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18650 rechargeable batteries do not charge. Charging schemes for li-ion batteries

Review of chargers for 18650 lithium batteries

Modern man is helped by many gadgets. In particular, we use laptops, smartphones, cameras, tablets, etc. Most of these devices run offline on lithium batteries. Batteries make these devices truly mobile. One of the types of lithium batteries is 18650. They look like AA batteries, but they are larger in size. Such battery cells are present in laptop batteries, flashlights, and electronic cigarettes. It was the latter that made this type of battery especially in demand. For those who have such batteries, it is important to know how to charge them correctly. In this article we will talk about chargers (chargers) for 18650 batteries. We will talk about the general requirements for such devices, and also look at several examples of such chargers.

Charging for lithium 18650 batteries should produce an output of 5 V and a current of 0.5 to 1 of the rated capacity of the battery. That is, a lithium cell with a capacity of 2600 mAh must be charged with a current of 1.3-2.6 amperes. Manufacturers of lithium battery chargers make chargers that carry out the process in several stages.

The first stage of charging is carried out with a current of (0.2─1) from the value of the capacitance. In this case, the voltage is maintained at 4.1-4.2 volts (on one bank). This stage lasts a little less than an hour. The second stage takes place at constant voltage. Some manufacturers produce devices that implement pulse mode. This allows for faster charging.

Examples of chargers for 18650 batteries

The Nitecore Digicharger D4 charger is designed to charge a maximum of four batteries. The Nitecore brand has managed to establish itself by producing high-quality devices. D4 only confirms the positive reputation.

The Nitecore D4 charger has a high-quality, informative display that displays a lot of useful data. Here you can see the charging speed and time, cell voltage, and other similar data. Controls allow you to switch between four compartments and view information for all chargeable items. Thanks to this, you can view the status of the batteries at any time. Charging is universal and batteries of different form factors can be inserted into the compartments. Including 18650 format.

The charger sets the charging speed and time automatically. There are advantages to this, but there are also disadvantages. After all, sometimes finer manual adjustments may be required, but here in Nitecore D4 there is none. Features include an optimized method for charging IMR batteries. In addition, it is worth noting that charging is automatically interrupted at the end of the process for all supported battery types. This is a definite plus for this device.

Overall, Nitecore D4 can be recommended for daily use for those who have many mobile devices with different types of batteries. Among them are 18650 lithium batteries. The functionality of the device is quite wide, but for the convenience of beginners, fully automatic operation is provided. A good combination of price, features and build quality.

In general, there can be only two situations:

  1. The battery seems to work, but discharges very quickly.
  2. The battery is dead and doesn't want to charge at all.

First situation: loss of capacity

In the first case, the battery capacity has dropped and you will have to come to terms with it. Complete restoration of batteries after a deep discharge is impossible (this applies to all Li-ion batteries: 18650, 14500, 10440, mobile phone batteries, etc.). Even theoretically, it is impossible to restore the capacity of a lithium battery.

A decrease in capacity is an absolutely normal process. This happens during every charge/discharge cycle, no matter how properly the battery is used. However, if during operation deep discharges are often allowed or, conversely, long-term recharges (more than 500%), then the rate of capacity loss can increase significantly.

Recent studies have shown that lithium batteries lose their capacity even if they are not used at all. For example, during normal storage in warehouses. According to research, the battery loses approximately 4-5% of its capacity per year.

Second situation: does not want to charge

Now consider the second case - the battery is not charging.

This situation usually occurs when a device (phone, tablet, MP3 player) has been left idle for a long time with a discharged battery. Or if the lithium battery has been subjected to deep cooling.

In principle, there should be no problems with charging such batteries. Inside each battery - between the battery bank itself and the terminals that we see - there is a protection module that disconnects the battery from the terminals when the voltage drops below a certain threshold. Outwardly, this manifests itself as a complete absence of voltage at the battery output (zero volts).

In fact, as a rule, at this moment the voltage on the bank itself is about 2.4-2.8 Volts.

If the battery is blocked due to overload (short circuit in the load), the protection module also blocks the FET1 transistor. It makes no difference what the protection was triggered from - from overdischarge or from short circuit. The result is the same - open transistor FET2 and closed field switch FET1.

Thus, during a deep discharge, the lithium-ion battery protection board does not in any way interfere with charging the battery.

The only problem is that some chargers consider themselves too smart and when they see that the voltage on the battery is too low (and in our case it will be zero), they believe that some unacceptable situation has occurred and completely refuse to issue a charger current.

