Automatic charger. DIY charger for the crown Charging for the crown from a dc-dc converter

Diagram and description of a homemade automatic charger for charging 9 volt batteries (7D-01 “crown”) and the like.

The charger circuit is shown in Figure 1.

Click on the picture to view.

It consists of a half-wave rectifier on diode VD1, a voltage stabilizer on zener diode VD2 and ballast resistors R1, R2, an electronic switch on transistor VT1 and diode VD3, a threshold device on thyristor VS1.

While the battery connected to the XP2 connector is charging and the voltage on it is below the nominal value, the thyristor is closed. As soon as the voltage on the battery increases to the nominal value, the thyristor opens. The HL1 signal lamp lights up and at the same time the transistor closes. Battery charging stops.

The triggering threshold of the machine depends on the resistance of resistor R4.

Diode D226D can be replaced with any other from the same series, D226B - with another rectifier diode with a rectified current of at least 50 mA and a reverse voltage of at least 300 V, zener diode D813 - with zener diode D814D, transistor KT315B - with another transistor of this series with a current transfer coefficient of at least 50 , thyristor KU103V - thyristor KU103A.

Set up a homemade charger with a connected battery and a DC control voltmeter that measures the battery voltage. As soon as the voltage reaches 9.45 V, the warning light should flash. If this does not happen, then select resistor R4. The device is connected to the network only after the battery is securely connected!!!

Popular charger schemes:

Let's consider a device for charging low-power 9-volt batteries, type 15F8K. The circuit allows you to charge the battery DC about 12 mA, and when finished it turns off automatically.

The memory has protection against short circuit under load. The device is a simple current source and additionally includes an indicator reference voltage on LED and automatic circuit turning off the current at the end of charging, which is performed on the zener diode VD1, the voltage comparator on the op-amp and the switch on transistor VT1.

Schematic electrical diagram.

The level of charging current is set by resistor R7 according to the formula, which you can see in the original article in the picture (click to enlarge).

Operating principle of the charger

Voltage at the non-inverting input of the microcircuit more voltage on inverting. Output voltage operational amplifier close to the supply voltage, transistor VT1 is open and a current of about 10 mA flows through the LED. As the battery charges, the voltage across it increases, which means the voltage at the inverting input also increases. As soon as it exceeds the voltage at the non-inverting input, the comparator will switch to another state, all transistors will close, the LED will go out and the battery will stop charging. The maximum voltage at which battery charging stops is set by resistor R2. To avoid unstable work of the comparator, in the dead zone, you can install a resistor, shown in the dashed line, with a resistance of 100 kOhm.

This circuit is well suited not only for conventional battery " Crowns", but also other types of batteries. You just need to select the resistance of resistor R7 and, if necessary, supply more power transistor VT3.

The finished memory can be placed in any plastic box of suitable size. Cases from non-working charges are also perfect mobile phones. For example, one working, converted to a higher voltage, charging - a voltage source of 15V, and the other will contain circuit elements of the charger itself and contacts for connecting " Crowns"Assembling and testing the device: sterc

Discuss the article CHARGING THE 9V BATTERY CROWN

Instructions

Familiarize yourself with the pinout of the Krona battery. The battery itself or an accumulator of this type, as well as the power supply that replaces it, has a large terminal - negative, and a small terminal - positive. For the charger, as well as for any device powered by the Krona, everything is the other way around: the small terminal is negative, the large terminal is positive.

Make sure that the battery you have is actually a rechargeable one.

Determine the charging current battery. To do this, divide its capacity, expressed in milliamp-hours, by 10. You get the charging current in milliamps. For example, for a battery with a capacity of 125 mAh, the charging current is 12.5 mA.

As a power source for the charger, use any power supply whose output voltage is about 15 V, and the maximum permissible current consumption does not exceed the charging current of the battery.

Check out the pinout of the LM317T stabilizer. If you put it with the front side with the markings facing you, and the terminals down, then there will be an adjustment terminal on the left, an output in the middle, and an input on the right. Install the microcircuit on a heat sink, which is isolated from any other current-carrying parts of the charger, since it is electrically connected to the output of the stabilizer.

The LM317T chip is a voltage stabilizer. To use it for other purposes - as a current stabilizer - connect a load resistor between its output and the control output. Calculate its resistance using Ohm's law, taking into account that the voltage at the output of the stabilizer is 1.25 V. To do this, substitute the charging current, expressed in milliamps, into the following formula:
R=1.25/I
The resistance will be in kilo-ohms. For example, for a charging current of 12.5 mA, the calculation would look like this:
I=12.5 mA=0.0125A

R=1.25/0.0125=100 Ohm

Calculate the power of the resistor in watts by multiplying the voltage drop across it, equal to 1.25 V, by the charging current, also previously converted to amperes. Round the result up to the nearest standard value.

