Many may say that for little money you can order a special board from China, through which you can charge lithium batteries via USB. It will cost about 1 dollar.

But there is no point in buying something that can be easily assembled in a few minutes. Do not forget that you will have to wait about a month for the ordered board. And a purchased device does not bring as much pleasure as a home-made one.
Initially it was planned to collect Charger based on the LM317 chip.

But then it will take more to power this charge high voltage than 5 V. The chip must have a difference of 2 V between the input and output voltages. A charged lithium battery has a voltage of 4.2 V. This does not meet the described requirements (5-4.2 = 0.8), so you need to look for another solution.

Almost everyone can repeat the exercise that will be discussed in this article. Its scheme is quite simple to repeat.

One of these programs can be downloaded at the end of the article.
To more accurately adjust the output voltage, you can change resistor R2 to a multi-turn one. Its resistance should be about 10 kOhm.

Attached files: :

How to make a simple Power Bank with your own hands: homemade diagram power bank Do-it-yourself lithium-ion battery: how to charge correctly

Modern electronic devices(type cell phones, laptops or tablets) are powered by lithium- ion batteries, which replaced alkaline analogues. Nickel-cadmium and nickel-metal hydride batteries have given way to Li─Ion batteries due to the better technical and consumer qualities of the latter. The available charge in such batteries from the moment of production ranges from four to six percent, after which it begins to decrease with use. During the first 12 months, battery capacity decreases by 10 to 20%.

Original chargers

Charging units for ion batteries are very similar to similar devices for lead-acid batteries, however, their batteries, called “banks” for their external similarity, have a higher voltage, so there are more stringent tolerance requirements (for example, the permissible voltage difference is only 0. 05 c). The most common format of a 18650 ion battery bank is that it has a diameter of 1.8 cm and a height of 6.5 cm.

On a note. A standard lithium-ion battery requires up to three hours to charge, and the more precise time is determined by its original capacity.

Manufacturers Li- ion batteries It is recommended to use only original chargers for charging, which are guaranteed to provide the required voltage for the battery and will not destroy part of its capacity by overcharging the element and disrupting the chemical system; it is also undesirable to fully charge the battery.

Note! During long-term storage, lithium batteries should optimally have a small (no more than 50%) charge, and it is also necessary to remove them from the units.

If lithium batteries have a protection board, then they are not in danger of being overcharged.

The built-in protection board cuts off excessive voltage (more than 3.7 volts per cell) during charging and turns off the battery if the charge level drops to a minimum, usually 2.4 volts. The charge controller detects the moment when the voltage on the bank reaches 3.7 volts and disconnects the charger from the battery. This essential device also monitors the temperature of the battery to prevent overheating and overcurrent. The protection is based on the DV01-P microcircuit. After the circuit is interrupted by the controller, its restoration is carried out automatically when the parameters are normalized.

On the chip, a red indicator means charge, and green or blue indicates that the battery is charged.

How to properly charge lithium batteries

Well-known manufacturers of li-ion batteries (for example, Sony) use a two- or three-stage charging principle in their chargers, which can significantly extend the battery life.

At the output, the charger has a voltage of five volts, and the current value ranges from 0.5 to 1.0 of the nominal capacity of the battery (for example, for an element with a capacity of 2200 milliamp-hours, the charger current should be from 1.1 amperes.)

At the initial stage, after connecting the charging for lithium batteries, the current value is from 0.2 to 1.0 rated capacity, while the voltage is 4.1 volts (per can). Under these conditions, the batteries charge in 40 to 50 minutes.

To achieve constant current, the charger circuit must be able to raise the voltage at the battery terminals, at which time the charger for most lithium-ion batteries acts as a conventional voltage regulator.

Important! If charging is needed lithium ion batteries, which have a built-in protection board, then the open circuit voltage should not be more than six to seven volts, otherwise it will deteriorate.

When the voltage reaches 4.2 volts, the battery capacity will be from 70 to 80 percent capacity, which will signal the end of the initial charging phase.

The next stage is carried out if there is DC voltage.

