How does phone charging work? Fast charging

In electrical engineering, batteries are usually called chemical current sources that can replenish and restore spent energy through the application of an external electric field.

Devices that supply electricity to the battery plates are called chargers: they bring the current source into working condition and charge it. To properly operate batteries, you need to understand the principles of their operation and the charger.

How does a battery work?

During operation, a chemical recirculated current source can:

1. power the connected load, for example, a light bulb, motor, mobile phone and other devices, using up its supply of electrical energy;

2. consume external electricity connected to it, spending it to restore its capacity reserve.

In the first case, the battery is discharged, and in the second, it receives a charge. There are many battery designs, but their operating principles are common. Let us examine this issue using the example of nickel-cadmium plates placed in an electrolyte solution.

Low battery

Two electrical circuits operate simultaneously:

1. external, applied to the output terminals;

2. internal.

When a light bulb is discharged, a current flows in the external circuit of the wires and filament, generated by the movement of electrons in the metals, and in the internal part, anions and cations move through the electrolyte.

Nickel oxides with added graphite form the basis of the positively charged plate, and cadmium sponge is used on the negative electrode.

When the battery is discharged, part of the active oxygen of the nickel oxides moves into the electrolyte and moves to the plate with cadmium, where it oxidizes it, reducing the overall capacity.

Battery charge

The load is most often removed from the output terminals for charging, although in practice the method is used with a connected load, such as on the battery of a moving car or a mobile phone on charge, on which a conversation is taking place.

The battery terminals are supplied with voltage from an external source of higher power. It has the appearance of a constant or smoothed, pulsating shape, exceeds the potential difference between the electrodes, and is directed unipolarly with them.

This energy causes current to flow in the internal circuit of the battery in the direction opposite to the discharge, when active oxygen particles are “squeezed out” from the cadmium sponge and return to their original place through the electrolyte. Due to this, the spent capacity is restored.

During charge and discharge, the chemical composition of the plates changes, and the electrolyte serves as a transfer medium for the passage of anions and cations. The intensity of the electric current passing in the internal circuit affects the rate of restoration of the properties of the plates during charging and the speed of discharge.

Accelerated processes lead to rapid release of gases and excessive heating, which can deform the structure of the plates and disrupt their mechanical condition.

Too low charging currents significantly lengthen the recovery time of used capacity. With frequent use of a slow charge, sulfation of the plates increases and capacity decreases. Therefore, the load applied to the battery and the power of the charger are always taken into account to create the optimal mode.

How does the charger work?

The modern range of batteries is quite extensive. For each model, optimal technologies are selected, which may not be suitable or may be harmful to others. Manufacturers of electronic and electrical equipment experimentally study the operating conditions of chemical current sources and create their own products for them, differing in appearance, design, and output electrical characteristics.

Charging structures for mobile electronic devices

The dimensions of chargers for mobile products of different power differ significantly from each other. They create special operating conditions for each model.

Even for batteries of the same type AA or AAA sizes of different capacities, it is recommended to use their own charging time, depending on the capacity and characteristics of the current source. Its values ​​are indicated in the accompanying technical documentation.

A certain part of chargers and batteries for mobile phones are equipped with automatic protection that turns off the power when the process is complete. However, monitoring their work should still be carried out visually.

Charging structures for car batteries

Charging technology should be observed especially precisely when using car batteries designed to operate in difficult conditions. For example, in cold winters, they need to be used to spin the cold rotor of an internal combustion engine with thickened lubricant through an intermediate electric motor—the starter.

Discharged or improperly prepared batteries usually do not cope with this task.

Empirical methods have revealed the relationship between the charging current for lead acid and alkaline batteries. It is generally accepted that the optimal charge value (ampere) is 0.1 the capacity value (ampere hours) for the first type and 0.25 for the second.

For example, the battery has a capacity of 25 ampere hours. If it is acidic, then it must be charged with a current of 0.1∙25 = 2.5 A, and for alkaline - 0.25∙25 = 6.25 A. To create such conditions, you will need to use different devices or use one universal one with a large amount functions.

A modern charger for lead acid batteries must support a number of tasks:

control and stabilize the charge current;

take into account the temperature of the electrolyte and prevent it from heating more than 45 degrees by stopping the power supply.

The ability to carry out a control and training cycle for a car's acid battery using a charger is a necessary function, which includes three stages:

1. fully charge the battery to reach maximum capacity;

2. ten-hour discharge with a current of 9÷10% of the rated capacity (empirical dependence);

3. recharge a discharged battery.

