DIY charger for 18650 batteries. How to design a charger for lithium-ion batteries at home. Precautions: overcharging is prohibited
Hi all! I want to tell you a little about Li- ion battery x 18650. Various wireless devices: portable and easy-to-use cordless drills, laptops that allow you to work for a long time without using electrical network. All this makes our daily life more convenient and easier. But a special place is occupied by the use of autonomous battery devices not near the house, where you can always charge the device, but far from power sources.
On a camping trip, hunting or fishing, the most necessary, and sometimes irreplaceable, electrical device is a flashlight. Modern flashlights equipped with LEDs have a huge number of advantages. But the main characteristic of any electric flashlight, of course, is the duration of its operation. For tourists who go on multi-day trips, it is the duration of the flashlight that is of great importance when choosing. And this characteristic directly depends on the type of battery that comes with the flashlight.
The compactness and lightness of equipment plays an important role for any tourist. That's why important characteristic for batteries are size and weight - the smaller the better. In this case, the batteries must have large capacity, which will ensure long and uninterrupted operation of the flashlight, often the main source of light in the dark. Modern technologies allow you to combine small size and weight with high battery capacity.
One of the most common batteries for LED flashlights are 18650 batteries. These compact batteries with a relatively large capacity are best suited for modern light sources, often used by tourists, fishermen and hunters.
A little theory about 18650 lithium batteries
The name itself indicates the dimensions of the battery - 18 millimeters in diameter, 65 millimeters in length. Despite the fact that they look similar in appearance to the AA-size batteries that many are familiar with (the so-called “pen-type” batteries), 18650 batteries are larger in size. Besides, distinctive feature 18650 batteries - the output voltage is 3.7 V, versus 1.5 V for batteries smaller size. The capacity of 18650 batteries varies: from 1600 to 3600 mAh. It is necessary to pay attention to the fact that the capacity of a high-quality battery cannot exceed 3600 mAh. Batteries can be used in flashlights either individually or in a system Power Bank– a device that combines several identical batteries.
One of the main qualities and advantages of batteries is the absence of memory effect and extremely low level of self-discharge. 18650 batteries can withstand up to 1000 charge/discharge cycles, which is a very good indicator for portable batteries. The battery charge life is gradually decreasing, but with the help of special technical devices The capacity can be restored; the only condition for restoration is the absence of mechanical damage to the battery.
It must be taken into account that in order to use the battery resource more rationally, you should not completely discharge it. It is optimal to recharge the battery when the capacity is reduced to 40% of the nominal value. If used properly, the battery will serve reliably for a long time. Despite their many advantages, 18650 batteries have one drawback associated with their design. Batteries often fail quickly if they are overcharged or overheated. Overcharging causes the battery to heat up, causing the battery to catch fire or explode. Manufacturers have provided an option to protect batteries from overheating. When using 18650 batteries in a Power Bank, when connected in series, an electronic board is installed in the circuit, which limits the charge of the entire device to a given capacity.
For 18650 batteries, used, for example, in flashlights, an individual system of protection against overcharging and subsequent overheating is used. The protection is a small electronic protective board that is installed on the negative terminal of an unprotected lithium-ion battery and welded to the case with steel tape. This prevents not only overheating, but also short circuit, which can damage not only the battery, but also the charger. The entire structure is packed in thermal film. To charge 18650 batteries, you will need a special charger that is suitable for all types of batteries of this size. For example, the ARE-X1 Fenix Charger, the i1 NiteCore Charger, or the Robiton SmartCharger Pro Charger.
This video tutorial shows how to charge the popular 18650 lithium-ion batteries; many people use similar ones. The video of the channel “Reviews of parcels and homemade products from jakson” about how to make it yourself for just half a dollar is at the bottom of the article.
The topic is relevant, for example, a flashlight that does not have a built-in function for charging such batteries; it cannot do without a homemade charger.
In China, the cheapest ones cost from $3 or more. You can buy it in this Chinese store.
The only thing to buy is inexpensive modules for charging lithium batteries; they are capable of charging those used in radio-controlled equipment and are inexpensive. It would be possible to make a similar module yourself, but there is no point in doing so; it will most likely cost more. Modules are sold cheaply in this Chinese store.
In order for 18650 batteries to charge independently of each other, since they have different capacities, we will use two modules.