Additional Information. In some units for more fast charging The pulse method is used. If the lithium-ion battery has a graphite system, then they must comply with the voltage limit of 4.1 volts per cell. If this parameter is exceeded, the energy density of the battery will increase and trigger oxidation reactions, shortening the life of the battery. IN modern models batteries use special additives that allow you to increase the voltage when connecting a charger for li ion batteries to 4.2 volts plus/minus 0.05 volts.

In simple lithium batteries, chargers maintain a voltage level of 3.9 volts, which for them is a reliable guarantee of long service life.

When delivering a current of 1 battery capacity, the time to obtain an optimally charged battery will be from 2 to 3 hours. As soon as the charge becomes full, the voltage reaches the cutoff norm, the current value rapidly drops and remains at the level of a couple of percent of the initial value.

If the charging current is artificially increased, the time of use of the charger to power lithium-ion batteries will hardly decrease. In this case, the voltage initially increases faster, but at the same time the duration of the second stage increases.

Some chargers can fully charge the battery in 60-70 minutes; during such charging, the second stage is eliminated, and the battery can be used after the initial stage (the charging level will also be at 70 percent capacity).

At the third and final charging stage, a compensating charge is carried out. It is not carried out every time, but only once every 3 weeks, when storing (not using) batteries. In battery storage conditions, it is impossible to use jet charging, because in this case lithium metallization occurs. However, short-term recharging with constant voltage current helps to avoid charge losses. Charging stops when the voltage reaches 4.2 volts.

Lithium metallization is dangerous due to the release of oxygen and a sudden increase in pressure, which can lead to ignition and even explosion.

DIY battery charger

A charger for lithium-ion batteries is inexpensive, but if you have a little knowledge of electronics, you can make one yourself. If there is no accurate information about the origin of the battery elements, and there are doubts about the accuracy of the measuring instruments, you should set the charge threshold in the region from 4.1 to 4.15 volts. This is especially true if the battery does not have a protective board.

To assemble a charger for lithium batteries with your own hands, one simplified circuit is enough, of which there are many freely available on the Internet.

For the indicator, you can use a charging type LED, which lights up when the battery charge is significantly reduced, and goes out when discharged to “zero”.

The charger is assembled in the following order:

• a suitable housing is located;
• a five-volt power supply and other circuit parts are mounted (strictly follow the sequence!);
• a pair of brass strips is cut out and attached to the socket holes;
• using a nut, the distance between the contacts and the connected battery is determined;
• A switch is installed to change the polarity (optional).

If the task is to assemble a charger for 18650 batteries with your own hands, then you will need more complex circuit and more technical skills.

All lithium-ion batteries require recharging from time to time, however, overcharging as well as completely discharging should be avoided. Maintaining the functionality of batteries and maintaining their working capacity for a long time is possible with the help of special chargers. It is advisable to use original chargers, but you can assemble them yourself.

Video

Majority modern gadgets receive power in two ways: from the network, from batteries. Which one will you choose? Probably the second one, as the most convenient. But then you will have to take care of charging them regularly. There is special equipment for this – a charger for lithium-ion batteries. When choosing it, they are usually interested in the charging speed and the number of batteries that can be restored at the same time.

But we should not forget that it must be optimized to work with specific batteries. Most foreign battery manufacturers also produce their own chargers, which saves you from the tedious search for a suitable model. What is their difference and how to navigate this sea of ​​products? Now we will tell you in more detail.

Charging for AA batteries

This device is a necessary item for people who prefer an active lifestyle and have switched the maximum number of gadgets they use to battery power. One of the most common of these devices is the mobile phone.

All of them are equipped with lithium-based batteries. Therefore, it is recommended for them to purchase a charger for a 18650 lithium battery. Since an attempt to restore the battery capacity using a device of the wrong model will lead to its damage.