When carrying out CTC, the change in electrolyte density and the completion time of the second stage are monitored. Its value is used to judge the degree of wear of the plates and the duration of the remaining service life.

Chargers for alkaline batteries can be used in less complex designs, because such current sources are not so sensitive to undercharging and overcharging conditions.

The graph of the optimal charge of acid-base batteries for cars shows the dependence of the capacity gain on the shape of the current change in the internal circuit.

At the beginning of the charging process, it is recommended to maintain the current at the maximum permissible value, and then reduce its value to the minimum for the final completion of the physicochemical reactions that restore capacity.

Even in this case, it is necessary to control the temperature of the electrolyte and introduce corrections for the environment.

The complete completion of the charging cycle of lead acid batteries is controlled by:

restore the voltage on each bank to 2.5÷2.6 volts;

achieving maximum electrolyte density, which ceases to change;

the formation of violent gas evolution when the electrolyte begins to “boil”;

achieving a battery capacity that exceeds by 15÷20% the value given during discharge.

Battery charger current forms

The condition for charging a battery is that a voltage must be applied to its plates, creating a current in the internal circuit in a certain direction. He can:

1. have a constant value;

2. or change over time according to a certain law.

In the first case, the physicochemical processes of the internal circuit proceed unchanged, and in the second, according to the proposed algorithms with a cyclic increase and decrease, creating oscillatory effects on anions and cations. The latest version of the technology is used to combat plate sulfation.

Some of the time dependences of the charge current are illustrated by graphs.

The lower right picture shows a clear difference in the shape of the output current of the charger, which uses thyristor control to limit the opening moment of the half-cycle of the sine wave. Due to this, the load on the electrical circuit is regulated.

Naturally, many modern chargers can create other forms of currents not shown in this diagram.

Principles of creating circuits for chargers

To power charger equipment, a single-phase 220 volt network is usually used. This voltage is converted into a safe low voltage, which is applied to the battery input terminals through various electronic and semiconductor parts.

There are three schemes for converting industrial sinusoidal voltage in chargers due to:

1. use of electromechanical voltage transformers operating on the principle of electromagnetic induction;

2. application of electronic transformers;

3. without the use of transformer devices based on voltage dividers.

Inverter voltage conversion is technically possible, which has become widely used for frequency converters that control electric motors. But, for charging batteries this is quite expensive equipment.

Charger circuits with transformer separation

The electromagnetic principle of transferring electrical energy from the primary winding of 220 volts to the secondary completely ensures the separation of the potentials of the supply circuit from the consumed circuit, eliminating its contact with the battery and damage in the event of insulation faults. This method is the safest.

The power circuits of devices with a transformer have many different designs. The picture below shows three principles for creating different power section currents from chargers through the use of:

1. diode bridge with a ripple-smoothing capacitor;

2. diode bridge without ripple smoothing;

3. a single diode that cuts off the negative half-wave.

Each of these circuits can be used independently, but usually one of them is the basis, the basis for creating another, more convenient for operation and control in terms of the output current.

The use of sets of power transistors with control circuits in the upper part of the picture in the diagram allows you to reduce the output voltage at the output contacts of the charger circuit, which ensures regulation of the magnitude of direct currents passed through the connected batteries.

One of the options for such a charger design with current regulation is shown in the figure below.

The same connections in the second circuit allow you to regulate the amplitude of the ripples and limit it at different stages of charging.

The same average circuit works effectively when replacing two opposite diodes in the diode bridge with thyristors that equally regulate the current strength in each alternating half-cycle. And the elimination of negative semi-harmonics is assigned to the remaining power diodes.

Replacing the single diode in the bottom picture with a semiconductor thyristor with a separate electronic circuit for the control electrode allows you to reduce current pulses due to their later opening, which is also used for various methods of charging batteries.

One of the options for such a circuit implementation is shown in the figure below.

Assembling it with your own hands is not difficult. It can be made independently from available parts and allows you to charge batteries with currents of up to 10 amperes.

The industrial version of the Electron-6 transformer charger circuit is made on the basis of two KU-202N thyristors. To regulate the opening cycles of semiharmonics, each control electrode has its own circuit of several transistors.

Devices that allow not only charging batteries, but also using the energy of the 220-volt supply network to parallel connect it to starting the car engine are popular among car enthusiasts. They are called starting or starting-charging. They have even more complex electronic and power circuitry.

