JP5678915B2 - Battery charge control device - Google Patents

Description

  The present invention relates to a battery charge control device.

  Conventionally, a battery mounted on an automobile or the like is configured by connecting a plurality of single secondary batteries called cells in series, and a battery module is formed by connecting a plurality of cells according to a desired voltage. Yes.

  The battery is charged while the engine is running, for example, by an alternator that generates electricity by power from the engine. In recent years, electric vehicles that have become widespread from the viewpoint of low pollution and energy saving are charged using regenerative energy from a motor for driving the vehicle.

  The charging control of these batteries is usually performed by a battery charging control device. The battery charge control device measures a voltage between terminals of a battery terminal mainly composed of a plurality of cells, calculates a remaining capacity of the battery based on the measured voltage value, and the remaining capacity is within a predetermined range. The charging / discharging of the battery is controlled so that it fits in

  The battery charge control device charges the battery when it detects that the battery voltage falls below a predetermined voltage and the remaining capacity of the battery falls below a predetermined range. On the other hand, when it is detected that the battery voltage exceeds a predetermined voltage and the remaining capacity of the battery has reached a predetermined range, charging is stopped to prevent overcharging of the battery.

  By the way, as described above, the battery to be charged is composed of a plurality of cells connected in series. Therefore, when a short circuit failure occurs in any cell, the remaining capacity varies between the cells. End up. In addition, if an internal short circuit failure occurs in any cell, the voltage of the entire battery decreases, but whether this voltage decrease is due to the occurrence of an internal short circuit or a voltage drop due to insufficient battery capacity between the terminals. It is difficult to distinguish only by the high and low voltage values.

  For this reason, if charging is continued when a voltage drop due to an internal short circuit occurs, there is a problem that some cells are overcharged.

  In Patent Document 1 (Japanese Patent Laid-Open No. 2010-218976), in order to determine an abnormality due to a short circuit in a battery module of a battery, the battery is being discharged when the remaining capacity of the battery is greater than or equal to a predetermined amount that should be prohibited from discharging the battery. In the battery module, when the voltage difference between the voltage of any one of the plurality of battery modules and the voltage of the remaining battery modules is equal to or greater than a predetermined voltage, An abnormality determination method is described.

  Patent Document 2 (Japanese Patent Laid-Open No. 2006-050784) describes an assembled battery charge state control device that controls a charge state according to cell variation.

JP 2010-218976 A JP 2006-050784 A

  However, the battery abnormality determination method described in Patent Document 1 and the charge state control device described in Patent Document 2 require measurement means for separately measuring the voltage of each cell, and increase the number of measurement parts. As a result, the cost of the battery charge control device increases. Further, the battery itself is required to have a special structure for measuring the voltage of each cell, and there is a problem that the cost of the battery increases.

  Accordingly, the present invention has been made in view of the problems in the battery charge control device described above, and detects an internal short circuit of a cell without measuring individual voltages of each cell, thereby preventing overcharge of the battery. The purpose is to do.

In view of the above problems, a battery charge control apparatus according to the present invention, two or more cell Le or Ranaru battery voltage of the battery of the N secondary battery is an integer connected in series is measured, the measured battery voltage A battery control unit that outputs an instruction of a charging voltage of the battery, and a charging voltage adjustment unit that charges the battery by adjusting a charging voltage of the battery according to the instruction from the battery control unit, The battery control unit instructs the charge voltage adjustment unit as a charge voltage ((N-1) / N) times when the measured battery voltage is lower than a first voltage value. The battery is charged for a predetermined period, and the battery voltage is measured again after the predetermined period. If the measured battery voltage is lower than the second voltage value, the charging voltage is multiplied by ((N−1) / N). As finger To.

  According to the embodiment of the present invention, it is possible to detect an internal short circuit of a cell and prevent overcharging of the battery without measuring the individual voltage of each cell. Thereby, the cost increase of a charge control apparatus and a battery can be suppressed.

It is the block diagram explaining the structure of the battery charge control apparatus of this invention. It is a figure explaining the internal structure of a battery. It is the block diagram explaining the detail of the structure of the voltage regulator. It is a flowchart explaining operation | movement of a battery charge control apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an example showing a block diagram illustrating a configuration of a battery charge control device of the present invention.

  In FIG. 1, the battery charge control device 1 includes a voltage adjustment device 20 and a battery control ECU (Electronic Control Unit) 30 to which a battery 10 and an electric load 60 are connected.

  The battery control ECU 30 constantly measures the voltage between the terminals of the battery 10. Further, the battery control ECU 30 outputs a charge voltage instruction to the voltage adjustment device 20.

