Chargers on chips of voltage stabilizers. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

 Comments on the article

The article describes simple chargers for lead-acid batteries, including automotive ones.

In recent years, maintenance-free (gel) lead-acid batteries with a voltage of 6 V, consisting of three batteries, have been used in various equipment. They are used in portable flashlights, electronic toys, uninterruptible power supplies, etc. Yes, and in the laboratory of a radio amateur they can be found quite often. If such batteries are not regularly used, they should be stored in a charged state.

Depending on the mode of operation, the voltage on lead-acid batteries must be maintained within certain limits. So, for example, for an RB640BS battery with a capacity of 4,5 Ah, the voltage in case of cyclic use should be within 7,2 ... 7,5 V, for backup use - 6,75 ... 6,9 V. Maximum current charging in this case should not exceed 1,35 A.

The voltage stabilizer chips of the 7809 series are available in two main versions: with a tolerance for an output voltage of 9 V ± 2% (output voltage in the range of 8,82 ... 9,18 V) and ± 4% (8,64 ... 9,36, 1 V). They provide a maximum load current of 1,5 A (some modifications - up to XNUMX A). Stabilizers are equipped with overcurrent and overheating protection units, which makes them very attractive for use in chargers.

The output voltage of the 7809 regulator can be reduced by connecting two or three diodes of the 1N400x or 1N540x series to the output to obtain the necessary value for charging lead-acid batteries with a nominal voltage of 6 V. Typical values ​​​​of the voltage drop across the diodes of the 1N400x and 1N540x series, depending on the current, are given in the table.

The charger circuit for lead-acid batteries with a nominal voltage of 6 V on 7809 microcircuits is shown in fig. 1.

Fig. 1

It contains four stabilizers DA1-DA4, to the outputs of which a series-connected resistor and two diodes are connected to reduce the voltage. Connectors XS10-XS13 connect rechargeable lead-acid batteries. A voltmeter can be connected to contacts XS2, XS3 (and, accordingly, XS4-XS9) to measure the charging current. Since the resistance of resistors R3-R6 is 1 ohm, the voltmeter readings in volts (millivolts) are numerically equal to the current in amperes (milliamps).

You can connect a load to the XS1 connector to supply it with an unstabilized voltage. If the load is connected to the XS14 connector, the charger can be used as an uninterruptible power supply. In normal mode, in the presence of mains voltage, the load is powered by the charger. The batteries are being charged, and since the current is limited to 1A by the regulators, there is no danger of overcharging the batteries.

When the mains voltage disappears, the load will be powered by batteries through the diodes VD5, VD8, VD11, VD14.

LED HL1 indicates the presence of voltage at the output of the rectifier diodes VD1, VD2.

The step-down transformer T1 must provide an open-circuit voltage on the secondary windings of 2x (12,5 ... 14,5) V and a load current of at least 3 A. Diodes VD1, VD2 are designed for this current. Diodes VD3-VD14 can be of the 1N400x or 1N540x series or any others that allow direct current not less than the charging current of the batteries. In addition, Schottky diodes such as 1N5819 (forward current rating 1 A, reverse voltage 40 V) or 1N5822 (3 A, 40 V) are applicable.

Stabilizers DA1-DA4 are installed on a common heat sink. Capacitor C4 can be increased to 6800-10000 uF.

Establishing the device comes down to a selection of diodes connected to the output of the stabilizers, and their number to set the required voltage on the batteries.

A similar charger can be assembled to charge car batteries with a voltage of 12 V. In this case, stabilizers of the 7815 series are used. Typically, car batteries are charged with a current of 4 ... 6 A, the voltage on them in a fully charged state is about 14,5 ... 15 V .

Fig. 2

On fig. 2 is a diagram of a simple device capable of charging and maintaining such batteries.

Transformer T1 lowers the mains voltage to 19 ... 20 V, which then rectifies the diode bridge VD1-VD4 and smoothes the capacitors C2-C7. The secondary winding of the transformer and the rectifier diodes must be rated for the charging current of the battery.

The charger itself is assembled on DA1-DA5 stabilizers connected in parallel. Resistors R3-R7 connected to the outputs of the stabilizers equalize the charging current. The output impedance of the stabilizers does not exceed 0,03 ohms. Since the resistance of the resistors is ten times greater, we can assume that all the regulator and resistor circuits have the same output impedance.

Stabilizer circuits of the 7815 series are available in three main modifications: with a tolerance for an output voltage of 15 V ± 2% (output voltage within 14,7 ... 15,3 V), ± 4% (14,4 ... 15,6 V), ±5% (14,25...15,75 V). All of them can be used in the charger, but regulators with a tolerance of ±2% are more preferable.

The rechargeable battery is connected to connector XS1. LED HL1 indicates the presence of voltage at the output of the charger. If necessary, the voltage on the battery being charged can be reduced. To do this, open the contacts of the SA2 switch by connecting the diode VD6 in series with the battery. If this is not required, the diode and switch are not installed. Diode VD5 protects the stabilizers in the event of a power failure with the battery connected.

Diodes FR602 (VD1-VD4) can be replaced by any rectifier diodes with a permissible forward current of at least 5 A and a reverse voltage of at least 50 V, for example, HER602 is suitable. Schottky diode SR1640 (VD6) will be replaced by SR3020.

The output current of the charger is limited by stabilizers DA1-DA5. The maximum power dissipated by them depends on the state of the rechargeable battery and can be significant, so all microcircuits are installed on a common heat sink with an area of ​​at least 200 cm².

Properly assembled from serviceable parts, the charger does not require adjustment.

Author: P. Petrov

See other articles Section Chargers, batteries, galvanic cells.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive Tape without glue 06.09.2003 The University of Manchester (England) has created adhesive tape without glue. True, so far only a small piece of one square centimeter has been obtained. The developers took advantage of the recently revealed secret of the gecko. This small lizard runs briskly along vertical surfaces, including glass. It was recently discovered that the legs of the gecko are covered with the finest hairs, which, in contact with any surface, are attracted to it simply due to intermolecular forces. Each hair provides only a very slight attraction, but there are many billions of such hairs. By shifting the sole so that the hairs form an acute angle with the surface, the gecko disengages the foot from the surface. Using nanotechnology methods, the researchers were able to apply hairs 2 microns long and 0,2 microns thick to a flexible polymer film, just like a natural sample. There are about a hundred million of them per square centimeter. It is estimated that if you make a glove with such a coating, a person can hang on the ceiling or wall on one hand wearing such a glove. But the mass production of such a film is not yet planned: the process is too complicated. And it is not clear how long the micro-hairs will last - in a gecko they grow as they are erased.

Other interesting news:

▪ The danger of permafrost

▪ Spray instead of solar panels

▪ Geoengineering weather control

▪ TV and health

▪ Heart attack awaits on the road

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ Telephony site section. Article selection

▪ article Strategic management. Crib

▪ article How Emperor Paul I was going to help Napoleon in the war against Great Britain? Detailed answer

▪ article Small-fruited double crest. Legends, cultivation, methods of application

▪ article Waterproof glue. Simple recipes and tips

▪ MARSHALL tube preamplifier. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024