Circuits with electronic transformer

Such devices are produced by manufacturers to power halogen lamps with a voltage of 24 or 12 volts. They are relatively cheap. Some enthusiasts are trying to connect them to charge low-power batteries. However, this technology has not been widely tested and has significant drawbacks.

Charger circuits without transformer separation

When several loads are connected in series to a current source, the total input voltage is divided into component sections. Due to this method, dividers work, creating a voltage drop to a certain value on the working element.

This principle is used to create numerous RC chargers for low-power batteries. Due to the small dimensions of the component parts, they are built directly inside the flashlight.

The internal electrical circuit is completely housed in a factory-insulated housing, which prevents human contact with the network potential during charging.

Numerous experimenters are trying to implement the same principle for charging car batteries, proposing a connection scheme from a household network through a capacitor assembly or an incandescent light bulb with a power of 150 watts and passing current pulses of the same polarity.

Similar designs can be found on the sites of do-it-yourself experts, praising the simplicity of the circuit, the cheapness of parts, and the ability to restore the capacity of a discharged battery.

But they are silent about the fact that:

open wiring 220 represents ;

The filament of the lamp under voltage heats up and changes its resistance according to a law unfavorable for the passage of optimal currents through the battery.

When switched on under load, very large currents pass through the cold thread and the entire series-connected chain. In addition, charging should be completed with small currents, which is also not done. Therefore, a battery that has been subjected to several series of such cycles quickly loses its capacity and performance.

Our advice: do not use this method!

Chargers are created to work with certain types of batteries, taking into account their characteristics and conditions for restoring capacity. When using universal, multifunctional devices, you should choose the charging mode that optimally suits a particular battery.

I wonder what the Siemens charger (power supply) consists of and whether it is possible to repair it yourself in the event of a breakdown.

First, the block needs to be disassembled. Judging by the seams on the body, this unit is not intended for disassembly, therefore it is a disposable item and you don’t have to place much hope in the event of a breakdown.

I literally had to tear apart the body of the charger; it consists of two tightly glued parts.

Inside is a primitive circuit board and several parts. The interesting thing is that the board is not soldered to the 220V plug, but is attached to it using a pair of contacts. In rare cases, these contacts may oxidize and lose contact, leaving you thinking the unit is broken. But the thickness of the wires going to the connector for the mobile phone was pleasantly pleasing; you don’t often see a normal wire in disposable devices; usually it is so thin that it’s scary to even touch it).

There were several parts on the back of the board; the circuit turned out to be not so simple, but still not so complicated that you couldn’t fix it yourself.

Below in the photo are the contacts of the inside of the case.

There is no step-down transformer in the charger circuit; its role is played by an ordinary resistor. Next, as usual, a couple of rectifying diodes, a pair of capacitors for rectifying the current, then comes a choke and finally a zener diode with a capacitor completes the chain and outputs the reduced voltage to a wire with a connector to the mobile phone.

The connector has only two contacts.

According to the principle of operation, chargers for mobile phones are divided as follows:

• Rechargeable - they work on the principle of accumulating charge and then transferring charge to the device.
• Network - powered from a central power supply network with a power of 220 V and convert this voltage into a voltage suitable for the device.
• Automotive - work from the cigarette lighter in the car. The vehicle's on-board network is used as power supply.
• Universal - they are a wire with a special connector for connecting a phone on one side and a USB connector on the other side, which allows you to charge the phone from a PC and laptop.
• Wireless - the device does not come into direct contact with electric current, but is simply placed on a special platform (we will look at the principle of their operation in more detail later).

Let's focus on network and wireless chargers.

AC charger

The design of a mobile phone charger is quite simple. In the modern world there are a huge number of them, including those that differ in the type of electrochemical system.

Each of them has its own specific work. Phone batteries typically use lithium-based batteries - lithium-ion (Li-ion) and lithium-polymer (Li-polymer). For such batteries, the design of a charger for a mobile phone comes down to the fact that the electrical circuit provides a voltage that exceeds the nominal voltage by 10-15% and allows for quick charging of the battery. Also an important element is the charge controller, which limits the supply of voltage to the device in critical cases.

Advantages and disadvantages

The main advantage of such chargers is their low cost, as well as relatively short charging time. The disadvantages include the presence of a wire that can wear out or break. Therefore, a wireless device may be preferable.