  The voltage adjustment device 20 supplies a direct current output at a predetermined voltage to the battery 10 and the electric load 60 in accordance with a charge voltage instruction from the battery control ECU 30.

  The connected electrical load 60 is, for example, a headlamp, an air conditioner, a vehicle driving motor in an electric vehicle, or the like.

  FIG. 2 is an example of a diagram illustrating the internal structure of the battery 10.

  In FIG. 2, the battery 10 is configured by connecting six cells (M1 to M6), which are secondary batteries, in series. The number of cells is selected according to the desired voltage. For example, when the nominal voltage of the unit cell is 2 [V], when six cells are connected in series, the nominal voltage between the terminals of the battery is 2 [V] * 6 = 12 [V]. The voltage measurement is performed by measuring the voltage between the terminals of the battery 10.

  In general, the voltage between the terminals of the battery shows a voltage value slightly higher than the nominal voltage in a state near full charge in a no-load state, and about 12.8 [V] in a battery with a nominal voltage of 12 [V]. Voltage. For this reason, it is necessary to set the charging voltage for fully charging a battery having a nominal voltage of 12 [V] higher than 12.8 [V].

  Here, if the charging voltage is close to 12.8 [V], a long time is required for charging. On the other hand, if the charging voltage is too high, side reactions such as heat generation and generation of hydrogen gas increase. For this reason, the voltage for charging the battery while suppressing side reactions is set as the normal charging voltage. This charging voltage is set to, for example, about 13.8 [V] to 16.5 [V]. The power generation voltage of the alternator that charges the battery varies depending on the engine speed, but here, 15 [V] is the normal charging voltage.

  When the battery is fully charged, the electrical energy supplied beyond it becomes an overcharged state that is used only for side reactions. Overcharging damages the battery electrodes and the like and shortens the battery life.

  When discharging of the battery 10 proceeds, the voltage between terminals shows a voltage value lower than the nominal voltage. Normally, charging is continued with the normal charging voltage until the voltage between the terminals recovers.

  On the other hand, the battery has an electrode plate composed of a positive electrode and a negative electrode inside each cell (M1 to M6). Even when an internal short circuit occurs due to corrosion or peeling of the electrode plate or contamination of impurities. The capacity of the battery is reduced and the voltage between the terminals is lowered. As described above, the reason why the voltage between the terminals of the battery 10 is low is assumed to be an overdischarge or an internal short circuit.

  Next, the configuration of the voltage regulator 20 in FIG. 1 will be described with reference to FIG.

  FIG. 3 is an example of a block diagram illustrating details of the configuration of the voltage regulator 20.

  FIG. 3A shows an embodiment in which the voltage regulator 20 is a DC-DC converter 20a.

  In FIG. 3A, a DC-DC converter 20a performs DC-DC voltage conversion by switching an input direct current using a switching element. When the switching frequency is increased at this time, the effective voltage increases and the DC output voltage increases. When the switching frequency is decreased, the effective voltage decreases and the DC output voltage decreases. This switching frequency is determined by a charge voltage instruction from the battery control ECU 30 in FIG.

  The charging voltage instruction is instructed by a voltage value within a predetermined range such as 0-5 [V], for example.

  When the switching frequency is controlled so as to linearly change the voltage value of the DC output corresponding to the voltage value of the charging voltage instruction, the following control is performed.

  For a charge voltage instruction of 5 [V], a normal DC output of 15 [V] is used. In addition, for a charge voltage instruction of 2.5 [V], a direct current output of 15 * 1/2 = 7.5 [V] is used. Furthermore, in response to the charge voltage instruction of 0 [V], control is performed to stop charging without performing DC output.

  Further, the charging voltage instruction may be instructed by a bit value based on a combination of a plurality of control lines. In this case, for example, with two control lines, it is possible to indicate four types of voltages (00), (01), (10), and (11) by a combination of on / off.

  In the above description, the operation of converting the voltage value of the DC output according to the switching frequency of the DC-DC converter 20a has been described. However, when the DC input can be output as it is, the voltage value of the DC input is directly adjusted without voltage adjustment by switching. It may be output. This operation can also be instructed by a charge voltage instruction. For example, when the charge voltage instruction is 0 [V], instead of stopping charging in the previous example, the direct current output without voltage conversion may be used as it is. Thereby, even if some abnormality occurs in the battery control ECU 30 or the control line for inputting the charging voltage instruction and the charging voltage instruction is not input, normal battery charging is possible. In addition, useless energy loss due to the switching circuit can be prevented.