This is done solely for security purposes. The fact is that if the battery has an internal short circuit, charging it becomes dangerous - it can overheat and swell (with all sorts of special effects like leaking electrolyte, squeezing out the tablet cover, etc.). If there is a break inside the battery, charging it becomes completely pointless. So the logic of operation of such smart chargers is quite clear and justified.

Read on to learn how to trick charging and restore functionality of a lithium battery after a deep discharge.

How to force it to charge?

In essence, restoring lithium-ion batteries after a deep discharge comes down to returning it to normal operation. You must understand that this in no way compensates for the loss of capacity (this is impossible in principle).

In order to still force a too cunning charger to charge our very low battery, it is necessary to ensure that the voltage on it exceeds a certain threshold. As a rule, 3.1-3.2 Volts are enough for the charger to consider the situation normal and allow charging.

You can only increase the voltage on the battery using a third-party (more stupid) charger. This is popularly called “pushing” the battery. To do this, simply connect an external power supply to the battery terminals, while limiting the maximum current.

For our purposes, any cell phone charger will do. Most often, modern chargers have an output in the form of a USB socket and, accordingly, produce 5V. All we have to do is select a resistor that limits the charge current.

The resistor's resistance is calculated using Ohm's law. Let's take the worst-case scenario - the voltage on the internal bank of a lithium-ion battery is 2.0 Volts (we won't be able to measure it without disassembling the battery, so we'll just assume that this is the case).

Then the difference between the power source voltage and the battery voltage will be:

Let's calculate the resistance of the current-limiting resistor so that the charge current does not exceed 50 mA (this is quite enough for the initial charge and at the same time quite safe):

R = 3V / 0.050A = 60 Ohm

Now we find out how much power will be dissipated by this resistor in the event of an internal short circuit of the battery (then the entire voltage of the power supply will drop across the resistor):

P = (5V) 2 / 60 Ohm = 0.42 W

Thus, to restore an 18650 battery after a deep discharge, we take any 5V power supply, the nearest suitable resistor is 62 Ohms (0.5W) and connect it all to the battery as follows:

The power supply will be suitable for a different voltage; it will be enough to recalculate the resistance and power of the limiting resistor. And you need to remember that in li-ion protection circuits, as a rule, field-effect transistors with a low drain-source voltage are used, so it is undesirable to take a power supply with a high output voltage.

Small neodymium magnets will help ensure reliable contact when connecting wires to the terminals of the 18650 battery.

If the charge does not work(the resistor does not heat up, and the battery is at full voltage from the power supply), then either the protection circuit has gone into very deep protection, or it has simply failed, or there is an internal break.

Then you can try to remove the outer polymer shell of the battery and connect our improvised charger directly to the can. Plus to plus, minus to minus. If in this case the charge does not go, then the battery is screwed. But if you do, you need to wait until the voltage rises to 3+ Volts and then you can charge as usual (with standard charging).

Of course, using this device you can charge the battery completely, but then you will have to wait a very long time (after all, the charge current is very small). In addition, in this case you will have to very closely control the voltage on the bank so as not to miss the moment when it becomes 4.2V. And, if anyone doesn’t know, the voltage towards the end of the charge will begin to rise very quickly!

Now the situation is different- the resistor, on the contrary, heats up noticeably, but there is zero voltage on the battery, which means there is a short circuit somewhere inside. We gut the battery, unsolder the protection module and try to charge the can itself. If it works, then the protection board is faulty and must be replaced. However, you can use the battery without it.

Today, one of the most popular battery formats for various electronic devices is 18650. It requires proper handling during operation. The durability and functionality of this power source depends on this.

How to charge a 18650 battery should be considered in detail. Expert advice will help you figure this out.

general characteristics

Today, many standard sizes are used and one of the most popular is the 18650 battery. It has a cylindrical shape. Externally, such a battery resembles AA batteries. Only the presented type is slightly larger in size than the usual devices.

During operation, the question always arises about how to charge an 18650 battery. This is a simple procedure. However, you need to treat it with full responsibility. The longevity of the battery depends on proper charging.

Batteries of this type are used today to power laptops, as well as electronic cigarettes. This made the presented standard size popular. Similar batteries are also installed in flashlights and laser pointers. Most often, the devices presented are of the lithium-ion type. This type of battery has proven its efficiency and ease of use.

Peculiarities

When considering how to charge an 18650 battery for a flashlight, electronic cigarette and other devices, it is necessary to describe the principle of its operation. The presented standard size is available in the lithium-ion battery category. It has small dimensions. The height is only 65 mm and the diameter is 18 mm.

Inside the device there are metal electrodes between which lithium ions circulate. This allows the generation of electric current to power equipment. When the charge is low or high, more ions are formed on one of the electrodes. They grow on the material, changing its volume and characteristics.

