Evaluation of the characteristics of one or another charger is difficult without understanding how an exemplary charge of a li-ion battery should actually flow. Therefore, before moving directly to the diagrams, let's remember a little theory.

What are lithium batteries?

Depending on what material the positive electrode is made of lithium battery, there are several varieties of them:

• with lithium cobaltate cathode;
• with a cathode based on lithiated iron phosphate;
• based on nickel-cobalt-aluminium;
• based on nickel-cobalt-manganese.

All of these batteries have their own characteristics, but since these nuances are not of fundamental importance for the general consumer, they will not be considered in this article.

Also, all li-ion batteries are produced in various sizes and form factors. They can be either cased (for example, the popular 18650 today) or laminated or prismatic (gel-polymer batteries). The latter are hermetically sealed bags made of a special film, which contain electrodes and electrode mass.

The most common sizes of li-ion batteries are shown in the table below (all of them have a nominal voltage of 3.7 volts):

Designation	Standard size	Similar size
XXYY0, Where XX- indication of diameter in mm, YY- length value in mm, 0 - reflects the design in the form of a cylinder	10180	2/5 AAA
	10220	1/2 AAA (Ø corresponds to AAA, but half the length)
	10280
	10430	AAA
	10440	AAA
	14250	1/2 AA
	14270	Ø AA, length CR2
	14430	Ø 14 mm (same as AA), but shorter length
	14500	AA
	14670
	15266, 15270	CR2
	16340	CR123
	17500	150S/300S
	17670	2xCR123 (or 168S/600S)
	18350
	18490
	18500	2xCR123 (or 150A/300P)
	18650	2xCR123 (or 168A/600P)
	18700
	22650
	25500
	26500	WITH
	26650
	32650
	33600	D
	42120

Internal electrochemical processes proceed in the same way and do not depend on the form factor and design of the battery, so everything said below applies equally to all lithium batteries.

How to properly charge lithium-ion batteries

The most correct way to charge lithium batteries is to charge in two stages. This is the method Sony uses in all of its chargers. Despite a more complex charge controller, this ensures a more complete charge of li-ion batteries without reducing their service life.

Here we are talking about a two-stage charge profile for lithium batteries, abbreviated as CC/CV (constant current, constant voltage). There are also options with pulse and step currents, but they are not discussed in this article. You can read more about charging with pulsed current.

So, let's look at both stages of charging in more detail.

1. At the first stage A constant charging current must be ensured. The current value is 0.2-0.5C. For accelerated charging, it is allowed to increase the current to 0.5-1.0C (where C is the battery capacity).

For example, for a battery with a capacity of 3000 mAh, the nominal charge current at the first stage is 600-1500 mA, and the accelerated charge current can be in the range of 1.5-3A.

To ensure a constant charging current of a given value, the charger circuit must be able to increase the voltage at the battery terminals. In fact, at the first stage the charger works as a classic current stabilizer.

Important: If you plan to charge batteries with a built-in protection board (PCB), then when designing the charger circuit you need to make sure that the open circuit voltage of the circuit can never exceed 6-7 volts. Otherwise, the protection board may be damaged.

At the moment when the voltage on the battery rises to 4.2 volts, the battery will gain approximately 70-80% of its capacity (the specific capacity value will depend on the charging current: with accelerated charging it will be a little less, with a nominal charge - a little more). This moment marks the end of the first stage of charging and serves as a signal for the transition to the second (and final) stage.

2. Second charge stage- this is charging the battery with a constant voltage, but a gradually decreasing (falling) current.

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.

An important nuance of the correct charger operation is its complete disconnection from the battery after charging is complete. This is due to the fact that for lithium batteries it is extremely undesirable for them to remain under increased voltage, which usually provides the charger (i.e. 4.18-4.24 volts). This leads to accelerated degradation of the chemical composition of the battery and, as a consequence, a decrease in its capacity. Long-term stay means tens of hours or more.

During the second stage of charging, the battery manages to gain approximately 0.1-0.15 more of its capacity. The total battery charge thus reaches 90-95%, which is an excellent indicator.

We looked at two main stages of charging. However, coverage of the issue of charging lithium batteries would be incomplete if another charging stage were not mentioned - the so-called. precharge.

