Charger for Ni-Cd and Ni-MH batteries on the TEA1101 chip. 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 an "intelligent" foreign-made charger for accelerated charging of nickel-cadmium and nickel-metal hydride batteries, made on the TEA1101 chip (Phillips), and its refinement in order to expand its capabilities.

For many years, Ni-Cd (nickel-cadmium) batteries and batteries can be found in stores and markets, which, under appropriate operating conditions, can withstand up to 1000 charge-discharge cycles. The disadvantages of these batteries include the so-called "memory effect". It consists in the fact that the used battery must be brought to a state of complete discharge (about 1 V per battery) and only then a new charging cycle should be started.

Along with the widespread nickel-cadmium batteries, relatively new ones - Ni-MH (nickel-metal hydride) - appeared and also became widely used. With the same dimensions as Ni-Cd, these batteries have almost twice the capacity. Naturally, they are also expensive and not without drawbacks. Ni-MH batteries have a high internal resistance and low peak discharge current, so they are not designed to power energy-consuming devices such as electric drills, electric screwdrivers, compressors, vacuum cleaners, etc.

Due to improper charging methods, the "lifetime" of batteries is reduced by up to 30%. Damaged batteries, in turn, cause irreparable damage to the environment during disposal. Therefore, proper and competent battery charging will bring not only fundamental financial savings, but also have a positive environmental effect.

The cheapest and simplest battery chargers consist of a transformer, a rectifier diode, a current limiting resistor, and an LED. The transformer lowers the mains voltage of 220 V to 4...12 V, which then rectifies the half-wave rectifier. The resistor limits the charging current, and the LED indicates that the battery is connected to the charger. Devices mainly manufactured in Asian countries with similar or identical circuits can often be found in stores. There is no overhead to manufacture such devices, but remember that they do not protect batteries from overcharging. After just a few cycles, irreversible changes can appear in the batteries, shortening their service life.

During charging, you must constantly monitor the current, maintaining it at a certain level. To reduce the time, the charging current is increased, it can reach a value numerically equal to 100% of the battery capacity. If, under such conditions, the moment of full charging is not monitored, gases can accumulate inside the battery and increase in pressure up to its mechanical damage and failure.

The state of charge can be monitored by constantly measuring the temperature of the battery case. This method is based on the so-called negative temperature coefficient (about -1 mV/°C) of Ni-Cd and Ni-MH batteries. Charging is stopped at the appropriate temperature value, which is calculated for each specific case. However, this method is not widely used, given the difficulties that arise when trying to accurately measure temperature and the need for accurate calculations.

There is another way to control the full charge of the battery, based on the detection of a decrease in voltage, in the literature it is often called the ΔV method [1-6]. It consists in tracking the change in voltage at the battery terminals over time and stopping charging at the moment the maximum characteristic is reached. It is this method - measuring the sign of ΔУ - that underlies the principle of operation of the device, which will be discussed further.

The maximum detection method is today the most accurate way to determine the end of charging Ni-Cd and Ni-MH batteries. The voltage at the battery terminals at a constant charging current is a monotonically increasing function. When the battery is fully charged, it stops storing energy, and gas begins to accumulate near the positive electrode. This leads to a rapid increase in temperature and a decrease in voltage at the battery terminals. A specialized microcircuit (in the described TEA1101 charger) at certain intervals measures the current voltage on the battery being charged and compares it with the previous measurement. If the comparison result takes a negative value, i.e. the current voltage is less than the previous one, and a similar phenomenon is repeated for several dozen measurements, the charger switches to conservative charging mode with a current within 1/20 ... 1/80 of the nominal battery capacity. Conservative charging does not cause further gassing in the battery and does not harm it.

The value of ΔV, which the charger is able to measure, depends on the microcircuit used, or rather, on the capacity of the analog-to-digital converter built into it, which converts the voltage into a digital code. In the TEA1101 chip, the number of bits is 12, which provides a discreteness of 0,025% of the absolute voltage value. This is sufficient for both types of batteries, while, for example, the TEA1100 chip has only a 10-bit ADC, the accuracy of which is only enough to work with Ni-Cd batteries.

The diagram of the "intelligent" charger is shown in fig. 1. Position designations of all elements correspond to the scheme of the manufacturer.

The basis of the device is a specialized TEA1101 (DA1) microcircuit. The supply voltage of the microcircuit stabilizes the VT3VD4R6R7 stabilizer at a level of 8 V, however, it remains operational up to a voltage of 11,5 V. A voltage proportional to the charging current of the battery is supplied to the input IB (pin 5) of the microcircuit, from the current sensor - resistor R4, which is compared with the specified values accelerated and conservative charging current, determined respectively by resistors R13 and R12. If the charging current deviates from the set value, a control voltage appears at the analog control output of the AO (pin 2). If a linear regulator is used in the charger, this voltage is supplied to the control transistor, which performs the correction. However, the TEA1101 chip has a built-in pulse-width modulator and, accordingly, a PWM output (pin 1).

Pulse regulation of the charging current has all the advantages of SHI-regulators over linear ones - higher efficiency, low power dissipation on the regulating element, etc. The described charger is built exactly on the principle of SHI-regulation, and the analog signal is fed to the control unit VT4R16 - R18 in two colors LED HL2, by the color and brightness of which you can approximately judge the charging current. The brightest glow of the red LED means that the battery is charging rapidly (transistor VT4 is maximally open). A smooth transition from red through orange to green indicates a decrease in the regulating voltage and covering the regulating element. A bright green glow comes from the moment of transition to the conservative charging mode.

