Li-ion batteries of the 18650 type of various capacities are now very widespread. With their acquisition, the problem of charging arises and must comply with the technical requirements for the charging process. Here are some of these requirements:
- charging with stable current;
- voltage stabilization mode;
- indication of the end of charging;
- not exceeding the permissible temperature during battery charging.
We present to your attention a Li-charger circuit that is easy to manufacture and set up. ion batteries, which has proven itself in work.
The circuit is a current and voltage stabilizer. Until the voltage on the battery during charging reaches the level Ustabil.=(R7/R5+1)*Uref (Uref-reference voltage TL431=2.5V), TL431 is in the closed state, and the circuit works as a current stabilizer. Ist.=0.6/R2 (0.6 is the opening voltage of the KT816V transistor). As soon as the voltage on the battery reaches Ustabil., the circuit goes into voltage stabilization mode. For a Li-ion battery, this value is 4.2V. When the battery voltage reaches 4.2V, the yellow LED starts to light up, indicating that the battery is 80-90% charged. The charging current decreases to 7...8mA. Leave the battery in this state for 10-15 hours until it reaches its full capacity.
A little about the purpose of the circuit elements.
LED1 - blue, lights up when the battery (AC) is installed in the charging box and the charger power is not connected. When the voltage across the battery is less than 3V, LED1 does not light up.
LED2 - yellow. Serves to indicate the end of the battery charging process. When an uncharged AK is placed in the box, LED2 does not light up. If it lights up, then this indicates that a charged AK is inserted into the box (with the charger power not connected).
R2 - limits the charging current of the AK.
R5, R7 - serve to set the voltage to 4.2V on the contacts of the charging box before installing the battery in it (any one can be used).
All charger parts, except the transistor, are installed on the printed circuit board on the side of the printed conductors:
Board option for those who are not lazy to drill holes in fiberglass:
The transistor is equipped with a small heatsink. During charging, the transistor heats up to 40°C. Resistor R2 also heats up, so it is better to install two 10 Ohm resistors in parallel to reduce heating.
The power supply voltage for charging one battery is approximately 5V DC. If it is necessary to charge several batteries at once, the power supply voltage is selected so that it is 4.2V on each unit. The power of the power supply is selected from the charging current for each battery. You can use a switching power supply. The dimensions of the charger will be smaller.
The process of setting up the charger is simple. Without inserting the battery, we supply power to the circuit. Both LEDs should light up. Next, we measure the voltage at the contacts of the charging box. If it is 4.2V, you are in luck and the setup is almost complete. If the voltage is more or less than 4.2V, turn off the power, instead of resistor R5 or R7, solder in a variable multi-turn resistor 10k and precisely set the voltage to 4.2V on the contacts of the box. Having measured the value of the resulting resistance of the adjustable resistor, we select the same constant and solder it into the circuit. Once again, check the voltage at the contacts of the charging box. We check the amount of charging current with an ammeter at the contacts of the charging box without inserting the battery. By selecting the value of resistor R2, you can set the desired charging current. We don’t get carried away with high currents; the battery may heat up, which is absolutely unacceptable. Overheating causes the capacity of Li-ion batteries to decrease and not be restored.
It is best to charge batteries one at a time. If you need to charge several batteries simultaneously, you can connect the blocks in series according to this scheme.
In this scheme, each battery is charged separately. The voltage at the end of charging on each battery will be 4.2V, and the charging current will be 0.5A. When charging, for example, seven batteries simultaneously, the power source voltage should be 4.2V*7=29.5V. The power of the power source is determined by the charging current of 0.5A for each battery, i.e. approximately 40W.
Photo of the finished device.
Modern electronic devices(such as cell phones, laptops or tablets) are powered by lithium-ion batteries, which have replaced their alkaline counterparts. 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 of Li-ion batteries recommend using only original chargers for charging, which are guaranteed to give 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 it is necessary to charge lithium-ion batteries that 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 in the presence of constant 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
Charger for lithium-ion batteries is inexpensive, but if you have a little knowledge of electronics, you can make it 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 a more complex circuit and more technical skills will be required.
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
Lithium-ion batteries are very popular nowadays; they are used in various gadgets, such as phones, smart watch, players, flashlights, laptops. For the first time, a battery of this type (Li-ion) was produced by the famous Japanese company Sony. Schematic diagram The simplest battery is shown in the picture below; by assembling it, you will have the opportunity to restore the charge in the batteries yourself.