Preliminary charge stage (precharge)- this stage is used only for deeply discharged batteries (below 2.5 V) to bring them to normal operating mode.

At this stage the charge is ensured DC reduced value until the battery voltage reaches 2.8 V.

The preliminary stage is necessary to prevent swelling and depressurization (or even explosion with fire) of damaged batteries that have, for example, an internal short circuit between the electrodes. If you immediately pass through such a battery high current charge, this will inevitably lead to its warming up, and then depending on your luck.

Another benefit of precharging is pre-warming the battery, which is important when charging at low temperatures environment(in an unheated room during the cold season).

Intelligent charging must be able to monitor the voltage on the battery during the preliminary charging phase and, in case the voltage for a long time does not rise, conclude that the battery is faulty.

All stages of charging a lithium-ion battery (including the pre-charge stage) are schematically depicted in this graph:

Exceeding the rated charging voltage by 0.15V can reduce the battery life by half. Lowering the charge voltage by 0.1 volt reduces the capacity of a charged battery by about 10%, but significantly extends its service life. The voltage of a fully charged battery after removing it from the charger is 4.1-4.15 volts.

Let me summarize the above and outline the main points:

1. What current should I use to charge a li-ion battery (for example, 18650 or any other)?

The current will depend on how quickly you would like to charge it and can range from 0.2C to 1C.

For example, for a battery size 18650 with a capacity of 3400 mAh, the minimum charge current is 680 mA, and the maximum is 3400 mA.

2. How long does it take to charge, for example, the same rechargeable batteries 18650?

The charging time directly depends on the charging current and is calculated using the formula:

T = C / I charge.

For example, the charging time of our 3400 mAh battery with a current of 1A will be about 3.5 hours.

3. How to properly charge a lithium polymer battery?

All lithium batteries charge the same way. It doesn't matter whether it is lithium polymer or lithium ion. For us, consumers, there is no difference.

What is a protection board?

The protection board (or PCB - power control board) is designed to protect against short circuit, overcharge and overdischarge of the lithium battery. As a rule, overheating protection is also built into the protection modules.

For safety reasons, it is prohibited to use lithium batteries in household appliances unless they have a built-in protection board. That's why all cell phone batteries always have a PCB board. The battery output terminals are located directly on the board:

These boards use a six-legged charge controller on a specialized device (JW01, JW11, K091, G2J, G3J, S8210, S8261, NE57600 and other analogues). The task of this controller is to disconnect the battery from the load when the battery is completely discharged and disconnect the battery from charging when it reaches 4.25V.

Here, for example, is a diagram of the BP-6M battery protection board that was supplied with old Nokia phones:

If we talk about 18650, they can be produced either with or without a protection board. The protection module is located near the negative terminal of the battery.

The board increases the length of the battery by 2-3 mm.

Batteries without a PCB module are usually included in batteries that come with their own protection circuits.

Any battery with protection can easily turn into a battery without protection; you just need to gut it.

Today, the maximum capacity of the 18650 battery is 3400 mAh. Batteries with protection must have a corresponding designation on the case ("Protected").

Do not confuse the PCB board with the PCM module (PCM - power charge module). If the former serve only the purpose of protecting the battery, then the latter are intended to control the charging process - they limit the charge current by given level, control the temperature and, in general, ensure the entire process. The PCM board is what we call a charge controller.

I hope now there are no questions left, how to charge an 18650 battery or any other lithium battery? Then we move on to a small selection of ready-made circuit solutions for chargers (the same charge controllers).

Charging schemes for li-ion batteries

All circuits are suitable for charging any lithium battery; all that remains is to decide on the charging current and the element base.

LM317

Diagram of a simple charger based on the LM317 chip with a charge indicator:

The circuit is the simplest, the whole setup comes down to setting the output voltage to 4.2 volts using trimming resistor R8 (without a connected battery!) and setting the charging current by selecting resistors R4, R6. The power of resistor R1 is at least 1 Watt.

As soon as the LED goes out, the charging process can be considered completed (the charging current will never decrease to zero). It is not recommended to keep the battery on this charge for a long time after it is fully charged.

