Li ion rechargeable batteries. Lithium-ion (Li-ion) batteries and batteries. Measuring battery capacity without measuring instruments
Lithium-ion (Li-ion) batteries are most often used in mobile devices (laptops, mobile phones, PDAs and others). This is due to their advantages over the previously widely used nickel-metal hydride (Ni-MH) and nickel-cadmium (Ni-Cd) batteries.
Li-ion batteries have much better parameters.
Primary cells ("batteries") with a lithium anode appeared in the early 70s of the 20th century and quickly found application due to their high specific energy and other advantages. Thus, a long-standing desire was realized to create a chemical current source with the most active reducing agent - an alkali metal, which made it possible to sharply increase both the operating voltage of the battery and its specific energy. If the development of primary cells with a lithium anode was crowned with relatively quick success and such cells firmly took their place as power sources for portable equipment, then the creation of lithium batteries ran into fundamental difficulties, which took more than 20 years to overcome.
After a lot of testing during the 1980s, it turned out that the problem of lithium batteries revolved around lithium electrodes. More precisely, around the activity of lithium: the processes that occurred during operation, in the end, led to a violent reaction, called "ventilation with the release of a flame." In 1991, a large number of lithium batteries, which were first used as a power source for mobile phones, were recalled to manufacturers. The reason is that during a conversation, when the current consumed is maximum, a flame erupted from the battery, burning the face of the mobile phone user.
Due to the inherent instability of lithium metal, especially during the charging process, research has shifted to the field of creating a battery without the use of Li, but using its ions. Although lithium-ion batteries provide a slightly lower energy density than lithium batteries, Li-ion batteries are nevertheless safe when providing correct modes charge and discharge.
Chemical processes of Li-ion batteries.
A revolution in the development of rechargeable lithium batteries was made by the announcement that batteries with a negative electrode made of carbon materials have been developed in Japan. Carbon turned out to be a very convenient matrix for lithium intercalation.
In order for the battery voltage to be large enough, Japanese researchers used cobalt oxides as the active material of the positive electrode. Literated cobalt oxide has a potential of about 4 V relative to the lithium electrode, so the operating voltage of a Li-ion battery has a characteristic value of 3 V and higher.
When a Li-ion battery is discharged, lithium is deintercalated from the carbon material (on the negative electrode) and lithium is intercalated into oxide (on the positive electrode). When the battery is charging, the processes go in the opposite direction. Consequently, there is no metallic (zero-valent) lithium in the entire system, and the processes of discharge and charge are reduced to the transfer of lithium ions from one electrode to another. Therefore, such batteries are called "lithium-ion", or rocking-chair type batteries.
Processes on the negative electrode of a Li-ion battery.
In all Li-ion batteries brought to commercialization, the negative electrode is made of carbon materials. The intercalation of lithium into carbon materials is a complex process, the mechanism and kinetics of which largely depend on the nature of the carbon material and the nature of the electrolyte.
The carbon matrix used as an anode can have an ordered layered structure, as in natural or synthetic graphite, disordered amorphous or partially ordered (coke, pyrolysis or mesophase carbon, soot, etc.). Lithium ions, when introduced, move apart the layers of the carbon matrix and are located between them, forming intercalates of various structures. The specific volume of carbon materials in the process of intercalation-deintercalation of lithium ions changes insignificantly.
In addition to carbon materials as a negative electrode matrix, structures based on tin, silver and their alloys, tin sulfides, cobalt phosphorides, carbon composites with silicon nanoparticles are being studied.
Processes on the positive electrode of a Li-ion battery.
While primary lithium cells use a variety of active materials for the positive electrode, in lithium batteries the choice of positive electrode material is limited. The positive electrodes of lithium-ion batteries are made exclusively from lithiated cobalt or nickel oxides and from lithium-manganese spinels.
Currently, materials based on mixed oxides or phosphates are increasingly used as cathode materials. It is shown that with mixed oxide cathodes, best performance battery. Technologies for coating the surface of cathodes with finely dispersed oxides are also being mastered.
Construction of Li-ion batteries
Structurally, Li-ion batteries, like alkaline (Ni-Cd, Ni-MH), are produced in cylindrical and prismatic versions. In cylindrical batteries, a coiled package of electrodes and a separator is placed in a steel or aluminum case, to which the negative electrode is connected. The positive pole of the battery is brought out through the insulator to the cover (Fig. 1). Prismatic batteries are made by stacking rectangular plates on top of each other. Prismatic batteries provide tighter packing in the battery but are more difficult than cylindrical batteries to maintain compressive forces on the electrodes. In some prismatic accumulators, a rolled assembly of an electrode package is used, which is twisted into an elliptical spiral (Fig. 2). This allows you to combine the advantages of the two design modifications described above.
Fig.1 The device of a cylindrical Li-Ion battery.
Fig.2. The device of a prismatic lithium-ion (Li-ion) battery with a rolled twist of electrodes.
Some design measures are usually taken to prevent rapid heating and ensure safe operation of Li-ion batteries. Under the battery cover there is a device that reacts to the positive temperature coefficient by increasing resistance, and another that breaks the electrical connection between the cathode and the positive terminal when the gas pressure inside the battery rises above the permissible limit.
To improve the safety of Li-ion batteries, the battery must also use external electronic protection, the purpose of which is to prevent the possibility of overcharging and overdischarging each battery, short circuit and excessive heating.
Most Li-ion batteries are made in prismatic versions, since the main purpose of Li-ion batteries is to ensure the operation of cell phones and laptops. As a rule, the designs of prismatic batteries are not unified, and most manufacturers of cell phones, laptops, etc. do not allow the use of third-party batteries in devices.
Characteristics of Li-ion batteries.
Modern Li-ion batteries have high specific characteristics: 100-180 Wh/kg and 250-400 Wh/l. Operating voltage - 3.5-3.7 V.
If a few years ago, developers considered the achievable capacity of Li-ion batteries to be no higher than a few ampere-hours, now most of the reasons limiting the increase in capacity have been overcome and many manufacturers began to produce batteries with a capacity of hundreds of ampere-hours.
Modern small-sized batteries are efficient at discharge currents up to 2 C, powerful ones - up to 10-20 C. Operating temperature range: from -20 to +60 °С. However, many manufacturers have already developed batteries that can operate at -40 °C. It is possible to extend the temperature range to higher temperatures.