Typically, devices labeled EP are used to charge lithium-based batteries. IN mobile phone The battery is considered the most vulnerable point. And if you use the wrong charger, its service life may be shortened, it will begin to discharge quickly, which will cause a lot of inconvenient moments. To avoid this, it is necessary to select the correct recovery equipment. Moreover, it is not necessary to purchase a ready-made model; you can make a charger for lithium batteries with your own hands. Such a device will cost less than an industrial product.

Design features of the charger

The classic 18650 lithium battery charger circuit includes two main parts:

• Transformer;
• Rectifier.

It is used to produce direct current with a voltage of 14.4V. This parameter value was not chosen by chance. It is necessary so that current can pass through a discharged battery. And since at this time the battery voltage is about 12V, it is impossible to charge it with a device whose output has the same value. That is why the value of 14.4V was chosen.

Operating principle of the charger

Restoring battery capacity begins when the charger is plugged into the network. Wherein internal resistance The battery voltage increases and the current decreases. As soon as the voltage on the battery reaches 12V, the current will approach zero. These parameters indicate that the battery has been charged successfully and the device can be turned off.

In addition to the usual process, which takes quite a long time, there is also an accelerated one. Rapid charging significantly reduces battery life, but at the same time negatively affects battery performance, so experts do not recommend using this method.

Criteria for choosing a charging device

You can determine how high quality the purchased device will be by the following points:

• Availability of independent charging channels;
• Toku;
• Discharge functions.

Let's look at each of them in detail. Let's start with the most important thing - independent charge channels. The presence of them in the selected model indicates that its electronic filling is capable of separately controlling the charging process and stopping it as soon as the battery capacity is restored. But at the same time, all the others will not have time to restore their capacity, which, if this situation is constantly repeated, leads to rapid failure of the batteries.

Replenishing battery energy is possible in three ways:

1. Weak current;
2. Average;
3. Tall.

The first involves choosing a charger for lithium-ion batteries based on the rated capacity of the battery. In this case, the current generated by it should not exceed 10%. This charging method is the slowest and most gentle. With its constant use, the battery life is practically not reduced.

The use of devices with a current of less than half the rated capacity of the battery is considered the golden mean. With it, the battery practically does not heat up and the cycle time is not very long, as in the first case.

The latter method, or charging with a high current almost equal to the rated capacity, is a kind of stress for the battery, leading to a significant reduction in service life. It generates intense heat, requiring active fan cooling. It is used only in extreme cases when you need to charge the battery in a couple of hours.

Watch a video review of chargers for lithium batteries:

There are also so-called smart devices. They are used to charge batteries by professional photographers, used in lighting applications and other similar applications. The cost of such a charger for lithium-ion batteries is quite high, but if the flawless operation of the gadget is important to you, then it is better to invest in the purchase of a device rather than constantly changing batteries.

Smart chargers have a discharge function. It is necessary to completely discharge the battery, thereby eliminating the memory effect. This slightly lengthens the charging cycle, but thereby extends the battery life.

Some models also have a training function. It is used to return partially damaged batteries to working condition.

The best manufacturers

Each product has its own characteristics. Therefore, when choosing a specific brand, you must first focus on the number and type of batteries that will have to be charged. If you plan to work with 4 batteries, then you can choose the Rodition Ecocharger model. This small device, capable of regenerating even disposable alkaline batteries. This function is activated using a toggle switch located on the side panel of the case.

The device has four channels and is capable of monitoring the charge level of each element separately. There is a light indication on the device panel showing which battery has already been restored. You can buy such a device for $20.

Watch a video about Rodition Ecocharger products:

One of the most popular and multifunctional is the La Crosse BC-700 lithium battery charger. It is classified as advanced and is designed for the restoration of nickel-based finger mounts in AA and AAA formats. The features of the device are such that it is capable of simultaneously charging 4 batteries of different capacities.

The devices operate in several modes. There is a current regulator that allows you to select the most optimal current value for each case.

Charging stages

Experts recommend starting the process of restoring the battery by completely discharging it. If for some reason you have to charge a battery that is not yet completely discharged, then you should choose an advanced model of the device.

