JP2013121243A - Secondary battery charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery charger capable of extending the life thereof by averagely lowering the charging voltage of the secondary battery without increasing the capacity of the secondary battery.SOLUTION: A secondary battery charger includes a switching circuit which selectively supplies an output voltage of a generator or an output voltage of a secondary battery to a load and a charge control circuit which inputs the output voltage of the generator and charges the secondary battery to a prescribed charge termination voltage or less. The secondary battery charger further comprises charge regulation means for changing a charge termination voltage of the charge control circuit and regulating a time average value of the charge termination voltage to a full charge voltage of the secondary battery or lower.

Description

  The present invention selectively supplies an output voltage of a generator or an output voltage of a secondary battery to a load via a switching circuit, and inputs the generator output voltage to charge the secondary battery to a predetermined charge. The present invention relates to a secondary battery charger having a charge control circuit for charging to a final voltage.

  The wireless transmitter that operates by charging the secondary battery with power generated from environmental energy such as solar cells as a power generator, measures the physical quantity of the process, and transmits it to the host device is placed in the field in the plant and used It is a field device that is equipped with various sensors according to and transmits measured values to a host system via wireless communication. In such a wireless transmitter, in order to reduce battery costs and maintenance man-hours, management is required to extend the life of the secondary battery used as long as possible and lengthen the replacement cycle.

  FIG. 4 is a functional block diagram showing a configuration example of a conventional secondary battery charging device. A power generator 10 (hereinafter, referred to as a solar cell 10) realized by a solar cell or the like converts light energy such as sunlight into electric energy having a voltage V1.

  The power supply circuit 20 stores the power generated by the solar battery 10 in the secondary battery 21 and supplies the power to the wireless transmitter (hereinafter referred to as the wireless transmitter 30) constituting the load 30 regardless of whether the solar battery 10 generates power or not. To do. The wireless transmitter 30 communicates with the host system 40 by wireless communication.

  The power supply circuit 20 includes a charge control circuit 22 that charges the secondary battery 21, and the charge control circuit 22 performs charge control so that the voltage V2 of the secondary battery 21 does not rise above the charge end voltage V0.

  The secondary battery 21 is assumed to be a lithium ion battery. The battery capacity has a capacity necessary for supplying power to the wireless transmitter 30 during a period when the solar battery 10 does not generate power. For example, when it is possible to supply power to the wireless transmitter 30 even if there is a period in which power generation is not performed for four consecutive days due to bad weather, the capacity can be stored more than the power used by the wireless transmitter in four days.

  The diodes D1 and D2 form a switch circuit (switching circuit) that selects V1 or V2 and supplies it to the wireless transmitter 30. The diode D1 supplies the electric power generated by the solar cell 10 from the OUT terminal to the wireless transmitter 30 and prevents the electric power charged in the secondary battery 21 from flowing backward to the solar cell 10 when the solar cell does not generate power. To.

  The diode D2 supplies power discharged from the secondary battery 21 to the wireless transmitter 30 from the OUT terminal when the solar battery 10 does not generate power, and reversely discharges the discharge path when the solar battery 10 generates power. Do not charge 21.

JP 2009-97878 A

The conventional apparatus has the following problems.
(1) As long as the solar cell 10 generates power, the charge control circuit 22 operates so as to maintain the secondary battery 21 at a fully charged voltage in preparation for the longest period during which power cannot be generated in the future. On the other hand, when a lithium ion battery is used as the secondary battery 21, since the battery has a property of being deteriorated as the charging voltage is higher, the secondary battery 21 is charged at a full charge voltage as the power generation period of the solar battery 10 becomes longer. Therefore, there is a drawback that the battery life is shortened because the voltage is maintained for a long period of time.

(2) In order to avoid shortening the battery life, the charging end voltage V0 is set low, while the capacity of the secondary battery 21 is increased to maintain the total charging power of the secondary battery. However, as the battery capacity is increased, the battery mounting volume is increased, and the required capacity of the battery itself is increased to increase the cost.

  An object of the present invention is to realize a secondary battery charger capable of extending the battery life without increasing the battery capacity by reducing the charging voltage of the secondary battery on average.