The self-discharge of Li-ion batteries is 4-6% for the first month, then it is much less: in 12 months, the batteries lose 10-20% of their stored capacity. The capacity loss of Li-ion batteries is several times less than that of nickel-cadmium batteries, both at 20 °C and at 40 °C. Resource-500-1000 cycles.
Charging Li-ion batteries.
Li-ion batteries are charged in combined mode: first at a constant current (in the range from 0.2 C to 1 C) up to a voltage of 4.1-4.2 V (depending on the manufacturer's recommendations), then at a constant voltage. The first stage of charging can last about 40 minutes, the second stage longer. Faster charging can be achieved with pulse mode.
In the initial period, when only Li-ion batteries using a graphite system appeared, it was required to limit the charge voltage at the rate of 4.1 V per cell. Although the use of more high voltage allows you to increase the energy density, oxidative reactions, which occurred in cells of this type at voltages exceeding the threshold of 4.1 V, led to a reduction in their service life. Over time, this drawback was eliminated through the use of chemical additives, and now Li-ion cells can be charged up to a voltage of 4.20 V. The voltage tolerance is only about ± 0.05 V per cell.
Li-ion batteries for industrial and military use should have a longer service life than batteries for commercial use. Therefore, for them, the threshold voltage of the end of the charge is 3.90 V per cell. Although the energy density (kWh/kg) of such batteries is lower, the increased service life at small sizes, low weight and higher energy density compared to other types of batteries put Li-ion batteries out of the competition.
When charging Li-ion batteries with a current of 1C, the charge time is 2-3 hours. The Li-ion battery reaches a state of full charge when the voltage on it becomes equal to the cutoff voltage, and the current decreases significantly and is approximately 3% of the initial charge current (Fig. 3).
Fig.3. Voltage and current versus time when charging a lithium-ion (Li-ion) battery
If Fig. 3 shows a typical charge graph for one of the types of Li-ion batteries, then Fig. 4 shows the charging process more clearly. With an increase in the charge current of a Li-ion battery, the charge time does not significantly decrease. Although the battery voltage rises faster with higher charge current, the recharging phase after the completion of the first stage of the charge cycle takes longer.
Some types of chargers require 1 hour or less to charge a lithium-ion battery. In such chargers, stage 2 is omitted and the battery enters the ready state immediately after the end of stage 1. At this point, the Li-ion battery will be approximately 70% charged, and after that additional recharging is possible.
Fig.4. The dependence of voltage and current on time when charging a Li-ion battery.
- STAGE 1 - The maximum allowable charge current flows through the battery until the voltage across it reaches the threshold value.
- STEP 2 - Max Voltage battery is reached, the charge current is gradually reduced until it is fully charged. The moment of completion of the charge occurs when the value of the charge current drops to a value of 3% of the initial value.
- STEP 3 - Periodic make-up charge during battery storage, approximately every 500 hours of storage.
The trickle charge stage for Li-ion batteries is not applicable due to the fact that they cannot absorb energy when overcharged. Moreover, trickle charging can cause lithium plating, which makes the battery unstable. On the contrary, a short DC charging is able to compensate for the small self-discharge of the Li-ion battery and compensate for the energy losses caused by the operation of its protection device. Depending on the type of charger and the degree of self-discharge of the Li-ion battery, such recharging can be performed every 500 hours, or 20 days. Usually it should be done when the open circuit voltage drops to 4.05 V/cell and stop when it reaches 4.20 V/cell.
So, Li-ion batteries have low resistance to overcharging. On the negative electrode on the surface of the carbon matrix, with a significant overcharge, it becomes possible to deposit metallic lithium (in the form of finely crushed mossy sediment), which has a high reactivity to the electrolyte, and active oxygen evolution begins at the cathode. There is a threat of thermal runaway, pressure increase and depressurization. Therefore, Li-ion batteries can only be charged up to the voltage recommended by the manufacturer. With an increased charging voltage, the battery life decreases.
The safe operation of Li-ion batteries must be given serious consideration. Commercial Li-ion batteries have special protection devices that prevent the charge voltage from exceeding a certain threshold value. Additional element protection ensures that the charge is completed if the battery temperature reaches 90 °C. The most advanced batteries have one more protection element - a mechanical switch, which is triggered by an increase in the internal pressure of the battery. The built-in voltage control system is configured for two cutoff voltages - high and low.
There are exceptions - Li-ion batteries, in which there are no protection devices at all. These are batteries that contain manganese. Due to its presence, during recharging, the anode metallization reactions and oxygen evolution at the cathode occur so slowly that it became possible to abandon the use of protection devices.
Safety of Li-ion batteries.
All lithium batteries are characterized by a fairly good safety. Loss of capacity due to self-discharge 5-10% per year.
The given indicators should be considered as some nominal reference points. For each particular battery, for example, the discharge voltage depends on the discharge current, discharge level, temperature; the resource depends on the modes (currents) of discharge and charge, temperature, depth of discharge; the range of operating temperatures depends on the level of resource depletion, allowable operating voltages, etc.
The disadvantages of Li-ion batteries include sensitivity to overcharging and overdischarging, because of this they must have charge and discharge limiters.
A typical view of the discharge characteristics of Li-ion batteries is shown in fig. 5 and 6. It can be seen from the figures that with an increase in the discharge current, the discharge capacity of the battery decreases slightly, but the operating voltage decreases. The same effect appears when discharging at temperatures below 10 °C. In addition, at low temperatures there is an initial voltage drop.
Fig.5. Discharge characteristics of a Li-ion battery at various currents.
Fig.6. Discharge characteristics of a Li-ion battery at different temperatures.
As for the operation of Li-ion batteries in general, then, given all the constructive and chemical methods protection of batteries from overheating and the already well-established idea of the need for external electronic protection of batteries from overcharging and overdischarging, the problem of safe operation of Li-ion batteries can be considered solved. And new cathode materials often provide even greater thermal stability for Li-ion batteries.
Li-ion battery safety.
In the development of lithium and lithium-ion batteries, as in the development of primary lithium cells, special attention was paid to the safety of storage and use. All batteries are protected against internal short circuits (and in some cases - against external short circuits). Effective way Such protection is the use of a two-layer separator, one of the layers of which is not made of polypropylene, but of a material similar to polyethylene. In cases of a short circuit (for example, due to the growth of lithium dendrites to the positive electrode), due to local heating, this separator layer melts and becomes impermeable, thus preventing further dendritic growth.
Li-ion battery protection devices.
