Rating of chargers for lithium-ion batteries. Charger circuit for lithium Li-Ion batteries

The first lithium-based battery appeared in 1991. But only against the backdrop of the popularization of mobile phones Li-ion devices also received wide demand. On at the moment lithium batteries are used wherever autonomous operation of electronic or technical device. Batteries provide energy household appliances, power tools, gadgets and various equipment. Due to the low self-discharge threshold, the ability to replenish energy without waiting for the power reserve to be completely consumed and the rich resource of Li-ion batteries, they are able to support the operation of devices that require high power.

Lithium battery design

According to the design, Li-ion batteries are produced in prismatic and cylindrical designs. The production of prismatic batteries occurs by applying plates rectangular shape one on top of the other. Such models provide for more dense packaging compared to cylindrical counterparts, but it is necessary to provide more intensive compressive forces against the electrodes. The cylindrical device of a lithium battery is a package with electrodes and a separator, rolled up and enclosed in a metal frame connected to the negative electrode. The positive electrode of the battery is connected to the cover via a special insulator. By the way, the roll assembly principle is also used in some versions of prismatic models in the form of an elliptical spiral. This design combines the advantages of both types. lithium batteries.

Why shouldn’t it be brought to “zero”?

Experts do not recommend using batteries until the energy is completely spent. U lithium devices There is no memory effect that other types of batteries have. In practice, this means that you need to charge the battery before its level drops to zero. By the way, the number of cycles by which lithium batteries are charged is an indicator of the durability of power sources - manufacturers indicate this figure in the labeling.

For example, for high-quality models the number of cycles can be 600. In order to increase the service life of the Li-ion battery, it is worth charging the device regularly. The optimal level at which you should start charging is 15%. This measure can increase the number of cycles to 1,100.

How is charging done?

Lithium batteries are charged according to a mixed scheme, that is, first from a direct current of 1C to an average voltage of 4.2 V, and then at a constant voltage level. The primary stage lasts about 40 minutes, and the second - longer. It is worth noting that only modern lithium batteries can be charged at voltages up to 4.2 V. Industrial and military battery models have a longer service life than standard models, as a result of which the threshold for the end of their charge has been pushed back to 3.90 V.

How long does it take to charge?

The process of charging a lithium cell with a 1C current usually takes 2.5 hours. The Li-ion battery fully replenishes energy when its voltage level corresponds to the same cutoff indicators. At the same time, the current should decrease by approximately 3% relative to the initial charge. There is an opinion that lithium batteries charge faster when the current increases. In reality, this is not the case, however, the increased charging current contributes to an increase in voltage, while recharging from the end of the first stage requires more time.

In some types of devices, charging lithium batteries takes less than 1 hour. The reduction in time is due to the fact that the second stage of the cycle is absent and the battery can be used immediately after the completion of the first stage. But there is one caveat: the battery does not completely replenish its energy reserve - it is only 70%.

It would seem, what is the point of such a charging scheme? This approach is beneficial if multiple cycles are required. fast charging. For example, a screwdriver with a lithium battery will require 30 minutes for each operation, after which you can charge the current battery and continue working with a spare one (power tools are usually equipped with two batteries).

Why do you need to overcharge the battery?

It is recommended to start charging before the energy is reduced to zero, however, once a month it is still worth completely discharging. After this, you should use the original charger for lithium batteries in order to replenish the energy 100%. The need for this procedure is due to the peculiarity Li-ion batteries. Experienced users of devices powered by lithium cells may have noticed that the indication of the remaining charge is not always correct. For example, the tablet screen displays that the device is only 50% discharged - in fact, only 10 minutes of active work can drain the battery.

To prevent such inconsistencies, lithium batteries should be completely discharged. As a result, the device will be able to more accurately calculate the capabilities of the power source and reliably display information on the display.

Reducing power consumption during charging

Although the power consumption of mobile devices and other gadgets that require lithium batteries is incomparable in terms of energy consumption with powerful household appliances, some simple tips will help not only save on electricity, but also extend the life of the devices:

• Using the capabilities of the device’s software to minimize power consumption.
• Disable functions that work unnecessarily. For example, the Internet, various networks and Bluetooth - according to statistics, their combined work can reduce working hours devices.
• Optimize the device settings - dimming the backlight, turning off unnecessary notifications and sound effects will extend the operation of the gadget by 10-15 minutes. This is not much, but in critical situations it will not be superfluous.

Rules for preserving lithium batteries

Durability is one of strengths Li-ion batteries. Thus, the annual reduction in volume as a result of self-discharge is no more than 10%. Despite this, chemical and structural methods for protecting batteries from overheating should be taken into account during operation. If modern lithium batteries have protection against improper charging, temperature effects still pose a danger to them. Therefore, it is recommended to reduce any unnecessary heating of the batteries. However, manufacturers are also working in this direction. The use of cathode elements, in particular, will increase the thermal safety of lithium power supplies.

