How to properly charge a lithium-ion battery and why is it even needed? Our modern devices operate thanks to the presence of autonomous power supplies. And it doesn’t matter what kind of devices they are: electric smartphones or laptops. This is why it is so important to know the answer to the question of how to properly charge a lithium-ion battery.

A little about what a lithium-ion battery is

Autonomous power supplies, which are used in modern smartphones and other devices, are usually divided into several different groups. There are quite a lot of them. Take the same ones. But it is in portable equipment, that is, in smartphones and laptops, that lithium-ion batteries (English designation Li-Ion) are most often installed. The reasons that led to this are of different nature.

The advantages of these types of batteries

The first thing to note is how simple and cheap it is to produce these energy sources. Their additional advantages are excellent operating characteristics. Self-discharge losses are a very small indicator, and this also played a role. But the supply of cycles for charging and discharging is very, very large. Together, all this makes lithium-ion batteries leaders among other similar devices in the field of their use in smartphones and laptops. Although exceptions to the rule exist, they account for about 10 percent of the total number of cases. That is why many users ask the question of how to properly charge a lithium-ion battery.

Important and interesting facts

A smartphone battery has its own specific features. Therefore, you need to know certain rules and be familiar with the relevant instructions before you begin the process of forced charging or discharging. It should be noted first of all that most batteries of this type are specially equipped with an additional monitoring device. Its use is determined by the need to maintain the charge at a certain level (also called critical). Thus, the control device, built into, among other things, the battery for a smartphone, does not allow us to cross that fatal line, after which the battery simply “dies,” as service specialists like to say. From the point of view of physics, everything looks like this: during the reverse process (critical discharge), the voltage of the lithium-ion battery simply drops to zero. At the same time, the flow of current is blocked.

How to properly charge digital equipment based on this source of battery life

If your smartphone is powered by a lithium-ion battery, then the device itself must be charged when the battery indicator shows approximately the following numbers: 10-20 percent. The same is true for phablets and tablet computers. This is a short answer to the question of how to properly charge a lithium-ion battery. It should be added that even when reaching 100 percent rated charge, the device must be kept connected to the electrical network for another one to two hours. The fact is that the devices interpret charging incorrectly, and the 100 percent that a smartphone or tablet gives is in fact no more than 70-80 percent.

If your device is equipped with a lithium-ion battery, you should know some of the intricacies of its operation. This will be very useful in the future, because by following them you can extend the life of not only this element, but the entire device as a whole. So, remember, once every three months you need to completely discharge the device. This is done for preventive purposes.

But we’ll talk about how to charge a discharged battery later. For now, we’ll just point out that a desktop computer and laptop are not capable of providing a sufficiently high voltage when connecting a mobile device to these technological wonders via a USB standard port. Accordingly, in order to fully charge the device from these sources, it will take more time. Interestingly, one technique can extend the life of a lithium-ion battery. It consists of alternating charging cycles. That is, once you charge the device completely, 100 percent, the second time - not completely (80 - 90 percent). And these two options alternate in turn. In this case, it can be used for lithium-ion batteries.

Terms of use

In general, lithium-ion power supplies can be called unpretentious. We have already talked about this topic and found out that this characteristic, along with others, has become the reason for their widespread use in computing. However, even such a smart battery architecture does not fully guarantee their long-term performance. This period depends primarily on the person. But we are not required to do anything out of the ordinary. If there are five simple rules that we can remember forever, apply them successfully. In this case, the lithium-ion power supply will serve you for a very, very long time.

Rule one

It lies in the fact that it is not necessary completely. It has already been said that such a procedure should be carried out only once every three months. Modern designs of these power supplies do not have a “memory effect”. Actually, that’s why it’s better to have time to charge the device before it completely runs out. By the way, it is quite noteworthy that some manufacturers of relevant products measure the service life of products in the number of cycles. High-end products can “survive” about six hundred cycles.

Rule two

It states that the mobile device needs to be completely discharged. It should be carried out once every three months for preventive purposes. On the contrary, irregular and unstable charging can shift the nominal minimum and maximum charge marks. Thus, the device into which this source of autonomous operation is built begins to receive false information about how much energy actually remains. And this, in turn, leads to incorrect calculations of energy consumption.