Unfortunately, such an indication does not allow you to accurately determine the moment when a full charge is reached. However, the TEA1101 chip has a special LED output (pin 15) for driving the LED. This LED (HL1) behaves differently in different charging phases, thereby providing complete information about the processes taking place in the charger. If the LED does not light up or glows very weakly, it may pulsate with a low brightness level, the battery is not connected to the charger. Constantly and brightly shines - there is an accelerated charging of the battery. Blinking brightly - the battery is fully charged. If at the first start-up the alarm is the same as at the end of charging, the battery is most likely out of order and cannot be restored. Naturally, in all these situations, you should also pay attention to the two-color LED, its glow indicates whether the charging is really going on or not.

Initially, the industrial device was designed to charge accumulators or batteries consisting of two or three accumulators with a capacity of 600...700 mAh. However, this device can be subjected to a simple refinement, as a result of which its capabilities are significantly expanded. The fact is that all the parameters of the charger can be set by selecting the appropriate elements and supply voltage.

The current of the fast charging mode is calculated by the formula

lfast = R8 Uref/(R4 R13) = 3,9 10³ 1,25/ /(0,27 27 10³) = 0,669A,

where Uref = 1,25 V is the reference voltage at the output Rref (pin 10).

Conservative charge current

lnorm \u0,1d 8R4 Uref / (R12 R0,1 P) \u9d 10x x Z.XNUMX XNUMX³ 1,25/(0,27 6,2 10³ 4) = 0,073 A,

where P is a multiplier, the value of which is determined by connecting pin 8 (PR) of the TEA1101 chip. When this pin is connected to pin 6 (Us) of the microcircuit, P \u1d 16, if to pin 4 (GND), - P \u2d XNUMX, and when the pin is not connected, P \uXNUMXd XNUMX.

Thus, from the above relations it can be seen that if resistors of different resistances are connected in place of R8, it is possible to charge batteries and batteries of various capacities C. In table. 1 shows the calculated values ​​of the resistance R8 and the current of the fast and conservative charging modes.

In addition, in order to charge batteries with a large number of batteries, you should change the transfer coefficient of the resistive divider R14R15 at the UAC input of the microcircuit (pin 7). In table. 2 shows six battery options containing from one to six batteries. Considering that the maximum fast charging current for batteries with a capacity of 1000 ... 1200 mAh should be approximately 1 A, and the voltage drop across the regulating element and two diodes will be about 2,5 V, the required voltage of the power source when charging batteries consisting of four or more batteries, choose equal to 18 V.

The scheme of the modified version of the device is shown in fig. 2.

The assessment of the minimum required supply voltage to provide one or another charging current was carried out very approximately, but subsequent experiments showed the correctness of the calculations.

Literature

1. Nachrustung von Ladenstationen fue NC-Akkuwerzeuge mit dem Ladecontroller TEA1101. - Funk Amateur, 2000, No. 2, p. 164-167.
2. "Intelligent" charger for Ni-Cd batteries. - Radio, 2001. No. 1.S.72.
3. Grigoriev B. Algorithm for fast charging of batteries. - Radio, 2001, No. 8, p. 38.
4. Boshboom W. Batteries recharge characteristics under TEA1101 charge management. Report No: NPO/AN9301.
5. Battery monitor for Ni-Cd and Ni-MH chargers. Philips Semiconductors - preliminary specification. Dec. 1992.
6. Inteligentna ladowarka akkumulatorow Ni-MH i Ni-Cd. - Radioelectronic Audio Hi-Fi-Video, 1998, No. 7-8. s. 21-26.

Author: V.Golutvin, Lviv, Ukraine

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 New system for nanotheranostics 12.07.2019 Scientists from the Federal Polytechnic School of Lausanne (EPFL) and the University of Geneva (Switzerland) have developed a new nanotheranostic system that uses "harmonic nanoparticles" - a family of metal oxide nanocrystals with unique optical properties: they respond to excitation not only from ultraviolet, but also from infrared light which is much safer for the patient. Theranostics is a developing field of medicine, the name of which contains the words "therapy" and "diagnosis". The idea of ​​theranostics is to create drugs and treatments that are simultaneously used for early diagnosis of the disease, and for treatment, and for monitoring the patient's response. This saves time and money, and may bypass some of the unwanted biological effects that can occur when these strategies are used alone. Today, nanoparticles are increasingly used in theranostics, which combine diagnostic molecules and drugs into a single agent. The nanoparticles act as carriers for a molecular "cargo" such as a drug or a radioisotope for cancer patients undergoing radiation therapy. This "transport" is directed to specific biological pathways in the patient's body and can avoid damage to healthy tissue. Once in the target tissue, the nanoparticles either help make diagnostic images or deliver their payload (or both). Specialists control them with the help of light. It is an advanced "nanotheranostics" technology that has become a mainstream of research. Although it has numerous limitations, there are disadvantages that must be overcome. A new system developed by the Gerber group avoids these problems by using bismuth-ferrite "harmonic nanoparticles" based on silicon oxide, which carry light-sensitive molecular weights. These systems can be easily activated with near infrared light (790 nanometers) and imaged at longer wavelength for drug discovery and isolation processes. Both of these features make the system safe for patients. Once the light is triggered, the nanoparticles release their cargo - in this case, L-tryptophan, which the researchers used as a model. The scientists monitored and quantified the release of the "cargo" using liquid chromatography and mass spectrometry.

Other interesting news:

▪ Touchpad Airboard

▪ Smartphone Lenovo Z6 Pro

▪ Record rope

▪ Created a device to simulate odors in computer games

▪ Drone vs Fighter

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Lightning protection. Article selection

▪ article They lived long and died on the same day. Popular expression

▪ article What did Captain Cook give his men to fight scurvy? Detailed answer

▪ article Pendulum saw. home workshop

▪ article ROM emulator. Encyclopedia of radio electronics and electrical engineering

▪ article Chess and inertia. physical experiment

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