Connect the plus of the power source to the plus of the battery, the minus of the battery to the input of the stabilizer, the adjusting terminal of the stabilizer to the minus of the power source. Between the input and the adjusting terminal of the stabilizer, turn on electrolytic capacitor at 100 µF, 25 V plus to the input. Shunt it with a ceramic one of any capacity.

Turn on the power supply and leave the battery to charge for 15 hours.

Video on the topic

Krona batteries appeared in the Soviet Union, but still remain in demand. This battery is indispensable for devices with high energy consumption, as it produces a much higher current compared to other batteries.

Characteristics of Krona batteries

The batteries are of types AA, AAA, C, D, they are cylindrical in shape and differ only in size. In contrast, the Krona battery has a standard size of PP3 and is a parallelepiped. Salt batteries are characterized by their fragility and cannot be used in high-tech devices. The maximum they are designed for is a watch or other simple device. Batteries are also distinguished by their electrochemical system. Alkaline and lithium batteries have better performance.

Krona mini-batteries are distinguished by fairly high performance; they have an output voltage of around nine (in comparison, a lithium or alkaline AA battery “produces” only 1.5 volts). The Krona battery consists of six one-and-a-half-volt batteries connected in series in one chain (the output is nine volts.) The batteries can have a current of up to 1200 mAh, the standard power is 625 mAh. The capacity of Krona batteries will vary depending on the types of chemical elements. Nickel-cadmium cells have a capacity of 50 mAh, nickel-metal hydride batteries are an order of magnitude more powerful (175-300 mAh). Lithium-ion cells have the highest capacity, their power is 350-700 mAh. The standard size of Krona batteries is 48.5x26.5x17.5 mm. These batteries are used in children's toys and control panels; they can be found in navigators and shockers.

How to charge a Krona battery

In the Soviet Union, carbon-manganese batteries of this size were produced, as well as alkaline ones, which had a higher price and were called “Korundum”. The batteries were produced from rectangular biscuits; for their manufacture, metal case made of tinned sheet metal, bottom made of plastic or genitax and contact pad. Simple disposable Krona batteries allowed a small number of recharges, although this was not recommended by the manufacturer. However, due to the shortage of these nutrients, many books and magazines published

Most radio amateurs use digital multimeters that are powered by rechargeable batteries or Krona batteries.

At the same time, taking into account the law of meanness, they are always discharged at the most inopportune moment, when the performance of the entire project depends on the accuracy of measurements.

After visiting the store, I decided for myself that using a Krona battery is more economical than constantly buying and keeping a battery in stock. But this is only on condition correct operation battery

Therefore, a simple charger was required. It can be purchased in many stores. BUT! Like many of you, I am not looking for easy ways. And it’s much more interesting and useful to come up with a scheme, assemble it, and set it up for high-quality work.

This is the charger I got.

This device allows you to charge Krona type batteries – 2 pcs. separate channels with optimal charging current(1/10 of the capacity) and has LED indication.

The indication consists of two LEDs. The 1st indicates that the battery is more than 50% discharged. 2nd – indicates that the battery is charged and can be removed from the device.

In addition, charging a discharged battery occurs in two stages: constant current charging and constant voltage charging.

Let's analyze the operation of the circuit. The circuit is powered by a constant (rectified) voltage from 12 to 30 V. But an increased supply voltage will cause a higher voltage difference across the LM317, which will lead to its heating and the need to install a heatsink. Therefore, I recommend powering the circuit with 12-15 V.

Turning on the LM317 in voltage stabilization mode allows you to obtain a constant (unchangeable) voltage at the output of the microcircuit when the supply voltage changes.

After LM317, a current stabilizer is made using two transistors. When we connect the terminals to a discharged battery, the voltage drop across the 27 ohm resistor significantly exceeds the opening threshold of the second transistor, which leads to the LED turning on and the first transistor partially closing and, thereby, limiting the charge current.

During the battery charging process, the voltage drop across the 27 ohm resistor at a certain moment closes the second transistor, which leads to an almost complete opening of the first transistor, which means that almost all of the input voltage goes to the emitter of the transistor, that is, to the output.

This ensures a safe charging current for the battery Krona.

The operational amplifier OP (LM358) acts as a comparator that monitors the voltage at the battery terminals and compares it with the installed variable resistor. As soon as the voltage exceeds the set value, the second LED will light up, indicating that the battery is charged.

We begin the setup by setting the output voltage. To do this, connect a voltmeter to the output terminals (without load) and use a trimmer resistor (in the LM317 stabilizer circuit) to set the voltage to 9.1-9.2V.

Next, to configure the operation of the LED, signaling the end of charging, we connect a voltmeter to the output terminals and connect the Krona battery. As soon as the voltage reaches 9V, rotating the trimming resistor (in the LM358 circuit) turns on the LED. This operation requires quite a lot of patience and precision, so I recommend using multi-turn resistors.

After adjustment, these resistors are covered with varnish or wax to eliminate the possibility of disrupting the previously made adjustment.

The board layout is made taking into account the available parts.