Today, many users have accumulated several working and unused lithium batteries that appear when replacing mobile phones with smartphones.

When using batteries in phones with their own charger, thanks to the use specialized chips to control the charge, there are practically no problems with charging. But when using lithium batteries in various homemade products, the question arises of how and with what to charge such batteries. Some people think that lithium batteries already contain built-in charge controllers, but in fact they have built-in protection circuits, such batteries are called protected batteries. The protection circuits in them are designed mainly to protect against deep discharge and overvoltage when charging above 4.25V, i.e. This is an emergency protection, not a charge controller.

Some “do-it-yourselfers” on the site will immediately write that for little money you can order a special board from China, with which you can charge lithium batteries. But this is only for “shopping” lovers. There is no point in buying something that can be easily assembled in a few minutes from cheap and common parts. We must not forget that you will have to wait about a month for the ordered board. And a purchased device does not bring as much satisfaction as a home-made one.

The proposed charger can be replicated by almost anyone. This scheme very primitive, but completely copes with its task. Everything you need for high-quality charging Li-Ion batteries, this is to stabilize the output voltage charger and limit the charging current.

The charger is reliable, compact and highly stable output voltage, and, as is known, this is very important for lithium-ion batteries. important characteristic when charging.

Charger circuit for li-ion battery

The charger circuit is made using an adjustable voltage stabilizer TL431 and a bipolar NPN transistor medium power. The circuit allows you to limit the battery charging current and stabilizes the output voltage.

Transistor T1 acts as a regulating element. Resistor R2 limits the charging current, the value of which depends only on the battery parameters. It is recommended to use a 1 W resistor. Other resistors may be 125 or 250 mW.

The choice of transistor is determined by the required charging current set to charge the battery. For the case under consideration, charging batteries from mobile phones, you can use domestic or imported NPN transistors medium power (for example, KT815, KT817, KT819). If the input voltage is high or a low power transistor is used, the transistor must be installed on a radiator.

LED1 (highlighted in red in the diagram) serves to visually indicate battery charge. When you turn on a discharged battery, the indicator glows brightly and dims as it charges. The indicator light is proportional to the battery charge current. But it should be taken into account that if the LED is completely extinguished, the battery will still be charged with a current of less than 50 mA, which requires periodic monitoring of the device to prevent overcharging.

To increase the accuracy of monitoring the end of charge, a additional option battery charge indication (highlighted green) on LED2, low-power PNP transistor KT361 and current sensor R5. The device can use any type of indicator depending on the required accuracy of battery charge monitoring.

The presented circuit is intended to charge only one Li-ion battery. But this charger can also be used to charge other types of batteries. You only need to set the required output voltage and charging current.

Making a charger

1. We purchase or select from those available, components for assembly in accordance with the diagram.

2. Assembling the circuit.
To check the functionality of the circuit and its settings, we assemble the charger on the circuit board.

The diode in the battery power circuit (negative bus - blue wire) is designed to prevent the lithium-ion battery from discharging in the absence of voltage at the charger input.

3. Setting the output voltage of the circuit.
We connect the circuit to a power source with a voltage of 5...9 volts. Using trimmer resistance R3, we set the output voltage of the charger within 4.18 - 4.20 volts (if necessary, at the end of the adjustment we measure its resistance and install a resistor with the required resistance).

4. Setting the charging current of the circuit.
Having connected a discharged battery to the circuit (as indicated by the LED turning on), we use resistor R2 to set the charging current value using the tester (100…300 mA). If the resistance R2 is less than 3 ohms, the LED may not light up.

5. Prepare the board for mounting and soldering parts.
We cut the required size from the universal board, carefully process the edges of the board with a file, clean and tin the contact tracks.

6. Installation of the debugged circuit on the working board
We transfer the parts from the circuit board to the working one, solder the parts, and make the missing connections using a thin mounting wire. Upon completion of assembly, we thoroughly check the installation.

The charger can be assembled by any in a convenient way, including wall-mounted installation. If installed without errors and with working parts, it starts working immediately after switching on.

When connected to a charger, the discharged battery begins to consume maximum current (limited by R2). As the battery voltage approaches the set value, the charging current will drop and when the battery voltage reaches 4.2 volts, the charging current will be almost zero.

However, it is not recommended to leave the battery connected to the charger for a long time, because it does not like to be overcharged even with a small current and can explode or catch fire.

If the device does not work, then it is necessary to check the control pin (1) of TL431 for the presence of voltage. Its value must be at least 2.5 V. This is the lowest permissible reference voltage value for this chip. The TL431 chip is found quite often, especially in computer power supplies.

Features of charging lithium batteries and chargers for them

Modern people use many electronic gadgets. This is a laptop mobile phone, tablet, camera and many others. Most of these devices are powered by lithium batteries. After all, we value them precisely for what they are. mobile devices. However, portability comes at the cost of having to constantly charge the batteries. To do this, you will need a lithium battery charger. In most cases, chargers are supplied with the device itself. This is the same power adapter for a laptop or phone. Ideally, of course, it should be used for charging standard charging. But what to do if it is lost or damaged. You need to choose a suitable charger. What to take into account will be discussed in this article.