Homemade lithium battery charging - electrical diagram
The basis for this device are two stabilizer microcircuits 317 and 431 (). Integral stabilizer LM317 in this case serves as a current source, we take this part in the TO-220 housing and be sure to install it on the heat sink using thermal paste. The TL431 voltage regulator manufactured by Texas Instruments is also available in SOT-89, TO-92, SOP-8, SOT-23, SOT-25 and other packages.
Light emitting diodes (LED) D1 and D2 of any color you like. I chose the following: LED1 red rectangular 2.5 mm (2.5 milCandelas) and LED2 green diffusion 3 mm (40-80 milCandelas). It is convenient to use SMD LEDs if you do not install the finished board in the case.
The minimum power of resistor R2 (22 Ohm) is 2 Watts, and R5 (11 Ohm) is 1 Watt. All other ones are 0.125-0.25W.
The 22 kiloOhm variable resistor must be of type SP5-2 (imported 3296W). Such variable resistors have very precise resistance adjustment, which can be smoothly adjusted by twisting a worm pair similar to a bronze bolt.
Photo of measuring the voltage of a li-ion battery from cell phone before charging (3.7V) and after (4.2V), capacity 1100 mA*h.
PCB for lithium charger
Printed circuit board (PCB) comes in two formats for different programs- the archive is located. The dimensions of the finished printed circuit board in my case are 5 by 2.5 cm. I left space on the sides for fastenings.
How does charging work?
How does the finished circuit of such a charger work? First, the battery is charged with a constant current, which is determined by the resistance of resistor R5; with a standard rating of 11 ohms, it will be approximately 100 mA. Further, when the rechargeable energy source has a voltage of 4.15-4.2 volts, charging with constant voltage will begin. When the charging current drops to small values, LED D1 will stop lighting.
As you know, the standard voltage for charging Li-ion is 4.2V; this figure must be set at the output of the circuit without load, using a voltmeter, so the battery will be fully charged. If you reduce the voltage a little, by about 0.05-0.10 Volts, then your battery will not be fully charged, but this way it will last longer. Author of the article EGOR.
Discuss the article CHARGING LITHIUM BATTERIES
Last time I considered the issue of replacing nickel-cadmium NiCd screwdriver batteries with lithium-ion ones. Now the only question left is charging these batteries. Li-ion 18650 batteries can typically be charged to 4.20 volts per cell with a tolerance of no more than 50 millivolts because increasing the voltage can damage the battery structure. The battery charge current can range from 0.1C to 1C (C is the battery capacity). It is better to select this value according to the datasheet for a specific battery. I used batteries in remaking a screwdriver Samsung brands INR18650-30Q 3000mAh 15A. We look at the datasheet - charging current -1.5A. 
The most correct way would be to charge lithium batteries in two stages using the CC/CV method (constant current, constant voltage- D.C., constant pressure). The first stage is to ensure a constant charging current. The current value is 0.2-0.5C. For a battery with a capacity of 3000 mAh, the nominal charge current in the first stage is 600-1500 mA. The second stage is charging the battery with a constant voltage, the current is constantly decreasing. The battery voltage is maintained within 4.15-4.25 V. The charging process will be completed when the current drops to 0.05-0.01C.
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.
Taking into account the above, I used ready-made electronic modules from Aliexpress. Step-down CC/CV board with current limiting on the XL4015E1 chip or on the LM2596. The XL4015E1 board is preferable as it is more convenient to configure. 
Characteristics of the board based on XL4015E1.
Maximum output current up to 5 Amperes.
Output voltage: 0.8V-30V.
Input voltage: 5V-32V.
The board based on LM2596 has similar parameters, only the current is slightly less - up to 3 Amperes.
The board for controlling the charge of the lithium-ion battery was selected earlier. As a power source, you can use any one with the following parameters - output voltage not lower than 18 Volts (for the 4S circuit), current not lower than 2-3 Amperes. As a first example of building a charger for lithium-ion screwdriver batteries, I used a 220\12 Volt, 3 Ampere adapter. 
First, I checked what current it can produce at the rated load. I connected a car lamp to the output and waited half an hour. Produces freely without overload 1.9 Amperes. I also measured the temperature on the transistor heatsink - 40 degrees Celsius. Quite good - normal mode. 
