CN204947671U - A kind of multifunctional electric energy meter battery charge circuit - Google Patents

Abstract

A battery charging circuit for a multifunctional electric energy meter is characterized in that it consists of rechargeable batteries BT1, BT2, button batteries BT3, diodes D1, D2, switches S11, S12, S21 and S22, capacitors C1, C2, resistors R, voltage detection terminals Composed of UB1, UB2, and UR; the utility model has the following advantages and beneficial effects: it solves the current problems of inaccurate battery capacity detection, shallow charging and shallow discharge, less online maintenance, and poor versatility, and avoids the external power failure and battery power failure of the electric energy meter If it is low, the register data will be lost, and the electricity cannot be recorded, resulting in economic loss. The reliability of the data of the electric energy meter is improved, and the cost of manual maintenance is reduced. The four working states proposed by the utility model can regularly maintain the battery online, activate the dormant power of the battery, prolong the life of the battery, effectively solve the problem of shallow charging and shallow discharge of the battery, and reduce the influence of the memory effect.

Description

A battery charging circuit for a multifunctional electric energy meter

technical field

The utility model belongs to the electric energy metering technology, in particular to a battery charging circuit of a multifunctional electric energy meter.

Background technique

The electric energy meter is an important part of the electric energy metering device. The electric energy meter is installed and used in thousands of households for the settlement and collection of electricity charges. In recent years, the consumption of electric energy has increased sharply, and the electric power sector needs electric energy meters with more functions to collect electric energy charges more fairly and reasonably, and to better plan electric energy production. The battery is an important part of the electric energy meter, which is related to the reliable work of the electric energy meter under the condition of external power failure. There are many types of batteries used in the field, and the charging management system must be able to manage the charging and discharging of nickel-metal hydride, nickel-cadmium and other batteries.

According to the requirements of the relevant technical specifications of the electric energy meter, after the electric energy meter is completely powered off, the rechargeable battery shall maintain the internal time and register data for at least 90 days, and the electric energy meter with special requirements shall maintain the internal time and register data for one year. However, in actual operation, the voltage of some watt-hour meter batteries drops sharply after power failure, and cannot provide the required power, which seriously affects the accuracy of metering data. The existing rechargeable battery management system in electric energy meter equipment mainly has the following problems:

1. The battery voltage is used to calculate the remaining power, which cannot truly reflect the remaining power. When the battery capacity decreases, an alarm message cannot be sent in time to remind the battery to be replaced.

2. Lack of battery maintenance function. When the battery does not work for a long time, the battery cannot be properly activated and maintained, resulting in a significant decrease in the actual capacity of the battery.

3. Frequent charging shortens battery life. Most energy meters use a constant voltage method to charge the battery instead of starting charging when the battery level falls below a threshold, resulting in frequent battery charging.

4. Poor versatility, the characteristics of different rechargeable batteries are different, and the battery management system is usually only suitable for a certain type of battery, which cannot meet the battery interchangeability requirements.

Contents of the invention

In order to solve the above problems, prolong the service life of the battery, and improve the stability and safety of the backup power supply system of the electric energy meter, the utility model provides a battery charging circuit of the electric energy meter, which consists of rechargeable batteries BT1, BT2, button batteries BT3, diodes D1, D2, It is composed of switches S11, S12, S21 and S22, capacitors C1 and C2, resistor R, and voltage detection terminals UB1, UB2 and UR.

Among them, the positive pole of button battery BT3 is connected to the positive pole of diode D1, the negative pole of BT3 is connected to the negative pole of diode D2, the rechargeable battery BT1 is connected to power supply U+ and U- through switch S11, the rechargeable battery BT2 is connected to power supply U+ and U- through switch S21, capacitors C1, C2 and R is connected in parallel, the middle of C1 and R is connected through switch S12, and the middle of C2 and R is connected through switch S22.