In general, the charger must have an output voltage of 5 volts and a current whose value corresponds to (0.5─1)*Cn. CH is the nominal capacity of the battery. For example, for a lithium cell with a capacity of 2200 mAh, charging should produce a current of 1.1 amperes.

Most chargers from reputable manufacturers charge Li batteries in several stages. The first stage occurs at a constant current value of 0.2─1 C and a voltage of 4.1─4.2 V (here we mean the voltage per element or jar). This stage lasts approximately 40-50 minutes. The second stage is carried out at constant voltage. There are devices that use pulse mode to speed up the charging process. For lithium-ion systems with a graphite system, voltages must be limited to 4.1 volts per cell.

If you use a voltage higher than 4.1 volts, you can increase energy density battery But at the same time, oxidative reactions begin, which shorten the battery life. In later models this problem was corrected with additives. And the voltage on them during charging can be increased to 4.2 volts with a deviation of 0.05 per element.

If we talk about lithium batteries for industrial use and for military sphere, then for them chargers support a voltage of 3.9 volts. This provides long term service and reliability.

If the charger produces a current of 1C, the battery will charge in about 2-3 hours. When the charge is fully charged and the voltage reaches the cutoff value, the current decreases sharply and amounts to several percent of the original value.

It is worth saying that as the charging current increases, the charging time practically does not decrease. At a higher current, the voltage rises faster in the first stage of the process, but the second stage of recharging in this case takes longer.

There are chargers that can charge a lithium battery in about an hour. This charger for lithium batteries does not have a second stage and the battery is ready for use after the completion of the first stage. The battery charge level will be 70 percent. But, due to the nature of lithium batteries, this is not critical for them.

In the graph above you can see three stages of charging a Li battery:

• First. The maximum possible (1C) charge current flows through the battery. This stage ends when the voltage increases to a threshold value;
• Second. The voltage remains maximum (4.1─4.2 volts), and the charging current decreases to 3 percent of the original value;
• Third. Compensating charge during storage (carried out approximately once every 20 days).

During the storage phase, trickle charging is not possible for lithium batteries due to the fact that this leads to metallization of the Li. But short-term recharging with direct current compensates for the loss of charge. This charging should be performed when the cell voltage drops to 4.05 volts. The charging process stops at 4.2 volts.

And one more important point. Lithium battery cells are very sensitive to overcharging. Even with a slight recharge, lithium metallization begins on the surface of the negative electrode. It is very active and interacts with the electrolyte. As a result of the reaction at the cathode, oxygen is released and the pressure increases. As a result, element depressurization, ignition, and even a small explosion may occur.

In addition, if the charging voltage is continually exceeded, the life of lithium batteries will be reduced. Therefore, in most lithium batteries, in addition to the cells themselves, there is a protection board.

The board controls the process of charging and discharging elements according to the lower and upper voltage limits. Temperature sensors are often used to switch off elements at 90 degrees Celsius. Some types of batteries have a mechanical valve that opens when the pressure inside the case increases above a certain limit.

There are exceptions. For example, batteries containing manganese do not have such protection. Manganese strongly inhibits metallization at the anode and the formation of oxygen. Therefore, such protection is not necessary.

All this needs to be kept in mind when choosing a charger. If you will charge the lithium can directly without a controller, the voltage must be monitored constantly. But it is much better to use devices with automatic control or charge the battery through a protection board.

Chargers for various gadgets

Chargers for smartphone batteries

If you have lost the standard charger for your phone, the “frog” will help you. This is one of the most common devices. The charge received its name for its characteristic shape.

It couldn't be easier to use. The charger has 2 width-adjustable contacts: plus and minus. You need to install them in a position suitable for the battery being charged. Then the battery is inserted so that there is contact with its terminals, and is fixed with the upper clamping bar. Naturally, polarity must be observed during installation. Then the device is inserted into the 220 volt connector and charged until the indicator shows the end of the process.

Assessing the characteristics of a particular charger is difficult without understanding how an exemplary charge of a li-ion battery should actually proceed. Therefore, before moving directly to the diagrams, let's remember a little theory.

What are lithium batteries?

Depending on what material the positive electrode of a lithium battery is made of, there are several varieties:

• with lithium cobaltate cathode;
• with a cathode based on lithiated iron phosphate;
• based on nickel-cobalt-aluminium;
• based on nickel-cobalt-manganese.

All of these batteries have their own characteristics, but since these nuances are not of fundamental importance for the general consumer, they will not be considered in this article.

Also, all li-ion batteries are produced in various sizes and form factors. They can be either cased (for example, the popular 18650 today) or laminated or prismatic (gel-polymer batteries). The latter are hermetically sealed bags made of a special film, which contain electrodes and electrode mass.