Commercial Li-ion batteries have the most advanced protection of all battery types. As a rule, in the protection circuit of Li-ion batteries, a field-effect transistor key is used, which, when a voltage of 4.30 V is reached on the battery cell, opens and thereby interrupts the charging process. In addition, the existing thermal fuse, when the battery is heated to 90 ° C, disconnects the circuit of its load, thus providing its thermal protection. But that's not all. Some batteries have a switch that is activated when the threshold pressure inside the case reaches 1034 kPa (10.5 kg/m2) and breaks the load circuit. There is also a deep discharge protection circuit that monitors the battery voltage and breaks the load circuit if the voltage drops to 2.5 V per cell.
The internal resistance of the mobile phone battery protection circuit in the on state is 0.05-0.1 ohm. Structurally, it consists of two keys connected in series. One of them is triggered when the upper, and the other - the lower voltage threshold on the battery is reached. The total resistance of these switches actually creates a doubling of its internal resistance, especially if the battery consists of only one battery. Mobile phone batteries must provide high load currents, which is possible with the lowest possible internal battery resistance. Thus, the protection circuit is an obstacle that limits the operating current of a Li-ion battery.
In some types of Li-ion batteries that use in their chemical composition manganese and consisting of 1-2 elements, the protection scheme is not applied. Instead, they have only one fuse installed. And such batteries are safe because of their small size and small capacity. In addition, manganese is quite tolerant of Li-ion battery abuse. The absence of a protection circuit reduces the cost of a Li-ion battery, but introduces new problems.
In particular, mobile phone users may use non-standard chargers to recharge their batteries. When using inexpensive chargers designed for recharging from the mains or from the on-board network of the car, you can be sure that if there is a protection circuit in the battery, it will turn it off when the voltage reaches the end of the charge. If there is no protection circuit, the battery will be overcharged and, as a result, its irreversible failure. This process is usually accompanied by increased heating and swelling of the battery case.
Mechanisms leading to a decrease in the capacity of Li-ion batteries
When cycling Li-ion batteries, among the possible mechanisms for reducing capacity, the following are most often considered:
- destruction crystal structure cathode material (especially LiMn2O4);
- exfoliation of graphite;
- build-up of a passivating film on both electrodes, which leads to a decrease in the active surface of the electrodes and blocking of small pores;
- deposition of metallic lithium;
- mechanical changes in the structure of the electrode as a result of volumetric vibrations of the active material during cycling.
Researchers disagree over which of the electrodes undergoes the most changes during cycling. This depends both on the nature of the chosen electrode materials and on their purity. Therefore, for Li-ion batteries, it is possible to describe only a qualitative change in their electrical and operational parameters during operation.
Typically, the resource of commercial Li-ion batteries until the discharge capacity is reduced by 20% is 500-1000 cycles, but it significantly depends on the value of the limiting charging voltage (Fig. 7). As the cycle depth decreases, the resource increases. The observed increase in service life is associated with a decrease in mechanical stress caused by changes in the volume of the interstitial electrodes, which depend on the degree of their charge.
Fig.7. Change in the capacity of a Li-ion battery at different limit charge voltages
An increase in the operating temperature (within the operating range) can increase the rate of side processes affecting the electrode-electrolyte interface and slightly increase the rate of decrease in the discharge capacity with cycles.
Conclusion.
As a result of searches best material for the cathode, modern Li-ion batteries turn into a whole family of chemical current sources, which differ markedly from each other both in energy consumption and in the parameters of the charge / discharge modes. This, in turn, requires a significant increase in the intelligence of control circuits, which have now become an integral part of batteries and powered devices - otherwise, damage (including irreversible damage) to both batteries and devices is possible. The task is further complicated by the fact that developers are trying to make the most of the energy of the batteries, seeking to increase the battery life with the minimum volume and weight occupied by the power source. This allows you to achieve significant competitive advantages. According to D. Hickok, Texas Instruments vice president of power components for mobile systems, when using cathodes from new materials, battery developers do not immediately achieve the same design and performance characteristics as in the case of more traditional cathodes. As a result, new batteries often have significant operating range limitations. Moreover, recently, in addition to traditional manufacturers of storage cells and batteries - Sanyo, Panasonic and Sony - new manufacturers, mostly from China, are very actively making their way to the market. Unlike traditional manufacturers, they supply products with a significantly wider range of parameters within one technology or even one batch. This is due to their desire to compete mainly on the basis of low product prices, which often results in savings on process compliance.
So, at present, the importance of information provided by the so-called. "smart batteries": battery identification, battery temperature, residual charge and allowable overvoltage. According to Hickok, if developers finished devices will design a power subsystem that takes into account both operating conditions and cell parameters, this will level out differences in battery parameters and increase the degree of freedom for end users, which will give them the opportunity to choose not only devices recommended by the manufacturer, but also batteries from other companies.
18650 has become more and more popular lately. According to their technical characteristics, they are ahead of the well-known finger-type batteries. The concepts of "finger" and "little finger", used for well-known from the point of view of the correct terminology, are incorrect. All batteries, regardless of size, have their own codes indicating their size. So, 18650 is also a code. That's the whole secret.
Battery size 18650
This five-digit code expresses the width and length of the battery, where the first two digits are the width (diameter) in mm, and the last three are the length in mm with tenths. There is an erroneous opinion that the zero at the end of this code indicates the cylindrical shape of the battery (there are batteries different shapes). Such an exact designation of the length of the battery is not necessary. When specifying its size, it is often limited to the first four digits (1865). By the way, finger and little finger batteries also have their own code - 14500 and 10440. In addition to the digital code, the size can also be indicated by letters. For example, the above two battery sizes have alternative letter codes - AA (finger-type) and AAA (little-finger type). There are many alphabetic and numerical codes indicating the sizes of various batteries: CR123 (16340), A (17500), Fat A (18500), 4/3 A (17670), etc.
For 18650 batteries, this size designation is inaccurate. Other parameters must also be taken into account. The size of an 18650 battery can be affected, for example, by the presence of a built-in special board (charge controller). Some batteries may have a slightly longer length in this case. There are often cases when the battery simply does not fit into the compartment of the device where they want to use it, despite the fact that this device (for example, the battery pack of an electronic cigarette) is designed to work with batteries of this type.
