Lithium ion li ion batteries. How to charge a Li-Ion (lithium-ion) battery and operating instructions

Progress is moving forward, and lithium batteries are increasingly replacing the traditionally used NiCd (nickel-cadmium) and NiMh (nickel-metal hydride) batteries.
With a comparable weight of one element, lithium has a larger capacity, in addition, the element voltage is three times higher - 3.6 V per element, instead of 1.2 V.
The cost of lithium batteries has begun to approach conventional alkaline batteries, their weight and size are much smaller, and besides, they can and should be charged. The manufacturer says they can withstand 300-600 cycles.
There are different sizes and choosing the right one is not difficult.
The self-discharge is so low that they sit for years and remain charged, i.e. The device remains operational when needed.

"C" stands for Capacity

You can do something simple or not so simple yourself charger, depending on your experience and capabilities.

Circuit diagram of a simple LM317 charger

Rice. 5.

The required charging current for a particular lithium-ion (Li-Ion) and lithium-polymer (Li-Pol) battery is selected by changing the Rx resistance.
The resistance Rx approximately corresponds to the following ratio: 0.95/Imax.
The value of resistor Rx indicated in the diagram corresponds to a current of 200 mA, this is an approximate value, it also depends on the transistor.

It is necessary to provide a radiator depending on the charging current and input voltage.
The input voltage must be at least 3 volts higher than the battery voltage to normal operation stabilizer, which for one can is? 7-9 V.

Circuit diagram of a simple charger on LTC4054

Rice. 6.

Rice. 7. This small 5-legged chip is labeled "LTH7" or "LTADY"

I won’t go into the smallest details of working with the microcircuit; everything is in the datasheet. I will describe only the most necessary features.
Charge current up to 800 mA.
The optimal supply voltage is from 4.3 to 6 Volts.
Charge indication.
Output short circuit protection.
Overheating protection (reduction of charge current at temperatures above 120°).
Does not charge the battery when its voltage is below 2.9 V.

The charge current is set by a resistor between the fifth terminal of the microcircuit and ground according to the formula

I=1000/R,
where I is the charge current in Amperes, R is the resistor resistance in Ohms.

Lithium battery low indicator

Rice. 8.

The nuance of durability

Operation and Precautions

Failure to comply with the first three points leads to a fire, the rest - to complete or partial loss of capacity.

From the experience of many years of use, I can say that the capacity of batteries changes little, but the internal resistance increases and the battery begins to work less time at high current consumption - it seems that the capacity has dropped.
For this reason, I usually install a larger container, as the dimensions of the device allow, and even old cans that are ten years old work quite well.

For not very high currents, old cell phone batteries are suitable.

Where do I use lithium batteries?

I put small batteries in children's toys, watches, etc., where 2-3 “button” cells were installed from the factory. Where exactly 3V is needed, I add one diode in series and it works just right.

I put them in LED flashlights.

Instead of the expensive and low-capacity Krona 9V, I installed 2 cans in the tester and forgot all the problems and extra costs.

In general, I put it wherever I can, instead of batteries.

Where do I buy lithium and related utilities

The Chinese usually lie about the capacity and it is less than what is written.

Honest Sanyo 18650

Today, special batteries are used for mobile, household appliances, and tools. They differ in performance characteristics. In order for the battery to work for a long time, without failures, you need to take into account the requirements of the manufacturers of the presented products.

One of the most popular types today are Li-Ion batteries. How to properly charge this type of battery, as well as the features of its operation, should be considered in detail before operating the device.

General characteristics

One of the most common types of batteries today is the Li-Ion type. Such devices are relatively low in cost. At the same time, they are undemanding to operating conditions. In this case, the user rarely has a question about how to properly charge a cylindrical Li-Ion 18650 battery or another type.

Most often, the presented batteries are installed in smartphones, laptops, tablets and other similar devices. The presented batteries are characterized by durability and reliability. They are not afraid of complete discharge.

One of the main features of the presented products is the absence of a “memory effect”. These batteries can be charged at almost any convenient time. The “memory effect” occurs when the battery is not completely discharged. If there is a small amount of charge left in it, the battery's capacity will begin to decrease over time. This will lead to insufficient power supply for the equipment. In lithium-ion batteries, the “memory effect” is minimized.