I made myself a charger for four lithium-ion batteries. Someone will now think: well, he did it and did it, there are plenty of them on the Internet. And I want to say right away that my design is capable of charging either one battery or four at once. All batteries are charged independently of each other.
This makes it possible to simultaneously charge batteries from different devices and with different initial charges.
I made a charger for 18650 batteries, which I use in a flashlight, powerbanks, laptop, etc.
The circuit consists of ready-made modules and is assembled very quickly and simply.

Will need

• - 4 things.
• - 4 things.
• Paper clips.

Manufacturing a charger for different numbers of batteries

First we'll make the battery compartment. To do this, take a universal circuit board with big amount holes and regular paper clips.

We bite off these corners from the paper clips.

We insert it into the board, having previously tried on the length of the batteries you need. Because such a charger can be made not only for 18650 batteries.

We solder parts of the paper clips to the bottom of the board.

Then we take the charging controllers and place them on the remaining space on the board, preferably opposite each battery.

The charging controller will be mounted on these legs, made from a PLS connector.

Solder the module on top and to the board below. These legs will carry the power current to the module and the charging current to the batteries.

Four sections are ready.

Next, to switch charging points, we will install buttons or toggle switches.

The whole thing connects like this:

You may ask - why are there only three buttons and not four? And I will answer - since one module will always work, because one battery will always be charged, otherwise there is no point in plugging in a charger at all.
We solder the conductive tracks.

The result is that with buttons you can connect a place to charge from 1 to 4 batteries.

An LED is installed on the charge module, which indicates that the battery that is being charged from it is charged or not.
I assembled the entire device in half an hour. It is powered by a 5-volt power supply (adapter), which, by the way, also needs to be chosen wisely so that it charges all four batteries at once. The entire circuit can also be powered from a USB computer.
We connect the adapter to the first module, and then turn on the necessary buttons and the voltage from the first module will go to other places, depending on the switches that are turned on.

Lithium batteries (Li-Io, Li-Po) are the most popular on this moment rechargeable sources of electrical energy. The lithium battery has a nominal voltage of 3.7 Volts, which is indicated on the case. However, a 100% charged battery has a voltage of 4.2 V, and a discharged one “to zero” has a voltage of 2.5 V. There is no point in discharging the battery below 3 V, firstly, it will deteriorate, and secondly, in the range from 3 to 2.5 It only supplies a couple of percent of energy to the battery. Thus, the operating voltage range is 3 – 4.2 Volts. You can watch my selection of tips for using and storing lithium batteries in this video

There are two options for connecting batteries, series and parallel.

With a series connection, the voltage on all batteries is summed up, when a load is connected, a current flows from each battery equal to the total current in the circuit; in general, the load resistance sets the discharge current. You should remember this from school. Now comes the fun part, capacity. The capacity of the assembly with this connection is fairly equal to the capacity of the battery with the smallest capacity. Let's imagine that all batteries are 100% charged. Look, the discharge current is the same everywhere, and the battery with the smallest capacity will be discharged first, this is at least logical. And as soon as it is discharged, it will no longer be possible to load this assembly. Yes, the remaining batteries are still charged. But if we continue to remove current, our weak battery will begin to overdischarge and fail. That is, it is correct to assume that the capacity of a series-connected assembly is equal to the capacity of the smallest or most discharged battery. From here we conclude: to assemble a series battery, firstly, you need to use batteries of equal capacity, and secondly, before assembly, they all must be charged equally, in other words, 100%. There is such a thing called BMS (Battery Monitoring System), it can monitor each battery in the battery, and as soon as one of them is discharged, it disconnects the entire battery from the load, this will be discussed below. Now as for charging such a battery. It must be charged with a voltage equal to the sum of the maximum voltages on all batteries. For lithium it is 4.2 volts. That is, we charge a battery of three with a voltage of 12.6 V. See what happens if the batteries are not the same. The battery with the smallest capacity will charge the fastest. But the rest have not yet charged. And our poor battery will fry and recharge until the rest are charged. Let me remind you that lithium also does not like overdischarge very much and deteriorates. To avoid this, recall the previous conclusion.

