Why do lithium-ion batteries die so early? Types of modern lithium batteries

The consumer market for lithium-ion (Li-ion) batteries is huge - about $10 billion, but it is quite stable, with a growth rate of only 2% per year. What about electric cars, you ask? Indeed, in the coming years, due to the development of electric vehicles, the annual growth rate of lithium-ion batteries is predicted to be 10%. Surprisingly, the biggest growth area for the Li-ion battery market continues to be “everything else,” from mobile phones to forklifts.

"Other" lithium-ion battery applications tend to have one thing in common - they are devices that are powered by sealed lead acid (SLA) batteries. Lead-acid batteries have dominated the electronics market for nearly 200 years, but they have been replaced by lithium-ion batteries for several years now. Since in many cases lithium-ion batteries have begun to replace lead-acid batteries (batteries), it is worth comparing these two types of energy storage devices, emphasizing the main technical features and economic feasibility of using Li-ion instead of traditional SLA devices.

History of the use of rechargeable batteries

The lead-acid battery was the first rechargeable battery, developed for commercial use in the 1850s. Despite their fairly respectable age of more than 150 years, they are still actively used in modern devices. Moreover, they are actively used in applications where it would seem quite possible to get by with modern technologies. Some common devices quite actively use SKB, such as uninterruptible power supplies (UPS), golf carts or forklifts. Surprisingly, the market for lead-acid batteries is still growing for certain niches and projects.

The first, fairly significant innovation in lead-acid technology came in the 1970s, when sealed SKB or maintenance-free SKB were invented. This modernization consisted of the appearance of special valves for bleeding gases when charging/discharging batteries. In addition, the use of a wetted separator made it possible to operate the battery in an inclined position without electrolyte leakage.

SKB, or English. SLAs are often classified by type or application. Currently, the two most common types are gel, also known as valve-regulated lead acid (VRLA) and absorbent glass mat AGM. AGM batteries are used for small UPSs, emergency lighting and wheelchair applications, while VRLA batteries are intended for larger format applications such as backup power for cellular relay towers, Internet hubs and forklifts. Lead-acid batteries can also be classified according to the following criteria: automobile (starter or SLI - starting, lighting, ignition); traction (traction or deep cycle); stationary (uninterruptible power supplies). The main disadvantage of SLAs in all these applications is the life cycle - if they are discharged repeatedly, they become severely damaged.

Surprisingly, lead-acid batteries were the undisputed leaders of the battery market for many decades, until the advent of lithium-ion batteries in the 1980s. A lithium-ion battery is a rechargeable cell in which lithium ions move from a negative electrode to a positive electrode during discharge, and vice versa during charging. Lithium-ion batteries use intercalated lithium compounds but do not contain lithium metal, which is used in disposable batteries.

The lithium-ion battery was first invented in the 1970s. In the 1980s, the first commercial version of the battery with a cobalt oxide cathode was brought to market. This type of device had significantly greater weight and capacity capabilities compared to nickel-based systems. New lithium-ion batteries have fueled enormous growth in the mobile phone and laptop market. Initially, due to safety concerns, safer options were introduced that included nickel- and manganese-based additives in the cobalt oxide cathode material, in addition to innovations in cell construction.

The first lithium-ion cells brought to market were in rigid aluminum or steel cans, and typically came in only a few form factors, either cylindrical or prismatic (brick-shaped). However, with the expansion of the range of applications of lithium-ion technology, their overall dimensions began to change.

For example, less expensive versions of older technology are used in laptops and cell phones. Today's thin lithium polymer cells are used in smartphones, tablets and wearable devices. Currently, lithium-ion batteries are used in power tools, electric bicycles and other devices. This variation heralds a complete replacement of lead-acid devices in more and more applications aimed at improving overall size and power performance.

Chemical features

The fundamentals of cell chemistry give lead-acid and lithium-ion devices specific properties and varying degrees of functionality. Below are some of the advantages of lead-acid batteries that have made it a staple for decades and the disadvantages that are now leading to its replacement, as well as similar considerations for lithium-ion devices.

Lead acid battery

• SKB is simple, reliable and inexpensive. It can be used over a wide temperature range.
• Batteries must be stored in a state of charge (SoC) and cannot be quickly charged.
• SKBs are heavy. Their gravimetric energy density is very low.
• The life cycle is usually 200 to 300 discharges/charges, which is very short.
• The charge/discharge curve allows SOC measurements with simple voltage control.