The most common sizes of li-ion batteries are shown in the table below (all of them have a nominal voltage of 3.7 volts):

Internal electrochemical processes proceed in the same way and do not depend on the form factor and design of the battery, so everything said below applies equally to all lithium batteries.

How to properly charge lithium-ion batteries

Most the right way Lithium batteries are charged in two stages. This is the method Sony uses in all of its chargers. Despite a more complex charge controller, this ensures a more complete charge of li-ion batteries without reducing their service life.

Here we are talking about a two-stage charge profile for lithium batteries, abbreviated as CC/CV (constant current, constant voltage). There are also options with pulse and step currents, but they are not discussed in this article. More about charging pulse current can be read.

So, let's look at both stages of charging in more detail.

1. At the first stage A constant charging current must be ensured. The current value is 0.2-0.5C. For accelerated charging, it is allowed to increase the current to 0.5-1.0C (where C is the battery capacity).

For example, for a battery with a capacity of 3000 mAh, the nominal charge current at the first stage is 600-1500 mA, and the accelerated charge current can be in the range of 1.5-3A.

To ensure a constant charging current of a given value, the charger circuit must be able to increase the voltage at the battery terminals. In fact, at the first stage the charger works as a classic current stabilizer.

Important: If you plan to charge batteries with a built-in protection board (PCB), then when designing the charger circuit you need to make sure that the voltage idle speed circuits will never be able to exceed 6-7 volts. Otherwise, the protection board may be damaged.

At the moment when the voltage on the battery rises to 4.2 volts, the battery will gain approximately 70-80% of its capacity (the specific capacity value will depend on the charging current: with accelerated charging it will be a little less, with a nominal charge - a little more). This moment marks the end of the first stage of charging and serves as a signal for the transition to the second (and final) stage.

2. Second charge stage- this is charging the battery with a constant voltage, but a gradually decreasing (falling) current.

At this stage, the charger maintains a voltage of 4.15-4.25 volts on the battery and controls the current value.

As the capacity increases, the charging current will decrease. As soon as its value decreases to 0.05-0.01C, the charging process is considered complete.

An important nuance of the operation of a proper charger is its complete shutdown from the battery after charging is complete. This is due to the fact that for lithium batteries it is extremely undesirable for them to remain under increased voltage, which usually provides the charger (i.e. 4.18-4.24 volts). This leads to accelerated degradation chemical composition battery and, as a result, a decrease in its capacity. Long-term stay means tens of hours or more.

During the second stage of charging, the battery manages to gain approximately 0.1-0.15 more of its capacity. The total battery charge thus reaches 90-95%, which is an excellent indicator.

We looked at two main stages of charging. However, coverage of the issue of charging lithium batteries would be incomplete if another charging stage were not mentioned - the so-called. precharge.

Preliminary charge stage (precharge)- this stage is used only for deeply discharged batteries (below 2.5 V) to bring them to normal operating mode.

At this stage, the charge is provided with a reduced constant current until the battery voltage reaches 2.8 V.

The preliminary stage is necessary to prevent swelling and depressurization (or even explosion with fire) of damaged batteries that have, for example, an internal short circuit between the electrodes. If you immediately pass through such a battery high current charge, this will inevitably lead to its heating, and then depending on your luck.

Another benefit of precharging is pre-warming the battery, which is important when charging at low temperatures environment (in an unheated room during the cold season).

Intelligent charging must be able to monitor the voltage on the battery during the preliminary charging phase and, in case the voltage for a long time does not rise, conclude that the battery is faulty.

All stages of charging a lithium-ion battery (including the pre-charge stage) are schematically depicted in this graph:

Exceeding the rated charging voltage by 0.15V can reduce the battery life by half. Lowering the charge voltage by 0.1 volt reduces the capacity of a charged battery by about 10%, but significantly extends its service life. The voltage of a fully charged battery after removing it from the charger is 4.1-4.15 volts.

Let me summarize the above and outline the main points:

1. What current should I use to charge a li-ion battery (for example, 18650 or any other)?

The current will depend on how quickly you would like to charge it and can range from 0.2C to 1C.

For example, for a battery size 18650 with a capacity of 3400 mAh, the minimum charge current is 680 mA, and the maximum is 3400 mA.

2. How long does it take to charge, for example, the same 18650 batteries?

The charging time directly depends on the charging current and is calculated using the formula:

T = C / I charge.

For example, the charging time for our 3400 mAh battery with a current of 1A will be about 3.5 hours.

3. How to properly charge a lithium polymer battery?

All lithium batteries charge the same way. It doesn't matter whether it is lithium polymer or lithium ion. For us, consumers, there is no difference.

What is a protection board?

The protection board (or PCB - power control board) is designed to protect against short circuit, overcharge and overdischarge lithium battery. As a rule, overheating protection is also built into the protection modules.