The lm317 microcircuit is widely used in various voltage and current stabilizers (depending on the connection circuit). It is sold on every corner and costs pennies (you can take 10 pieces for only 55 rubles).

LM317 comes in different housings:

Pin assignment (pinout):

Analogues of the LM317 chip are: GL317, SG31, SG317, UC317T, ECG1900, LM31MDT, SP900, KR142EN12, KR1157EN1 (the last two are domestically produced).

The charging current can be increased to 3A if you take LM350 instead of LM317. It will, however, be more expensive - 11 rubles/piece.

The printed circuit board and circuit assembly are shown below:

The old Soviet transistor KT361 can be replaced with similar to p-n-p transistor (for example, KT3107, KT3108 or bourgeois 2N5086, 2SA733, BC308A). It can be removed altogether if the charge indicator is not needed.

Disadvantage of the circuit: the supply voltage must be in the range of 8-12V. This is due to the fact that for normal operation of the LM317 chip, the difference between the battery voltage and the supply voltage must be at least 4.25 Volts. Thus, it will not be possible to power it from the USB port.

MAX1555 or MAX1551

MAX1551/MAX1555 are specialized chargers for Li+ batteries, capable of operating from USB or from a separate power adapter (for example, a phone charger).

The only difference between these microcircuits is that MAX1555 produces a signal to indicate the charging process, and MAX1551 produces a signal that the power is on. Those. 1555 is still preferable in most cases, so 1551 is now difficult to find on sale.

A detailed description of these microcircuits from the manufacturer is.

The maximum input voltage from the DC adapter is 7 V, when powered by USB - 6 V. When the supply voltage drops to 3.52 V, the microcircuit turns off and charging stops.

The microcircuit itself detects at which input the supply voltage is present and connects to it. If the power is supplied via the USB bus, then the maximum charging current is limited to 100 mA - this allows you to plug the charger into the USB port of any computer without fear of burning the south bridge.

When powered by a separate power supply, the typical charging current is 280 mA.

The chips have built-in overheating protection. But even in this case, the circuit continues to operate, reducing the charge current by 17 mA for each degree above 110 ° C.

There is a pre-charge function (see above): as long as the battery voltage is below 3V, the microcircuit limits the charge current to 40 mA.

The microcircuit has 5 pins. Here typical diagram inclusions:

If there is a guarantee that the voltage at the output of your adapter cannot under any circumstances exceed 7 volts, then you can do without the 7805 stabilizer.

The USB charging option can be assembled, for example, on this one.

The microcircuit does not require either external diodes or external transistors. In general, of course, gorgeous little things! Only they are too small and inconvenient to solder. And they are also expensive ().

LP2951

The LP2951 stabilizer is manufactured by National Semiconductors (). It provides the implementation of a built-in current limiting function and allows you to generate a stable charge voltage level for a lithium-ion battery at the output of the circuit.

The charge voltage is 4.08 - 4.26 volts and is set by resistor R3 when the battery is disconnected. The voltage is kept very accurately.

The charge current is 150 - 300mA, this value is limited by the internal circuits of the LP2951 chip (depending on the manufacturer).

Use the diode with a small reverse current. For example, it can be any of the 1N400X series that you can purchase. The diode is used as a blocking diode to prevent reverse current from the battery into the LP2951 chip when the input voltage is turned off.

This charger produces a fairly low charging current, so any 18650 battery can charge overnight.

The microcircuit can be purchased both in a DIP package and in a SOIC package (costs about 10 rubles per piece).

MCP73831

The chip allows you to create the right chargers, and it’s also cheaper than the much-hyped MAX1555.

A typical connection diagram is taken from:

An important advantage of the circuit is the absence of low-resistance powerful resistors that limit the charge current. Here the current is set by a resistor connected to the 5th pin of the microcircuit. Its resistance should be in the range of 2-10 kOhm.

The assembled charger looks like this:

The microcircuit heats up quite well during operation, but this does not seem to bother it. It fulfills its function.

Here's another option printed circuit board With smd led and micro USB connector:

LTC4054 (STC4054)

Very simple circuit, great option! Allows charging with current up to 800 mA (see). True, it tends to get very hot, but in this case the built-in overheating protection reduces the current.