Prophylactic discharge is designed to prevent this. When this happens, the control circuit will automatically reset the minimum charge value. However, there are some tricks here. For example, after a complete discharge, it is necessary to “fill in” the power source, holding it for an additional 12 hours. Apart from an ordinary electrical network and a wire, we don’t need anything else for charging in this matter. But the operation of the battery after a preventive discharge will become more stable, and you will be able to immediately notice it.

Rule three

If you don't use your battery, you still need to monitor its condition. At the same time, the temperature in the room where you store it should preferably be no more and no less than 15 degrees. It is clear that it is not always possible to achieve exactly this figure, but still, the smaller the deviation from this value, the better it will be. It should be noted that the battery itself must be charged 30-50 percent. Such conditions will allow you to maintain the power source for a long time without serious damage. Why shouldn't it be fully charged? But because a “full to capacity” battery, due to physical processes, loses quite a large part of its capacity. If the power source is stored for a long time in a discharged state, then it becomes practically useless. And the only place where it will really be useful is in the trash. The only way, although unlikely, is to remanufacture lithium-ion batteries.

Rule four

The price of which ranges from several hundred to several thousand rubles, should be charged only using original devices. This applies to a lesser extent to mobile devices, since adapters are already included in their package (if you buy them from the official store). But in this case they only stabilize the supplied voltage, and the charger, in fact, is already built into your device. Which, by the way, cannot be said about video cameras and cameras. This is exactly what we are talking about, here the use of third-party devices when charging batteries can cause noticeable harm.

Rule five

Monitor the temperature. Lithium-ion batteries can withstand heat stress, but overheating is detrimental to them. And low temperatures for a power source are not the best that can happen. Although the greatest danger comes precisely from the process of overheating. Remember that the battery should not be exposed to direct sunlight. The range of temperatures and their permissible values ​​starts at - 40 degrees and ends at + 50 degrees Celsius.

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

The most correct way to charge lithium batteries is to charge 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. You can read more about charging with pulsed current.

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 open circuit voltage of the circuit can never 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 correct charger operation is its complete disconnection 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 high voltage for a long time, which is usually provided by the charger (i.e. 4.18-4.24 volts). This leads to accelerated degradation of the chemical composition of the battery and, as a consequence, 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 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-heating the battery, which is important when charging at low ambient temperatures (in an unheated room during the cold season).

Intelligent charging should be able to monitor the voltage on the battery during the preliminary charging stage and, if the voltage does not rise for a long time, draw a conclusion 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, it is prohibited to use lithium batteries in household appliances unless they 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 we move on to a small selection of 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 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 the power is supplied via the USB bus, then 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 is another version of a printed circuit board with an SMD LED and a 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 couple 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, VS6102 , 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 a 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 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).

Any pnp transistor is suitable, 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.

The LT1716 comparator 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 most difficult thing here is to find 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 the maximum value of the 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 charging (by changing the capacitance of the capacitor C t, you can set the maximum charging time from 6.6 to 784 minutes).

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

A more detailed description is 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.

Initially, when the battery is still discharged, the laboratory 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 it can’t do automatically is make a decision to fully charge the 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.

What current charges the li-ion 18650 and how to use the battery correctly? How can such a power source extend its service life? These questions arise in a wide variety of electronics industries. A lithium-ion battery is a type of electric current battery. In 1991, SONY launched the battery into the market, and it immediately began to be widely used in household and electronic appliances.

These batteries serve as power sources for mobile phones, laptops and video cameras, electronic cigarettes and electric vehicles. All modern lithium-ion batteries prevent overheating and overcharging. However, the problem of charge loss at low temperatures has not disappeared.

Among the undeniable advantages of lithium-ion batteries, we would like to highlight the following:

1. good capacity;
2. low self-discharge;
3. no maintenance required.

Original chargers

A lithium-ion battery charger is quite similar to a lead-acid battery charger. They differ only in that the lithium-ion power source has a very high voltage on each bank and strict tolerance requirements for it.