In fact, there is nothing tricky about these modules, at the input there is a mini usb connector for powering the module, at the output there are two contacts: positive and negative for connecting the battery, there are also two LEDs - charging indicators, one shows the charging percentage, the second indicates that the battery is already charged.
The only task that you have to do with your own hands is to make a housing for the charger - for this we will use fiberboard scraps, they are easy to process.
To cut them without dust and shavings, we use a scalpel; another sharp cutting tool, for example, a construction stationery knife, will do.
The structure of the material is quite soft, more reminiscent of cardboard than some kind of wood.
In general, I cut the fiberboard using a scalpel, it took about 10 minutes, but it didn’t turn out neatly, since the blade sometimes jumped off. The edges where the cut was made are not straight, they are at an angle, but this is not critical, since hot-melt adhesive will be poured into these places, which will be used to fasten the structure. And on the edges you can work with sandpaper, which will smooth out all the flaws.
The charger body will be assembled.
From this side we will bring out one mini usb connector, from it the second module, since there is no point in making two holes in the case.
We will also make recesses on the side walls of the homemade charger to remove the batteries.
I prepared all the parts of the body, made holes in them, and fastened them with hot glue.
The case for the charger is almost ready, it’s time to move on to the filling, hot-melt adhesive is good for fastening fiberboard, it grabs almost immediately, unlike PVA glue, you practically don’t have to wait when gluing, and it’s also easy to get rid of it with a scalpel.
We use pieces of foil PCB as contact pads that will come into contact with 18650 batteries. Let's tin them, it will be easy to solder wires to them.
The two modules need to be connected to each other, since we will use only one mini usb; to do this, we simply solder the power contacts at the input to each other, minus to minus, plus to plus.
And this is what should happen in the end: we connected the incoming power contacts to each other.
Continued from 5 minutes about a device for regularly replenishing the charge of lithium-ion batteries type 18650
There is a related topic.
Modern Li-ion batteries have high weight and dimensions and have good energy capacity. On this moment These are the most efficient portable power sources capable of powering high power devices. These batteries appeared to me after my laptop broke down, namely, I removed them from battery, and the question arose, how to charge these batteries? As always, I didn’t want to buy a specialized charger, so I decided to start assembling a charger for Li-ion batteries. The figure below shows circuit diagram charger, this circuit is highly repeatable and reliable, the parts are easily accessible, and most importantly inexpensive.
In order for Li-ion batteries to serve for a long time, they must be charged correctly. Towards the end of charging, the voltage should decrease, and when the battery is charged, i.e. The charging current will become almost zero, charging should stop. This scheme fully satisfies these requirements. The discharged battery connected to it is charged with a current of ~300 mA, towards the end of the charge the current decreases to 30 mA and then the VD2 LED lights up, which signals the completion of charging.
LED VD1 signals the operation of the device, VD3 lights up when the battery is connected.
The circuit uses an operational amplifier LM358N, its analogue is KR1040UD1. But if you don’t have either one or the other at hand, you can replace it with the KR574UD2, only the location of its pins is different. Transistor VT1 S8550 or any other suitable parameters. LEDs for voltage 1.5 volts, red, green and yellow. The circuit does not require any adjustment after assembly and starts working immediately. The average charging time for a 18650 battery with a capacity of 2200 mAh is 2 hours.
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| D1 | Operational amplifier | LM358N | 1 | To notepad | ||
| VT1 | Bipolar transistor | S8550 | 1 | To notepad | ||
| VD1-VD3 | Light-emitting diode | 3 | To notepad | |||
| C1 | Capacitor | 0.068 µF | 1 | To notepad | ||
| C2 | electrolytic capacitor | 220uF 10V | 1 | To notepad | ||
| R1 | Resistor | 3.6 kOhm | 1 | To notepad | ||
| R2 | Resistor | 1 kOhm | 1 | To notepad | ||
| R3 | Resistor | 470 Ohm | 1 | To notepad | ||
| R4 | Resistor | 4.7 kOhm | 1 | To notepad | ||
| R5 | Resistor | 2.2 kOhm | 1 | To notepad | ||
| R6 | Resistor | 220 Ohm | 1 | To notepad | ||
| R7 | Resistor | 1 ohm | 1 | To notepad | ||
| R8 | Resistor | 2.7 kOhm | 1 | To notepad | ||
| R9 | Resistor | 12 kOhm | 1 | To notepad | ||
| R10 | Resistor | 680 kOhm | 1 |
18650 Li-ion batteries are very widely used in many electronic devices that we use today. For example, LED lights, laptop batteries, electric bicycles or Power Bank.