Li-ion battery

• They have maximum energy density in terms of size and weight.
• The life cycle is typically between 300 and 500, but can be in the thousands for lithium phosphate cells;
• The operating temperature range is very small;
• Various cell sizes, shapes and other options are available;
• No maintenance required. The self-discharge level is very low.
• Implementation of operational safety schemes is required. Complex charging algorithm.
• SoC measurements require complex solutions due to the non-linearity of the voltage curve.

Electronics

It is important to understand the difference between a battery pack and a rechargeable battery. The cell is the main component of the package. In addition, the package also includes electronics, connectors and housing. The figure above shows examples of these devices. A lithium-ion battery must have, at a minimum, cell protection and control circuitry implemented, and the charger and voltage sensing system are much more complex than those found in lead-acid devices.

When using lithium-ion and lead-acid batteries, the main differences in electronics will be as follows:

Charger

Charging a lead-acid battery is quite simple as long as certain voltage thresholds are met. Lithium-ion batteries use a more complex algorithm, with the exception of iron phosphate-based packs. The standard charging method for such devices is the constant current/constant voltage (CC/CV) method. It includes a two-step charging process. At the first stage, charging occurs with a constant current. This lasts until the voltage on the cell reaches a certain threshold, after which the voltage remains constant, and the current decreases exponentially until it reaches the cutoff value.

Charge counting and communication

As mentioned earlier, the charge of the SCB can be measured using simple voltage measurements. When using lithium-ion batteries, it is necessary to control the charge level of the cells, which requires the implementation of complex algorithms and learning cycles.

I 2 C is the most common and cost-effective communication protocol used in lithium-ion batteries, but it has limitations in terms of noise immunity, signal integrity over distance, and overall bandwidth. SMBus (System Management Bus), a derivative of I 2 C, is very common in smaller batteries, but does not currently have any effective support for high-power or larger packages. CAN is great for high noise environments or where long runs are required, such as in many SKB applications, but it is quite expensive.

Direct replacements

It should be emphasized that there are now several standard lead-acid battery formats. For example - U1, a standard form factor used in medical equipment backup power applications. The lithium iron phosphate battery has proven to be quite a worthy replacement for lead acid. Iron phosphate has excellent life cycle, good charge conductivity, improved safety and low impedance. Lithium iron phosphate battery voltages are also well matched to lead acid battery voltages (12V and 24V), allowing the same chargers to be used. Battery maintenance and monitoring software packages include smart features such as charge tracking, charge/discharge cycle counter, and more.

Lithium iron phosphate batteries retain 100% capacity during storage, unlike SKB batteries, which lose capacity over several months of storage. The figure above compares the two products and the types of advances made in the transition from SKB to Li-ion.

Conclusions

There are very few batteries that can store as much energy as lead-acid batteries, making this type of battery cost-effective for many high-power devices. Lithium-ion technology is constantly falling in price, as well as constant improvements in their chemical structures and safety systems, making them a worthy competitor to lead-acid technology. Devices for their use can be very different, ranging from uninterruptible power supply devices to electric vehicles and drones.

Lithium batteries

Lithium or lithium-ion (Li-ion) batteries are mainly found in cell phones, laptops, and video cameras. The products are expensive, and so are the batteries, so you need to handle them even more competently than any other batteries. So what is the power of Li-Ion? There are probably even more rumors and myths here. Firstly, it begins to appear by itself, if only because sellers of equipment with Li-ion batteries do not give any special instructions, saying that the battery is “smart” and will do everything as it should. But not herself. After all, there are so many cases when owners of new laptops rendered the battery unusable within a month and then paid good money for a new battery. Of course, lithium batteries are expensive because they are packed with electronics, but, unfortunately, they do not save you from being a fool.

Overdischarge

As with nickel batteries, lithium batteries are also very susceptible to overcharging and overdischarging. But, since these batteries are used in smart devices and come with their own chargers, their electronics do not allow overcharging - i.e. you don't have to be afraid of him. But overdischarge is more difficult to control, which is why it is the most common cause of premature battery failure. Of course, in expensive and complex devices, such as laptops, shutdown occurs before the voltage drops to a critical value. But precedents indicate that this emergency shutdown is best viewed as an emergency measure, which, if possible, is best avoided. It is the most important rule to avoid complete discharge, since low voltage can disable the emergency protection circuit. It happens that people “kill” their batteries when they get carried away by training. Training is a good thing, but for lithium batteries 2-3 full cycles are enough.

There is no memory effect for lithium batteries, so they can be charged whenever you want, so it is better not to completely discharge the batteries after training. The recommended lower threshold is 5-10%. The critical lower threshold is 3%.