In order for the battery to work long and fully, it is necessary to prevent the appearance of a deep or too high charge. Otherwise, the device will quickly fail. Depending on the battery ratings, special types of chargers are used.

Battery protection

Today, the types of batteries presented are available complete with a special controller or contain manganese. Previously, batteries were produced without protection. In this case, you needed to know how to charge an 18650 battery correctly for your own safety.

The fact is that a device that did not have special protection could overheat greatly if it was charged incorrectly or for too long. In this case, a short circuit and even a fire could occur, or Today, the use of such structures has sunk into oblivion.

All lithium-ion batteries are designed to protect against such negative phenomena. Most often, a special controller is used. It monitors the battery capacity level. If necessary, it simply turns off the battery. Some types of structures contain manganese. It significantly influences the chemical reactions inside. Therefore, such batteries do not need a controller.

Charging Features

Many buyers are interested in how to charge a 18650 Li-Ion battery (3.7V). You need to familiarize yourself with the features of such a process. It's quite simple. Modern manufacturers make special devices that control battery charging.

Lithium-ion batteries have virtually no memory effect. This provides a set of rules when charging and operating batteries. The memory effect is a gradual decrease in battery capacity when it is not fully discharged. This property was typical for nickel-cadmium batteries. They had to be completely discharged.

On the contrary, they do not tolerate deep discharge. They need to be charged to 80% and discharged to 14-20%. In such conditions, the device will serve as long and productively as possible. The presence of special boards in the design simplifies this process. When the capacity level drops to a critical value (most often to 2.4 V), the device disconnects the battery from the consumer.

Charging

Many buyers of various electrical equipment are interested in how to charge a 18650 Li-Ion battery (3.7V, 6800mah). This process is carried out using a special device. It starts charging at a voltage of 0.05 V, and ends at a maximum level of 4.2 V. The battery of this type cannot be charged above this value.

You can charge 18650 batteries with a current of 0.5-1A. The larger it is, the faster the process goes. However, a smoother current is preferable. It is better not to speed up the charging process if the battery is not needed urgently.

The procedure takes no more than 3 hours. After this, the device will turn off the battery. This prevents it from overheating and failure. There are charging devices on sale that cannot control the progress of this process. In this case, the user must monitor its implementation himself. Experts recommend purchasing devices that control the process themselves. This is a safe method.

Options

Batteries with different capacities are available for sale. This affects the operating time and charging process. Batteries of 1100-2600 mAh have a low capacity. The most popular in this category are products from UltraFire. This manufacturer produces high-quality flashlights. Therefore, consumers reasonably have a question about how to charge the 18650 UltraFire battery.

In this case, it should be noted that devices with a capacity of up to 2600 mAh must be charged with a current of 1.3-2.6 A. This process is carried out in several stages. At the beginning of charging, the battery receives a current that is 0.2-1 of the battery capacity. At this point, the voltage is maintained at about 4.1 V. This stage lasts about an hour.

During the second stage, the voltage is kept at a constant level. For some charger manufacturers, this procedure may be carried out using alternating current. It should also be noted that if there is a graphite electrode in the battery design, it cannot be charged with a current exceeding 4.1 V.

Types of chargers

There is a simple method for charging a battery. To do this, you will need to buy a certain type of device. There is a large selection of charging equipment for batteries of this type on sale. The simplest and most inexpensive is a device for one battery. The current level in it can reach 1 A.

Devices that can accommodate several batteries at once are very popular. Most often, such designs are equipped with an indicator. Some models can also be used for other types of lithium-ion batteries. Their landing nests are designed accordingly. Such devices are distinguished by reasonable cost and high functionality.

Universal chargers are also available for sale. They can charge not only lithium-ion batteries, but also other types. Such units must be properly configured before carrying out the procedure.

Homemade device

Some users have a question about how to charge an 18650 battery in an emergency when a special device is not at hand. In this case, you can do it yourself. An old phone charger (for example, Nokia) will do.

You need to remove the wire sheath and disconnect the minus (black) and plus (red) wires. Using plasticine, you can attach the exposed contacts to the battery. Proper polarity must be observed. Next, the device is connected to the network.

This charging can last about an hour. This will be enough for the battery to ensure proper operation of the equipment.

Experts recommend taking the charging process responsibly and its durability depends on this. It is not worth discharging the battery completely and charging it to 100%. It is better to limit the charging process to 90%. However, periodically (every three months) you can completely discharge and fully charge the battery. This is necessary to calibrate the controller.

The battery can be stored for quite a long time. To do this, you need to charge it 50%. She can remain in this state for about a month. At the same time, the room should not be too hot or too cold. Ideal conditions are considered to be keeping the temperature at 15 ºС.