The utility model adopts the ampere-hour integration method to evaluate the capacity of the battery, first charges the battery to make the voltage reach the upper limit value, and then uses the resistance R to discharge, detects and records the voltage UB1, UB2, UR and the discharge time t until the battery voltage drops to the lower limit. Then the capacity of the battery can be calculated by formula (1):

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; t</span>}}\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Compared with the open circuit voltage method to detect battery capacity, the detection result of the ampere-hour integration method is more accurate.

At present, the power outage time of the power grid is less and less, and the operation reliability is high. The power outage time of the electric energy meter is less during use, and the rechargeable battery is not in the discharge state for a long time. According to the characteristics of Ni-MH batteries and lithium batteries, if the batteries are not charged and discharged for a long time, their lifespan will be affected. Therefore, after each charge and discharge cycle, record the idle time T, and when T exceeds the threshold Td, the battery needs to be maintained. Td can be set according to the characteristics of the battery, generally set to 3 months. Due to the "memory effect", nickel-cadmium batteries need a maintenance discharge every once in a while to restore battery performance. Considering the redundant function of the battery, the rechargeable batteries BT1 and BT2 cannot be discharged at the same time. The maintenance of one battery must be completed before the maintenance of another battery is allowed to ensure that the energy meter has an appropriate reserve power. During maintenance, both BT1 and BT2 use the resistor R to discharge. According to formula (2), the discharge current i _R is set by the duty cycle of the switch S12 or S22, and the battery can be discharged according to the preset discharge curve.

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; D.</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

At present, the nickel-metal hydride and nickel-cadmium batteries that meet the requirements are different in terms of capacity and charge cut-off voltage. In order to be compatible with different types of batteries and meet the requirement of on-site battery interchangeability, the charging current is preferably set to 60mA, and the discharging current in the maintenance state is preferably set to 120mA. The charging cut-off voltage is preferably set to 6.6V, and the charging state is constant current and voltage limiting. In order to reduce the impact of "memory effect" on battery capacity, the charging lower limit voltage is preferably set to 4.4V. When discharging, first select the battery with less remaining power to discharge until the voltage drops to 4.2V, and then select the battery with larger remaining power to discharge. Since the energy meter is in the external power supply state most of the time, the charging circuit of the energy meter battery does not pursue fast charging, but chooses a smaller charging current.

The utility model has the following advantages and beneficial effects: it solves the current problems of inaccurate battery capacity detection, shallow charging and shallow discharge, less online maintenance, and poor versatility, and avoids the loss of register data of the electric energy meter due to external power failure and low battery power. Failure to record electricity leads to economic loss. The reliability of the data of the electric energy meter is improved, and the cost of manual maintenance is reduced. The four working states proposed by the utility model can regularly maintain the battery online, activate the dormant power of the battery, prolong the life of the battery, effectively solve the problem of shallow charge and discharge of the battery, and reduce the influence of the memory effect.

Description of drawings

Fig. 1 is the schematic circuit diagram of the utility model.

detailed description

The technical scheme of the utility model will be clearly and completely described below in conjunction with the accompanying drawings:

As shown in Figure 1, the utility model provides a battery charging circuit of a multifunctional electric energy meter, which consists of rechargeable batteries BT1, BT2, button batteries BT3, diodes D1, D2, switches S11, S12, S21 and S22, capacitors C1, C2 , Resistor R, composed of voltage detection terminals UB1, UB2, and UR.

Among them, the positive pole of button battery BT3 is connected to the positive pole of diode D1, the negative pole of BT3 is connected to the negative pole of diode D2, the rechargeable battery BT1 is connected to power supply U+ and U- through switch S11, the rechargeable battery BT2 is connected to power supply U+ and U- through switch S21, capacitors C1, C2 and R is connected in parallel, the middle of C1 and R is connected through switch S12, and the middle of C2 and R is connected through switch S22.

The voltage detection terminal UB1 is used to detect the voltage of the rechargeable battery BT1.