The circuit can be significantly simplified by throwing out one or even both LEDs with a transistor. Then it will look like this (you must admit, it couldn’t be simpler: a couple of resistors and one condenser):

One of the printed circuit board options is available at . The board is designed for elements of standard size 0805.

I=1000/R. You shouldn’t set a high current right away; first see how hot the microcircuit gets. For my purposes, I took a 2.7 kOhm resistor, and the charge current turned out to be about 360 mA.

It is unlikely that it will be possible to adapt a radiator to this microcircuit, and it is not a fact that it will be effective due to the high thermal resistance of the crystal-case junction. The manufacturer recommends making the heat sink “through the leads” - making the traces as thick as possible and leaving the foil under the chip body. In general, the more “earth” foil left, the better.

By the way, most of the heat is dissipated through the 3rd leg, so you can make this trace very wide and thick (fill it with excess solder).

The LTC4054 chip package may be labeled LTH7 or LTADY.

LTH7 differs from LTADY in that the first can lift a very low battery (on which the voltage is less than 2.9 volts), while the second cannot (you need to swing it separately).

The chip turned out to be very successful, so it has a bunch of analogues: STC4054, MCP73831, TB4054, QX4054, TP4054, SGM4054, ACE4054, LP4054, U4054, BL4054, WPM4054, IT4504, Y1880, PT6102, PT6181, VS6102 , HX6001, LC6000, LN5060, CX9058, EC49016, CYT5026, Q7051. Before using any of the analogues, check the datasheets.

TP4056

The microcircuit is made in a SOP-8 housing (see), it has a metal heat sink on its belly that is not connected to the contacts, which allows for more efficient heat removal. Allows you to charge the battery with a current of up to 1A (the current depends on the current-setting resistor).

The connection diagram requires the bare minimum of hanging elements:

The circuit implements the classical charging process - first charging with a constant current, then with a constant voltage and a falling current. Everything is scientific. If you look at charging step by step, you can distinguish several stages:

1. Monitoring the voltage of the connected battery (this happens all the time).
2. Precharge phase (if the battery is discharged below 2.9 V). Charge with a current of 1/10 from the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm) to a level of 2.9 V.
3. Charging with a maximum constant current (1000 mA at R prog = 1.2 kOhm);
4. When the battery reaches 4.2 V, the voltage on the battery is fixed at this level. A gradual decrease in the charging current begins.
5. When the current reaches 1/10 of the one programmed by the resistor R prog (100 mA at R prog = 1.2 kOhm), the charger turns off.
6. After charging is complete, the controller continues monitoring the battery voltage (see point 1). The current consumed by the monitoring circuit is 2-3 µA. After the voltage drops to 4.0V, charging starts again. And so on in a circle.

The charge current (in amperes) is calculated by the formula I=1200/R prog. The permissible maximum is 1000 mA.

A real charging test with a 3400 mAh 18650 battery is shown in the graph:

The advantage of the microcircuit is that the charge current is set by just one resistor. Powerful low-resistance resistors are not required. Plus there is an indicator of the charging process, as well as an indication of the end of charging. When the battery is not connected, the indicator blinks every few seconds.

The supply voltage of the circuit should be within 4.5...8 volts. The closer to 4.5V, the better (so the chip heats up less).

The first leg is used to connect a temperature sensor built into the lithium-ion battery (usually the middle terminal of a cell phone battery). If the output voltage is below 45% or above 80% of the supply voltage, charging is suspended. If you don't need temperature control, just plant that foot on the ground.

Attention! This circuit has one significant drawback: the absence of a battery reverse polarity protection circuit. In this case, the controller is guaranteed to burn out due to exceeding the maximum current. In this case, the supply voltage of the circuit directly goes to the battery, which is very dangerous.

The signet is simple and can be done in an hour on your knee. If time is of the essence, you can order ready-made modules. Some manufacturers of ready-made modules add protection against overcurrent and overdischarge (for example, you can choose which board you need - with or without protection, and with which connector).

You can also find ready-made boards with a contact for a temperature sensor. Or even a charging module with several parallel TP4056 microcircuits to increase the charging current and with reverse polarity protection (example).

LTC1734

Also a very simple scheme. The charging current is set by resistor R prog (for example, if you install a 3 kOhm resistor, the current will be 500 mA).