Design

The design of a lithium-ion battery depends on the type of device for which it is intended. A mobile phone uses a battery called a “jar”. She has rectangular shape and includes one structural element. Its nominal voltage is 3.7 V.

The presented type of battery for a laptop has a completely different design. There may be several individual battery cells in it (2-12 pieces). Each of them has a cylindrical shape. These are Li-Ion 18650 batteries. The manufacturer of the equipment indicates in detail how to charge them correctly. This design includes a special controller. It looks like a microcircuit. The controller controls the charging procedure and does not allow the battery's rated capacity to be exceeded.

Modern batteries for tablets and smartphones also provide a charge control function. This significantly extends the battery life. It is protected from various adverse factors.

Charging Features

When considering how to properly charge Li-Ion batteries of a phone, laptop and other equipment, you need to pay attention to the operating features of the presented device. It should be said that lithium-ion batteries do not tolerate deep discharge and overcharging. This is controlled by a special device that is added to the design (controller).

It is ideal to maintain the charge of the presented type of battery at a level from 20 to 80% of full capacity. The controller monitors this. However, experts do not recommend leaving the device connected to charging all the time. This significantly reduces battery life. In this case, the controller is subject to a constant load. Over time, its functionality may decrease because of this.

At the same time, the controller will also not allow deep discharge. It will simply turn off the battery at a certain moment. This protective function is extremely necessary. Otherwise, the user could accidentally overcharge or over-discharge the battery. Modern batteries also provide high-quality protection against overheating.

Battery operating principle

To understand how to properly charge a Li-Ion battery (new or used), you need to consider the principle of its operation. This will allow you to assess the need to monitor the level of discharge and charge of the device.

Lithium ions in a battery of this type move from one electrode to another. In this case, an electric current appears. Electrodes can be made from different materials. This indicator has a lesser impact on the performance characteristics of the device.

Lithium ions grow on the crystal lattice of the electrodes. The latter, in turn, change their volume and composition. When the battery is charged or discharged, there are more ions on one of the electrodes. The higher the load on metal structural elements that lithium places, the shorter the service life of the device will be. Therefore it is better not to allow high percentage deposition of ions on one or another electrode.

Charging options

Before using the battery, you need to consider how to properly charge the Li-Ion battery of a smartphone, tablet and other equipment. There are several ways to do this.

One of the most correct solutions would be to use a charger. It is supplied complete with electronic equipment by every manufacturer.

The second option is to charge the battery from desktop computer connected to a household network. A USB cable is used for this. In this case, the charging procedure will take longer than when using the first method.

You can perform this procedure using the cigarette lighter in your car. Another less popular method is to charge a lithium-ion battery using universal device. It is also called "frog". Most often, such devices are used to recharge smartphone batteries. The contacts of this device can be adjusted in width.

Charging a new battery

The new battery must be put into operation correctly. To do this, your phone, tablet or other equipment must be completely discharged. Only when the device turns off can it be connected to the network. The controller will prevent the battery from draining too much. It is he who turns off the device when the battery loses capacity to a predetermined level.

Next, you need to connect the electrical equipment to the network using a standard charger. The procedure is performed until the indicator lights up green. You can leave the device online for a few more hours. This procedure is carried out several times. There is no need to specifically discharge your phone, tablet or laptop.

Normal charging

Knowing how to properly charge Li-Ion batteries can significantly extend the life of the battery. Experts recommend following the correct procedure for this process for a new battery. After this, it is not advisable to completely discharge the battery. When the indicator shows that the battery capacity is only 14-15% charged, it needs to be connected to the network.

At the same time, it is also not recommended to use devices other than the standard one to fill the battery capacity. It has the maximum acceptable current values ​​permissible for specific model batteries. Other options should only be used if absolutely necessary.

Calibration

There is one more nuance that you need to know when studying the question of how to properly charge Li-Ion batteries. Experts recommend periodically calibrating this device. It is held once every three months.

First in normal mode You need to discharge the electrical equipment before turning it off. Next it is connected to the network. Charging continues until the indicator turns green (battery is 100% charged). This procedure must be performed for proper operation controller.

