I discovered that I have a number of quite serviceable ones lying around. lithium batteries from dead mobile phones, laptops, etc., which can be used in various crafts. They need to be charged with something. Suitable parts were found in the deposits, and away we go...

Charger circuit

We draw a diagram, keeping an eye on the presence of parts in the desk drawer. I’m too lazy to run to the store for such a simple product.

limits current, TL431+IRF limits voltage. Nothing special, probably dozens of exactly the same diagrams have already been drawn. The current limit is set to 125 mA based on the capabilities of the transformer used and the limitation on heat dissipation in the small plastic case. In fact, even small cell phone batteries hold a much higher charging current without overheating.
The board was made compact enough to fit into the existing plastic case.

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Thank you for your attention!
Igor Kotov, editor-in-chief of Datagor magazine

Thank you for your attention!

Surely, every radio amateur has encountered a problem when connecting lithium batteries in series, noticed that one runs out quickly and the other still holds a charge, but because of the other one the entire battery does not give out required voltage. This happens because when charging the entire battery pack, they are not charged evenly, and some batteries gain full capacity while others do not. This leads not only to rapid discharge, but also to failure individual elements, due to constant not charging.
Fixing the problem is quite simple; for each battery cell you need a so-called balancer, a device that after fully charged The battery blocks its further recharging, and the control transistor bypasses the charging current past the element.
The balancer circuit is quite simple, assembled on a precision controlled zener diode TL431A and a direct conduction transistor BD140.

After much experimentation, the circuit changed a little, 3 1N4007 diodes connected in series were installed in place of the resistors, the balancer, in my opinion, became more stable, the diodes get noticeably warm when charging, this should be taken into account when laying out the board.

Principle of operation very simple, as long as the voltage on the element is less than 4.2 volts, charging in progress, the controlled zener diode and transistor are closed and do not affect the charging process. As soon as the voltage reaches 4.2 volts, the zener diode begins to open the transistor, which shunts the battery through resistors with a total resistance of 4 Ohms, thereby preventing the voltage from rising above the upper threshold of 4.2 volts, and allows the remaining batteries to charge. A transistor with resistors calmly passes a current of about 500 mA, while it heats up to 40-45 degrees. As soon as the LED on the balancer lights up, the battery connected to it is fully charged. That is, if you have 3 batteries connected, then the end of the charge should be considered the lighting of the LEDs on all three balancers.
Settings It’s very simple, we apply a voltage of 5 volts to the board (without a battery) through a resistor of approximately 220 Ohms, and measure the voltage on the board, it should be 4.2 volts, if it differs, then we select a 220 kOhm resistor within small limits.
The voltage for charging needs to be supplied approximately 0.1-0.2 volts more than the voltage on each element in the charged state, example: we have 3 batteries connected in series, 4.2 volts each in the charged state, the total voltage is 12.6 volts. 12.6 + 0.1 + 0.1 + 0.1 = 12.9 volts. You should also limit the charge current to 0.5 A.
As an option for a voltage and current stabilizer, you can use the LM317 microcircuit, the connection is standard from the datasheet, the circuit looks like this.

The transformer must be selected based on the voltage of the charged battery + 3 volts according to the variable, for correct operation LM317. Example: you have a 12.6 volt + 3 volt battery = a transformer needs 15-16 volts alternating voltage.
Since LM317 is a linear regulator, and the voltage drop across it will turn into heat, we must install it on a radiator.
Now a little about how to calculate the divisor R3-R4 for voltage stabilization, but very simply according to the formula R3+R4=(Vo/1.25-1)*R2, the Vo value is the end-of-charge voltage (maximum output after the stabilizer).
Example: we need to get 12.9 volts output for 3. batteries with balancers. R3+R4=(12.9/1.25-1)*240=2476.8 Ohm. which is approximately equal to 2.4 kOhm + we have a tuning resistor for precise adjustment (470 Ohm), which will allow us to easily set the calculated output voltage.
Now calculate the output current, the resistor Ri is responsible for it, the formula is simple Ri=0.6/Iз, where Iз - maximum current charge. Example: we need a current of 500 mA, Ri=0.6/0.5A= 1.2 Ohm. It should be taken into account that a charging current flows through this resistor, so its power should be 2 W. That's all, I'm not posting the boards, they will be when I assemble a charger with a balancer for my metal detector.

Features of charging lithium batteries and chargers for them

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

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

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

. For lithium-ion systems with a graphite system, voltages must be limited to 4.1 volts per cell.