How does a wireless device work?

A wireless charger for mobile phones is a panel on which the phone is placed, where it charges. Sounds too fantastic? But it's true. It is based on the operating principle of an electric coil, the main property of which is the ability to transmit electric current.

We know from school that if you connect one coil to a current source, a magnetic field will arise in it. And if the second coil is placed within the range of the magnetic field, then an electric current will also arise in it. The only important condition is that the coils should not touch each other.

Advantages and disadvantages

The main advantage here is that no wires are connected to the mobile phone, hence the USB connector will not become loose. Moreover, you can use multiple chargers, which will greatly please any mobile phone user.

If we talk about the disadvantages, this is, of course, its cost and the longer charging process. If your phone is completely discharged and you urgently need to charge it, at least by 20-30 percent, then this option is clearly not suitable for you. Therefore, having wireless charging, it is better to always be on guard and have your phone charged when going somewhere.

So, as you may have noticed from the article, the design of a mobile phone charger can be different, and you can give preference to any of the types, depending on your personal desires.

A bad charger can greatly harm not only your smartphone or tablet, but also put your life in danger! Therefore, it is important to know something about charging.

We already talked to you once about, but in that article we paid more attention specifically to the battery. However, the battery itself will not charge - it requires a special Charger, which has its own characteristics and characteristics that affect the charging process and the operation of the device being charged in general.

Therefore, today we will pay attention to all kinds of chargers for phones, tablets, etc. Let's look at the questions of whether it is possible to leave the charger in the outlet all the time, what will happen if you charge your smartphone with a non-original charger, and when the charger can burn out your favorite device...

Types of chargers

Let's start with the fact that there are a great variety of chargers for various devices. Therefore, you need to limit yourself in advance to the scope of their application. We will only consider chargers for small household appliances, starting with wearable gadgets (fitness bracelets, smart watches, etc.) and ending with tablets.

We could also include chargers for laptops in our review, however, in fact, most of them are not chargers, but external power supplies. The difference here is very relative, however, roughly speaking, power supplies usually produce more current. It is capable of not only effectively charging the battery, but also fully powering the laptop from the network.

A classic charger is usually an electrical device that is capable of delivering a direct current of low voltage and power sufficient to charge the battery, but not always for normal power supply. Conventional chargers are a small current converter that is inserted into a 220 V socket (or a 10-15 V car cigarette lighter) and powers the battery of the desired device via a wire:

Wired chargers They differ from each other in the parameters of the output current (more on them below), as well as the type of plug connected to the connector of the device being charged. Today, the most common standardized plugs are microUSB, miniUSB, USB type C and Lightning. However, just a few years ago there was a lot of confusion in the mobile technology market, since even within the same brand there could be several types of sockets for charging and data transfer:

With the beginning of standardization, the market for chargers began to develop. In particular, many types have appeared portable memory. These, first of all, include power banks (from the English “power bank” - literally “power storage”). In essence, they are portable batteries that allow you to charge any mobile equipment using a standard USB port. At the same time, they themselves are charged from standard wired chargers or from alternative sources, such as solar panels:

Portable chargers can also include various devices that convert kinetic energy into electrical energy. They are based Dynamo machine, which generates current from rotating a special handle or constantly pressing the lever with your hands or other devices (for example, a bicycle wheel). The advantage of such chargers is their complete independence from the mains. However, the disadvantages are the labor intensity of generation and not always satisfactory quality of current.

Back in the early 2000s, they were popular on the market universal chargers crabs and crocodiles. The main disadvantage of both types of chargers is that they require removal of the battery. However, at one time they saved many owners of phones with specific charging connectors, since they connected directly to the terminals of any batteries and even allowed them to adjust the current parameters (though not all models):

Recently there have also appeared wireless chargers. They can be either already integrated into modern technology (mainly smartphones) or supplied in plug-in form (removable back covers, covers, etc.). Such devices consist of a base connected to the mains, which emits a current of the required value (in the form of an electromagnetic field), and a receiver inside the charging device, which picks up the radiation and charges the battery with it:

The advantage of wireless charging is that there is no need to constantly pull the power connector, which gradually wears out and eventually fails altogether. However, due to the fact that the technology is just beginning to be implemented, it also has a number of disadvantages:

• small radius and narrow focus of radiation (when charging, the smartphone must be placed on the base in a strictly certain place, otherwise even a slight displacement may cause it not to charge at all or to charge only slightly);
• increased heating of the device being charged;
• slower charging speed compared to wired;
• noise from the cooling cooler inside the base;
• high cost of a high-quality charger.