In order to achieve such a subject, the present invention has the following configuration.
(1) A switching circuit for selectively supplying the output voltage of the generator or the output voltage of the secondary battery to the load, and the generator output voltage are input, and the secondary battery is below a predetermined end-of-charge voltage. In a secondary battery charger having a charge control circuit for charging
A secondary battery charging apparatus, comprising: charge regulation means for changing a charge termination voltage of the charge control circuit and regulating a time average value of the charge termination voltage to be equal to or lower than a full charge voltage of the secondary battery.

(2) The secondary battery charging device according to (1), wherein the charging regulation unit changes the charge end voltage by a control signal given from a host system communicating with the load.

(3) The charge regulation unit receives from the host system a control signal for changing the charge end voltage depending on at least one of the power generation capability prediction information of the generator and the operating state of the load. The secondary battery charger according to 2).

(4) The charge regulation means includes timer means for switching the charge end voltage to a full charge voltage when a control signal from the host system is stopped for a predetermined time or longer. (2) or (3) The secondary battery charging device described in 1.

(5) The secondary battery charging device according to any one of (2) to (4), wherein the charge regulation unit notifies the voltage value of the secondary battery to the host system.

(6) The secondary battery charging device according to any one of (1) to (5), wherein the load is an internal circuit of a field device that communicates with the host system by wireless means.

According to the present invention, the following effects can be expected.
(1) In the present invention, since the end-of-charge voltage of the secondary battery 21 can be changed from the host system 40, when the future sunshine can be sufficiently expected, the end-of-charge voltage of the secondary battery is set to the fully charged voltage of the secondary battery 21. It can be set lower.

(2) For this reason, since the secondary battery 21 is not charged more than the required amount of power, the voltage of the secondary battery can be lowered, the deterioration of the secondary battery is suppressed, and the maintenance period of the wireless transmitter 30 is reduced. Can be extended.

It is a functional block diagram which shows one Example of the secondary battery charging device to which this invention is applied. It is a functional block diagram which shows the other Example of the secondary battery charging device to which this invention is applied. It is a functional block diagram which shows the other Example of the secondary battery charging device to which this invention is applied. It is a functional block diagram which shows the structural example of the conventional secondary battery charging device.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of a secondary battery charging device to which the present invention is applied. The same elements as those of the conventional apparatus described with reference to FIG.

  A feature of the present invention added to the conventional configuration shown in FIG. 4 is a configuration in which the charge regulating means 100 is provided for the power supply circuit 20. The charging regulation unit 100 includes a register 101 that holds a control signal C supplied from the host device 40 via the wireless transmitter 30, and a D / A converter that converts the register holding value into an analog voltage setting signal Vs. 102.

  The voltage setting signal Vs output from the D / A converter 102 is input to the charge control circuit 22 as a set value of the charge end voltage, and this charge end voltage is controlled via wireless communication, and from the host system 40 side. It becomes possible to change.

  Hereinafter, the operation of the apparatus of the present invention will be described. The host system 40 collects power management information F such as future sunshine information, for example, and obtains a charge end voltage. For example, if the sunshine is sufficient for the next several days, the battery voltage should not be increased more than necessary as an end-of-charge voltage sufficient to cover the power used at night of the day. The power management information F is the power generation capability prediction information of the solar cell 10, the operating state information of the wireless transmitter 30, and the like.

  If power generation is not possible without sunshine for several days in the future, the charging is set to the end-of-charge voltage that can cover the power for the number of days, and charging is performed during the power generation period. As described above, the end-of-charge battery can be set according to the amount of power required in the future based on the prediction of the amount of power generation in the future, so that the average voltage of the secondary battery 21 is lowered to the full charge voltage or less, and the secondary battery is deteriorated. Can be suppressed.

  According to the present invention, since the life of the secondary battery 21 is extended, maintenance can be reduced and the period during which the wireless transmitter 30 operates can be extended as compared with the conventional configuration. Even when the control signal C or the wireless communication failure occurs and the register 101 for setting the charge end voltage cannot be updated, the charge end capacity is maximized by changing the charge end voltage to the maximum (for example, full charge voltage) after a certain period of time. It can be secured and made fail safe.