Li-ion 18650 battery life
The time that a given battery is able to work out depends on such a thing as “milliamps per hour” (mAh). For large batteries, such as automobiles, the term "amps per hour" is used. For a 18650 mAh battery, this is a derived value. One ampere is equal to 1000 milliamps. A milliamp per hour is the current that a battery can produce during a conventional hour of use. In other words, if you divide this value by a certain number of hours, you can find out the battery life. For example, the battery has a capacity of 3000 mAh. This means that for two hours of operation it will produce 1500 milliamps. Four - 750. The battery from the above example will be completely discharged after 10 hours of operation, when its capacity reaches 300 milliamps (deep discharge limit).
Such calculations give only a rough idea of the battery life. Its real operating time depends on what load it has to deal with, that is, on the device that it must provide power.
Current, voltage and power
Before stopping at general description specifications 18650 lithium-ion batteries and precautions in working with them, we will briefly define the above concepts. The current (maximum discharge current, current output) is expressed in amperes and is marked on the battery with the letter "A". Voltage is expressed in volts and is denoted by the letter "V". On many batteries you can find such designations. For a lithium-ion battery, the voltage is always 3.7 volts, and the current can be different. Battery power as the dominant parameter of its strength is expressed as the product of voltage and current (volts must be multiplied by amperes).
Description of the pros and cons of a lithium-ion battery
The main disadvantage of 18650 batteries made using lithium-ion technology is that they have a small operating temperature range. Normal operation of a lithium-ion battery is possible only in the range from -20 to +20 degrees Celsius. If it is used or charged at temperatures below or above those indicated, it spoils it. For comparison, nickel-cadmium and nickel-metal hydride batteries have a wider temperature range - from -40 to +40. But, unlike the latter, lithium-ion batteries have a higher nominal voltage - 3.7 volts versus 1.2 volts for nickel batteries.
Also, lithium-ion batteries are practically not subject to the self-discharge and memory effects common among many types of batteries. Self-discharge is the loss of charged energy when idle. The memory effect occurs in some types of batteries as a result of systematic charging after incomplete discharge. That is, it develops on batteries that are not completely discharged.
With the memory effect, the battery “remembers” the degree of discharge after which it is started to be charged, and is discharged, having reached this limit in the next cycle. Its true capacity at that time is actually greater. If there is a display board, then it will also show a discharge. This effect does not develop immediately, but gradually. It can also develop in conditions where the battery is constantly powered by the mains, that is, it is continuously charging.
Self-discharge and memory effect are extremely insignificant in lithium-ion batteries.
There is one more point that you should pay attention to: such batteries cannot be stored in a discharged state, otherwise they will quickly fail.
Li-ion battery precautions
Many are prone to fire and explosions. It depends on the chemical composition of the internal structure of the battery. For 18650 lithium-ion batteries, this problem is quite acute. It is not uncommon for e-cigarette users to suffer severe burns on their hands and face, or even more serious injuries. Since lithium-ion batteries are found in laptops, tablets, and cell phones, it is not uncommon for them to ignite.
In the first place among the causes of such incidents is, of course, low-quality (cheap) battery assembly. However, in the case of e-cigarettes, it is easy to provoke a lithium-ion battery explosion on your own, even if the battery is not cheap. To do this, you need to understand a little about what electrical resistance is.
If we explain this concept in the most plain language, then this is a parameter that determines the requirements of the conductor to the battery. The lower the resistance of the conductor, the more current (amperes) the battery must give. If the resistance is very low, then the battery will work with such a conductor to a large load. The resistance can be so low that it will provoke an excessive load on the battery and its subsequent explosion or ignition. In other words, it will be a short circuit. Since electronic cigarettes work on the principle of evaporation, which requires a heating element (filament coil), inept users can mistakenly force the battery to work with heating element with extremely low resistance. Knowing the current output of a particular battery and the resistance of the conductor, using simple calculations using the Ohm's law formula, you can determine whether this battery can handle a particular conductor.
These hazards do not always occur in all cases. Battery protection technologies are constantly evolving. Many batteries have a special charge controller inside that can de-energize the battery in time when a short circuit occurs. These are protected batteries.
Li-ion battery device
The 18650 battery is based on an electrolyte - a special liquid in which chemical reactions occur.
These chemical reactions are reversible. This is the principle of operation of any battery. In simple terms, the formula for such reactions can proceed both from left to right (discharge) and from right to left (charge). Such reactions occur between the cathode and anode of the cell. The cathode is the negative electrode (minus), the anode is the positive electrode (plus) of the power supply. Between them at the time of the reaction is formed electricity. chemical reactions discharge and charge between the cathode and the anode are the processes of oxidation and reduction, but that's a completely different story. We will not delve into the process of electrolysis. The current is formed at the moment when the cathode and anode begin to interact, that is, something is connected to the plus and minus of the battery. The cathode and anode must be electrically conductive.
During violation of operating conditions, molecules appear in the electrolyte chemical elements, which close the cathode and anode, which leads to internal short circuits. As a result of this, the temperature of the battery increases and more molecules appear, closing the plus and minus. This whole process, like a snowball, acquires speed exponentially. Without the possibility of taking the electrolyte out (the battery case is sealed), an increasing internal pressure arises. What happens next can be understood without comment.
Charging the lithium-ion battery
As a charger for a 18650 battery, any device designed for batteries of this format is suitable. The main thing is not to change the correct polarity when charging. Place the batteries in the slots exactly according to the plus and minus symbols. It's a good idea to read the other precautions for using the 18650 battery charger, which are always listed on the battery case.
The best option for charging lithium-ion batteries is to use more expensive chargers with fine-tuned charging process. Many of them have the function of charging batteries using the CC / CV method, which stands for constant current, constant voltage. This method is good because it can charge the battery more than conventional chargers. This is due to such a concept as reloading.
During the charging or discharging of the battery, its voltage changes. Increases when charging, decreases when discharging. The nominal 3.7 volts is the average value.
There are two effects that adversely affect the battery - overcharging and overdischarging. There are thresholds for charging and discharging the battery. If the battery voltage goes beyond these limits, then the battery gets overcharged or overdischarged, depending on whether it is charging or discharging. In the normal charging mode for 18650 Li-ion, the charger and charge controller inside the battery itself (if any) read the voltage of the battery and cut off the charge when it reaches the threshold to avoid overcharging. In this case, the battery is not actually fully charged. Its capacity may allow it to charge more, but the threshold prevents it from doing so.
The principle of charging by the CC / CV method is designed so that the current supplied to the charge is not cut off, but is sharply reduced, preventing internal tension battery go beyond the threshold. Thus, the battery is fully charged without getting overcharged.