But in this case there is not enough tension. This can be easily fixed using just one cheap radio component - a variable resistor (potentiometer) of 10-20 kOhm. Let's look at a typical adapter circuit. 
In the diagram there is a controlled zener diode TL431, it is located in the circuit feedback. Its task is to maintain a stable output voltage in accordance with the load. Through a divider of two resistors, it is connected to the positive output of the adapter. We need to solder to the resistor (or unsolder it completely and solder it in its place, then the voltage will be regulated downwards) which is connected to pin 1 of the TL431 zener diode and to the negative bus a variable resistor. Rotate the potentiometer axis and set the desired voltage. In my case, I set it to 18 Volts (a small margin from 16.8 V for the drop on the CCCV board). If the voltage indicated on the housings of the electrolytic capacitors located at the output of the circuit is greater than the new voltage, they may explode. Then you need to replace them with a 30% voltage reserve.
Next, we connect the charge control board to the adapter. We set the voltage on the board to 16.8 Volts using the trimmer resistor. Using another trimming resistor, we set the current to 1.5 Amperes, and first connect the tester in ammeter mode to the output of the board. Now you can connect the lithium-ion screwdriver assembly. Charging went well, the current dropped to a minimum at the end of the charge, and the battery was charged. The temperature on the adapter was between 40-43 degrees Celsius, which is quite normal. In the future, you can drill holes in the adapter body to improve ventilation (especially in the summer).
The end of the battery charge can be seen by the LED on the board on the XL4015E1 turning on. In this example, I used another LM2596 board in the same way that I accidentally burned the XL4015E1 during experiments. I advise you to do better charging on the XL4015E1 board.
I also have a standard charger from another screwdriver. It is designed to charge nickel-cadmium batteries. I wanted to use this standard charger to charge both nickel-cadmium and lithium-ion batteries. 
This was solved simply - I soldered the wires to the CCCV board to the output wires (red plus, black minus).
The idle voltage at the output of the standard charger was 27 Volts, this is quite suitable for our charging board. Then I connected it in the same way as in the version with the adapter. 
We can see the end of charging here by the change in the color of the LED (switched from red to green).
I placed the CCCV board itself in a suitable plastic box, bringing the wires out. 
If you have a standard charger on a transformer, then you can connect the CCCV board after the diode bridge of the rectifier.
The method of converting the adapter can be done by beginners and can be useful for other purposes; as a result, we get a budget unit for powering various devices.
I wish you all health and success in shopping and life.
You can see the process of working with a charger for a converted screwdriver in more detail in the video
The product was provided for writing a review by the store. The review was published in accordance with clause 18 of the Site Rules.
I'm planning to buy +27 Add to favorites I liked the review +28 +51The first company to launch mass production of a rechargeable lithium ion battery Sony has become a high-capacity battery, while the battery life has become significantly longer than its nickel-cadmium counterpart.
Unfortunately, the first models had a significant drawback, which manifested itself in the fact that at a high discharge current the lithium anode ignited.
It took about 20 years to fix this problem, the solution was a controller that does not allow pure lithium to form on the anode of a lithium-ion battery.
Modern models are reliable and safe; they have gradually replaced nickel-metal hydride and nickel-cadmium models from the market. rechargeable batteries in portable devices, they are installed as a power source for a laptop, camera, mobile phone etc.
The only niche in which lithium-ion batteries are inferior to nickel-cadmium batteries is in devices whose operation requires a high discharge current, for example, for screwdrivers. This type of battery is called industrial.
Separately, it is worth mentioning the Li-Pol elements. The only difference from a lithium polymer battery is that a different electrolyte is used in the base, while the principle of operation, features and characteristics of these types are almost identical.
Peculiarities
Any type of power source has its own advantages and, accordingly, disadvantages; lithium-ion batteries only confirm this axiom. Let us consider in detail their characteristic features.
The advantages undoubtedly include:
- low self-discharge parameters;
- If you take a single cell of a lithium-ion battery, the dimensions of which are equal to batteries of another type, then it will have a larger charge (3.7V, as opposed to 1.2V). Thanks to this, it became possible to significantly simplify and lighten the battery;
- There is no such parameter as power memory, that is, the battery does not require regular discharge to restore power (capacity), which simplifies operation.