Let's move on to parallel connection. The capacity of such a battery is equal to the sum of the capacities of all batteries included in it. The discharge current for each cell is equal to the total load current divided by the number of cells. That is, the more Akum in such an assembly, the more current it can deliver. But what happens with tension? interesting thing. If we collect batteries that have different voltages, that is, roughly speaking, charged to different percentages, then after connecting they will begin to exchange energy until the voltage on all cells becomes the same. We conclude: before assembly, the batteries must again be charged equally, otherwise large currents will flow during connection, and the discharged battery will be damaged, and most likely may even catch fire. During the discharge process, the batteries also exchange energy, that is, if one of the cans has a lower capacity, the others will not allow it to discharge faster than themselves, that is, in a parallel assembly you can use batteries with different capacities. The only exception is operation at high currents. On different batteries under load, the voltage drops differently, and current will start flowing between the “strong” and “weak” batteries, and we don’t need this at all. And the same goes for charging. You can absolutely safely charge batteries of different capacities in parallel, that is, balancing is not needed, the assembly will balance itself.

In both cases considered, the charging current and discharge current must be observed. The charging current for Li-Io should not exceed half the battery capacity in amperes (1000 mah battery - charge 0.5 A, 2 Ah battery, charge 1 A). The maximum discharge current is usually indicated in the datasheet (TTX) of the battery. For example: 18650 laptops and smartphone batteries cannot be loaded with a current exceeding 2 battery capacities in Amperes (example: a 2500 mah battery, which means the maximum you need to take from it is 2.5 * 2 = 5 Amps). But there are high-current batteries, where the discharge current is clearly indicated in the characteristics.

Features of charging batteries using Chinese modules

Standard purchased charging and protection module for 20 rubles for lithium battery ( link to Aliexpress)
(positioned by the seller as a module for one 18650 can) can and will charge any lithium battery, regardless of shape, size and capacity to the correct voltage of 4.2 volts (the voltage of a fully charged battery, to capacity). Even if it is a huge 8000mah lithium package (of course we are talking about one 3.6-3.7v cell). The module provides a charging current of 1 ampere, this means that they can safely charge any battery with a capacity of 2000mAh and above (2Ah, which means the charging current is half the capacity, 1A) and, accordingly, the charging time in hours will be equal to the battery capacity in amperes (in fact, a little more, one and a half to two hours for every 1000mah). By the way, the battery can be connected to the load while charging.

Important! If you want to charge a smaller capacity battery (for example, one old 900mAh can or a tiny 230mAh lithium pack), then the charging current of 1A is too much and should be reduced. This is done by replacing resistor R3 on the module according to the attached table. The resistor is not necessarily smd, the most ordinary one will do. Let me remind you that the charging current should be half the battery capacity (or less, no big deal).

But if the seller says that this module is for one 18650 can, can it charge two cans? Or three? What if you need to assemble a capacious power bank from several batteries?
CAN! All lithium batteries can be connected in parallel (all pluses to pluses, all minuses to minuses) REGARDLESS OF CAPACITY. Batteries soldered in parallel maintain an operating voltage of 4.2v and their capacity is added up. Even if you take one can at 3400mah and the second at 900, you will get 4300. The batteries will work as one unit and will discharge in proportion to their capacity.
The voltage in a PARALLEL assembly is ALWAYS THE SAME ON ALL BATTERIES! And not a single battery can physically discharge in the assembly before the others; the principle of communicating vessels works here. Those who claim the opposite and say that batteries with a lower capacity will discharge faster and die are confused with SERIAL assembly, spit in their faces.
Important! Before connecting to each other, all batteries must have approximately the same voltage, so that at the time of soldering, equalizing currents do not flow between them; they can be very large. Therefore, it is best to simply charge each battery separately before assembly. Of course, the charging time of the entire assembly will increase, since you are using the same 1A module. But you can parallel two modules, obtaining a charging current of up to 2A (if your charger can provide that much). To do this, you need to connect all similar terminals of the modules with jumpers (except for Out- and B+, they are duplicated on the boards with other nickels and will already be connected anyway). Or you can buy a module ( link to Aliexpress), on which the microcircuits are already in parallel. This module is capable of charging with a current of 3 Amps.