When carrying out such a procedure, the battery circuit board determines the charging and discharging limits. This is necessary to ensure normal operation of the controller and avoid failures. In this case, a standard charger is used, which is supplied by the manufacturer with the phone, tablet or laptop.

Storage

In order for the battery to work as long and efficiently as possible, you also need to consider the question of how to properly charge a Li-Ion battery for storage. In some cases, a situation may arise when the device for powering equipment is temporarily not in use. In this case, it must be properly prepared for storage.

The battery is charged to 50%. In this state it can be stored for quite a long time. However, the ambient temperature should be around 15 ºC. If it increases, the rate at which the battery loses its capacity will increase.

If the battery needs to be stored for a sufficiently long time, it must be completely discharged and charged once a month. The battery reaches 100% of its specified capacity. Then the device is discharged again and charged to 50%. If this procedure is carried out regularly, the battery can be stored for a very long time. After this, it will be fully usable.

By considering how to properly charge Li-Ion batteries, you can significantly extend the life of this type of battery.

When they talk about lithium batteries or accumulators, most often they don’t even realize that almost a dozen of them have appeared in the last couple of years, each of which is lithium with various additives of other chemical elements, which ultimately differ significantly from each other.

Let's look at their types and start with the classics:

Lithium-ion batteries are classic rechargeable batteries in which lithium ions move from the negative electrode to the positive electrode during discharge and back again when charging. Lithium-ion batteries are widely used in consumer electronics. They are one of the most popular types batteries for portable electronics, with one of the best energy densities, no memory effect and slow loss of charge when not in use (low self-discharge).

This series covers cylindrical and prismatic battery sizes. Li-ion has the highest power density of any old type battery. Very light weight and long life cycle makes it an ideal product for many solutions.

Lithium titanate (lithium titanate) is a relatively new class of lithium-ion batteries - (more details). It is characterized by a very long life cycle, measured in thousands of cycles. Lithium lead titanate is also very safe and comparable in this regard to iron phosphate. Energy density lower than other lithium-ion current sources and its rated voltage is 2.4V.

This technology is very different fast charging, low internal resistance, very high life cycle and excellent endurance (also safety). LTO has found its application mainly in electric vehicles and wristwatch. IN lately it is beginning to find application in mobile medical devices due to its high security. One of the features of the technology is that it uses nanocrystals on the anode instead of carbon, which provides a much more efficient surface area. Unfortunately, this battery has lower voltages than other types of lithium batteries.

Peculiarities:

• Specific energy: about 30-110Wh/kg
• Energy density: 177 W * h/l
• Specific power: 3,000-5,100 W/kg
• Discharge efficiency: approximately 85%; charging efficiency more than 95%
• Energy-price: 0.5 W/dollar
• Shelf life: >10 years
• Self-discharge: 2-5%/month
• Durability: 6000 cycles to 90% capacity
• Nominal voltage: 1.9 to 2.4 V
• Temperature: -40 to +55°C
• Charging method: Uses stable constant current, then constant voltage until it reaches the threshold.

Chemical formula: Li4Ti5O12 + 6LiCoO2< >Li7Ti5O12 + 6Li0.5CoO2(E=2.1 V)

Lithium polymer has a higher energy density in terms of weight than lithium-ion batteries. In very thin cells (up to 5 mm), lithium polymer provides high volumetric energy density. Excellent stability in overvoltage and high temperatures.

This series of batteries can be produced in the range from 30 to 23000 mAh, prismatic and cylindrical housing types. Lithium polymer batteries offer a number of advantages: greater energy density by volume, flexibility in cell sizes and a wider margin of safety, with excellent voltage stability even at high temperature. Main applications: portable players, Bluetooth, wireless devices, PDAs and digital cameras, electric bicycles, GPS navigators, laptops, e-books.

Peculiarities:

• Rated voltage: 3.7V
• Charging voltage: 4.2±0.05V
• Charge current, speed: 0.2-10C
• Discharge voltage limit: 2.5 V
• Discharge speed: up to 50C
• Cycle endurance: 400 cycles

Lithium iron phosphate has good safety characteristics, long service life (up to 2000 cycles), and low production cost. LiFePO4 batteries are well suited for high discharge currents, such as military equipment, power tools, electric bicycles, mobile computers, UPS and solar energy systems.