Many incomplete cycles or one complete

Lithium batteries have a service life of approximately 300 cycles. A full cycle is considered to be a cycle of full charge and complete (i.e. up to approximately 3% capacity) discharge, or vice versa. If you discharge the battery to 50% and then charge it, it will be 1/2 cycle, if to 75% and charge it will be 1/4 cycle, etc. So, for phones and laptops, the difference in benefits between full and incomplete cycles is different. It is persistently stated on the Internet that a lot of people charged their phones when they were not fully discharged (i.e., they recharged the phone every day) and eventually ruined them. At the same time, for laptops it is reliably known that full cycles wear out the battery faster than incomplete ones. The situation becomes clearer with a detailed examination of the structure of Li-ion batteries (see additional materials). It turns out that a lot depends on the controller. It is he who controls the charge current, monitors the condition of the battery, etc. So, in laptops the controller is located in the battery itself and is adjusted by system utilities, such as calibration. In cell phones, the controller is located in the phone itself and cannot be easily adjusted. Although there is no memory effect in lithium batteries, there is a so-called “digital memory” effect. The fact is that the charge-discharge control electronics located in the battery itself operate independently of the device using the battery. Internal electronics monitor the voltage level of the element, interrupt the charge when the set maximum value is reached (taking into account the change in voltage due to the charging current and battery temperature), interrupt the discharge when a critical value is reached and report this “upstream” (for these purposes, a large range of specialized microcircuits). The battery monitoring system “at the top” calculates the charge level based on information about the moments of switching off the charge and discharge from the battery and the readings of the current measurement system. But if the operating conditions are such that a complete discharge before a hardware shutdown or full charging does not occur, these calculations after several cycles may not be entirely correct - the battery capacity drops over time, and the current meter readings may not always correspond to reality. Typically, deviations do not exceed one percent for each cycle, unless serious changes occur during operation, associated, for example, with the failure of one of the battery cells. The monitoring system has the ability to “learn”, that is, recalculate the value of the full capacity of the battery, but for this it is necessary to perform at least one full charge-discharge cycle before the hardware circuits of the battery itself are triggered. So it turns out that with very frequent cycles, the controller gets confused, and, therefore, incorrectly calculates the battery charge and carries out incorrect charging, as a result of which the battery deteriorates. Unlike a laptop, a phone cannot be recalibrated. All that remains in this case is to do a couple of full cycles to get the controller in order. I recommend, ideally, combining full and incomplete cycles, adhering to the “golden mean” principle. Personally, I did this with my cell phone - as a result, after 2 years of operation, the drop in capacity was no more than 40%, which is the norm. In part, time is also not kind to lithium batteries - they wear out over time, regardless of use; Their lifespan is short and it is reasonable to change batteries every 2-3 years.

Storage

When the battery is not in use, it is recommended to store it at 40% capacity in a cool place. The lower temperature limit for storage and operation is 00 C. In general, lithium batteries like to be charged, i.e. They are better to store and keep in a charged state, unlike nickel ones. But during long-term storage, the maximum charge still wears out the battery more, so the optimal state is considered to be 40% charge.

Battery resuscitation

In general, if the battery is dead, it is better to buy a new one; this is the most logical option, although it is expensive. I have not seen any reliable recipes for resuscitating batteries. There are real legends here, especially about laptops, that people have revived their ruined laptop battery and everything is fine with them. One of them sounds like this: “You need to completely discharge the battery, leave the laptop for a week; then fully charge the battery and also leave it for a week; in two months the capacity should be restored.”

For cell phones: combine full and incomplete cycles (in the “XZ” proportion).
For laptops: as few full cycles as possible (after training).
For everyone: it is recommended to do 80% cycles; do not allow complete discharge (below 3%).

When they talk about lithium batteries or accumulators, most often they don’t even realize that almost a dozen of them have appeared in the last couple of years, each of which is lithium with various additives of other chemical elements, which ultimately differ significantly from each other.

Let's look at their types and start with the classics:

Lithium-ion batteries are classic rechargeable batteries in which lithium ions move from the negative electrode to the positive electrode during discharge and back again when charging. Lithium-ion batteries are widely used in consumer electronics. They are one of the most popular types of rechargeable batteries for portable electronics, with one of the best energy densities, no memory effect and slow loss of charge when not in use (low self-discharge).

This series covers cylindrical and prismatic battery sizes. Li-ion has the highest power density of any old type battery. Very light weight and long life cycle makes it an ideal product for many solutions.