For safety reasons, the use of lithium batteries in household appliances, if they do not have a built-in protection board. That's why all cell phone batteries always have a PCB board. The battery output terminals are located directly on the board:

These boards use a six-legged charge controller on a specialized device (JW01, JW11, K091, G2J, G3J, S8210, S8261, NE57600 and other analogues). The task of this controller is to disconnect the battery from the load when the battery is completely discharged and disconnect the battery from charging when it reaches 4.25V.

Here, for example, is a diagram of the BP-6M battery protection board that was supplied with old Nokia phones:

If we talk about 18650, they can be produced either with or without a protection board. The protection module is located near the negative terminal of the battery.

The board increases the length of the battery by 2-3 mm.

Batteries without a PCB module are usually included in batteries that come with their own protection circuits.

Any battery with protection can easily turn into a battery without protection; you just need to gut it.

Today, the maximum capacity of the 18650 battery is 3400 mAh. Batteries with protection must have a corresponding designation on the case ("Protected").

Do not confuse the PCB board with the PCM module (PCM - power charge module). If the former serve only the purpose of protecting the battery, then the latter are designed to control the charging process - they limit the charge current at a given level, control the temperature and, in general, ensure the entire process. The PCM board is what we call a charge controller.

I hope now there are no questions left, how to charge an 18650 battery or any other lithium battery? Then let's move on to small selection ready-made circuit solutions for chargers (the same charge controllers).

Charging schemes for li-ion batteries

All circuits are suitable for charging any lithium battery; all that remains is to decide on the charging current and the element base.

LM317

Diagram of a simple charger based on the LM317 chip with a charge indicator:

The circuit is the simplest, the whole setup comes down to setting the output voltage to 4.2 volts using trimming resistor R8 (without a connected battery!) and setting the charging current by selecting resistors R4, R6. The power of resistor R1 is at least 1 Watt.

As soon as the LED goes out, the charging process can be considered completed (the charging current will never decrease to zero). It is not recommended to keep the battery on this charge for a long time after it is fully charged.

The lm317 microcircuit is widely used in various voltage and current stabilizers (depending on the connection circuit). It is sold on every corner and costs pennies (you can take 10 pieces for only 55 rubles).

LM317 comes in different housings:

Pin assignment (pinout):

Analogues of the LM317 chip are: GL317, SG31, SG317, UC317T, ECG1900, LM31MDT, SP900, KR142EN12, KR1157EN1 (the last two are domestically produced).

The charging current can be increased to 3A if you take LM350 instead of LM317. It will, however, be more expensive - 11 rubles/piece.

The printed circuit board and circuit assembly are shown below:

The old Soviet transistor KT361 can be replaced with a similar one pnp transistor(for example, KT3107, KT3108 or bourgeois 2N5086, 2SA733, BC308A). It can be removed altogether if the charge indicator is not needed.

Disadvantage of the circuit: the supply voltage must be in the range of 8-12V. This is due to the fact that for normal operation LM317 microcircuit, the difference between the battery voltage and the supply voltage must be at least 4.25 Volts. Thus, it will not be possible to power it from the USB port.

MAX1555 or MAX1551

MAX1551/MAX1555 are specialized chargers for Li+ batteries, capable of operating from USB or from a separate power adapter (for example, a phone charger).

The only difference between these microcircuits is that MAX1555 produces a signal to indicate the charging process, and MAX1551 produces a signal that the power is on. Those. 1555 is still preferable in most cases, so 1551 is now difficult to find on sale.

A detailed description of these microcircuits from the manufacturer is.

The maximum input voltage from the DC adapter is 7 V, when powered by USB - 6 V. When the supply voltage drops to 3.52 V, the microcircuit turns off and charging stops.

The microcircuit itself detects at which input the supply voltage is present and connects to it. If food is coming via the USB bus, the maximum charging current is limited to 100 mA - this allows you to plug the charger into the USB port of any computer without fear of burning the south bridge.

When powered by a separate power supply, the typical charging current is 280 mA.

The chips have built-in overheating protection. But even in this case, the circuit continues to operate, reducing the charge current by 17 mA for every degree above 110°C.

There is a pre-charge function (see above): as long as the battery voltage is below 3V, the microcircuit limits the charge current to 40 mA.

The microcircuit has 5 pins. Here typical diagram inclusions:

If there is a guarantee that the voltage at the output of your adapter cannot under any circumstances exceed 7 volts, then you can do without the 7805 stabilizer.

The USB charging option can be assembled, for example, on this one.

The microcircuit does not require either external diodes or external transistors. In general, of course, gorgeous little things! Only they are too small and inconvenient to solder. And they are also expensive ().

LP2951

The LP2951 stabilizer is manufactured by National Semiconductors (). It provides the implementation of a built-in current limiting function and allows you to generate a stable charge voltage level for a lithium-ion battery at the output of the circuit.

The charge voltage is 4.08 - 4.26 volts and is set by resistor R3 when the battery is disconnected. The voltage is kept very precisely.

The charge current is 150 - 300mA, this value is limited by the internal circuits of the LP2951 chip (depending on the manufacturer).

