voltage transition of a cell having a maximum voltage and a cell having a minimum voltage. That is, (c) of FIG. 3 shows a temporal voltage transition of the cell having the minimum voltage Vs and the cell having the maximum voltage Vm when the charging time T is plotted on the horizontal axis and the cell voltage V is plotted on the vertical axis. .

In FIG. 3 (c), when the battery pack is charged, first, at time t1, when the cell voltage of the maximum voltage Vm reaches the set voltage V0, the first "OR" is sent to the OR judgment circuit 3a. Since the H ″ signal is input, as shown in FIG.
At time t1, a logical sum signal FLG1 is generated from the logical sum determination circuit 3a of the logic circuit unit 3, and is input to the host ECU 4. Further, in FIG. 3 (c), the charging of the assembled battery is continued, and when the cell voltage having the minimum voltage Vs reaches the set voltage V0 at time t2, all the cell voltages have reached the set voltage V0. become. Therefore, FIG.
At time t2, the logical product determination circuit 3b of the logic circuit unit 3 receives the "H" signal at all the input terminals, so that the output of the logical product determination circuit becomes the "H" signal. And an AND signal FLG2 is generated.
G2 is input to the host ECU 4.

Then, the host ECU 4 outputs the logical sum signal FLG1
Is transmitted and the time at which the AND signal FLG2 is transmitted
The difference from t2, that is, (t2−t1) is recognized as the cell variation determination time t. Further, the host ECU 4 estimates a voltage difference between the maximum voltage and the minimum voltage (that is, a variation in the cell voltage) from the variation determination time t. Therefore, when the variation determination time t is large, the host ECU 4 determines that the voltage difference between the maximum voltage and the minimum voltage of the cell is large.
It is determined that the variation of the cell voltage is large, and if the variation determination time t is short, it is determined that the variation of the cell voltage is small.

The criterion value of the variation determination time t for determining the magnitude of the variation of the cell voltage depends on the type of battery,
It is set in advance according to the ambient temperature, the charging current, and the like.
FIG. 4 is a three-dimensional representation of the variation determination time with respect to the ambient temperature and the charging current.
P. That is, in FIG. 4, for example, the temperature (° C.) is plotted on the X axis, the charging current value (A) is plotted on the Y axis, and the variation time (sec) is plotted on the Z axis, and the relationship between the ambient temperature and the charging current value and the variation time is shown. Therefore, it is determined whether or not the variation of the cell voltage is within the allowable range. That is, if the variation time is equal to or more than the MAP value (point A) shown in FIG. 4 using the ambient temperature and the charging current value as parameters, it is determined that the variation in the cell voltage is outside the allowable range.

Here, when it is determined that the variation of each cell voltage is out of the allowable range, when the vehicle travels,
At the timing when there is no problem in safety, in order to equalize the variation of the cell voltage, equalize the entire assembled battery with a voltage higher than the normal charging voltage, or through a bypass circuit or bleeder resistor, etc. For example, equalization processing is performed on each cell.

The embodiment described above is an example for describing the present invention, and the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the invention. is there. For example, in the above embodiment, the case where a lithium ion battery is used as the secondary battery has been described.However, the present invention is not limited to this. For example, a nickel cadmium battery, an alkaline battery, or another battery may be used. Absent. In addition, the battery voltage detection method described in the above embodiment is not limited to a secondary battery mounted on an EV or HEV, and can be applied as a battery voltage detection method for any secondary battery used for power equipment. Needless to say. Further, in the above-described embodiment, the case where the variation of the cell voltage is determined from the transition of the cell voltage in the charging process of the assembled battery has been described. However, the present invention is not limited to this, and the transition of the cell voltage is measured in the discharging process of the assembled battery. However, it is also possible to determine the variation in the cell voltage.

[0027]

As described above, according to the cell voltage measuring method according to the battery voltage detecting method of the present invention, during charging or discharging, the cell voltage of any cell first exceeds the predetermined voltage. Since the elapsed time until the cell voltages of all the cells exceed the predetermined voltage is measured to determine the variation in the cell voltage, the absolute amount of the variation in the cell voltage can be detected. As a result, the equalization process is not performed in a state where the variation in the cell voltage is small.
Waste of energy can be avoided, and energy efficiency can be improved. Also,
Since the cell voltage can be detected during the operation of charging and discharging the assembled battery and the magnitude of the variation can be determined, there is no need to stop the vehicle and measure the cell voltage, and as a result, The effect that the convenience of a vehicle improves is acquired. Further, in terms of hardware, a microcomputer for communicating the measured voltage value of the cell is not required, so that the cost of the measuring device can be reduced.