As you can see, the external charges differ quite greatly. But as for the internal structure and application, let’s figure it out now.

Charger Specifications

All important characteristics of the charger are usually indicated on a special label pasted on its case, or engraved or written directly on it. Let's see what it says there:

The most important characteristics are the parameters incoming(“In”, “Input” or “AC”) and coming out(“Out”, “Output”, “DC”) current. Most chargers intended for import into post-Soviet countries are designed for operation with our electrical networks, in which the nominal voltage is 220 Volts. However, in some countries the current in the network is lower than ours (from 100 to 150 V), so chargers from those countries can simply burn out when connected to our sockets. Therefore, the first thing you need to do is make sure that in the “Input” group the upper permissible value is indicated - 220 (or better 240) Volts.

Now let's look at the values ​​in the "Output" group. The most important here are the output indicators voltage and current strength. Despite the fact that modern charge controllers in smartphones and tablets are equipped with good protective mechanisms that reduce too much current to the required parameters, it is better not to overload these systems again and select charging in accordance with the nominal voltage of the battery of your device.

Now about current strength. The higher it is, the faster the battery will charge. However, each battery has a certain limit, which should not be exceeded. For example, a battery with a recommended current of 1 Ampere can be charged at 1A or lower, but when charging at, for example, 2A, there is a chance that the charge controller's protective circuit will fail and it will burn out (literally!).

Therefore, if for some reason you cannot charge your mobile device from a “native” charger, then it is better to use the USB output of a computer or laptop. It produces a rated current of 0.5 A and a voltage of 5 V, which is safe for most gadgets. True, this approach also has a downside. If your device is equipped with high current charging (fast charging technology), then at low current the battery will take charge either very slowly or not at all.

And one more nuance that is worth paying attention to is the charger cable. Nowadays, many chargers come with a replaceable cable that plugs into a regular USB socket. This approach is fully justified, because it is the cable that most often fails with frequent use. However, when it comes to replacing the cable, it is important to choose a good one.

Firstly, it must be flexible, but at the same time, durable. Many people advise taking fabric-braided cables: they look more presentable and have additional protection. Secondly, it is better to take a shielded cable, which is less susceptible to electromagnetic interference. And thirdly, the cable length should ideally be in the range of 50 - 100 cm, since longer cables will have greater current losses.

In order not to be unfounded, I will give a real example of charging my phone from one charger (nominal: 4.5V 0.7A) with different cables: the original half-meter and the cheap two-meter from Uncle Liao (measurements were carried out using the Ampere application). I think comments are unnecessary:

Features of operation

Well, now it’s time to dispel and confirm various rumors related to chargers.

- It’s better to charge your phone with low current (MYTH)

Many people advise using the principle “less is more” to charge mobile equipment only from USB ports or from low-power chargers. An increase in battery life and capacity is stated as an advantage. Alas, this is a myth! Of course, such charging will not make things worse, but the battery capacity will never increase above the specified rating. In addition, low current will very slowly charge modern smartphones with fast charging function...

- To speed up charging you need to take a short wire (TRUE)

The shorter the wire from the charger to the device being charged, the less current loss will occur in it. Accordingly, charging will be more efficient and faster. The only condition for this rule to work is a high-quality cable and wire plug, since in cheap Chinese USB cords, even with a short length, serious losses can be observed (see screenshot in the previous section).

- You can’t leave your device charging overnight (MYTH)

This myth is due to the fact that in older phones the battery charge controller did not stop charging after reaching 100%. As a result, the battery gradually warmed up and could catch fire! Modern mobile devices are reliably protected from this problem. Once fully charged, the controller simply cuts off the current and recharges your device to 100% when the charge drops.

However, it is worth considering that, like any automation, the controller’s protection may fail. In this case, the battery, when overcharged, actually begins to overheat and may explode or catch fire. Therefore, if you notice that after reaching 100% charge your device is suspiciously warm, it’s time to contact a service center to check and possibly replace the battery.

- You cannot completely discharge the battery (TRUE)

Modern mobile devices are usually equipped with lithium-ion or lithium-polymer batteries, which really cannot be discharged to zero. Due to such a discharge, the charge controller may fail and the battery will have to be replaced.