Microcircuits are usually marked on the case: LTRG (they can often be found in old Samsung phones).

A transistor will do just fine any p-n-p, the main thing is that it is designed for a given charging current.

There is no charge indicator on the indicated diagram, but on the LTC1734 it is said that pin “4” (Prog) has two functions - setting the current and monitoring the end of the battery charge. For example, a circuit with control of the end of charge using the LT1716 comparator is shown.

The LT1716 comparator in this case can be replaced with a cheap LM358.

TL431 + transistor

It is probably difficult to come up with a circuit using more affordable components. The most difficult thing here is to find the TL431 reference voltage source. But they are so common that they are found almost everywhere (rarely does a power source do without this microcircuit).

Well, the TIP41 transistor can be replaced with any other one with a suitable collector current. Even the old Soviet KT819, KT805 (or less powerful KT815, KT817) will do.

Setting up the circuit comes down to setting the output voltage (without a battery!!!) using a trim resistor at 4.2 volts. Resistor R1 sets the maximum value of the charging current.

This circuit fully implements the two-stage process of charging lithium batteries - first charging with direct current, then moving to the voltage stabilization phase and smoothly reducing the current to almost zero. The only drawback is the poor repeatability of the circuit (it is capricious in setup and demanding on the components used).

MCP73812

There is another undeservedly neglected microcircuit from Microchip - MCP73812 (see). Based on it, a very budget charging option is obtained (and inexpensive!). The whole body kit is just one resistor!

By the way, the microcircuit is made in a solder-friendly package - SOT23-5.

The only negative is that it gets very hot and there is no charge indication. It also somehow doesn’t work very reliably if you have a low-power power source (which causes a voltage drop).

In general, if the charge indication is not important for you, and a current of 500 mA suits you, then the MCP73812 is a very good option.

NCP1835

A fully integrated solution is offered - NCP1835B, providing high stability of the charging voltage (4.2 ±0.05 V).

Perhaps the only drawback of this microcircuit is its too miniature size (DFN-10 case, size 3x3 mm). Not everyone can provide high-quality soldering of such miniature elements.

Among the undeniable advantages I would like to note the following:

1. Minimum number of body parts.
2. Possibility of charging a completely discharged battery (precharge current 30 mA);
3. Determining the end of charging.
4. Programmable charging current - up to 1000 mA.
5. Charge and error indication (capable of detecting non-chargeable batteries and signaling this).
6. Protection against long-term charging (by changing the capacitance of the capacitor C t, you can set the maximum charging time from 6.6 to 784 minutes).

The cost of the microcircuit is not exactly cheap, but also not so high (~$1) that you can refuse to use it. If you are comfortable with a soldering iron, I would recommend choosing this option.

More detailed description is in .

Can I charge a lithium-ion battery without a controller?

Yes, you can. However, this will require close control of the charging current and voltage.

In general, it will not be possible to charge a battery, for example, our 18650, without a charger. You still need to somehow limit the maximum charge current, so at least the most primitive memory will still be required.

The simplest charger for any lithium battery is a resistor connected in series with the battery:

The resistance and power dissipation of the resistor depend on the voltage of the power source that will be used for charging.

As an example, let's calculate a resistor for a 5 Volt power supply. We will charge an 18650 battery with a capacity of 2400 mAh.

So, at the very beginning of charging, the voltage drop across the resistor will be:

U r = 5 - 2.8 = 2.2 Volts

Let's say our 5V power supply is rated for a maximum current of 1A. The circuit will consume the highest current at the very beginning of the charge, when the voltage on the battery is minimal and amounts to 2.7-2.8 Volts.

Attention: these calculations do not take into account the possibility that the battery may be very deeply discharged and the voltage on it may be much lower, even to zero.

Thus, the resistor resistance required to limit the current at the very beginning of the charge at 1 Ampere should be:

R = U / I = 2.2 / 1 = 2.2 Ohm

Resistor power dissipation:

P r = I 2 R = 1*1*2.2 = 2.2 W

At the very end of the battery charge, when the voltage on it approaches 4.2 V, the charge current will be:

I charge = (U ip - 4.2) / R = (5 - 4.2) / 2.2 = 0.3 A

That is, as we see, all values ​​do not go beyond the permissible limits for of this battery: the initial current does not exceed the maximum permissible current charge for a given battery (2.4 A), and the final current exceeds the current at which the battery no longer gains capacity (0.24 A).