According to the second aspect of the present invention, an accurate variation time according to the surrounding situation is determined with reference to a three-dimensional map in which a charging current value, an ambient temperature, and a variation determination time are used as parameters. . Since the voltage variation between the cells is determined based on the accurate variation time, the variation in the remaining capacity between the cells can be accurately determined, so that the equalization process can be performed only when necessary. . As a result, an effect is obtained that the frequency of processing is reduced evenly and energy loss can be minimized.

According to a third aspect of the present invention, in the battery voltage detecting device of the present invention, a plurality of voltage detecting means for detecting a cell voltage of each cell, and each of the voltage detecting means detects a desired voltage. Logic operation means for performing a logical operation on the basis of the signal generated when the operation is performed, and determination means for measuring the charging time of the cell based on the signal input from the logic operation means and determining the voltage variation between the cells. With such a configuration, the time when the cell with the maximum voltage passes the predetermined voltage and the time when the cell with the minimum voltage passes the predetermined voltage are derived, and the time difference is calculated from the time difference, and the magnitude of the voltage variation between the cells is calculated. Can be determined. This eliminates the need for a microcomputer for communicating the measured voltage value of the cell, and thus has the effect of reducing the cost of the measuring device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of a battery voltage detection method according to the present invention.

FIGS. 2A and 2B are specific configuration diagrams of a logic circuit in the logic circuit unit in FIG. 1; FIG.
Indicates a logical product judgment circuit.

FIG. 3 is a timing chart showing a transition of a cell voltage at the time of charging and a time relationship between an OR signal and an AND signal.

FIG. 4 is a diagram showing a three-dimensional cell voltage variation determination MA representing variation determination time with respect to ambient temperature and charging current.
P.

[Explanation of symbols]

 1a, 1b, 1c, 1d ... cells 2a, 2b, 2c, 2d ... voltage detection unit (voltage detection means) 3 logic circuit unit 3a logical sum judgment circuit (logical sum means) 3b logical product judgment circuit (logical product means) 4 Upper ECU (judgment means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02J 7/00 302 H02J 7/00 302C (72) Inventor Yasuo Yamada 1-4-1, Chuo, Wako-shi, Saitama No. F-term in Honda R & D Co., Ltd. (reference) 2G016 CA03 CB31 CB33 CC01 CC04 CC27 CD01 2G035 AA15 AB03 AC01 AC16 AC19 AD27 AD28 5G003 BA03 DA07 EA09 GC05 5H030 AA10 AS08 FF44 FF52 5H115 PA11 PC06 PG04 PI14 PI06 PO02 PO03 TI02 TI05 TI06 TO05

Claims (3)

[Claims] 1. A battery voltage detection method for detecting a variation in remaining capacity of a cell in a power storage device including a plurality of cells, the cell voltage of one of the cells being charged or discharged. The elapsed time from when the voltage exceeds the predetermined voltage until the cell voltages of all cells exceed the predetermined voltage is measured, and the voltage variation between the cells is determined based on whether or not the elapsed time exceeds the predetermined time. A battery voltage detection method. 2. The battery voltage detecting method according to claim 1, wherein the predetermined time is determined from a temperature of the power storage device and a current of the power storage device. 3. A battery voltage detecting device for detecting a variation in remaining capacity of a cell in a power storage device including a plurality of cells, wherein each of the cell voltages is measured, and each cell voltage is set to a predetermined value. At the time when the voltage is exceeded, a plurality of voltage detecting means for transmitting a signal of a predetermined level, and the signals transmitted from the plurality of voltage detecting means are received, a logical sum operation is performed, and a logical sum signal according to the result is obtained. AND means for receiving the signals sent from the plurality of voltage detection means, performing a logical product operation, and outputting a logical product signal according to the result, and the logical sum signal The AND signal is input, and the voltage variation between the cells is determined based on whether or not the elapsed time from the time when the OR signal is received to the time when the AND signal is received exceeds the predetermined time. You Battery voltage detection device characterized by comprising: a judging means.