Speaking about the advantages that this battery cell has, certain disadvantages cannot be ignored, which include:
- built-in “fuse”, that is, a protection board whose task is to limit the supply voltage during charging and prevent the battery from being completely discharged; in addition, the maximum current is smoothed out, and the temperature is also controlled. Because of this, the price of lithium-ion batteries is higher than that of analogues;
- Despite the remanufacturing of lithium-ion batteries, they are subject to “aging”, even if they are stored in accordance with the operating rules. How to slow down this process will be discussed below, where operation and its features will be discussed.
Video: review, opening of a lithium-ion battery from a mobile phone
Form factor
Lithium ion batteries are available in two form factors - cylindrical and tablet.
Many devices use several lithium-ion batteries connected together, for example, to achieve a voltage of 12V or to increase the discharge current, this must be taken into account if you want to buy such a device (usually the type of connection is indicated on the case).
How to charge correctly
There are rules that can significantly extend the life of lithium-ion batteries.
Rule one: you should not allow a complete discharge, thanks to this you can increase the number of cycles during which charging and discharging occurs. By charging the battery by 20%, you can significantly extend its service life, at least twice. As an example, we give a table of the dependence of recharging cycles, depending on the depth of battery discharge.
Rule two: once every three months it is necessary to carry out a full cycle (that is, completely discharge and charge), thanks to this the process of “aging” of the batteries slows down significantly.
Rule three: you cannot store a lithium-ion battery completely discharged; it is advisable that the battery be charged 30-50%, otherwise restoring its capacity is not possible.
Rule four: to charge the battery, use the original charger that came with the manufacturer; this is required by the difference in the design of the battery protection circuit. That is, for example, batteries HTC, En-El, Sanyo, IRC, ICR, Lir, Mah, Pocket, ID-Security, etc. It is not advisable to charge with a device for Samsung batteries.
Rule five: do not allow the battery to overheat, operate lithium ion device possible at ambient temperatures ranging from -40 to 50 °C. If the temperature conditions It is not possible to restore the battery or repair it; it will only need to be replaced.
Separately, it is necessary to emphasize that rechargeable batteries famous brands significantly superior in characteristics to analogues from unknown manufacturers. You can rest assured that DMW-BCG, VPG-BPS, SAFT batteries, as well as original models, for example, BL-5C, BP-4L (Nokia), D-Li8, NB-10L (Canon), NP-BG1 (Sony ) or LP243454-PCB-LD will definitely be better than their Chinese counterparts.
Homemade charger
If you wish, you can make a device with your own hands that will serve to charge lithium-ion batteries; its diagram is shown below.
Designations in the figure:
- R1- 22Ohm;
- R2 – 5.1 kOhm;
- R3- 2kOhm;
- R4 -11Ohm;
- R5 – 1kOhm;
- RV1 – 22 kOhm;
- R7 – 1kOhm;
- U1 – stabilizer LM317T (must be installed on a radiator with a large dispersion area);
- U2 – TL431 (voltage regulator);
- D1, D2 – LEDs, you can use smd type, the first one, signaling the start of the charging process, it is advisable to select red, the second – green;
- transistor Q1 – BC557;
- capacitors C1, C2 – 100n.
The input voltage to the lithium-ion battery charging circuit should be from 9 to 20V; it can be altered for this purpose pulse block nutrition. The resistor power must be selected as follows:
- R1 – minimum 2W;
- R5 – 1W
- the rest are no less than 0.125W.
It is advisable to take CG5-2 or its imported analogue 3296W as a variable resistor RV1. This type allows you to more accurately set the output voltage, which should be about 4.2V.
The principle by which the charging circuit works is as follows:
When turned on charging in progress batteries, the current value depends on resistor R5 (in our case it will be at the level of 100 mA), the charging voltage ranges from 4.15 to 4.2 V, the start of the process will be signaled by diode D1. When the battery approaches the charging threshold, the load current will decrease, causing LED D1 to turn off and D2 to turn on.
Note that by reducing the voltage by approximately 0.05-0.1V, you can significantly increase the life of the battery, since it will not be fully charged.
The contacts for the charging unit, through which the battery will be connected, can be taken from a broken device; do not forget to clean them before doing this.
It is necessary to note that when incorrect setting, for example, excessive voltage or charging current, can damage the battery.
The production of a charger is much cheaper than the price of a lithium-ion battery, be it in Moscow or St. Petersburg, so saving (considering how their sales are developed) at the risk of damaging the battery using a homemade device does not make sense.