Sorry for the obvious stuff, but people still get confused, so we'll have to discuss the difference between parallel and serial connections.
PARALLEL connection (all pluses to pluses, all minuses to minuses) maintains the battery voltage of 4.2 volts, but increases the capacity by adding all the capacities together. All power banks use parallel connection of several batteries. Such an assembly can still be charged from USB and the voltage is raised to an output of 5v by a boost converter.
CONSISTENT connection (each plus to minus of the subsequent battery) gives a multiple increase in the voltage of one charged bank 4.2V (2s - 8.4V, 3s - 12.6V and so on), but the capacity remains the same. If three 2000mah batteries are used, then the assembly capacity is 2000mah.
Important! It is believed that for sequential assembly it is strictly necessary to use only batteries of the same capacity. Actually this is not true. You can use different ones, but then the battery capacity will be determined by the SMALLEST capacity in the assembly. Add 3000+3000+800 and you get an 800mah assembly. Then the specialists begin to crow that the less capacious battery will then discharge faster and die. But it doesn’t matter! The main and truly sacred rule is that for sequential assembly it is always necessary to use a BMS protection board for the required number of cans. It will detect the voltage on each cell and turn off the entire assembly if one discharges first. In the case of an 800 bank, it will discharge, the BMS will disconnect the load from the battery, the discharge will stop and residual charge 2200mah on other banks will no longer matter - you need to charge.

The BMS board, unlike a single charging module, IS NOT A sequential charger. Needed for charging configured source of the required voltage and current. Guyver made a video about this, so don’t waste your time, watch it, it’s about this in as much detail as possible.

Is it possible to charge a daisy chain assembly by connecting several single charging modules?
In fact, under certain assumptions, it is possible. For some homemade products, a scheme using single modules, also connected in series, has proven itself, but EACH module needs its own SEPARATE POWER SOURCE. If you charge 3s, take three phone chargers and connect each to one module. When using one source - short circuit on nutrition, nothing works. This system also works as protection for the assembly (but the modules are capable of delivering no more than 3 amperes). Or, simply charge the assembly one by one, connecting the module to each battery until fully charged.

Battery charge indicator

Another pressing problem is to at least know approximately how much charge remains on the battery so that it does not run out at the most critical moment.
For parallel 4.2-volt assemblies, the most obvious solution would be to immediately purchase a ready-made power bank board, which already has a display showing charge percentages. These percentages aren't super accurate, but they still help. The issue price is approximately 150-200 rubles, all are presented on the Guyver website. Even if you are not building a power bank but something else, this board is quite cheap and small to fit into a homemade product. Plus, it already has the function of charging and protecting batteries.
There are ready-made miniature indicators for one or several cans, 90-100 rubles
Well, the cheapest and most popular method is to use an MT3608 boost converter (30 rubles), set to 5-5.1v. Actually, if you make a power bank using any 5-volt converter, then you don’t even need to buy anything additional. The modification consists of installing a red or green LED (other colors will work at a different output voltage, from 6V and higher) through a 200-500 ohm current-limiting resistor between the output positive terminal (this will be a plus) and the input positive terminal (for an LED this will be a minus). You read that right, between two pluses! The fact is that when the converter operates, a voltage difference is created between the pluses; +4.2 and +5V give each other a voltage of 0.8V. When the battery is discharged, its voltage will drop, but the output from the converter is always stable, which means the difference will increase. And when the voltage on the bank is 3.2-3.4V, the difference will reach the required value to light the LED - it begins to show that it is time to charge.

How to measure battery capacity?

We are already accustomed to the idea that for measurements you need an Imax b6, but it costs money and is redundant for most radio amateurs. But there is a way to measure the capacity of a 1-2-3 can battery with sufficient accuracy and cheaply - a simple USB tester.