The voltage detection terminal UB2 is used to detect the voltage of the rechargeable battery BT2.

The voltage detection terminal UR is used to detect the voltage of the resistor R.

The preferred voltage of the button battery BT3 is 6V.

The preferred voltage of the rechargeable batteries BT1 and BT2 is 6V, and the rated capacity is greater than 500mAh.

The utility model has four working states: normal state, maintenance state, power-down state and protection state.

1. Normal state

When the external power supply of the electric energy meter is normal, the management system operates in a normal state to realize the function of charging the battery. When the switches S11 and S21 are closed and S12 and S22 are open, the system is in a normal state. At this time, the batteries BT1 and BT2 are connected to both ends of the power supply U+ and U-. The power supply U+ and U- can charge the battery, and the charging current is set by the duty cycle of the switches S11 and S21. When the capacity or remaining power of the two batteries is different, different charging currents can be set through the switches S11 and S21 to optimize the charging efficiency of each battery and shorten the overall charging time.

2. Maintenance status

The maintenance state provides a discharge circuit for the battery. When the switches S11, S21, S22 are open and S12 is closed, or when the switches S11, S12, S21 are open and S22 is closed, the system is in the maintenance state, and the battery BT1 or BT2 discharges to the load resistor R alone. The main function of the maintenance state is to test the battery capacity and to activate and maintain the battery. The capacity of the battery will decrease after a long time of use, so it is necessary to test the battery capacity regularly.

3. Power-down state

When the external power supply of the electric energy meter is abnormal, the voltage of the power supply U+ and U- is lower than the set value, preferably 4.2V, and the electric energy meter is in a power-off state. At this time, switches S12 and S22 are disconnected, S11 and S21 are closed, and batteries BT1 and BT2 are connected in parallel to supply power to the electric energy meter. If the internal resistance difference or the voltage difference is large when BT1 and BT2 are connected in parallel, the output effect may be affected. The discharge currents of BT1 and BT2 can be set respectively by adjusting the duty ratios of S11 and S21 to balance the discharge currents of the two batteries and improve the discharge efficiency in the power-off state.

4. Protection status

When the switches S11, S12, S21, and S22 are disconnected, the system is in a protection state, and the batteries BT1 and BT2 are completely separated from the power supply of the electric energy meter. Detect the voltage of the power supply U+ and U-, and detect the voltage change of the voltage detection terminals UB1, UB2, UR. When the energy meter is disturbed by the external power supply (such as surge impact, overvoltage) and the power supply U+ and U- are too high, in order to protect BT1 and BT2 from overvoltage damage, the battery system enters the protection state. Exit the protection state after the external power supply returns to normal.

If the energy meter is completely powered off at this time, the power supply U+ and U- are completely powered off, and the button battery BT3 supplies power to the energy meter through the power supply U+ and U- to ensure that the clock and register data of the energy meter are not lost. Diodes D1 and D2 are installed at the positive and negative poles of the button battery BT3, which can ensure that BT3 is not subject to external power surge impact, overvoltage impact or electromagnetic disturbance.

Claims (2)

1. A battery charging circuit for a multifunctional watt-hour meter is characterized in that, by rechargeable battery BT1, BT2, button battery BT3, diode D1, D2, switch S11, S12, S21 and S22, capacitor C1, C2, resistance R, voltage Detection terminal UB1, UB2, UR composition; Among them, the positive pole of button battery BT3 is connected to the positive pole of diode D1, the negative pole of BT3 is connected to the negative pole of diode D2, the rechargeable battery BT1 is connected to power supply U+ and U- through switch S11, the rechargeable battery BT2 is connected to power supply U+ and U- through switch S21, capacitors C1, C2 and R is connected in parallel, the middle of C1 and R is connected through switch S12, and the middle of C2 and R is connected through switch S22. 2. A battery charging circuit for a multifunctional electric energy meter according to claim 1, wherein the preferred voltage of the button battery BT3 is 6V.