Types of lithium-ion batteries
Types of 18650 Li-ion batteries:
- lithium iron phosphate (LFP);
- lithium-manganese (IMR);
- lithium-cobalt (ICR);
- lithium polymer (LiPo).
All types except the last one are cylindrical and can be made in 18650 format. Lithium polymer batteries differ in that they do not have a specific shape. This is due to the fact that they have a solid electrolyte (polymer). It is due to this unusual property of the electrolyte that these batteries are often used in tablets and cell phones.
Applications of lithium-ion batteries
As already mentioned, 18650 Li-ion batteries are widely used in electronic cigarettes. They can be built into the battery pack or removable, i.e. installed separately in it. There may also be several of them, connected in parallel or in series.
Lithium-ion batteries have long been used in the construction of various batteries, such as laptop batteries. Such batteries are a chain of several interconnected 18650 batteries inside a single case. Such batteries can also be found as capacious power banks - portable chargers.
The scope of the batteries themselves is very wide: from the named chargers to the constituent elements of modern large mechanisms (automobile or aviation). At the same time, the number of 18650 lithium-ion batteries that make up a single battery can vary from a few to hundreds. It is worth mentioning the lithium-polymer batteries. Although they are not available in 18650 Li-ion format, they are the most common, as they are used in tablets and cell phones.
Reading the "tips for operation" of batteries on the forums, you involuntarily wonder whether people skipped physics and chemistry at school, or they think that the rules for operating lead and ion batteries are the same.
Let's start with the principles of the Li-Ion battery. Everything is extremely simple on the fingers - there is a negative electrode (usually made of copper), there is a positive one (made of aluminum), between them there is a porous substance (separator) saturated with electrolyte (it prevents the "unauthorized" transition of lithium ions between the electrodes):
The principle of operation is based on the ability of lithium ions to integrate into the crystal lattice various materials- usually graphite or silicon oxide - with the formation of chemical bonds: accordingly, when charging, the ions are built into the crystal lattice, thereby accumulating a charge on one electrode, when discharging, respectively, they go back to another electrode, giving up the electron we need (who is interested in a more accurate explanation of the ongoing processes - google intercalation). As an electrolyte, water-containing solutions are used that do not contain a free proton and are stable in a wide voltage range. As you can see, in modern batteries everything is done quite safely - there is no metal lithium, there is nothing to explode, only ions run through the separator.
Now that everything has become more or less clear with the principle of operation, let's move on to the most common myths about Li-Ion batteries:
- Myth one. The Li-Ion battery in the device cannot be discharged to zero percent.
In fact, everything sounds right and is consistent with physics - when discharging to ~2.5 V Li-Ion, the battery begins to degrade very quickly, and even one such discharge can significantly (up to 10%!) reduce its capacity. In addition, when discharged to such a voltage, it will no longer be possible to charge it with a standard charger - if the battery cell voltage drops below ~ 3 V, the "smart" controller will turn it off as damaged, and if there are all such cells, the battery can be taken to the trash.
But there is one very important but that everyone forgets about: in phones, tablets and other mobile devices, the operating voltage range on the battery is 3.5-4.2 V. When the voltage drops below 3.5 V, the indicator shows zero percent charge and the device turns off, but up to " critical "2.5 V is still very far away. This is confirmed by the fact that if you connect an LED to such a "discharged" battery, then it can burn for a long time (maybe someone remembers that phones with flashlights used to be sold, which were turned on by a button regardless of the system. So there the light continued to burn after discharging and turn off the phone). That is, as you can see, during normal use, discharge up to 2.5 V does not occur, which means that it is quite possible to discharge Akum to zero percent. - Myth two. Li-Ion batteries explode if damaged.
We all remember the "explosive" Samsung Galaxy Note 7. However, this is rather an exception to the rule - yes, lithium is a very active metal, and it is not difficult to blow it up in the air (and it burns very brightly in water). However, modern batteries do not use lithium, but its ions, which are much less active. So in order for an explosion to occur, you need to try hard - either physically damage the charging battery (arrange a short circuit), or charge it with a very high voltage (then it will be damaged, but most likely the controller will simply burn itself out and will not allow charging the battery). Therefore, if you suddenly have a damaged or smoking battery in your hands - do not throw it on the table and run away from the room shouting "we will all die" - just put it in a metal container and take it out to the balcony (so as not to breathe chemistry) - the battery will smolder for a while and then go out. The main thing is not to fill it with water, the ions are of course less active than lithium, but still some amount of hydrogen will also be released when reacting with water (and he likes to explode). - Myth three. When a Li-Ion battery reaches 300 (500/700/1000/100500) cycles, it becomes unsafe and needs to be changed urgently.
A myth, fortunately less and less walking around the forums and not having any physical or chemical explanation at all. Yes, during operation, the electrodes oxidize and corrode, which reduces the battery capacity, but this does not threaten you with anything other than shorter battery life and unstable behavior at 10-20% of the charge. - Myth four. With Li-Ion batteries, you can not work in the cold.
This is more of a recommendation than a ban. Many manufacturers prohibit the use of phones at negative temperatures, and many have experienced rapid discharge and generally turning off phones in the cold. The explanation for this is very simple: the electrolyte is a water-containing gel, and what happens to water when negative temperatures everyone knows (yes, it freezes if anything), thereby taking some area of the battery out of work. This leads to a voltage drop, and the controller begins to consider this a discharge. This is not useful for the battery, but it’s not fatal either (after heating, the capacity will return), so if you desperately need to use your phone in the cold (it’s just to use it - get it out of a warm pocket, look at the time and hide it back), then it’s better to charge it 100% and turn on any process that loads the processor - so the cooling will be slower. - Myth five. A swollen Li-Ion battery is dangerous and should be thrown out immediately.
This is not quite a myth, but rather a precaution - a swollen battery can simply burst. From a chemical point of view, everything is simple: during the intercalation process, the electrodes and electrolyte are decomposed, as a result of which gas is released (it can also be released during recharging, but more on that below). But it stands out very little, and in order for the battery to seem swollen, several hundreds (if not thousands) of recharge cycles must go through (unless, of course, it is defective). There are no problems getting rid of the gas - just pierce the valve (in some batteries it opens on its own under excess pressure) and bleed it (I don’t recommend breathing it), after which you can cover up the hole epoxy resin. Of course, this will not return the battery to its former capacity, but at least now it will definitely not burst. - Myth six. Li-Ion batteries are harmful to overcharging.