By the way, it is for this reason (and not so that the buyer can test) even switched off phones in stores are periodically recharged. Moreover, it is recommended to do this according to the instructions when the charge drops below 30 - 40%.

True, there is a nuance here too. Even in a discharged battery, a small supply of current still remains. This is a kind of emergency reserve that keeps the battery controller operational even after the user completely discharges his device and it turns off. That is why, even if you completely discharge your phone, but put it on charge in the evening, then most likely nothing will happen to it! But if it lies unloaded for a couple of days, then anything can happen...

- You cannot use the phone while charging (MYTH)

In fact, if you use the original charger, you can easily use your device while charging. The charge current in this case, as a rule, is greater than the discharge current, so the maximum that this threatens is a slightly longer process of charge accumulation.

At the same time, when using weak chargers or when charging from a poor-quality electrical network, the charge current may be less than the nominal one. If it turns out to be lower than the discharge current, then your device will continue to discharge, even when connected to the network, or the charge simply will not accumulate.

- It is better not to keep the charger in the outlet all the time (TRUE)

And there are two reasons for this. Even when the charger is not charging anything, but is simply plugged into a socket, it does its job. Consequently, firstly, it wears out slowly, and secondly, there is a small current consumption, which in a month can amount (depending on the power of the charger) to a couple of kilowatt-hours!

You can calculate the current consumption by multiplying the rated voltage by the current indicated on the charger body, and then multiplying the resulting value by the required amount of time in hours. For example, for a standard 5V 1A charger, the current consumption will be 5 Watts per hour. Hence, per day we have 24x5 = 120 Watts, and in a month it will accumulate 120x30 = 3600 Watts! That is, 3.6 kilowatt-hours.

- You cannot use non-original chargers (MYTH)

If the current ratings on the original and “non-original” charger are the same, then it is quite possible to use any of them. The maximum that can result from using a non-original charger is a weaker current output, which will charge your device more slowly.

conclusions

Today there is quite a large selection of chargers for literally all occasions. However, if you know their main characteristics, which affect the quality of the charge, you can choose exactly what suits you without any problems. And at the same time, it is not so important whether it is an original charger or from a third-party manufacturer. It is only important that it is not some kind of consumer goods at all.

When choosing a charger, pay attention to the manufacturer (it’s better to take, after all, the original or chargers from well-known companies, like Belkin or AUKEY) and try to avoid Chinese counterfeits. The length of the charger cable should ideally be 50 - 100 cm. And, naturally, the rated current should correspond to that indicated on the battery of the device being charged. That's all the wisdom :)

P.S. Permission is granted to freely copy and quote this article, provided that an open active link to the source is indicated and the authorship of Ruslan Tertyshny is preserved.

Nowadays, electronics manufacturers more often use batteries based on lithium technology for power supply: lithium polymer ( Li-Po), lithium ion ( Li-ion). The advantage of such batteries is that they have a large specific capacity, low self-discharge, the ability to deliver high currents when discharged, and such batteries are manufactured in any shape and size. To charge such batteries, special chargers are needed.

Note that such chargers are often used to recharge various electrical tools used by housing and communal services employees. Products for housing and communal services, by the way, can be purchased at a relatively low price from the ZHKH-MARKET company, which has been supplying housing and communal services in Moscow and the Moscow region for more than 10 years.

Standard batteries

Consumers often purchase devices that run on standard AA or AAA batteries. They can be replaced with regular batteries and no special charger is required. People who used NiMH batteries are appearing less and less often. They have a capacity of 40% more than NiCD batteries. NiMH batteries are improving every day. For example, if previously their self-discharge was high, now some batteries have minimal self-discharge.

Battery charging methods

When a battery is charged, chemical changes occur in it. The energy that comes during charging, part of it is spent on these transformations, and part of it turns into heat. NiMH batteries get hotter when charging than NicD batteries because the chemical reactions that occur when charging are exothermic.

The battery charging speed depends on the charging current. The charging current will be measured in units of C - the numerical value of the battery capacity. There are several types of charging:

trickle charge – current 0.1 C
fast charging (quick charge) – current 0.3 C
accelerated charging (fast charge) – current 0.5-1.0 C

Drip charging

With trickle charging, a small current is chosen because charging continues even if the battery is charged. With such a low current, the battery does not heat up as much. It is impossible to accurately determine the end of the charging process here.

Fast battery charging

Such charging with a current of 1C is not recommended for all batteries, because the battery ventilation hole may open at high ambient temperatures (up to +40). When fast charging, you need to stop the charging process during the charging process.