If for lead-acid batteries some inaccuracies in the boundary voltages during charging can be tolerated, then with lithium-ion cells everything is completely different. When the voltage increases to 4.2 V during charging, the voltage supply must be stopped.

It is allowed to exceed only 0.05 V. The most ideal charger for lithium-ion batteries is a voltage stabilizer. Lithium must be charged at a stable voltage with a current limit at the beginning of the charge. It is very important. Charging will be considered complete if, with a stable charge of 4.2 V, there is no current or it has a very small value of about 5-7 mA.

Electrical circuit for charging an 18650 cell

On top of that, when you install the stabilizer on the radiator, you can safely recharge your batteries without fear that the charger will overheat and then catch fire. This can happen with Chinese chargers. The operation of the circuit is quite simple. First, the battery is charged with a constant current determined by the resistance of resistor R4.

When the battery has a voltage of 4.2 V, the direct current will begin to charge it. When it drops to the lowest values, the LED in the circuit will stop lighting. Recommended currents for charging lithium-ion batteries should not exceed 10% of the volume of the battery itself in order to increase the life of your power source. With a resistor R4 value of 11 Ohms, the current in the circuit will be 100 mA. If a 5 ohm resistance is used, the charging current will be 230 mA.

How to extend the life of your 18650

If you are leaving a lithium-ion battery unused for a period of time, we recommend storing the battery separately from the device it powers. A fully charged cell will lose some of its charge after some time. If the battery has a very low charge or is completely discharged, it may permanently fail after a long period of hibernation. It is optimal to store the 18650 at a charge level of 50%.

Do not allow the battery to be completely discharged or recharged. Lithium-ion batteries do not have a memory effect. Such batteries are charged only when the charge is completely exhausted. This will also extend the life of the battery.

Lithium ions do not like heat or cold. Optimal temperatures for the battery range from 10 to 25 degrees. Cold will not only reduce operating time, but will also destroy the chemical system of the battery. Probably everyone has noticed how the charge level on your phone instantly drops in cold weather.

If you are going to charge a lithium-ion battery with a charger from a store, make sure that it is not Chinese. Very often they are assembled from cheap materials and not always using the correct technology.

This, in turn, can lead to a fire. When using such batteries, always follow the operating and storage instructions to avoid the possibility of an explosion due to overheating or complete failure. This will extend the life of the lithium-ion battery and save you from unnecessary costs.

Take care of your battery! She is your assistant.

From this article you will understand how to properly charge a Li-Ion (lithium-ion) battery, as well as learn its proper operation and maintenance. This kind of knowledge will extend the life of your battery.

The lithium-ion battery has become so widespread due to its ease of production, low cost and a large number of charge-discharge cycles. But to appreciate these benefits, it is necessary to use the Li-Ion battery correctly.

Operating instructions vary depending on the type of battery. For example, Ni-MH and Ni-Cd batteries must be completely discharged before charging. Otherwise, the elements become larger and the battery volume decreases. However, the rule “bought a phone - discharge it to zero, and then charge it and repeat the cycle several times” is not universal and does not apply to Li-Ion.

Therefore, before applying the recommendations below, take a look at your battery. It should say that it is lithium-ion (Li-Ion). Only in this case, use the following operating rules.

Do not discharge the battery to zero too often.

It will still not be possible to completely discharge the battery. The protection board turns off the device when a certain minimum is reached. Complete discharge is only possible if you disassemble the battery and remove the protective board. Li-Ion and Li-Pol batteries do not tolerate frequent complete discharge. That's why they are sold 2/3 charged.

Place the device to charge when the battery has 10-20% remaining

A message like “Please connect the charger” appears when the charge reaches 10-20% for a reason. Follow the manufacturers' recommendations and connect the charger.

But you don’t have to wait for such a fall. If you can charge your phone or laptop, do it. Regular charging is not a panacea, but the more often you charge your Li-Ion, the longer it will last.

Calibrate your battery periodically

Calibration involves completely discharging and then charging the device. There is no contradiction with the first rule: calibration must be done approximately once every three months.

Calibration does not directly extend battery life, but only helps the controller correctly determine the battery capacity. If the controller determines the amount of charge incorrectly, the device will have to be charged more often. Charge-discharge cycles are wasted and the battery fails faster.