These batteries are a reliable source of power, so they are also very convenient to use in DIY projects. The shape of 18650 lithium-ion batteries resembles a AA battery, but the output voltage is 3.7 V with a capacity of 1600 to 3600 mAh (AA or AAA batteries have a voltage of 1.5 V/1.2 V).
However, at the moment, charging these batteries is still not an easy matter as commercial chargers are quite expensive. In addition, lithium-ion batteries require a charger good quality, otherwise the battery life will deteriorate. A balanced charger works well, but it is available at a higher price range.
So in this tutorial we decided to make a Li-Ion charger that can charge four 18650s at the same time. This charger is very easy to make and does the job of a balanced charger by cutting off power to individual batteries once fully charged.
Step 1: Accessories
We will need several "spare parts" for our charger:
- general purpose printed circuit board
- module TP4056
- paper clips
- connector
- PCB switches
- 3.7V Li-Ion batteries
- Soldering iron
You can buy all this in different stores, especially in foreign ones, for example, Amazon or E-bay.
Step 2: Let's start collecting
- Take printed circuit board general purpose and place the batteries on top of the board;
- Mark the distance between the edges of the batteries and their width on the circuit board;
- Unfold 8 paper clips and use pliers to cut clips from the edges as seen in the image above;
- A total of 8 U-clamps must be made (depending on the number of batteries being charged);
- Insert the U-shaped clamps into the circuit board so that the batteries can be installed between the clamps;
- The clips will act as battery holders;
- Also, use leftover pieces from the paperclips to make side supports;
- Attach the clamps well to the board as shown in the picture.
Note: Make sure the clamps are not connected to each other while soldering.
Step 3: Add Components
- Place the TP4056 charging module on the PCB as shown in the picture above;
- Using a marker, mark the module holes on the board;
- Solder a pin into each of the marked holes;
- Insert the module over the pins and solder carefully;
- Use the number of modules equal to the number of batteries being charged, i.e. one module per battery;
- Solder all modules onto the board as shown in the picture;
- Take the switches and solder them between each module on the PCB.
Note: Be sure to watch the video (below) and look at the images to avoid any mistakes.
Step 4: Connecting the Components
- Refer to the wiring diagram above and solder all components together;
- Be sure to mark the polarity on the U-clip battery holders;
- Connect the terminals of the battery holder to the input terminals of the TP4056 charging module according to the polarity;
- Connect the modules so that they can transfer power from one stationary charger;
- Also, install connections between switches so that they can be used to independently control the power of the modules.
Step 5: Test the charger
- Insert the batteries into the battery holders on the board;
- Connect the charger mobile phone to one of the modules and turn on the power;
- An indicator will light on the module to indicate charging;
- Use switches to control the power supplied to the batteries;
- Turn off all switches if you only want to charge one battery;
- Turn on the switches according to the amount of battery charge at a certain time;
- Because each battery has a separate charger, so they will never face the problem of overcharging and recharging (the most common problem that damages lithium-ion cells).
Note: The TP4056 charging module is capable of providing 1A at 5V. Since we made the charger for 4 batteries, it is necessary to use a 2A mobile charger, such that at least 500mA is supplied to each cell.
Step 6: Video lesson
So, friends, this concludes the lesson. Make it at home and use any number of lithium-ion cells without worrying about charging it.
If you may have missed something, watch the video on how to make this wonderful and very useful charger.
In addition, do not forget to leave your feedback and suggestions in the comments in our VKontakte group. Stay tuned for updates on our lessons.
Today you can see a wide range of different charging systems. Each is intended for a specific device. Charger 18650 is somewhat different from a similar device for charging acid batteries. The 18650 lithium battery has high voltage each jar.
Stores selling electrical equipment offer a huge range of chargers. The cheapest charger for a li ion 18650 battery provides a current of 1 ampere. The device is designed to charge one 18650 battery.
The industry is releasing an improved charging system designed to work with 18650 batteries. You can fit 2-4 cells at once here. The maximum voltage does not exceed 4.2 volts. The device has a high cost, since it is equipped with a charge controller that monitors the charge time and voltage.
For lovers universal devices, charging for such batteries is offered different types. This charger is capable of simultaneously charging nickel as well as 18650 lithium-ion batteries. Most modern chargers are equipped with a safety system that monitors the voltage as well as the charging current. Naturally, the higher the quality of the charger, the higher its cost.