But this is no longer a myth, but a harsh reality - when recharging, there is a great chance that the battery will swell, burst and catch fire - believe me, there is little pleasure in being splashed with boiling electrolyte. Therefore, in all batteries there are controllers that simply do not allow charging the battery above a certain voltage. But here you have to be extremely careful in choosing a battery - the controllers of Chinese handicrafts can often fail, and I think fireworks from the phone at 3 am will not please you. Of course, the same problem exists in branded batteries, but firstly, this happens much less often there, and secondly, the entire phone will be replaced under warranty. Usually this myth gives rise to the following: - Myth seven. When reaching 100%, you need to remove the phone from charging.
From the sixth myth, this seems reasonable, but in reality it makes no sense to get up in the middle of the night and remove the device from charging: firstly, controller failures are extremely rare, and secondly, even when 100% on the indicator is reached, the battery recharges to the very, very maximum for some time low currents, which adds another 1-3% capacity. So it really shouldn't be that much of a stretch. - Myth eight. The device can only be charged with the original charger.
The myth takes place due to the poor quality of Chinese chargers - with normal voltage at 5 + - 5% volts, they can produce both 6 and 7 - the controller, of course, will smooth out such voltage for some time, but in the future it will lead to the controller burning out at best, at worst - to an explosion and (or) motherboard failure. The opposite happens - under load, the Chinese charger produces 3-4 volts: this will lead to the fact that the battery cannot be fully charged.
Lithium-ion (Li-ion) batteries, which are used in most modern tablets, smartphones and laptops, require different maintenance and operation procedures compared to nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) batteries used in earlier devices.
In fact, proper care for a lithium-ion battery can increase its lifespan by 15 times compared to misused cases. In this article, we will give tips on how to maximize life cycle expensive lithium-ion batteries in all your portable devices.
More recently, Fred Langa, a journalist for the Windows Secrets Internet portal, had to replace a damaged smartphone - and it was his mistake.
The main symptom did not bode well - the phone case was deformed, because the body of the device itself began to bend.
Upon parsing and detailed examination, it turned out that the battery of the smartphone was swollen.
Initially, Fred did not notice any changes: the battery looked more or less normal when viewed face-on (Figure 1). However, when the battery was placed on a flat surface, it became obvious that its top and bottom faces were no longer flat and parallel to each other. A severe bulge has formed on one side of the battery (Figure 2). This bulge caused the phone to bend and deform.
The bulge of the battery was indicative of a serious problem: a buildup of high-pressure toxic gases inside the battery.
The battery case did a great job, but the toxic gases made the battery look like a tiny pressure cooker bomb just waiting to detonate.
In Fred's case, both the phone and the battery are damaged - it's time to buy a new smartphone.
The saddest thing is that this problem could have been easily prevented. In the final part of the article, Fred's mistakes will be given.
To avoid repeating the mistakes of the past with the new smartphone and other lithium-ion devices such as tablets, laptops, Fred began to seriously research the proper operation and maintenance of lithium-ion batteries.
Fred was not interested in extending battery life - these techniques are well known. Most devices offer manual or automatic power saving modes and methods to adjust screen brightness, slow down processor performance, and reduce the number of applications running.
Fred rather focused on extending battery life - ways to keep the battery in good working condition and maximize battery life.
This article includes brief thesis conclusions based on Fred's research. Follow these five suggested tips and then your lithium-ion batteries will work fully, long and safely in all your portable devices.
Tip 1: Watch the temperature and don't overheat your battery
Surprisingly, heat is one of the main enemies of lithium-ion batteries. Misuse factors such as the speed and length of battery charge and discharge cycles can cause the battery to overheat.
The external physical environment also matters. Simply leaving your Lithium-Ion battery in the sun or in a closed car can significantly reduce the battery's ability to accept and hold a charge.
Ideal temperature conditions for lithium-ion batteries is a room temperature of 20 degrees Celsius. If the device is heated to 30C, its ability to carry a charge is reduced by 20 percent. If the device is used at 45C, which is easily achievable in the sun, or when the device is used intensively with resource-intensive applications, the battery capacity is reduced by about half.
Thus, if your device or battery becomes noticeably warm while in use, try moving to a cooler area. If this is not possible, try to reduce the amount of power your device consumes by disabling unnecessary applications, services, and features, lowering the screen brightness, or activating the device's power saving mode.
If this still does not help, turn off the device completely until the temperature returns to normal. For even faster cooling, remove the battery (of course, if the design of the device allows it) - this way the device will cool down faster due to the physical separation from the power source.
By the way, despite the fact that high temperatures- This the main problem with lithium-ion batteries, low-temperature operation is not a major concern. Low temperatures do not cause long-term battery damage, although a cold battery will not be able to deliver all the power it can potentially deliver at optimum temperature. The drop in power becomes very noticeable at temperatures below 4C. Most consumer-grade lithium-ion batteries essentially become useless at temperatures near or below the freezing point.
If a device with a lithium-ion power supply becomes excessively cold for any reason, do not attempt to use it. Leave it unplugged and take it to a warm place (pocket or heated room) until the device returns to normal temperature. Just as with overheating, physically remove the battery and separate heating will speed up the warm-up process. After the battery warms up to normal temperature, its electrolytic properties will be restored.
Tip 2: Unplug your charger to save battery
Reload - i.e. Connecting the battery to a high voltage power source for too long can also reduce the battery's ability to hold a charge, shorten its lifespan, or kill it outright.
Most consumer-grade lithium-ion batteries are designed to operate at 3.6V per cell, but operate at a higher 4.2V during charging. If the charger is too long time overvoltage, the internal battery may be damaged.
In severe cases, overcharging can lead to what engineers call “catastrophic” consequences. Even in moderate cases, the excess heat generated by recharging will create the negative thermal effect described in the first tip.
High-quality chargers can work in harmony with modern lithium-ion battery circuitry, reducing the danger of overcharging by reducing the charging current in proportion to the battery charge.
These properties differ significantly depending on the kind of technology used in the battery. For example, when using nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) batteries, try to leave them connected to the charger as long as possible. This is because older types of batteries have high level self-discharge, i.e. they begin to lose a significant amount of stored energy immediately after being disconnected from the charger, even if the portable device itself is turned off.
In fact, a nickel-cadmium battery can lose up to 10 percent of its charge in the first 24 hours after being charged. After this period of time, the self-discharge curve begins to level off, but nickel cadmium battery continues to lose 10-20 percent per month.
The situation with nickel-metal hydride batteries is even worse. Their self-discharge rate is 30 percent faster than their nickel-cadmium counterparts.