  An alternator 40 or a motor regeneration circuit 50 is connected to the DC-DC converter 20a. The alternator 40 and the motor regeneration circuit 50 are examples of DC input. Accordingly, a DC input other than those not shown may be used. Further, either one of the alternator 40 or the motor regeneration circuit 50 may be input, or both may be input.

  The alternator 40 generates power by transmitting a rotational force from an engine (not shown) through a pulley and a belt. This power may be transmitted / interrupted by, for example, an electromagnetic clutch. The alternator 40 may be a general-purpose alternator having an AC generator circuit, a rectifier circuit, and an IC regulator for adjusting the voltage.

  The motor regenerative circuit 50 supplies regenerative energy of a vehicle driving motor used in an electric vehicle or the like. The motor performs regenerative operation to convert the kinetic energy of the vehicle into regenerative power. Energy saving operation is possible by charging the battery with this electric power. A lithium ion battery or the like is used as a battery used for an electric vehicle or the like. However, since the charging voltage can be set in the present invention, various types of batteries can be used.

  Direct current generated by the alternator 40 or regenerated from the motor regeneration circuit 50 is input to a DC-DC converter, converted into a predetermined voltage according to a charge voltage instruction, and converted into a direct current output as a battery 10 or an electric load in FIG. 60.

  The current and voltage of the DC input from the alternator 40 and the motor regeneration circuit 50 vary depending on the operating state. For example, the alternator generates a small amount of power when the engine speed is as low as idling, and sufficient power for charging the battery is not supplied. Further, the regenerative power from the motor is not supplied unless the regenerative cycle in which the vehicle is braked by the motor is reached. Therefore, the DC-DC converter 20a may monitor the voltage input from the alternator 40 or the like and not charge the battery when the voltage is low.

  FIG. 3B shows an embodiment in which the voltage regulator 20 is an alternator 20b.

3 (b), the alternator 20b comprises a generator-rectifier unit 201, IC regulator 202.

Here, the difference between the alternator 20b and the alternator 40 described with reference to FIG. In the alternator, an AC generator circuit, a rectifier circuit, and an IC regulator for adjusting the voltage are built in the same manner. However, while the IC regulator of the alternator 40 performs voltage control so as to keep the output voltage within a specified range, the IC regulator 202 of the alternator 20b changes the switching frequency according to the charging voltage instruction input from the battery control ECU 30. The operation differs in that the specified output voltage is used. That is, the IC regulator 202 has the same function as the DC-DC converter 20a described with reference to FIG. 3A in the function of converting the DC input voltage from the power generation / clearing section 201 into a desired voltage to generate a DC output. Will be provided. In the embodiment of FIG. 3B, the number of parts can be reduced as compared with the embodiment of FIG. 3A by combining the functions of DC-DC conversion into one, and the cost can be reduced.
[Preventing battery overcharge]
Next, a specific method for preventing overcharging of the battery according to the present invention will be described.

  As described above, the battery is charged at a slightly higher charge voltage than the fully charged voltage in order to obtain a full charge while suppressing side reactions such as heat generation and hydrogen gas generation due to overvoltage. This voltage is referred to as “normal charging voltage Va”.

  When a defect such as an internal short-circuit occurs in the cell, the charge capacity is reduced. Therefore, when the cell is charged with a normal charging voltage, it is overcharged.

  Therefore, in the present invention, when the number of battery cells is N, the battery is charged with a charge voltage of (N-1) cells in order to prevent overcharging. This charge voltage is referred to as “overcharge prevention voltage Vb”.

  The overcharge prevention voltage Vb is obtained by the following equation.

Vb = Va * (N−1) / N (1)
For example, when the normal charging voltage Va of a battery having a nominal voltage of 12V is 15 [V], in the case of a battery having 6 cells, the overcharge prevention voltage Vb is
Vb = 15 * (6-1) /6=12.5 [V]
It becomes.

  Next, the control operation of the battery charge control device 1 using the overcharge prevention voltage Vb described above will be described based on the flowchart of FIG.

  FIG. 4 is an example of a flowchart illustrating the operation of the battery charge control device.

  In FIG. 4, first, the battery control ECU 30 measures the voltage of the battery voltage (V1) before charging (S11).

  Next, it is determined whether the measured voltage V1 is less than 10 [V] (S12).

  Here, in a battery having a nominal voltage of 12 [V], the fact that the measured voltage is less than 10 [V] may be an overdischarged state or a capacity drop due to an internal short circuit of the cell. There is.

  In S12, when V1 is 10 [V] or more, the battery control ECU 30 outputs a charge voltage instruction to the voltage adjustment device 20 so as to set the charge voltage to the normal charge voltage Va (S14). ). In this embodiment, Va = 15 [V].