By looking at how to charge a 18650 battery, you can properly maintain and operate the battery. In this case, its service life will be much longer.

Batteries

What current should I use to charge a li ion 18650 battery? How to properly use such a battery. What should lithium-ion power sources be afraid of and how can such a battery extend its service life? Similar questions can arise in a wide variety of electronics industries.

And if you decide to assemble your first flashlight or electronic cigarette with your own hands, then you definitely need to familiarize yourself with the rules for working with such current sources.

A lithium-ion battery is a type of electric battery that has become widespread in modern household and electronic equipment since 1991, after it was introduced to the market by SONY. As a power source, such batteries are used in cell phones, laptops and video cameras, as a current source for electronic cigarettes and electric cars.

The disadvantages of this type of battery start with the fact that the first generation lithium-ion batteries were a blast in the market. Not only literally, but also figuratively. These batteries exploded.

This was explained by the fact that a lithium metal anode was used inside. During the process of numerous charging and discharging of such a battery, spatial formations appeared on the anode, which led to the short circuit of the electrodes, and as a result, to a fire or explosion.

After this material was replaced by graphite, this problem was eliminated, but problems could still arise on the cathode, which was made of cobalt oxide. If operating conditions are violated, or rather recharging, the problem could recur. This was corrected with the introduction of lithium ferrophosphate batteries.

All modern lithium-ion batteries prevent overheating and overcharging, but the problem of loss of charge remains at low temperatures when using devices.

Among the undeniable advantages of lithium-ion batteries, I would like to note the following:

  • high battery capacity;
  • low self-discharge;
  • no need for maintenance.

Original chargers

The charger for lithium-ion batteries is quite similar to the charger for lead-acid batteries. The only difference is that the lithium-ion battery has very high voltages on each bank and more stringent voltage tolerance requirements.

This type of battery is called a can because of its external similarity to aluminum beverage cans. The most common battery of this shape is 18650. The battery received this designation due to its dimensions: 18 millimeters in diameter and 65 millimeters in height.

If for lead-acid batteries some inaccuracies in indicating the limit voltages during charging are acceptable, with lithium-ion cells everything is much more specific. During the charging process, when the voltage increases to 4.2 Volts, the supply of voltage to the element should stop. The permissible error is only 0.05 Volt.

Chinese chargers that can be found on the market can be designed for batteries made from different materials. Li-ion, without compromising its performance, can be charged with a current of 0.8 A. In this case, you need to very carefully control the voltage on the bank. It is advisable not to allow values ​​above 4.2 Volts. If the assembly with the battery includes a controller, then you don’t need to worry about anything, the controller will do everything for you.

The most ideal charger for lithium-ion batteries will be a voltage stabilizer and current limiter at the beginning of the charge.

Lithium must be charged with a stable voltage and limited current at the beginning of the charge.

Homemade charger

To charge the 18650, you can buy a universal charger, and not worry about how to check the necessary parameters with a multimeter. But such a purchase will cost you a pretty penny.

The price for such a device will vary around $45. But you can still spend 2-3 hours and assemble the charger with your own hands. Moreover, this charger will be cheap, reliable and will automatically turn off your battery.

The parts that we will use today to create our charger are available to every radio amateur. If there is no radio amateur with the necessary parts at hand, then on the radio market you can buy all the parts for no more than 2-4 dollars. A circuit that is assembled correctly and installed carefully starts working immediately and does not require any additional debugging.

Electrical circuit for charging a 18650 battery.

In addition to everything, when you install the stabilizer on a suitable radiator, you can safely charge your batteries without fear that the charger will overheat and catch fire. The same cannot be said about Chinese chargers.

The scheme works quite simply. First, the battery must be charged with a constant current, which is determined by the resistance of resistor R4. After the battery has a voltage of 4.2 Volts, constant voltage charging begins. When the charging current drops to very small values, the LED in the circuit will stop lighting.

The currents recommended for charging lithium-ion batteries should not exceed 10% of the battery capacity. This will increase the life of your battery. If the value of resistor R4 is 11 Ohms, the current in the circuit will be 100 mA. If you use a 5 Ohm resistance, the charging current will be 230 mA.

How to extend the life of your 18650

Disassembled battery.

If you have to leave your lithium-ion battery unused for some time, it is better to store the batteries separately from the device they power. A fully charged element will lose some of its charge over time.

An element that is charged very little, or discharged completely, may permanently lose its functionality after a long period of hibernation. It would be optimal to store the 18650 at a charge level of about 50 percent.