However, lithium-ion batteries are very low level self-discharge. A well-functioning battery will lose only 5 percent of its charge in the first 24 hours after charging, and another 2 percent within the first month after that.
Thus, there is no need to leave the device with a lithium-ion battery connected to the charger until the last moment. For best results and battery life, unplug charger when full charge is shown.
New Lithium-ion battery devices do not need to be charged for extended periods of time before first use (nickel-cadmium and nickel-metal hydride devices recommend charging between 8 and 24 hours). Lithium-ion batteries are at their maximum capacity when they show 100 percent charge. There is no need for extended charging.
Not all discharge cycles affect battery health in the same way. Long and intensive use generates more heat, seriously stressing the battery, while shorter, more frequent discharge cycles, on the contrary, prolong battery life.
You might think that excessive small charge/discharge cycles can seriously reduce the life of a power supply. This was natural only for outdated technologies, but does not apply to modern lithium-ion batteries.
Battery specifications can be misleading because Many manufacturers consider a charge cycle to be the time it takes to reach 100 percent charge. For example, two charges from 50 to 100 percent are equivalent to one full charge cycle. Similarly, three cycles of 33 percent or 5 cycles of 20 percent are also equivalent to one full cycle.
In short, a large number of small charge-discharge cycles does not reduce the total volume of cycles. full charge lithium battery.
Again, heat and high stress from heavy discharges reduce battery life. Thus, try to keep the number of deep discharges to a minimum. Do not allow the battery level to drop to values close to zero (when the device turns itself off). Instead, treat the bottom 15-20 percent of your battery life as an emergency reserve - for emergencies only. Get in the habit of replacing the battery if possible, or connecting the device to an external power source before the battery is fully depleted.
As you know, fast discharging and fast charging are accompanied by the release of excess heat and adversely affect battery life.
If you have used the device intensively at high loads, let the batteries cool down to room temperature before connecting to the charger. The battery will not be able to take a full charge if it is warm.
While charging the device, monitor the temperature of the battery - it should not overheat much. A hot battery during charging usually indicates that too much current is flowing quickly.
Overcharging is most likely with cheap generic chargers using circuits fast charging or with wireless (inductive) chargers.
A cheap charger can be a simple transformer with wires connected to it. Such “silent charges” simply distribute the current and practically do not receive feedback from the device being charged. Overheating and overvoltage are very common when using these chargers, which slowly destroys the battery.
“Quick” charges are designed to provide a one-minute charge, not an hour-long charge. There are various approaches to fast charge technology, and not all of them are compatible with lithium-ion batteries. If the charger and battery are not designed to work together, fast charging can cause overvoltage and overheating. Generally speaking, it's best not to use one brand's charger to charge another brand's portable device.
Wireless (inductive) chargers use a special charging surface to recharge the battery. At first glance, this is very convenient, but the fact is that such charges generate excess heat even in normal operation (Some stoves use the phenomenon of induction to heat pots and pans).
Lithium batteries not only suffer from heat, but also waste energy when charging wirelessly. By its nature, the efficiency of an inductive charger is always lower than that of a conventional charger. Here everyone is free to make their own choice, but for Fred, increased heat and lower efficiency are sufficient factors to abandon such devices.
In any case, the safest approach is to use the supplied charger recommended by the manufacturer. This is the only guaranteed way to keep temperature and voltage within normal limits.
If an OEM charger is not available, use a device with a low output current to reduce the chance of battery damage due to high power being delivered quickly.
One low current power source is a USB port on a typical computer. A standard USB 2.0 port provides 500mA (0.5A) per port, while USB 3.0 provides 900mA (0.9A) per port. For comparison, some dedicated chargers can deliver 3000-4000mA (3-4A). The low amperage of the USB ports generally guarantee safe charging with normal temperature regime for most modern lithium-ion batteries.
Tip 5: If possible, use a spare battery
If your device allows you to quickly replace the battery, having a spare battery is a great insurance policy. This not only doubles the battery life, but also eliminates the need to completely drain the battery or use a quick charge. When the battery reaches the 15-20 percent mark, simply swap out the depleted battery for a spare and you'll instantly get a full charge without any overheating issues.
A spare battery has other benefits as well. For example, if you find yourself in a situation where the installed battery is overheated (for example, due to intensive use of the device or high ambient temperature), you can change the hot battery to cool it down faster while still using the device.
Having two batteries eliminates the need to use a quick charge - you can safely use the device when the battery is slowly charging from a safe power source.
Fred's Fatal Mistakes
Fred suggested that he may have damaged the smartphone's battery during the road trip. He used the device's GPS function to navigate on a clear sunny day. The smartphone was in the sun for a long time in the holder near the dashboard of the car, the brightness of the smartphone was turned on to the maximum in order to distinguish the map among the bright sun rays.
In addition, all standard background applications - email, instant messenger, etc. were launched. The device used a 4G module to download music tracks and a Bluetooth wireless module to transmit sound to the car's head audio unit. Definitely, the phone was under stress.
In order for the phone to receive power, it was connected to a 12V adapter, purchased according to the criteria of a low price and the presence of the correct connector.
The combination of direct sunlight, high CPU load, maximum screen brightness, and dubious quality of the adapter led to excessive overheating of the smartphone. Fred remembers with horror how hot the device was when it was pulled out of its holder. This severe overheating was the catalyst for battery death.
The problem seemed to worsen at night, when Fred left the device plugged in all night using a third-party charger, with no control over when the battery was fully charged.
With his new smartphone, Fred will only use the integrated charger and spare battery. Fred hopes for a long and safe life for both the battery and the phone, which he intends to achieve with these tips.
Found a typo? Select and press Ctrl + Enter
At this time, li ion batteries and Li-pol (lithium polymer) batteries are widespread.
The difference between them is in the electrolyte. In the first version, helium is used as it, in the second, a polymer saturated with a solution containing lithium. Today, due to the popularity of cars with electric motors, the question of finding the ideal type of li ion battery that is optimal for such a vehicle is acute.
It consists, like other batteries, of an anode (porous carbon) and a cathode (lithium), a separator separating them and an electrolyte conductor. The discharge process is accompanied by the transition of "anode" ions to the cathode through the separator and electrolyte. Their direction is reversed during charging (picture below).
Ions circulate in the process of discharging and charging the cell between oppositely charged electrodes.
Ion batteries have a cathode made of different metals, which is their main difference. Manufacturers using for electrodes different materials improve battery performance.