Lithium titanate (lithium titanate) is a relatively new class of lithium-ion batteries - (more details). It is characterized by a very long life cycle, measured in thousands of cycles. Lithium lead titanate is also very safe and comparable in this regard to iron phosphate. The energy density is lower than other lithium-ion power sources and its rated voltage is 2.4V.

This technology features very fast charging, low internal resistance, very high life cycle and excellent endurance (also safety). LTO has found its application mainly in electric vehicles and wristwatches. Recently, it has begun to find application in mobile medical devices due to its high security. One of the features of the technology is that it uses nanocrystals on the anode instead of carbon, which provides a much more efficient surface area. Unfortunately, this battery has lower voltages than other types of lithium batteries.

Peculiarities:

• Specific energy: about 30-110Wh/kg
• Energy density: 177 W * h/l
• Specific power: 3,000-5,100 W/kg
• Discharge efficiency: approximately 85%; charging efficiency more than 95%
• Energy-price: 0.5 W/dollar
• Shelf life: >10 years
• Self-discharge: 2-5%/month
• Durability: 6000 cycles to 90% capacity
• Nominal voltage: 1.9 to 2.4 V
• Temperature: -40 to +55°C
• Charging method: Uses stable constant current, then constant voltage until it reaches the threshold.

Chemical formula: Li4Ti5O12 + 6LiCoO2< >Li7Ti5O12 + 6Li0.5CoO2(E=2.1 V)

Lithium polymer has a higher energy density in terms of weight than lithium-ion batteries. In very thin cells (up to 5 mm), lithium polymer provides high volumetric energy density. Excellent stability in overvoltage and high temperatures.

This series of batteries can be produced in the range from 30 to 23000 mAh, prismatic and cylindrical housing types. Lithium polymer batteries offer a number of advantages: greater energy density by volume, flexibility in cell sizes, and a wider margin of safety, with excellent voltage stability even at high temperatures. Main areas of application: portable players, Bluetooth, wireless devices, PDAs and digital cameras, electric bicycles, GPS navigators, laptops, e-readers.

Peculiarities:

• Rated voltage: 3.7V
• Charging voltage: 4.2±0.05V
• Charge current, speed: 0.2-10C
• Discharge voltage limit: 2.5 V
• Discharge speed: up to 50C
• Cycle endurance: 400 cycles

Lithium iron phosphate has good safety characteristics, long service life (up to 2000 cycles), and low production cost. LiFePO4 batteries are well suited for high discharge current applications such as military equipment, power tools, electric bicycles, mobile computers, UPS and solar power systems.

As a new anode material for lithium-ion batteries, lifepo4 was first introduced in 1997 and has been continuously improved to date. It has attracted the attention of experts due to its reliable safety, durability, low environmental impact during disposal, and convenient charging and discharging characteristics. Many experts claim that lifepo4 batteries are by far the best option for autonomously powering electronics.

Lithium sulfur dioxide (Li and SO2 battery) - these batteries have high energy density and good resistance to high power discharge. Such elements are used mainly in military science, meteorology and astronautics.

Lithium sulfur dioxide batteries with a lithium metal anode (the lightest of all metals) and a liquid cathode containing a porous carbon current collector filled with sulfur dioxide (SO2) produce a voltage of 2.9 V and are cylindrical in shape.

Peculiarities:

• High operating voltage, stable throughout most of the discharge
• Extremely low self-discharge
• Performance in extreme conditions
• Wide operating temperature range (-55°C to +65°C)

Lithium manganese dioxide (Li-MnO2 battery) - these batteries have a lightweight lithium metal anode and a solid manganese dioxide cathode, immersed in a non-corrosive, non-toxic organic electrolyte. This type of battery is EU RoHS compliant and is characterized by large capacity, high discharge capacity and long service life.

Li-MnO2 is widely used in backup power supplies, emergency beacons, fire alarms, electronic access control systems, digital cameras, medical equipment.

Peculiarities:

• High energy density
• Very stable discharge voltage
• More than 10 year shelf life
• Operating temperature: -40 to +60°C

Lithium thionyl chloride (lithium-SOCl2) batteries feature a lightweight lithium metal anode and a liquid cathode containing a porous carbon current collector filled with thionyl chloride (SOCl2). Li-SOCL2 batteries are ideal for automotive devices, medical devices, and military and aerospace applications. They have the widest operating temperature range from -60 to + 150°C.