You should not allow the element to be completely discharged and overcharged. Lithium-ion batteries have no memory effect at all. It is advisable to charge such batteries until their charge is completely exhausted. This can also extend the life of the battery.

Lithium-ion batteries do not like either heat or cold. The optimal temperature conditions for these batteries will be in the range from +10 to +25 degrees Celsius.

Cold can not only reduce the operating time of the element, but also destroy its chemical system. I think each of us has noticed how the charge level in a mobile phone quickly drops in the cold.

Conclusion

Summarizing all of the above, I would like to note that if you are going to charge a lithium-ion battery using a store-made charger, pay attention to the fact that it is not made in China. Very often, these chargers are made from cheap materials and do not always follow the required technology, which can lead to undesirable consequences in the form of fires.

If you want to assemble the device yourself, then you need to charge the lithium-ion battery with a current that will be 10% of the battery capacity. The maximum figure may be 20 percent, but this value is no longer desirable.

When using such batteries, you should follow the rules of operation and storage in order to exclude the possibility of an explosion, for example, from overheating, or failure.

Compliance with the operating conditions and rules will extend the life of the lithium-ion battery, and as a result, save you from unnecessary financial costs. The battery is your assistant. Take care of her!

16.10.2018

The idea of ​​restoring a Li-ion 18650 battery usually arises in 2 situations: when it quickly discharges during operation or does not charge after a strong discharge. In the first case, there is a natural loss of capacity, which gradually occurs with each charge-discharge cycle. It is impossible to restore the capacity of a lithium-ion battery that discharges quickly, regardless of its size.

Capacity loss occurs faster due to overcharges and strong discharges of energy storage devices. Therefore, to maintain their functionality, it is important to use chargers that limit the charge level, over-discharge protection circuits, and low-battery indicators. These simple measures will help you no longer wonder how to restore 18650 capacity.

Is it possible to restore a Li-ion battery if it does not want to charge?

Typically, problems with recharging batteries arise after they have been left in a discharged state for a long time and after severe cooling. Most 18650 batteries have a protection module. It is located between the can and the external terminals. Its task is to disconnect the can from the terminals when the voltage drops below the permissible limit. This shutdown looks like a lack of voltage at the battery output.

If the battery was blocked due to overload, it similarly closes the 1st transistor and leaves the 2nd open. Is it possible to recondition a 18650 Li-ion battery in such situations? Yes, you can. But some chargers perceive low voltage as a dangerous situation and, for safety reasons, refuse to charge such batteries. Next we will tell you what to do in such situations.

How to resurrect a 18650 battery if it won't charge?

Restoring a battery of 18650 cells or a single battery after a critical discharge involves returning it to normal operation. But the lost capacity cannot be restored, even theoretically. In order for the charger to “agree” to charge a deeply discharged battery, you need to “push” it - increase the voltage on it above the limit of 3.1–3.2 V.


This is done using a different (not so “smart”) charger. You need to connect a third-party power supply to the battery terminals and limit the current limit. In particular, a mobile phone charger is suitable. Typically, such devices have a USB output and produce a voltage of 5 V. All that remains is to select a resistor to limit the charging current. The resistor's resistance is calculated using Ohm's law.

Let's assume that the voltage on the internal bank has reached a critical value of 2 V. Subtracting this value from the charger voltage, we get a difference of 3 V. To ensure that the charging current does not exceed 50 mA, the resistance of the current-limiting resistor must be 3 V / 0.050 A = 60 Ohms. During an internal short circuit, when the resistor bears all the voltage, power (5V)2 / 60 Ohm = 0.42 W is distributed to it.

Conclusion: If you are puzzled by the question of how to restore an 18650 battery after a deep discharge, take any 5 V charger and a suitable resistor. The optimal option is 62 Ohm (0.5 W). Connect them to the battery. To fix the wires to the battery terminals, it is convenient to use miniature neodymium magnets.

If it's not charging

If charging does not occur (the resistor is cold), there are several possible reasons:

  1. the protection circuit is faulty or has gone into very deep protection;
  2. an internal failure occurred.

How to restore lithium batteries or 18650 cells in this case? You can try to remove the outer polymer shell of each battery and connect the created charge directly to the can, “+” to “+”, “-” to “-”. If the charge still does not work, the battery cannot be restored. If it does, wait until the voltage exceeds the threshold of 3.1–3.2 V and then charge the battery using standard charging.

If, on the contrary, the resistor gets very hot and the voltage on the battery is zero, this indicates the presence of a short circuit inside. You need to remove the outer polymer shell from the battery, unsolder the protective board and try to charge the can directly. If successful, this means that the problem is a faulty protection board and it needs to be replaced.