But, it happens that the improvement of some characteristics leads to a sharp deterioration in others. For example, by optimizing the capacity needed to increase travel time, you can increase power, safety, reduce the negative impact on environment. At the same time, you can reduce the load current, increase the cost or size of the battery.
Get to know the main parameters different types lithium batteries (lithium-manganese, lithium - cobalt, lithium - phosphate and nickel-manganese - cobalt) can be in the table:
Rules for users of electric transport
The capacity of such batteries practically does not decrease during long-term storage. Li-ion batteries are discharged by only 23% if stored at a temperature of 60 degrees for 15 years. It is due to these properties that they are widely used in electric transport technologies.
Lithium-ion batteries are suitable for electric vehicles, which have a complete control system built into the case.
For this reason, users during operation forget about the basic rules that can extend their service life:
- the battery must be fully charged immediately after purchase in the store, since the electrodes are charged by 50% during the production process. Therefore, the available capacity will decrease, i.e. operating time if there is no initial charge;
- the battery must not be allowed to completely discharge in order to save its resource;
- it is necessary to charge the battery after each departure, even if the charge is still left;
- Do not heat batteries as high temperatures contribute to the aging process. In order to use the resource to the maximum, it is necessary to carry out operation at optimal temperature, which is 20-25 degrees. Therefore, the battery cannot be stored near a heat source;
- in cold weather, it is recommended to wrap the battery in a plastic bag with a vacuum lock to store at 3-4 degrees, i.e. in an unheated room. The charge should be at least 50% of the full;
- after the battery has been operated at low temperatures, it cannot be charged without holding it for some time at room temperature, i.e. it needs to be warmed up;
- You need to charge the battery with the charger supplied with the kit.
The PU of these batteries has several subspecies - lithium - LiFePO4 (iron - phosphate), using an iron phosphate cathode. Their characteristics allow us to talk about batteries as the pinnacle of technology used for the production of batteries.
Their main advantages are:
- the number of charge-discharge cycles, which reaches 5000 until the moment when the capacity decreases by 20%;
- long service life;
- missing "memory effect";
- wide temperature range with unchanged performance (300-700 degrees Celsius);
- chemical stability and thermal, which increase safety.
The most widely used batteries
Among the many, the most common are 18650 li ion batteries manufactured by five companies: LG, Sony, Panasonic, Samsung, Sanyo, whose factories are located in Japan, China, Malaysia and South Korea. It was planned that li ion 18650 batteries would be used in laptops. However, due to the successful format, they are used in radio-controlled models, electric vehicles, lanterns, etc.
Like any quality product, such batteries have many fakes, therefore, in order to extend the life of the device, you only need to purchase batteries from well-known brands.
Protected and unprotected lithium-ion batteries
It is also important for lithium batteries whether they are protected or not. The operating range of the former is 4.2-2.5V (used in devices designed to work with lithium-ion sources): LED lights, low-power household appliances, etc.
In power tools, bicycles with electric motors, laptops, video and photo equipment, unprotected batteries are used, controlled by the controller.
What you need to know about lithium-ion batteries?
First of all, the restrictions that must be observed during operation:
- recharging voltage (maximum) cannot be higher than 4.35V;
- its minimum value cannot be lower than 2.3 V;
- the discharge current should not exceed more than twice the capacitance value. If the value of the latter is 2200 mAh, the maximum current is 4400 mA.
Functions performed by the controller
Why do you need a li ion battery charge controller? It performs several functions:
- supplies a current that compensates for self-discharge. Its value is less than the maximum charge current, but more than the self-discharge current;
- implements an efficient charge / discharge cycle algorithm for a specific battery;
- compensates for the difference in energy flows while charging and providing energy to the consumer. For example, when charging and powering a laptop;
- measures the temperature during overheating or hypothermia, preventing damage to the battery.
A li ion battery charge controller is made either in the form of a microcircuit built into the battery, or as a separate device.
To charge the batteries, it is better to use the standard charger for 18650 li ion batteries supplied in the kit. The charger for 18650 lithium batteries usually has a charge level indication. More often it is an LED that shows when the charge is in progress and its end.
On more advanced devices, you can track the time remaining until the end of the charge, the current voltage on the display. For a 18650 battery with a capacity of 2200mA, the charging time is 2 hours.
But, it is important to know how to charge a li ion 18650 battery with what current. It should be half the nominal capacity, i.e., if it is 2000 mAh, then the optimal current is 1A. By charging the battery with a high current, its degradation quickly sets in. When using low current, it will take more time.
Video: How to charge a Li ion battery charger with your own hands
Scheme of a device for charging batteries
It looks like this:
The circuit is distinguished by reliability and repeatability, and the incoming parts are inexpensive and readily available. In order to increase the battery life, competent charging of li ion batteries is required: by the end of charging, the voltage should decrease.
After its completion, i.e. when the current reaches zero, the charging of the li ion battery should stop. The circuit above satisfies these requirements: a discharged battery connected to the charger (VD3 lights up) uses a current of 300mA.
The ongoing process is indicated by the burning LED VD1. The current gradually decreasing to 30 mA indicates that the battery is charging. The end of the process is signaled by the lit LED VD2.
The circuit uses an LM358N operational amplifier (you can replace it with an analog KR1040UD1 or KR574UD2, which has a different pin arrangement), as well as a VT1 S8550 transistor 9 yellow, red and green LEDs (1.5V).
Can the battery be revived?
After a couple of years of active use, batteries catastrophically lose capacity, creating problems when using your favorite device. Is it possible and how to restore a li ion battery while the user is looking for a replacement?
Recovery of a li ion battery is possible temporarily in several ways.
If the battery is swollen, ie. stopped holding a charge, which means that gases have accumulated inside.
Then proceed as follows:
- the battery case is carefully disconnected from the sensor;
- separating the electronic sensor;
- find a cap with control electronics under it and pierce it carefully with a needle;
- then, they find a heavy flat object, larger in area than the area of \u200b\u200bthe battery, which will be used as a press (do not use a vice and similar devices);
- put the battery on a horizontal plane, and press down with a press, remembering that the battery can be damaged by applying excessive force. If it is not enough, the result may not be achieved. This is the most crucial moment;
- it remains to drip epoxy onto the hole and solder the sensor.
There are other ways, which you can read about on the Internet.
You can choose a charger on the site http://18650.in.ua/chargers/.
Video: Li-ion batteries, tips for using li-ion batteries