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

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

It is worth saying that as the charging current increases, the charging time practically does not decrease. With more high current The voltage increases faster at the first stage of the process, but the second stage of recharging in this case takes longer.

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

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

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

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

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

In addition, if the charging voltage is constantly exceeded, the service life lithium batteries decreases.

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

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

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

Chargers for various gadgets

Chargers for smartphone batteries

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

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

How to properly charge a lithium-ion battery and why is it even needed? Our modern devices work thanks to the availability of sources autonomous power supply. 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 that 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 But exactly in portable equipment, that is, in smartphones and laptops, 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. Additional benefits their 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 there are exceptions to the rule, they account for about 10 percent of total number 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 additional device control. 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 lithium ion battery it just 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 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 will simply point out that desktop computer and the laptop are not able to provide a high enough voltage when connected mobile device to these marvels of technology through the port USB standard. Accordingly, in order to fully charge the device from these sources, you will need large quantity 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 computer technology. 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 five simple rules, which 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. Thus, the device in which this source is built battery life, 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 minimum value charge. 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 the battery is “filled to capacity” due to physical processes loses quite a large part of its capacity. If the power source is stored for a long time when discharged, 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 in 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 is the use third party devices may cause significant harm when charging batteries.

Rule five

Monitor the temperature. Lithium-ion batteries can resist 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 sun rays. Temperature range and their acceptable values starts at - 40 degrees and ends at + 50 degrees Celsius.

You can get acquainted with the charger circuit, which is perfect for lithium Li-Ion batteries.

At first, its author wanted to present a simple version on the lm317 chip, but in this case the charging needs to be powered from a more high voltage than 5 volts. The reason is that the difference between the input and output voltages of the lm317 microcircuit must be at least 2 Volts. The voltage of a charged lithium-ion battery is approximately 4.2 Volts. Therefore, the voltage difference is less than 1 volt. And this means that you can come up with another solution.

On AliExpress you can buy a specialized board for charging lithium batteries, which costs about a dollar. Yes, that's true, but why buy something that can be done in a couple of minutes. Moreover, it takes a month until you receive the order. But if you decide to buy a ready-made one so you can use it right away, buy it in this Chinese store. In the store search, enter: TP4056 1A

The simplest scheme

Today we’ll look at options for a UDB charger for lithium batteries that anyone can replicate. The scheme is the simplest one you can think of.

Solution

This hybrid scheme, where there is voltage stabilization and battery charging current limitation.

Description of charging operation

Voltage stabilization is based on the rather popular tl431 adjustable zener diode microcircuit. Transistor as an amplifying element. The charge current is set by resistor R1 and depends only on the parameters of the battery being charged. This resistor is advised with a power of 1 watt. And all other resistors are 0.25 or 0.125 watts.

As we know, the voltage of one can of a fully charged lithium-ion battery is about 4.2 Volts. Therefore, at the output of the charger we must set exactly this voltage, which is set by selecting resistors R2 and R3. There are a lot online programs by calculating the stabilization voltage of the tl431 microcircuit.
For the most fine tuning output voltage, it is recommended to replace resistor R2 with a multi-turn resistance of about 10 kilo-ohms. By the way, such a solution is possible. We use an LED as a charge indicator; almost any LED, color to your taste, will do.
The whole setup comes down to setting the output voltage to 4.2 volts.
A few words about the tl431 zener diode. This is a very popular microcircuit, do not confuse it with transistors in a similar package. This microcircuit is found in almost any pulse block power supply, for example a computer, where the microcircuit is most often located in the harness.
The power transistor is not critical, any transistor will do reverse conduction medium or high power, for example, from the Soviet ones, KT819, KT805 are suitable. Of the less powerful KT815, KT817 and any other transistors with similar parameters.

What batteries is the device suitable for?

The circuit is designed to charge only one can of a lithium battery. You can charge standard 18 650 batteries and other batteries, you just need to set the appropriate voltage at the output of the charger.
If suddenly for some reason the circuit does not work, then check the presence of voltage at the control pin of the microcircuit. It must be at least 2.5 Volts. This is the minimum operating voltage For external source reference voltage of the microcircuit. Although there are versions where the minimum operating voltage is 3 Volts.
It is also advisable to build a small test stand for the specified chip to check its functionality before soldering. And after assembly, we carefully check the installation.

In another publication there is material about improvement.