  FIG. 2 is a functional block diagram showing another embodiment of the secondary battery charging device to which the present invention is applied. Elements added to the configuration of the charging regulation unit 100 in FIG. 1 are a register 103 that holds a fixed value, a changeover switch 104, and a timer 105.

  The operation will be described below. If the register 101 is not reset by the control signal C within a certain period set in the timer 105, the changeover switch 104 switches the charge end voltage from the output value Vs of the register 101 to the fixed value of the register 103.

  The value of the register 103 is a fixed value or a value set from the control signal C, for example, the maximum charging voltage (full charge voltage) of the secondary battery. When the wireless communication with the control signal C or the host system 40 becomes defective, the setting by the register 101 is not updated, and thus charging is performed so that charging is performed with a charge end voltage based on the value of the register 103 after a certain time based on the timer 105. The control circuit 22 operates. Thus, even when the control signal and wireless communication are defective, the operable time of the wireless transmitter 30 can be made equivalent to that of the conventional circuit.

  FIG. 3 is a functional block diagram showing still another embodiment of the secondary battery charging device to which the present invention is applied. An element added to the configuration of the charge regulating means 100 in FIG. 1 is a configuration in which an A / D converter 106 is provided. The A / D converter 106 converts the voltage value V2 of the secondary battery 21 into a digital value and notifies the host device 40 via the wireless transmitter 30 as a control signal C.

  By reading back the secondary battery voltage to the host device 40, the secondary battery 21 is currently insufficient based on the charge end voltage based on the amount of power required for the wireless transmitter 30 and the current secondary battery voltage. The amount of power required for charging can be estimated.

  If the amount of power that the solar cell can generate on the day is more than the amount of power that is currently insufficient for the secondary battery, the charge that intentionally requires the end-of-charge voltage in the first half of the period during which the solar cell generates electricity. The average voltage of the secondary battery can be further reduced by setting it lower than the end voltage and changing it to the charge end voltage required in the second half of the period when the solar cell generates power. Thereby, the deterioration of the battery can be suppressed and the battery life can be further extended.

  In the embodiment described above, the generator 10 has been described as a solar cell, but a generator that generates power using environmental energy whose future power generation amount can be predicted by the host system, such as temperature difference power generation or vibration power generation, etc. Even in the case where is used, the battery life can be extended by optimizing the end-of-charge voltage of the secondary battery based on the prediction.

  In the embodiment, the load 10 is described as a wireless transmitter. However, the internal circuit of the wireless transmitter may be used, and the power supply circuit 20 may be built in the wireless transmitter. The load 10 can be applied to a general transmitter that communicates with the host system 40 via a transmission line or a network.

10 Generator (solar cell)
20 Power supply circuit 21 Secondary battery 22 Charge control circuit 30 Load (wireless transmitter)
40 Host System 100 Charge Control Unit 101 Register 102 D / A Converter 103 Register 104 Changeover Switch 105 Timer 106 A / D Converter

Claims (6)

A switching circuit for selectively supplying the output voltage of the generator or the output voltage of the secondary battery to the load, and the generator output voltage are input to charge the secondary battery to a predetermined charge end voltage or lower. In a secondary battery charger having a charge control circuit,
A secondary battery charging apparatus, comprising: charge regulation means for changing a charge termination voltage of the charge control circuit and regulating a time average value of the charge termination voltage to be equal to or lower than a full charge voltage of the secondary battery.   2. The secondary battery charging device according to claim 1, wherein the charging regulation unit changes the end-of-charge voltage according to a control signal given from a host system communicating with the load.   The said charge regulation means receives the control signal which changes the said charge end voltage from the said high-order system by either the power generation capability prediction information of the said generator, or the operation state of the said load at least. The secondary battery charging device described.   4. The secondary according to claim 2, wherein the charge regulation unit includes a timer unit that switches the charge end voltage to a full charge voltage when a control signal from the host system is stopped for a predetermined time or more. Battery charger.   5. The secondary battery charging device according to claim 2, wherein the charge regulation unit notifies the host system of a voltage value of the secondary battery. 6.   The secondary battery charging device according to claim 1, wherein the load is an internal circuit of a field device that communicates with the host system by wireless means.

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