The fast charger operating algorithm consists of several phases:

1. Determining the presence of a battery
2. Battery qualification
3. Pre-charge
4. Transition to fast charging (Ramp)
5. Fast charge
6. Top-of Tcharge
7. Maintenance charge

Battery detection phase. Here the voltage at the battery terminals is checked with the charging current generator turned on, approximately 0.1C. If the voltage is 1.8 V, the battery is missing or damaged. When the voltage is high, charging should not start, as soon as low voltage is detected, charging will start. In the remaining phases, the presence of the battery must be checked, because in any phase the battery can be removed and the charger must return to the first phase.

Battery qualification phase. This phase begins charging the battery. This phase is needed to estimate the initial battery charge. Judging by the voltage on the battery, you need to determine whether pre-charging is needed or not.

Pre-charge phase. This phase should not last more than 30 minutes. A pre-charge phase is required for deeply discharged batteries. For all long phases, temperature control is required; it should not exceed 60 degrees during charging.

Transition phase to fast charging. It is not advisable to immediately turn on the fast current; it is better to gradually increase it over 2 minutes. Fast charging can begin if the battery voltage is above 0.8 V.

Fast charge phase. The most important thing in this phase is to stop charging in time, otherwise the battery will be destroyed. To stop charging in time, you can use several methods to determine the charge.

For NiCd batteries The dV method is used - this is the fastest method for determining charge; towards the end of charging, the voltage on the battery decreases.

For NiMH batteries The dV method doesn't work as well. And they use the dV=0 method. Here the constant voltage on the battery is detected. If the voltage remains the same for 10 minutes, then it’s time to turn off charging.

Also, the end of charging can be determined by the temperature, since towards the end of charging the pressure inside the battery increases and the temperature rises. Some chargers use pulse instead of DC. Current pulses last 1 second. The advantage of this method is that it better equalizes the concentration of active substances throughout the entire volume, reduces the likelihood of the formation of large crystalline formations on the electrodes and their passivation.

Recharging phase. In this phase, the charging current should be 0.1-0.3 C. The duration of recharging is 30 minutes, then there will be a recharge. After a quick charge, it is better to cool the battery and then begin the charging process.

Maintenance charging phase. Direct current is harmful to the battery, as the battery will constantly be at a high temperature. After charging is complete, NiCd batteries go into trickle mode to maintain the charge. But NiMH batteries do not tolerate overcharging and therefore maintaining a charge will do them little good. In principle, you can do without this phase.

Ultra-fast charge

You can use current up to 3C. When the battery is 70% charged, the charge should be reduced and continued as usual. If this is not done, the ultra-high heating of the battery will destroy it or even explode.

Smart charger

Batteries of the same form factor. For example, AA size NiMH batteries have a capacity of 1900-2850 mAh, and AAA size batteries have a capacity of 750-1100 mAh. The charging current must be proportional to the battery capacity. When charging a battery with a small capacity with a high current, there will be heating. When charging with a small current, the charging time will be long. In general, the charger should control the current, that is, use a high current for batteries with a large capacity and a small current for a smaller capacity. This is the meaning of a smart charger.

Charger power off problem

If the charger power is turned off during the charging process, then when the power is turned on, a transition to the phase of determining the presence of a battery should occur. In this case, charging starts from the beginning and recharging will be completed completely. The disadvantage of frequent recharging is that it can develop into overcharging. A “smart” Li+ battery contains a controller that measures the amount of charge.

Primary current sources

Primary sources of current are batteries (alkaline and manganese-zinc). The difference between primary sources and batteries is the internal resistance, which is higher for primary sources. If the internal resistance is greater than normal, the charging process will be interrupted.

Memory and battery recovery effect

The memory effect appears in NiCd batteries. The meaning of the effect is that large crystalline formations form on the electrodes, as a result of which part of the volume of the active substance of the battery ceases to be used. To eliminate the memory effect, a complete discharge is recommended. This complete discharge is recommended for NiMH batteries before charging them. It will be better if you have a charger with a discharge function.

Interaction of batteries in the assembly

Separate batteries into batteries may have different characteristics. Batteries that have a lower capacity will be destroyed during the discharging process of the assembly. And each battery in the battery must be charged separately, but in ready-made assemblies there are only two terminals and only joint charging is possible. In this case, alignment is needed.