The main disadvantage of such charging is the need to constantly monitor the voltage on the battery. And manually turn off the charge as soon as the voltage reaches 4.2 Volts. The fact is that lithium batteries tolerate even short-term overvoltage very poorly - the electrode masses begin to quickly degrade, which inevitably leads to loss of capacity. At the same time, all the prerequisites for overheating and depressurization are created.

If your battery has a built-in protection board, which was discussed just above, then everything becomes simpler. When a certain voltage is reached on the battery, the board itself will disconnect it from the charger. However, this charging method has significant disadvantages, which we discussed in.

The protection built into the battery will not allow it to be overcharged under any circumstances. All you have to do is control the charge current so that it does not exceed the permissible values ​​for a given battery (protection boards cannot limit the charge current, unfortunately).

Charging using a laboratory power supply

If you have a power supply with current protection (limitation), then you are saved! Such a power source is already a full-fledged charger that implements the correct charge profile, which we wrote about above (CC/CV).

All you need to do to charge li-ion is set the power supply to 4.2 volts and set the desired current limit. And you can connect the battery.

At first, when the battery is still discharged, laboratory block power supply will operate in current protection mode (i.e. it will stabilize the output current at a given level). Then, when the voltage on the bank rises to the set 4.2V, the power supply will switch to voltage stabilization mode, and the current will begin to drop.

When the current drops to 0.05-0.1C, the battery can be considered fully charged.

As you can see, the laboratory power supply is an almost ideal charger! The only thing it can’t do automatically is make a decision to fully charge the battery and turn off. But this is a small thing that you shouldn’t even pay attention to.

How to charge lithium batteries?

And if we are talking about a disposable battery that is not intended for recharging, then the correct (and only correct) answer to this question is NO.

The point is that any lithium battery(for example, the common CR2032 in the form of a flat tablet) is characterized by the presence of an internal passivation layer that covers the lithium anode. This layer prevents a chemical reaction between the anode and the electrolyte. And the supply of external current destroys the above protective layer, leading to damage to the battery.

By the way, if we talk about the non-rechargeable CR2032 battery, then the LIR2032, which is very similar to it, is already a full-fledged battery. It can and should be charged. Only its voltage is not 3, but 3.6V.

How to charge lithium batteries (be it a phone battery, 18650 or any other li-ion battery) was discussed at the beginning of the article.

85 kopecks/pcs. Buy MCP73812 65 RUR/pcs. Buy NCP1835 83 RUR/pcs. Buy *All chips with free shipping

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How to charge 18650 battery correctly?

December 12, 2017

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 sizes and types of batteries are used. One of the most popular is the 18650 battery. It has a cylindrical shape. Externally, this 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 a 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 the device in which there was no special protection, could overheat greatly if charged incorrectly or for too long. In this case, a short circuit and even a fire or explosion of the battery could occur. 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.

Lithium-ion batteries, on the contrary, 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 on how to charge an 18650 battery with a charger. To do this, you will need to buy a certain type of device. Available for sale big choice charging equipment for batteries of this type. 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 quite enough for the battery to provide correct work technology.

Experts recommend taking a responsible approach to the process of charging and discharging the battery. 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.

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 recover lithium ion battery 18650 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, the charger is suitable for mobile phone. 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.

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. Full recovery 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 think they are too smart and when they see that the battery is too low voltage(and in our case it will generally be equal to zero), they believe that some unacceptable situation has occurred and completely refuse to provide charging 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 the diagrams li-ion protection are usually used field effect transistors with a small drain-source voltage, so it is not advisable 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.

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.

Lithium-ion battery is a type of battery electric current, which since 1991, after it was presented to the market by SONY, has become widespread in modern household and electronic equipment. As a power source, such batteries are used in cell phones, laptops and video cameras, as a current source for an electronic cigarette and an electric car.

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, which can be found on the market, can rely on batteries for 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 with a multimeter required parameters. 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 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 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!