Use the diode with a small reverse current. For example, it can be any of the 1N400X series that you can purchase. The diode is used as a blocking diode to prevent reverse current from the battery into the LP2951 chip when the input voltage is turned off.

This charger produces a fairly low charging current, so any 18650 battery can charge overnight.

The microcircuit can be purchased both in a DIP package and in a SOIC package (costs about 10 rubles per piece).

MCP73831

The chip allows you to create the right chargers, and it is also cheaper than the hyped MAX1555.

A typical connection diagram is taken from:

An important advantage of the circuit is the absence of low-resistance powerful resistors that limit the charge current. Here the current is set by a resistor connected to the 5th pin of the microcircuit. Its resistance should be in the range of 2-10 kOhm.

The assembled charger looks like this:

The microcircuit heats up quite well during operation, but this does not seem to bother it. It fulfills its function.

Here's another option printed circuit board with SMD LED and micro USB connector:

LTC4054 (STC4054)

Very simple circuit, great option! Allows charging with current up to 800 mA (see). True, it tends to get very hot, but in this case the built-in overheating protection reduces the current.

The circuit can be significantly simplified by throwing out one or even both LEDs with a transistor. Then it will look like this (you must admit, it couldn’t be simpler: a pair of resistors and one condenser):

One of the printed circuit board options is available at . The board is designed for elements of standard size 0805.

I=1000/R. You shouldn’t set a high current right away; first see how hot the microcircuit gets. For my purposes, I took a 2.7 kOhm resistor, and the charge current turned out to be about 360 mA.

It is unlikely that it will be possible to adapt a radiator to this microcircuit, and it is not a fact that it will be effective due to the high thermal resistance of the crystal-case junction. The manufacturer recommends making the heat sink “through the leads” - making the traces as thick as possible and leaving the foil under the chip body. In general, the more “earth” foil left, the better.

By the way, most of the heat is dissipated through the 3rd leg, so you can make this trace very wide and thick (fill it with excess solder).

The LTC4054 chip package may be labeled LTH7 or LTADY.

LTH7 differs from LTADY in that the first can lift a very low battery (on which the voltage is less than 2.9 volts), while the second cannot (you need to swing it separately).

The chip turned out to be very successful, so it has a bunch of analogues: STC4054, MCP73831, TB4054, QX4054, TP4054, SGM4054, ACE4054, LP4054, U4054, BL4054, WPM4054, IT4504, Y1880, PT6102, PT6181, 2, HX6001, LC6000, LN5060, CX9058, EC49016, CYT5026, Q7051. Before using any of the analogues, check the datasheets.

TP4056

The microcircuit is made in a SOP-8 housing (see), it has a metal heat sink on its belly that is not connected to contacts, which allows for more efficient heat removal. Allows you to charge the battery with a current of up to 1A (the current depends on the current-setting resistor).

The connection diagram requires the bare minimum of hanging elements:

The circuit implements the classical charging process - first charging with a constant current, then with a constant voltage and a falling current. Everything is scientific. If you look at charging step by step, you can distinguish several stages:

1. Monitoring the voltage of the connected battery (this happens all the time).
2. Precharge phase (if the battery is discharged below 2.9 V). Charge with a current of 1/10 from the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm) to a level of 2.9 V.
3. Charging with a maximum constant current (1000 mA at R prog = 1.2 kOhm);
4. When the battery reaches 4.2 V, the voltage on the battery is fixed at this level. A gradual decrease in the charging current begins.
5. When the current reaches 1/10 of the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm), the charger turns off.
6. After charging is complete, the controller continues monitoring the battery voltage (see point 1). The current consumed by the monitoring circuit is 2-3 µA. After the voltage drops to 4.0V, charging starts again. And so on in a circle.

The charge current (in amperes) is calculated by the formula I=1200/R prog. The permissible maximum is 1000 mA.

A real charging test with a 3400 mAh 18650 battery is shown in the graph:

The advantage of the microcircuit is that the charge current is set by just one resistor. Powerful low-resistance resistors are not required. Plus there is an indicator of the charging process, as well as an indication of the end of charging. When the battery is not connected, the indicator blinks every few seconds.

The supply voltage of the circuit should be within 4.5...8 volts. The closer to 4.5V, the better (so the chip heats up less).

The first leg is used to connect the temperature sensor built into the lithium-ion battery(usually this is the middle terminal of the battery cell phone). If the voltage at the output is below 45% or above 80% of the supply voltage, charging is suspended. If you don't need temperature control, just plant that foot on the ground.

Attention! This circuit has one significant drawback: the absence of a battery reverse polarity protection circuit. In this case, the controller is guaranteed to burn out due to exceeding the maximum current. In this case, the supply voltage of the circuit directly goes to the battery, which is very dangerous.

The signet is simple and can be done in an hour on your knee. If time is of the essence, you can order ready-made modules. Some manufacturers of ready-made modules add protection against overcurrent and overdischarge (for example, you can choose which board you need - with or without protection, and with which connector).