Factory products initially supply a large current, gradually reducing its value. As a result, the product does not overheat, and the service life of the ion battery increases.
To charge four 18650 batteries at the same time, use the Nitecore Digicharger D4 charger. The device is equipped with an informative display showing useful information. The screen will display the charging time, charging speed, and cell voltage. Controlling the device makes it possible to switch between different compartments to read information about each battery being charged. The device belongs to the universal group, so it can charge batteries of various types.
The product automatically sets the charging time and regulates its speed. Unfortunately, the charger is not equipped manual setting, which eliminates fine tuning. The device automatically completes the charging process of any battery.
Nitecore D4 will be the optimal device if there is a need for daily use. This is especially true for people who have several mobile devices with different types of batteries.
Homemade charger
To charge 18650 batteries yourself, it is important to first study how they work electrical circuit, as well as parameters that allow charging the battery. Several methods are known.
The simplest option is to recharge the battery with a charger suitable for Samsung phones. The current and voltage of this charger are suitable for 18650 batteries.
The connection diagram is quite simple. The charger wires are released from the retaining sheath. The negative contact is determined, as well as the positive wire. The plus is always supplied with a red wire, the minus with a black wire. It's impossible to mix it up.
The bare contacts are connected to the battery, observing the polarity. The wires are fixed with ordinary plasticine. All that remains is to apply power and start charging, regularly monitoring the process. Within an hour, the capacity parameters will be completely restored.
Another method is designed to improve charging. But the connection diagram will be more complicated. For work you need:
- soldering iron;
- solder;
- glue;
- flux.
The most important element for home device is considered a charging board. It is sold in online stores. Assembly is performed in a certain sequence. First, prepare a plastic box with wires (plus, minus). The charging board is soldered to it. The battery is inserted into the box, power is supplied, and charging begins. 
To use this option, it is important to select a box (container) whose dimensions correspond to the dimensions of the 18650 battery. The wires must be soldered to places specially marked on the board. To control the amount of charge, the board is equipped with several LED indicators of different shades (red, green).
The board is fixed to the box anywhere, allowing you to see the operation of the indicators. Then the wires are soldered, maintaining the polarity. The ends, before starting soldering, are thoroughly cleaned and then covered with rosin. Liquid flux is dripped onto the surface of the board (2-3 drops).
During soldering, the wires should not contact each other. You can assemble the described circuit yourself very quickly. It is inexpensive, but it is highly reliable and has an excellent charge. After applying voltage, all you have to do is look at the indicator. The green light indicates the battery charge strength.
General charging requirements for 18650 batteries
While charging lithium batteries 18650, the output must have a voltage of 5 V, a current value of 0.5 - 1A (taken from the minimum value of the battery capacity). In other words, a lithium battery with a capacity of 2600 mAh must be charged with a current in the range of 1.32.6 amperes. Manufacturers of chargers for such batteries produce devices that perform this process in several steps.
First, a current of 0.2 A is supplied. Moreover, the voltage of one can reaches 4.1–4.2 volts. This operation takes less than one hour. At the second stage it is fed constant pressure. To reduce charging time, production began to produce a charger with a pulse mode
Some lithium-ion batteries are equipped with a graphite electrode. In order for the charge to proceed normally, it is necessary that a voltage exceeding 4.1 volts be applied to each element. If we take a regular lithium battery, an increase in voltage will lead to an increase in energy density, and at the same time oxidative processes will begin to be active.
As a result, the service life of the lithium battery is sharply reduced. This phenomenon is not observed in batteries equipped with graphite electrodes. Oxidation is reduced by special additives. In other words, increasing the voltage in graphite batteries is not critical, but it is better not to do it.
If you start charging 18650 batteries with a current of 1A, for full charge it will take approximately 2–3 hours. During this time, the voltage will rise to a certain value. During operation, the charger quickly reduces the current by several percent (calculated from the original value). Increasing the charge current (more than 1 ampere) does not have a serious effect on charging time. The second stage of charging usually lasts much longer than at the very beginning.
The industry produces chargers that can fully charge a 18650 lithium battery in approximately one hour. These devices are not able to carry out the second stage; it is completely absent. At the initial stage, the battery is charged approximately 60–80 percent. Then it begins to be used in the device. Such a charge cannot be considered critical for lithium cells. On the contrary, they should not be fully charged, the battery should not be greatly discharged