Peculiarities:

• High energy density
• Long shelf life
• Wide temperature range
• Good sealing
• Stable discharge voltage

Li-FeS2 batteries

Li-FeS2 batteries and batteries stand for lithium iron disulfide. Information about them will be added later.

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

What are lithium batteries?

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

• 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):

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 the 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 high voltage for a long time, which is usually provided by 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 provided with a reduced constant current 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 a large charge current is immediately passed through such a battery, this will inevitably lead to its heating, and then it depends.

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

Intelligent charging should be able to monitor the voltage on the battery during the preliminary charging stage and, if the voltage does not rise for a long time, draw a conclusion 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 18650 batteries?

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 designed to control the charging process - they limit the charge current at a 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’s sold on every corner and costs just a penny (you can get 10 pieces for just 55 rubles).

LM317 comes in different housings:

Pin assignment (pinout):

Analogs 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 a similar pnp 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 is a typical connection diagram:

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 precisely.

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 is also cheaper than the 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 is another version of a printed circuit board with an SMD LED and a micro-USB connector:

LTC4054 (STC4054)

Very simple scheme, 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 pair 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, 2, 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 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 voltage at the output 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).

Any pnp transistor is suitable, 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. As an 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 it would be unnecessary to use it. If you are comfortable with a soldering iron, I would recommend choosing this option.

A 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 a given battery: the initial current does not exceed the maximum permissible charging current 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.

Initially, when the battery is still discharged, the laboratory 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 fact 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 passivating 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.

Where to buy microchips?

You can, of course, buy it in Chipe-Dip, but it’s expensive there. That's why I always buy from one very secret store)) The most important thing is to choose the right seller, then the order will arrive quickly and for sure.

For your convenience, I have collected the most reliable sellers in one table, use it for your health:

The lithium battery is a safe and energy-consuming device. Its main advantage is working without charging for a long time. It can function at even the lowest temperatures. Because of its ability to store energy, the lithium battery is superior to other types. That is why their production increases every year. They can be of two shapes: cylindrical and prismatic.

Application

They are widely used in computer equipment, mobile phones and other equipment. Lithium battery chargers have an operating voltage of 4 V. The most important advantage is operation over a wide temperature range, which ranges from -20 °C to +60 °C. Today, there are batteries that can function at temperatures below -30 °C. Every year, developers are trying to increase both positive and negative temperature ranges.

At first, a lithium battery loses about 5% of its capacity, and this figure increases every month. This indicator is better than that of other battery representatives. Depending on the charging voltage, they can last from 500 to 1000 cycles.

Types of Lithium Batteries

There are such types of lithium batteries that are found in different areas of household and industrial economy:

• lithium-ion - for main or backup power supply, transport, power tools;
• nickel-salt - road and rail transport;
• nickel-cadmium - shipbuilding and aircraft manufacturing;
• iron-nickel - power supply;
• nickel-hydrogen - space;
• nickel-zinc - cameras;
• silver-zinc - military industry, etc.

The main type is lithium-ion batteries. They are used in the areas of power supply, production of power tools, telephones, etc. Batteries can operate at temperatures from -20 ºС to +40 ºС, but developments are underway to increase these ranges.

With a voltage of only 4 V, a sufficient amount of specific heat is generated.

They are divided into different subtypes, which differ in the composition of the cathode. It is modified by replacing graphite or adding special substances to it.

Lithium batteries: device

As a rule, such devices are produced in a prismatic shape, but there are also models in a cylindrical body. The internal part consists of electrodes or separators. Steel or aluminum is used to make the body. The contacts are output to the battery cover, and they must be insulated. Prismatic batteries contain a certain number of plates. They are stacked on top of each other. To provide additional safety, the lithium battery has a special device. It is located inside and serves to control the work process.

In case of dangerous situations, the device turns off the battery. In addition, the equipment is provided with external protection. The case is completely sealed, so there is no leakage of electrolyte, as well as no water getting inside. The electric charge appears due to lithium ions, which interact with the crystal lattice of other elements.

Screwdriver with lithium battery

It can accommodate three types of batteries, which differ in their cathode composition:

• cobalt-lithium;
• lithium ferrophosphate;
• lithium manganese.

A screwdriver with a lithium battery differs from others in its low level of self-discharge. Another important advantage is that it does not require maintenance. If a lithium battery breaks down, you can throw it away as it does not harm people or the environment. The only negative is the low charging of lithium batteries, as well as high safety requirements. It is difficult to charge it at subzero temperatures.