You can also find ready-made boards with a contact for a temperature sensor. Or even a charging module with several parallel TP4056 microcircuits to increase the charging current and with reverse polarity protection (example).

LTC1734

Also a very simple scheme. The charging current is set by resistor R prog (for example, if you install a 3 kOhm resistor, the current will be 500 mA).

Microcircuits are usually marked on the case: LTRG (they can often be found in old Samsung phones).

A transistor will do just fine any p-n-p, the main thing is that it is designed for a given charging current.

There is no charge indicator on the indicated diagram, but on the LTC1734 it is said that pin “4” (Prog) has two functions - setting the current and monitoring the end of the battery charge. For example, a circuit with control of the end of charge using the LT1716 comparator is shown.

Comparator LT1716 in this case can be replaced with a cheap LM358.

TL431 + transistor

It is probably difficult to come up with a circuit using more affordable components. The hardest part here is finding the TL431 reference voltage source. But they are so common that they are found almost everywhere (rarely does a power source do without this microcircuit).

Well, the TIP41 transistor can be replaced with any other one with a suitable collector current. Even the old Soviet KT819, KT805 (or less powerful KT815, KT817) will do.

Setting up the circuit comes down to setting the output voltage (without a battery!!!) using a trim resistor at 4.2 volts. Resistor R1 sets maximum value charging current.

This circuit fully implements the two-stage process of charging lithium batteries - first charging with direct current, then moving to the voltage stabilization phase and smoothly reducing the current to almost zero. The only drawback is the poor repeatability of the circuit (it is capricious in setup and demanding on the components used).

MCP73812

There is another undeservedly neglected microcircuit from Microchip - MCP73812 (see). Based on it, we get a very budget-friendly charging option (and inexpensive!). The whole body kit is just one resistor!

By the way, the microcircuit is made in a solder-friendly package - SOT23-5.

The only negative is that it gets very hot and there is no charge indication. It also somehow doesn’t work very reliably if you have a low-power power source (which causes a voltage drop).

In general, if the charge indication is not important for you, and a current of 500 mA suits you, then the MCP73812 is a very good option.

NCP1835

A fully integrated solution is offered - NCP1835B, providing high stability of the charging voltage (4.2 ±0.05 V).

Perhaps the only drawback of this microcircuit is its too miniature size (DFN-10 case, size 3x3 mm). Not everyone can provide high-quality soldering of such miniature elements.

From undeniable advantages I would like to note the following:

1. Minimum number of body parts.
2. Possibility of charging a completely discharged battery (precharge current 30 mA);
3. Determining the end of charging.
4. Programmable charging current - up to 1000 mA.
5. Charge and error indication (capable of detecting non-chargeable batteries and signaling this).
6. Protection against long-term charge (by changing the capacitance of the capacitor C t, you can set maximum time charge from 6.6 to 784 minutes).

The cost of the microcircuit is not exactly cheap, but also not so high (~$1) that it would be unnecessary to use it. If you are comfortable with a soldering iron, I would recommend choosing this option.

More detailed description is located in .

Can I charge a lithium-ion battery without a controller?

Yes, you can. However, this will require close control of the charging current and voltage.

In general, it will not be possible to charge a battery, for example, our 18650, without a charger. You still need to somehow limit the maximum charge current, so at least the most primitive memory will still be required.

The simplest charger for any lithium battery is a resistor connected in series with the battery:

The resistance and power dissipation of the resistor depend on the voltage of the power source that will be used for charging.

As an example, let's calculate a resistor for a 5 Volt power supply. We will charge an 18650 battery with a capacity of 2400 mAh.

So, at the very beginning of charging, the voltage drop across the resistor will be:

U r = 5 - 2.8 = 2.2 Volts

Let's say our 5V power supply is rated for a maximum current of 1A. The circuit will consume the highest current at the very beginning of the charge, when the voltage on the battery is minimal and amounts to 2.7-2.8 Volts.

Attention: these calculations do not take into account the possibility that the battery may be very deeply discharged and the voltage on it may be much lower, even to zero.

Thus, the resistor resistance required to limit the current at the very beginning of the charge at 1 Ampere should be:

R = U / I = 2.2 / 1 = 2.2 Ohm

Resistor power dissipation:

P r = I 2 R = 1*1*2.2 = 2.2 W

At the very end of the battery charge, when the voltage on it approaches 4.2 V, the charge current will be:

I charge = (U ip - 4.2) / R = (5 - 4.2) / 2.2 = 0.3 A

That is, as we see, all values ​​do not go beyond the permissible limits for a given battery: the initial current does not exceed the maximum permissible charging current for a given battery (2.4 A), and the final current exceeds the current at which the battery no longer gains capacity ( 0.24 A).