  Further, for Va, when the DC input described in FIGS. 3A and 3B is higher than the nominal voltage of 12 [V], the voltage regulator 20 responds to the charging voltage instruction. It can also be used as a direct current output without converting the voltage of the direct current input. That is, Va may be a fixed value or a variable value.

At S12, if V1 is less than 10 [V] sets the charging voltage to the anti-overcharging voltage Vb. In this embodiment, when Va = 15 [V], Vb = 12.5 [V] as calculated in the above equation (1).

  Next, it is determined whether a certain time has elapsed (S15), and the battery 10 is charged for a certain time with the charging voltage set in S13 or S14. The charging time is set to such a time that the battery recovers from the overdischarged state. The charging time may be a fixed time, or may be a variable time based on the value of V1, such that the charging time is lengthened when the voltage is low, or the charging time is shortened when the voltage is high.

  After a predetermined time has elapsed, the battery control ECU 30 instructs the voltage regulator 20 to stop charging in response to the charge voltage instruction (S16), and measures the battery voltage again (S17). Here, the voltage measured again is V2.

  The charging is temporarily stopped in S16 because, as described above, the DC input from the alternator 40 and the like constantly fluctuates depending on the engine speed and the like, so the influence of the DC output from the voltage regulator is eliminated and the battery terminal This is to accurately measure the voltage.

  Next, it is determined whether V2 is 11 [V] or more (S18).

  As described above, since the voltage between terminals in a full charge of a battery having a nominal voltage of 12 [V] is about 12.8 [V], if one cell is short-circuited and another cell is fully charged , 12.8 [V] * 5/6 = 10.2 [V] terminal voltage V2 should be measured. Therefore, when V2 is 11 [V] or more, there is no occurrence of an internal short circuit of the cell, and it is estimated that the voltage drop is caused by overdischarge. In that case, the charging voltage is set to the normal charging voltage Va (S19).

  On the other hand, in S18, when V2 is less than 11 [V], an internal short circuit of the cell is estimated. In this case, the charge voltage is set to the overcharge prevention voltage Vb (S20) to prevent overcharge.

  If the short circuit of the cell is estimated and the charging voltage is set in S20, the battery control ECU may display a battery abnormality warning on an automobile instrument panel (not shown).

  In the above description, the influence of the battery temperature is not taken into account, but the voltage of the battery may decrease when the temperature is low. Correction may be performed.

  In addition, since the battery deteriorates depending on the use state and the battery capacity also decreases, the measurement of V1 and V2, and further the setting of Va and Vb may be corrected to perform charging control of the battery. .

  In the above description, the case where one cell is internally short-circuited and the charging voltage is lowered has been described. Here, when an internal short circuit of one cell is detected, voltage measurement in (N-2) cells is performed next, whereby an internal short circuit of two cells can be detected. In that case, the overcharge can be further prevented by setting the charging voltage to (N-2) cells. Furthermore, the internal short circuit of n cells can be detected by measuring the voltage in (N−n) cells.

  In addition, when the inside of a cell is completely short-circuited, as described above, the cell has been treated as having a voltage of 0 [V]. However, in the case of peeling of the electrode plate or the like, the voltage of the cell does not necessarily become 0 [V]. In this case, instead of performing voltage measurement and voltage control with a voltage width in cell units. In addition, it can be performed with a smaller voltage width.

  As mentioned above, although the form for implementing this invention was explained in full detail, this invention is not limited to such specific embodiment, In the range of the summary of this invention described in the claim, Various modifications and changes are possible.

DESCRIPTION OF SYMBOLS 1 Battery charge control apparatus 10 Battery 20 Voltage adjustment apparatus 20a DC-DC converter 20b Alternator 30 Battery control ECU
40 Alternator 50 Motor regeneration circuit 60 Electric load 201 Power generation / rectification unit 202 IC regulator

Claims (1)

Two or more of the N cell Le or Ranaru battery voltage of the battery of the secondary battery is an integer series measured in accordance with the measured battery voltage, and outputs an instruction to the charging voltage of the battery A battery control unit;
A charging voltage adjusting unit that adjusts a charging voltage of the battery and charges the battery in accordance with the instruction from the battery control unit;
When the measured battery voltage is lower than the first voltage value, the battery control unit instructs the charging voltage adjustment unit to charge the voltage as ((N-1) / N) times, and determines the battery as a predetermined value. period is charged, again measured battery voltage after a lapse the predetermined time period, the measured battery voltage is lower than the second voltage value indicates the charging voltage as the ((N-1) / N ) times Battery charge control device.

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