Main Features

The operation of the screwdriver, the state of its power, and the time of possible operation depend on the technical characteristics. Other technical indicators include:

• the voltage of one battery in the device can range from 3 to 5 V;
• the maximum energy intensity indicator reaches 400 Wh/l;
• loss of own charge by 5%, and over time by 20%;
• complex charging mode;
• The battery is fully charged in 2 hours;
• resistance from 5 to 15 mOhm/Ah;
• number of cycles - 1000 times;
• service life - from 3 to 5 years;
• the use of different types of current for certain battery capacities, for example, a capacity of 65 ºС - direct current is used.

Production

Most manufacturers are striving to make power tools more advanced and compliant with modern technology.

To do this, it is necessary to provide good batteries in the design. The most popular manufacturing companies are:

1. Bosh company. The lithium battery is manufactured using new ECP technology. It is she who controls the discharge of the device. Another useful property is protection against overheating. At high power, a special device lowers the temperature. The battery design has holes that serve as ventilation and cool the battery. Another technology is Charge, thanks to which charging occurs much faster. In addition, Bosh produces batteries for various electric tools. Many users leave good reviews about this company.
2. Makita company. It produces its own microcircuits that control all operating parameters and processes in the battery, for example, temperature, charge content. Thanks to this, you can choose the charging mode and charging time. Such microcircuits increase the service life. The batteries are manufactured with a fairly powerful housing, so they are not subject to mechanical stress.
3. Hitachi company. Thanks to its latest technology, the weight and overall dimensions of the battery are reduced. This is why electric tools become lightweight and mobile.

Features of operation

When using a battery, you must adhere to the following rules:

1. There is no need to use a lithium battery for individual unprotected elements, and buy cheap Chinese parts. Such a device will not be safe, since there will be no system that protects against short circuits and elevated temperatures. That is, if the battery overheats significantly, it can explode and its service life will be much shorter.
2. Do not heat the battery. As the temperature inside the device increases, the pressure increases. These actions will lead to an explosion. Therefore, there is no need to open the top cover of the battery and place it in places exposed to sunlight. Such actions will shorten the service life.
3. Do not bring additional sources of electricity near the contacts at the top of the cover, as a short circuit may occur. Built-in protection systems will not always help in this matter.
4. The battery must be charged in compliance with all rules. When charging, you should use ones that distribute the current evenly.
5. The battery charging procedure is carried out at a positive temperature.
6. If there is a need to connect several lithium batteries, then you need to use models from the same manufacturer and similar in technical characteristics.
7. Lithium batteries should be stored in a dry place that is not exposed to sunlight with temperatures exceeding 5ºC. When equipment is exposed to high temperatures, the charge will decrease. Before storing during the winter, the battery is charged to 50% of its capacity. Care must be taken to ensure that the battery is not completely discharged. If this happens, charge it immediately. If mechanical damage occurs on the body, as well as signs of rust, the device cannot be used.
8. If during operation the battery experiences significant overheating or smoke, you should immediately stop using it. After this, move the damaged device to a safe place. If a substance is released from the body, it must be prevented from coming into contact with the skin or other organs.
9. Do not throw away or burn lithium batteries. Their disposal occurs in the event of mechanical damage to the housing, explosions, or ingress of water or steam.

About the fire

If a fire occurs in a lithium battery, it cannot be extinguished with water and a fire extinguisher - carbon dioxide and water can react with lithium. To extinguish it, you should use sand, salt, and also with a thick cloth.

Charging process

A lithium battery, the charger from which is connected to direct current, is charged at a voltage of 5 V and above.

There is a drawback - they are not resistant to overcharging. An increase in temperature inside the housing leads to damage.

The operating instructions indicate a special level. When it is reached, it should be charged. If you increase the charging voltage, the properties of a lithium battery will significantly decrease.

As stated earlier, the battery life is 3 years. To maintain this period, you must adhere to the operating, charging and storage conditions. In addition, they must be permanently functional and not stored.

Overcharge

The battery design includes a recharging system, so you don’t have to disconnect the charger and not be afraid that the composition inside will boil, as happens with car batteries.

If the equipment will be stored for more than one month, it must be completely discharged. This will significantly extend the service life.

Price

The price of a lithium-ion battery depends on the capacity and technical characteristics.

On average, it varies from 100 to 500 rubles. Despite this cost, many users leave positive reviews. Among the positive aspects are a wide range of operating temperatures, high power and the ability to operate for more than 1000 cycles (about 3 years of intensive use). The devices are widely used in various fields, so everyone can appreciate their benefits.

So, we found out what lithium batteries are.