The main disadvantage of such charging is the need to constantly monitor the voltage on the battery. And manually turn off the charge as soon as the voltage reaches 4.2 Volts. The fact is that lithium batteries tolerate even short-term overvoltage very poorly - the electrode masses begin to quickly degrade, which inevitably leads to loss of capacity. At the same time, all the prerequisites for overheating and depressurization are created.

If your battery has a built-in protection board, which was discussed just above, then everything becomes simpler. When a certain voltage is reached on the battery, the board itself will disconnect it from the charger. However, this charging method has significant disadvantages, which we discussed in.

The protection built into the battery will not allow it to be overcharged under any circumstances. All you have to do is control the charge current so that it does not exceed the permissible values ​​for a given battery (protection boards cannot limit the charge current, unfortunately).

Charging using a laboratory power supply

If you have a power supply with current protection (limitation), then you are saved! Such a power source is already a full-fledged charger that implements the correct charge profile, which we wrote about above (CC/CV).

All you need to do to charge li-ion is set the power supply to 4.2 volts and set the desired current limit. And you can connect the battery.

At first, when the battery is still discharged, laboratory block power supply will operate in current protection mode (i.e. it will stabilize the output current at a given level). Then, when the voltage on the bank rises to the set 4.2V, the power supply will switch to voltage stabilization mode, and the current will begin to drop.

When the current drops to 0.05-0.1C, the battery can be considered fully charged.

As you can see, a laboratory power supply is an almost ideal charger! The only thing he cannot do automatically is make decisions about fully charged battery and turn off. But this is a small thing that you shouldn’t even pay attention to.

How to charge lithium batteries?

And if we are talking about a disposable battery that is not intended for recharging, then the correct (and only correct) answer to this question is NO.

The fact is that any lithium battery (for example, the common CR2032 in the form of a flat tablet) is characterized by the presence of an internal passivating layer that covers the lithium anode. This layer prevents a chemical reaction between the anode and the electrolyte. And the supply of external current destroys the above protective layer, leading to damage to the battery.

By the way, if we talk about the non-rechargeable CR2032 battery, then the LIR2032, which is very similar to it, is already a full-fledged battery. It can and should be charged. Only its voltage is not 3, but 3.6V.

How to charge lithium batteries (be it a phone battery, 18650 or any other li-ion battery) was discussed at the beginning of the article.

Where to buy microchips?

You can, of course, buy it in Chipe-Dip, but it’s expensive there. That's why I always buy from one very secret store)) The most important thing is to choose the right seller, then the order will arrive quickly and for sure.

For your convenience, I have collected the most reliable sellers in one table, use it for your health:

Very popular nowadays lithium ion batteries, they are used in various gadgets, for example phones, smart watch, players, flashlights, laptops. For the first time, a battery of this type (Li-ion) was produced by the famous Japanese company Sony. Schematic diagram The simplest battery is shown in the picture below; by assembling it, you will have the opportunity to restore the charge in the batteries yourself.

Homemade lithium battery charging - electrical diagram

The basis for this device are two stabilizer microcircuits 317 and 431 (). In this case, the LM317 integrated stabilizer serves as a current source; we take this part in the TO-220 housing and must install it on the heat sink using thermal paste. The TL431 voltage regulator manufactured by Texas Instruments also exists in SOT-89, TO-92, SOP-8, SOT-23, SOT-25 and other packages.

Light emitting diodes (LED) D1 and D2 of any color you like. I chose the following: LED1 red rectangular 2.5 mm (2.5 milCandelas) and LED2 green diffusion 3 mm (40-80 milCandelas). Convenient to use smd leds if you don't install ready-made board into the body.

The minimum power of resistor R2 (22 Ohm) is 2 Watts, and R5 (11 Ohm) is 1 Watt. All other ones are 0.125-0.25W.

The 22 kiloOhm variable resistor must be of type SP5-2 (imported 3296W). Such variable resistors have very precise resistance adjustment, which can be smoothly adjusted by twisting a worm pair, similar to a bronze bolt.

Photo measuring the voltage of a li-ion battery from a cell phone before charging (3.7V) and after (4.2V), capacity 1100 mA*h.

PCB for lithium charger

Printed circuit board (PCB) comes in two formats for different programs- the archive is located. The dimensions of the finished printed circuit board in my case are 5 by 2.5 cm. I left space on the sides for fastenings.

How does charging work?

How does the finished circuit of such a charger work? First, the battery is charged with a constant current, which is determined by the resistance of resistor R5; with a standard rating of 11 ohms, it will be approximately 100 mA. Further, when the rechargeable energy source has a voltage of 4.15-4.2 volts, charging with constant voltage will begin. When the charging current drops to small values, LED D1 will stop lighting.

As is known, the standard voltage for Li-ion charging is 4.2V, this figure It is necessary to install the circuit at the output without load, using a voltmeter, so the battery will be fully charged. If you reduce the voltage a little, by about 0.05-0.10 Volts, then your battery will not be fully charged, but this way it will last longer. Author of the article EGOR.

Discuss the article CHARGING LITHIUM BATTERIES