Use original charger

Originality in the context of the problem under consideration is needed to protect yourself from using low-quality products. If you are sure that the technical characteristics of the third-party device correspond to the characteristics of the original charger, then no problems will arise.

Try not to use "frogs"

If possible, avoid charging batteries using a frog. The use of uncertified devices is unsafe; there are cases when “frogs” ignite during charging.

How to properly charge and operate a lithium-ion (Li-Ion) battery?

In modern life, a person is surrounded by many electronic assistants. In everyday life, we use tablets, mobile phones, laptops, etc. At work, we use screwdrivers, portable drills, flashlights, power banks and car battery boosters. All of these devices use different types of batteries. But the most common are lithium-ion batteries. They have become popular due to their small size and weight combined with high energy intensity. At a reasonable cost, they have a decent service life (300-400 charge-discharge cycles). Since these batteries are widely used in various devices that surround us, we need to understand how to charge them correctly. Therefore, today’s material is devoted to charging Li─Ion batteries.

Since many users have a vague idea of ​​what a lithium-ion battery is, let’s say a few words about its structure. If you look at the example of a mobile phone battery, the battery there has the following design.

In the vast majority of cases, a mobile phone battery has one battery element in its design, which is often called a can. The voltage rating of the can is typically 3.7 volts. In laptop batteries there can be from 2 to 12 such elements. But there they are not rectangular, but cylindrical (type). The battery also contains a controller, which is a board with a control chip soldered on it. It controls the process of charging and discharging the can, preventing it from overcharging or deep discharge.

Thus, battery manufacturers have already taken care to avoid emergency situations when charging and discharging the battery. And the user can only follow some operating rules, which will be discussed below.
If you are interested, you can read detailed material about it in the article at the link.

How to properly charge a lithium-ion battery?

When charging a Li-Ion battery, you need to remember that it is best to maintain the battery charge at 20-80% of full capacity. Lithium-ion batteries do not like to be overcharged. As mentioned above, the controller controls the state of charge of the battery cell or cells, if there are several of them. He will not allow them to recharge. But this does not mean that the battery can be charged for days. This is completely useless.

Why is overcharging and deep discharge critical for a lithium-ion battery? The fact is that the current in such batteries is provided by the movement of lithium ions from one electrode to another. The composition of these electrodes may vary. In this case, these details are not important. The important thing is that lithium ions are introduced into the crystal lattice of the electrode substance. As a result, gradual changes in the volume and composition of the electrodes occur. The more charged or discharged a battery is, the more lithium ions are present in one of the electrodes. Such operation leads to the fact that the battery life is significantly reduced. Therefore, it is better not to create such borderline states and keep the charge at a level of 20-80% of the nominal value.

In any case, the controller does not allow overcharging and deep discharge of the can. He simply disconnects the jar from the outside world. In addition, many lithium-ion batteries have built-in overheating protection.

Now we list several options for charging a Li─Ion battery.

• Standard charger. This is the best and recommended option. It is recommended to charge the Li─Ion battery using standard charging. It's safe and as fast as possible;
• From the USB connector of the computer. The option is also safe, but quite lengthy. The fact is that in the case of a USB port, the current is limited to 0.5 amperes;
• From the cigarette lighter in the car. If this is a standard USB adapter, then the process may also take longer. But now there are quite a few devices on sale that have a set of USB ports with different current strengths. There are even models that allow you to charge laptop batteries with a nominal voltage of 19 volts with a current of 4 amperes. You can find out the maximum permissible current for charging the battery of your device from the documentation or look at the standard charger. For smartphone batteries it is usually 1, and for tablets – 2 amperes;
• "Frog". This is what they call universal chargers. They are usually used to charge lithium batteries for mobile phones. One of these “frogs” is shown in the image below. The design includes a dock for installing the battery and contacts that are adjustable in width for different models. There is an LED indication to inform you about the end of charging.

As you can see, you can charge a lithium-ion battery in various ways. But it is recommended to charge the battery using standard charging, and use other methods only if necessary. Immediately after purchasing a gadget, get used to charging it correctly. You can read about it at the given link.