As a new anode material for lithium-ion batteries, lifepo4 was first introduced in 1997 and has been continuously improved to date. It has attracted the attention of experts due to its reliable safety, durability, low environmental impact during disposal, and convenient charging and discharging characteristics. Many experts claim that lifepo4 batteries are today's the best option for autonomous power supply of electronics.

Lithium sulfur dioxide (Li and SO2 battery) - these batteries have high energy density and good discharge resistance high power. Such elements are used mainly in military science, meteorology and astronautics.

Lithium sulfur dioxide batteries with a lithium metal anode (the lightest of all metals) and a liquid cathode containing a porous carbon current collector filled with sulfur dioxide (SO2) produce a voltage of 2.9 V and are cylindrical in shape.

Peculiarities:

• High operating voltage, stable throughout most of the discharge
• Extremely low self-discharge
• Performance in extreme conditions
• Wide operating temperature range (-55°C to +65°C)

Lithium manganese dioxide (Li-MnO2 battery) - these batteries have a lightweight lithium metal anode and a solid manganese dioxide cathode, immersed in a non-corrosive, non-toxic organic electrolyte. This type of battery complies with EU RoHS and is characterized by large capacity, high discharge capacity and long service life.

Li-MnO2 is widely used in backup power supplies, emergency beacons, fire alarms, electronic systems access control, digital cameras, medical equipment.

Peculiarities:

• High energy density
• Very stable discharge voltage
• More than 10 year shelf life
• Operating temperature: -40 to +60°C

Lithium thionyl chloride (lithium-SOCl2) batteries feature a lightweight lithium metal anode and a liquid cathode containing a porous carbon current collector filled with thionyl chloride (SOCl2). Li-SOCL2 batteries are ideal for automotive devices, medical devices, and military and aerospace applications. They have the widest operating temperature range from -60 to + 150°C.

Peculiarities:

• High energy density
• Long shelf life
• Wide temperature range
• Good sealing
• Stable discharge voltage

Li-FeS2 batteries

Li-FeS2 batteries and batteries stand for lithium iron disulfide. Information about them will be added later.

Testing Features

The main difficulty in the experiments is the discrepancy between the declared capacity and the real one. All batteries have a capacity higher than stated, ranging from 0.1% to 5%, which introduces an additional element of unpredictability.

NCA and NMC batteries were most commonly used, but lithium cobalt and lithium phosphate batteries were also tested.

A few terms:
DoD - Depth of Discharge - depth of discharge.
SoC - State of Charge - charge level.

Using Batteries

Number of cycles

This curve is called the Wöhler curve. The main idea came from mechanics about the dependence of the number of stretches of a spring on the degree of stretching. The initial value of 3000 cycles at 100% battery discharge is a weighted average at 0.1C discharge. Some batteries show better results, some worse. At a current of 1C, the number of full cycles at 100% discharge drops from 3000 to 1000-1500, depending on the manufacturer.

In general, this relationship, presented in the graphs, was confirmed by the results of experiments, because It is advisable to charge the battery whenever possible.

Calculation of superposition of cycles

According to the results of the experiments, the combined cycle showed results similar to the addition of complete equivalent cycles of two independent cycles. Those. The relative capacity of the battery in the combined cycle fell according to the sum of the discharges in the small and large cycles (the linearized graph is presented below).


The effect of large discharge cycles is more significant, which means that it is better to charge the battery at every opportunity.

Memory effect

Battery storage

Storage temperatures

Charge level

Main problems of the experimental results

Results of the experiments

Sources

Assessing the characteristics of a particular charger is difficult without understanding how an exemplary charge should actually flow li-ion battery A. 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 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 the 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 in the operation of a proper charger is its complete disconnection from the battery after charging is completed. 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 ensured DC reduced value 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 a large charge current is immediately passed through such a battery, this will inevitably lead to its heating, and then it depends.

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 of 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 of the 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):

Analogs 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 of the LM317 chip, 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 each 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 is a typical connection diagram:

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’s also cheaper than the much-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 scheme, 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 the 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 the middle terminal of a cell phone battery). If the output voltage 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 the 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, a very budget charging option is obtained (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.

Among the 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, the 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: