What is LiFePO4 battery. LiFePO4 batteries Ferrum polymer battery

Marble 12.01.2022

Marble

Modern electronics makes ever higher demands on the power and capacity of energy sources. While nickel-cadmium and nickel-metal hydride batteries are close to their theoretical limit, lithium-ion technologies are only at the beginning of the journey.

Li-Fe (lithium phosphate) batteries are distinguished not only by their high capacity, but also by their fast charging. In just 15 minutes, you can fully charge the battery. In addition, such batteries allow 10 times more charge-discharge cycles than conventional models. The idea of a Li-Fe battery is to activate the lithium-ion exchange between the electrodes. With the help of nanoparticles, it was possible to develop the exchange surface of the electrodes and obtain a more intense ion flux. To avoid too strong heating and a possible explosion of the electrodes, the authors of the development used lithium / iron phosphate instead of lithium / cobalt oxide in the cathodes. The insufficient electrical conductivity of the new material is compensated by the introduction of aluminum, manganese, or titanium nanoparticles.

To charge Li-Fe batteries, a special charger with a marking must be used, which says that this type of charger is capable of working with Li-Fe batteries, otherwise you will destroy the battery!

Advantages

Safe, durable case, unlike Li-Po battery shells
Ultra-fast charge (at a current of 7A, a full charge in 15 minutes !!!)
Very high output current 60A - operating mode; 132A - short-term mode (up to 10 seconds)
Self-discharge 3% for 3 years
Work in the cold (up to -30 degrees C) without loss of working properties
MTBF 1000 cycles (three times more than nickel batteries)

Flaws

Requires a dedicated charger (not compatible with LiPo chargers)
Heavier than Li-Po

A bit of history

Li-ion batteries are twice as large as NiMH counterparts in terms of capacity and almost three times in terms of power density. The energy density of Li-ion is three times higher than that of NiMH. Li-ion withstands very high discharge currents, which NiMH batteries are not even theoretically able to handle. Also, NiMH is of little use for powerful portable tools, which are characterized by high impulse loads, take a long time to charge and usually “live” no more than 500 cycles. Storage of NiMH is another major problem. These batteries suffer from very high self-discharge - up to 20% per month, while for Li-ion this figure is only 2-5%. NiMH batteries are subject to the so-called memory effect, which is also characteristic of NiCd batteries.

But Li-ion batteries also have their drawbacks. They are very expensive, require a complex multi-level electronic control system due to the tendency to irreversibly degrade when discharged too deeply or spontaneously ignite at high loads. They owe this to the main electrode material, lithium cobaltate (LiCoO2). Scientists have been struggling for years to find a replacement for cobalt. Various lithium compounds – manganates, titanates, stannates, silicates and others – are candidates for the position of the main electrode material of the future. But the absolute favorite today is lithium ferrophosphate Li-Fe, obtained for the first time back in 1996 by Professor John Goodenough from the University of Texas. For a long time, this topic was gathering dust on the shelf, since Li-Fe did not differ in anything outstanding, except for its cheapness, and its potential remained unexplored. Everything changed in 2003 with the advent of A123 Systems.

Characteristics of Li-Fe batteries

Like all batteries, Li-Fe has several basic electrical parameters:

Fully charged cell voltage: Li-Fe is about 3.65V. Due to the peculiarities of this technology, these elements are not very afraid of overcharging (at least it does not cause fire and explosion, as happens with elements based on lithium cobaltate Li-ion, Li-pol), although manufacturers it is highly discouraged to charge above 3.9V and only a few charges up to 4.2V over the entire life of the cell.

Fully discharged cell voltage: Here, manufacturers' recommendations differ somewhat, some recommend discharging cells to 2.5V, some to 2.0V. But in any case, according to the practice of operating all types of batteries, it has been established that the smaller the depth of discharge, the more cycles this battery can survive, and the amount of energy that falls on the last 0.5V discharge (for Li-Fe) is only a few percent of its capacity.

Midpoint voltage: for elements of this technology from different manufacturers varies (declared) from 3.2V to 3.3V. The midpoint voltage is the voltage that is calculated based on the discharge curve and is intended to calculate the overall capacity of the battery, which is expressed in Wh (watt hours) for this, the midpoint voltage is multiplied by the current capacity, i.e. for example, you have a cell with a capacity of 1.1Ah and voltage midpoint 3.3V, then its overall capacity is 3.3*1.1=3.65Wh. (Many people often confuse the mid-point voltage with the voltage of a fully charged cell.)

In this regard, I would like to pay attention to the performance characteristics of batteries, or rather, the voltage of the midpoint of 36V and 48V Li-Fe batteries. So the voltage of 36V and 48V is indicated conditionally in relation to the lead-acid battery more familiar to many, or rather to the midpoint voltage of 3 or 4 12V lead-acid batteries connected in series. A 36V Li-Fe battery has 12 cells (elements) connected in series, which is 3.2 * 12 = 38.4V (for a 48V battery 3.2 * 16 = 51.2V) which is slightly higher than the average points of lead-acid batteries, i.e. with equal capacities ( in Ah) Li-Fe battery has a larger overall capacity than a lead-acid battery.

At the moment, the main production base for the manufacture of Li-Fe elements is China. There are factories of both well-known companies (A123System, BMI) and factories of unknown companies. Many sellers of finished batteries (who sell them at retail) claim that they are also manufacturers of the cells themselves, which in fact turns out to be false. Large manufacturers of elements producing them in millions of pieces a year are not interested in working with retail customers and simply ignore questions about selling dozens of pieces of elements, or offer to make a purchase in volumes of several thousand pieces. There are also small enterprises where elements are made in small batches in a semi-handicraft way, but the quality of such elements is extremely low, the reason for this is the lack of high-quality materials, equipment and low technological discipline. Such elements have a very large variation in capacitance and internal resistance within even one batch. Also on the market for assembling finished batteries there are elements produced by large manufacturers, but due to the fact that they have not been rejected by certain parameters (capacity, internal resistance, voltage drop during storage), they do not enter the market and must be disposed of. These elements are the basis for the assembly of batteries by small handicraft enterprises. The main difference between such elements and elements of standard quality produced by large manufacturers is no markings on each element. The marking is applied at the factory during the final tests and serves as an identifier of the manufacturer's factory, date and change of manufacture. This information is necessary for large manufacturers in order to further monitor the quality of elements during operation and, in case of claims, to be able to find the cause of the problem. As you yourself understand, for those who produce elements in artisanal conditions, there is no point in such an operation.
Follow these links to see the tests of the most famous manufacturers of elements:

http://www.zeva.com.au/tech/LiFePO4.php

By the way, what is interesting according to the results of the checks, almost all manufacturers declare the capacity is greater than it is available (the only exception is the A123 system), while Huanyu generally has a quarter lower than the declared one.

unexpected discovery

A123 Systems is an unusual company. In conversations, its employees, from an ordinary engineer to the president, often repeat one phrase that is not often heard these days: “We are only at the beginning of the road. By following it to the end, we will turn the world upside down!” The history of A123 Systems began at the end of 2000 in the laboratory of Professor Yeet Ming Chang from the Massachusetts Institute of Technology (MIT). Chang, who had been working on Li-ion technology for a long time, almost accidentally discovered a startling phenomenon. With a certain impact on the colloidal solution of electrode materials, the structure of the battery began to reproduce itself! The forces of attraction and repulsion depended on many factors - the size, shape and number of the particles themselves, the properties of the electrolyte, the electromagnetic field and temperature. Chang conducted detailed studies of the physicochemical properties of electrode nanomaterials and determined the basic parameters for starting the process of spontaneous self-organization. The resulting batteries had a specific capacity one third higher than that of conventional lithium cobaltate batteries and withstood hundreds of charge-discharge cycles. The microstructure of the electrodes, created in a natural way, made it possible to increase the total active surface area by an order of magnitude and accelerate ion exchange, which in turn increased the capacity and performance of the battery.

Self-organization according to the Chang method is as follows: a mixture of nanoparticles of cobalt oxide and graphite is placed in the case of the future battery, an electrolyte is added and the necessary external conditions are created - temperature, electromagnetic field and pressure. Cobalt oxide particles are attracted to each other, but graphite particles are repelled. The process continues until the forces of attraction and repulsion reach equilibrium. As a result, an anode–cathode pair is formed, completely separated by the interphase–electrolyte. Due to the identical size of the nanoparticles, Chang was able to create battery samples with specified capacity and performance parameters in the laboratory. Further study of this phenomenon and the development of production technology based on it promised fantastic prospects. According to Chang's calculations, the capacity of the batteries could be doubled compared to existing analogues, and the cost could be reduced by half. The self-organization method made it possible to create batteries of any shape smaller than a match head, including directly inside the current consumers themselves.

Step into big business

At that time, electrochemical engineer Bart Riley worked for American Semiconductor, which produced a wide range of semiconductors. He was connected with Chang by a long acquaintance and common scientific interests. When Chang told Riley about his unexpected discovery, the idea of creating a business based on the phenomenon of self-organization was born almost immediately. But neither one nor the other had a clue how companies are created. The third founder of A123 Systems was Rick Fulap, an entrepreneur with a knack for turning good ideas into big money. By the age of 26, Fulap has managed to create five companies from scratch and launch into the open spaces of big business. One day, in an MIT scientific journal, Fulap came across an article by Professor Chang on lithium-ion technology. Not understanding anything he read, Rick dialed the professor's phone number. In response to an offer to go into the carbon nanofiber business, Chang replied that he had a better idea, and Fulap was unable to sleep until morning.

First of all, the partners managed to obtain a license from MIT for the industrial use of the battery self-organization technique and redeem the rights to the cathode material obtained in Chang's laboratory - lithium iron phosphate. He had nothing to do with the phenomenon of self-organization, but Fulap decided that the rights to Li-Fe would not hurt. Don't waste good! In addition, Chang received a special grant to continue research on Li-Fe. In September 2001, Rick Fulap was already roaming venture capital funds in search of funds to raise money. He managed to create competition among investors, fueling it with more and more press reports about the fantastic market prospects for Li-ion batteries.

Already in December 2001, the company's accounts received the first $8 million. Four months after the start of work on the project, in April 2002, the leaders of the mobile electronics market Motorola and Qualcomm entered the business, seeing huge potential in the new technology. Bart Riley recalls with a smile how, at some conference, Fulap jumped up to Paul Jacobs, vice president of Qualcomm. Within a minute, almost holding Jacobs by the lapel of his jacket, Rick was able to intelligibly explain to him the advantages of A123 technology over competitors, and after a few seconds he posed the question point-blank - invest today, tomorrow it will be too late! And after a couple of days, Jacobs made the right decision. Soon, among the investors of A123 were: the famous company Sequoia Capital, with the money of which Google and Yahoo, General Electric, Procter & Gamble and many other large companies were once created.

reserve parachute

By the beginning of 2003, work had come to a standstill. It turned out that the promising technology only partially works - the process of self-organization turned out to be unstable. Serious difficulties arose with the technology of obtaining electrode nanomaterials uniform in size and properties of particles. As a result, the performance of the product "floated" in the range from outstanding to worthless. The service life of the obtained batteries was significantly inferior to the available analogues due to the weakness of the crystal lattice of the electrodes. It simply collapsed in several discharge cycles. Chang realized that the creation of industrial technology for ideal batteries was still very far away. The project cracked at the seams...

By that time, work on lithium ferrophosphate had yielded unexpected results. At first, the electrical properties of iron phosphate looked very modest. The advantages of Li-Fe over LiCoO2 were its non-toxicity, low cost, and less sensitivity to heat. In the rest, ferrophosphate was significantly inferior to cobaltate - by 20% in terms of energy consumption, by 30% in terms of productivity and the number of work cycles. This means that a battery with a primary Li-Fe cathode was not suitable for mobile electronics, where capacity is of paramount importance. Ferrophosphate required deep modification. Chang began experimenting with adding niobium and other metals to the electrode structure and reducing the size of individual Li-Fe particles down to a hundred nanometers. And the material has literally changed! Due to the increased active surface area by thousands of times and the improvement in electrical conductivity due to the introduction of gold and copper, batteries with a cathode made of nanostructured Li-Fe exceeded conventional cobalt ones in discharge currents by ten times. The crystal structure of the electrodes practically did not wear out over time. Metal additions strengthened it, as reinforcement strengthens concrete, so the number of battery cycles increased more than ten times - up to 7000! In fact, such a battery is capable of surviving several generations of the devices it powers. In addition, nothing new in the production technology had to be created for Li-Fe. This meant that the product that Riley, Chang, and Fulap made was ready for immediate mass production.

“If you're a small company with limited funding, you usually focus on one thing,” Riley says. – But it turned out that we had two ideas in our pocket! Investors demanded to continue work on the original theme of the project, and leave the nanophosphate until better times. But we did our own thing. We sent a small team of engineers to the new direction. They were given a specific goal – to develop a technology for the industrial production of cathode nanomaterials.” As it turned out later, this stubborn decision saved the entire project from collapse. After the first obvious successes on nanophosphate, further work on self-organization was shelved, but not forgotten. After all, history may someday repeat itself exactly the opposite.

industrial giant

Literally a month after that, A123 entered into a fateful contract with the famous Black & Decker company. It turned out that Black & Decker had been developing a new generation of construction power tools for several years - mobile and powerful portable devices. But the introduction of new items was delayed due to the lack of a suitable current source. NiMH and NiCd batteries were not suitable for the company in terms of weight, size and performance. Ordinary Li-ion batteries were capacious enough, but did not provide a high load current and, when discharged quickly, they got so hot that they could catch fire. In addition, the time needed to charge them was too long, and a portable tool had to be always ready. A123 batteries were ideal for this purpose. They were very compact, powerful and absolutely safe. The charge time to 80% capacity was only 12 minutes, and at peak loads Li-Fe batteries developed power exceeding the power of networked tools! In short, Black & Decker found exactly what they were looking for.

By then, the A123 only had a prototype battery the size of a dime, and Black & Decker needed millions of actual batteries. Fulap and Riley did a great job of creating their own production facilities and a year after signing the contract, they began mass production of marketable products in China. The energy and drive of Fulap in a deal with Black & Decker allowed the A123 to enter the big industrial clip in the shortest possible time. In less than six years, the Massachusetts-based company has grown from a pure idea to a large research and production complex with six factories and a staff of 900 employees. Today, A123 Systems holds 120 patents and patent applications in the field of electrochemistry, and its lithium-ion technology research center is considered the best in North America.

But the company does not stop there. Over the past year and a half, the properties of the original nanophosphate have been radically improved and new types of electrolytes have been developed. More advanced and reliable electronic charge control systems have been created. Several designs of battery packs have been developed for use in various fields of technology. But the main step forward is, of course, the development of a battery for the future Chevrolet Volt hybrid car.

Battery production technologies do not stand still and gradually Ni-Cd (nickel-cadmium) and Ni-MH (nickel-metal hydride) batteries are being replaced on the market by batteries, in ...

List of companies that produce lithium-ion (Li-ion), lithium-polymer (Li-Po), lithium-phosphate (Li-Fe / LiFePO4) batteries in various countries of the world. Manufacturer name Location...

Tested battery voltage out of the box:

Health testing:
I will check the operation of the batteries in the flashlights I have on XML-T6.

Battery of standard sizes, fits perfectly in a flashlight:

In flashlights based on XML-T6, the design feature (the absence of a protrusion on the plus side) did not interfere with the work:

thanks to the presence of a spring:

The battery simply does not reach the positive contact:

It was not without refinement, at first I wanted to disassemble the battery compartment by unscrewing the screws, but the screws did not unwind, I had to break and glue:

So what is LiFePo4?
The Wikipedia article presents LiFePo4 as a kind of prodigy with excellent characteristics: charge speed of 15 minutes at 7A, frost resistance up to -30C, huge recoil currents up to 60A, long-lived, durable. More details on LiFe can be found in the translated article on rcdesign, which compares lithium polymer and lithium phosphates.

Let's move on to testing LiFePo4:
IMAX B6 with LiFe mode support:

First Battery Test - Discharge
The battery “out of the box” is recharged, we perform a discharge with a current of 0.5A (which approximately corresponds to 0.5C), as a result, about 1055mAh was obtained.

The highest value out of 3, although I discharged / charged the rest with currents up to 1A (current 1A and FastCharge 1A mode).
The discharge graph obtained using LogView v2.7.5, the settings are taken from the preset from the Habr article about IMAX B6:

First Battery Test - Charge
Charge IMAX B6 using FastCharge 1A method:

See description of the test in the signature.

CONCLUSIONS
I made the following conclusions
Pros:
* Frost-resistant,
* Fast charge 1s.
Minuses:
* Small capacity (1000mAh), and, accordingly, the operating time.
Peculiarity:
* Requires special charging (I have an IMAX B6, so I don’t count it as a minus).
* UPD - LiFePo4 voltages are significantly lower than LiIon (3.2 vs. 3.6). Some lights are much less bright.

* UPD 2 (2013.03.09) - Must be used with direct drive lights with low undervoltage cutoff (2.7V).

The flashlight on the left shines less brightly on LiFePo4 than on LiIon, the flashlight on the right does not lose as much brightness.

Update 2013.03.09 Discharge graphs at negative temperatures:

Frost-resistant LiFePo4 18650 1000mAh battery with (for flashlights with direct drive)
Many have already bought “powerful” flashlights on 18650 batteries. The usual LiIon battery in such cases does not work at low temperatures, and if it does, it does not work for very long, while

Welcome to the duplicate page of the project “Accumulator of the 21st century. VistaBattery”

Batteries sold and VistaBattery customer records (those on the drive)

A brief selection of characteristics that distinguishes these batteries from the rest.
Main advantages:
-Good efficiency (gives 80% capacity at a voltage difference of 1V)
-High recoil currents with a voltage drop of less than 1V, for lead, the starter scrolling at 9V is considered the norm, you will not see it immediately below 12V
- Weak self-discharge (loss of charge 5% in 3 years)
-Fast charging (filling the battery from 0 to 80% in about 15-20 minutes depends on the generator and the capacity of the battery itself)
-Low weight (for example, 1.8 kg versus 15 kg with the same recoil currents)
-2000 full charge-discharge cycles (discharge to zero and again to full, and so on 2000 times without loss of capacity!)
- Frost resistance. Work in temperature conditions up to -25C

But there are also disadvantages:
-Cost (elements America and bought over the hill)
-The impossibility of working together with lead-acid (as I wrote above, due to the voltage difference of 12.3 lead - 13.5 ferrophorsate)
- The impossibility of working under water (decided by pouring into the compound) was decided by switching to plastic sealed cases

Specifications:
Drift, rally, ring, daily operation:
4.4 Ah - 190*170*60mm, 1.2kg, 260A nominal, 475A peak
8 Ah - 190*170*60mm, 1.5kg, 260A nominal, 510A peak
20 Ah - 280*230*100mm, 3kg, 300A nominal, 500A peak
Trophy, car audio, expeditions:
40 Ah - 280*230*100mm, 5kg, 600A nominal, peak 1000A
80 Ah - 280*230*160mm, 10kg, 1000A nominal, 5000A peak

Any variations are also possible with a container, cases, conclusions for the most comfortable installation in an existing project.

Operation in trophy:
As practice has shown - on a light SUV like Dzhimnik - 20A / h feels great. For extreme and heavier categories, I would still recommend 40A / h there you definitely won’t have to stop yourself and swans as much as you like. The stock performance is very good. 20Ah = 55Ah optima
80Ah= over 300Ah lead

Price
4.4 Ah - 15.000r
20 Ah - 25.000r
40 Ah - 40.000r
80 Ah - 60.000r
160 Ah - 110.000r

Warranty and lifetime:
- My warranty is a year without any questions
-5 years of technical support (test elements, monitoring their condition, maintenance)
- service life of 10 years. Since their mass production only began in 2006, no one else has died of old age.

The whole product is supplied. Production is agreed with the customer (nature of use, requirements in the form of reinforced tires, wires, terminals, input of air pressure fittings and other requirements). All batteries are supplied in shockproof, sealed, CHECKED IP67 class enclosures

One client - one solution. This is not mass production, but an individual approach.
#VistaBattery

Vladekin › Blog › LiFePo4 batteries
Vladekin user blog on DRIVE2. Welcome to the duplicate page of the project "Accumulator of the 21st century. VistaBattery", So, the main cycle of tests is completed. Batteries made using this technology have been tested in different conditions and situations. A brief selection of tests: -Test of the smallest battery from Yegor2 -Laboratory battery test ...

They often began to bring batteries to us for assembly and diagnostics, supposedly LiFePO4 bought very cheaply. Many asked after such cases that we write an article on this subject, in order to be aware of such pitfalls. It can be a shame when you bought a battery that does not allow you to operate the motor-wheels of the series Magic Pie (1500W) in full power.

In this article, we compare batteries LiFePo4-48V-10Ah from Golden Motor With low quality batteries(sometimes under this name they simply hide the usual Li-ion).

Parameter

LiFePo4-48V-10Ah

quality

LiFePo4-48V-10Ah

low quality

(or fake)

Dimensions

36.0 X 15 X 8.4 cm

36.0 X 14 X 7.4 cm

On both sides, it is 1 cm less and, from the point of view of the buyer, it seems to be a plus - it takes up less space.

From the point of view of physics: the volume is less by 17%, with the same performance characteristics, i.e. made from a different material.

It is 1 kg lighter and seems to be a plus from the point of view of the buyer, because weighs less.

Continuous discharge current, A

20A is 1000W, 25A-1200 W - low performance

Discharge power (constant)

750, 1000, 1200W

Understated power ratings

Maximum discharge current, A

Low peak currents

Maximum Discharge Power

750, 1500, 1700W

Low peak power

Charge voltage

Different voltage on the charger.

54 volts is Li-ion / Li-Po- be careful!

Charge current

Slow charging so as not to kill cells with high internal resistance.

charge/discharge cycles

Cells have a shorter lifespan

Consider sellers of such batteries. As already shown in the table above, you can already draw a conclusion yourself - are these exactly the characteristics that you need?

Regarding the location of such sellers: they often do not have a permanent location:

1) “You can pick up your order only by prior agreement at the address. ". Are you sure that they work there, and will not drive up to the place to meet you?

2) “Address: Russia, Moscow”. With this wording, you can meet anywhere, even on Red Square. Usually, you meet near the subway, in the car. Sitting in the car, holding the battery (without any identification stickers) in your hands, you think that you don’t want to look for them yet, then go somewhere and yet, relying on chance, you agree to buy. Are you sure that you will definitely find them, if something goes wrong? And if you still don’t have a receipt, how will you prove the purchase?

How to identify dishonest sellers:

Search for reviews in Yandex: “Site_name reviews” and “Name_legal entities reviews”.
Search Google for reviews: “Site_name reviews” and “Legal_entity_name reviews”.
Search reviews of industry forums (electric transport, bike shops).
Check the domain - when it is registered.

Most often, such sellers do not write about the guarantee (in fact, they initially do not promise you anything). Or a 2-week guarantee - even if Li-ion is slipped, during this period they will not have time to degrade, even if you operate in excess of the permitted currents. They can also write a guarantee - 1 year (if you find them). Some sellers don't even know what they're selling! Ask for a warranty card!

In addition, read what are the LiFePO4 cells from which the battery is assembled. Most often there are prismatic elements for 10Ah, 12Ah. There is no LiFePO4- 13Ah! If they write such a capacity, then this is definitely not LiFePO4, and they try to slip you a cheap Li-ion. If the battery has a non-rectangular, bizarre shape, then think about how manufacturers could tightly squeeze rectangular elements into it?

They already came to us with such - below is a photo for comparison (the buyer was sure that he had LiFePO4, but there are no stickers on the battery regarding the chemistry of HIT, only the rated voltage and capacity):

And some people know that slipped Li-ion after such cases (spontaneous combustion during driving - burning cylindrical elements are visible):

In addition, there are buyers in China of used batteries, they sort them, good ones at a good price, medium ones are cheaper, and dead cells are for scrap. Other buyers buy them up and collect batteries in the garage, and calmly sell them on Aliexpress (this is an analogue of our Yandex Market, a regular aggregator), no one checks their quality there, the main thing is to pay an annual fee for placement. Sometimes you come (as you think, to a large plant), and there is just a call center, you ask to go to the plant, they say it takes 7-10 days to get a pass (they know that you won’t wait so long for this).

It is possible to identify the bu cell only if you measure the internal resistance. The more used, the higher the internal resistance. But who will measure it and show it to you?

Summary: Forewarned is forearmed. The joy of a cheap purchase is quickly replaced by the bitterness of disappointment. Enjoy the shopping!

Pitfalls when buying LiFePO4 batteries
The article discusses the pitfalls, errors, nuances when buying LiFePO4 (lithium iron phosphate) batteries. Table of characteristics. What not to make a mistake when buying?

The modern market is replete with a variety of electronic equipment. For their functioning, more and more advanced power sources are being developed. Among them, a special place is occupied by lithium iron phosphate batteries. They are safe, have a high electrical capacity, practically do not emit toxins, and are durable. Perhaps soon these batteries will be forced out of their "brothers" devices.

Maintenance

What is lithium iron phosphate battery

LiFePo4 batteries are high quality and reliable power sources with high performance. They are actively replacing not only obsolete lead-acid, but also modern Li-ion batteries. Today, these batteries are found not only in industrial equipment, but also in household devices - from smartphones to electric bicycles.

LFP batteries were developed by the Massachusetts Institute of Technology in 2003. They are based on advanced Li-ion technology with a modified chemical composition: lithium ferrophosphate is used for the anode instead of lithium cobaltate. Batteries have become widespread thanks to companies such as Motorola and Qualcomm.

How LiFePo4 batteries are produced

The main components for the manufacture of LiFePo4 batteries are delivered to the factory in the form of a dark gray powder with a metallic sheen. The scheme for the production of anodes and cathodes is the same, but due to the inadmissibility of mixing components, all technological operations are performed at different workshops. All production is divided into several stages.

First step. Creation of electrodes. To do this, the finished chemical composition is covered on both sides with a metal foil (usually aluminum for the cathode, and copper for the anode). The foil is pre-treated with a suspension so that it can act as a current receiver and conductive element. Finished elements are cut into thin strips and folded several times, forming square cells.

Second step. Direct assembly of the battery. Cathodes and anodes in the form of cells are located on both sides of the separator made of porous material, tightly fixed on it. The resulting block is placed in a plastic container, filled with electrolyte and sealed.

The final stage. Control charging / discharging the battery. Charging produces with a gradual increase in the voltage of the electric current, so that an explosion or ignition does not occur due to the release of a large amount of heat. For discharge, the battery is connected to a powerful consumer. Without revealing deviations, the finished items are sent to the customer.

The principle of operation and the device of a lithium iron phosphate battery

LFP batteries consist of electrodes pressed tightly against a porous separator on both sides. To power the devices, both the cathode and the anode are connected to current collectors. All components are placed in a plastic case, filled with electrolyte. A controller is placed on the case, which regulates the current supply during charging.

The principle of operation of LiFePo4 batteries is based on the interaction of lithium ferrophosphate and carbon. The reaction itself proceeds according to the formula:

LiFePO 4 + 6C → Li 1-x FePO 4 + LiC 6

The charge carrier of the battery is the positively charged lithium ion. It has the ability to be introduced into the crystal lattice of other materials, with the formation of chemical bonds.

Specifications of LiFePo4 batteries

Regardless of the manufacturer, all LFP cells have the same technical characteristics:

peak voltage - 3.65 V;
voltage at the midpoint - 3.3 V;
voltage in a fully discharged state - 2.0 V;
rated operating voltage - 3.0-3.3 V;
minimum voltage under load - 2.8 V;
durability - from 2 to 7 thousand charge / discharge cycles;
self-charging at a temperature of 15-18 C o - up to 5% per year.

The presented technical specifications refer specifically to LiFePo4 cells. Depending on how many of them are combined by one battery, the parameters of the batteries will also vary.

Copies of domestic production have the following characteristics:

capacity - up to 2000 Ah;
voltage - 12v, 24v, 36v and 48v;
with a range of operating temperatures - from -30 to +60 С o;
with charge current - from 4 to 30A.

All batteries do not lose their quality during storage for 15 years, have a stable voltage and are characterized by low toxicity.

What are LiFePo4 batteries

Unlike batteries familiar to us, which are marked with the symbols AA or AAA, lithium iron phosphate cells have a completely different form factor marking - their dimensions are encrypted with a 5-digit number. All of them are presented in the table.

Size	Dimensions, DxL (mm)
14430	14x43
14505	14x50
17335	17x33
18500	18x50
18650	18x65
26650	26x65
32600	32x60
32900	32x90
38120	38x120
40160	40x160
42120	42x120

Even without a table with a marking designation in front of you, you can easily navigate the dimensions of the battery. The first two digits of the code indicate the diameter, the rest - the length of the power source (mm). The number 5 at the end of some sizes corresponds to half a millimeter.

Lithium iron phosphate battery: pros and cons

LFP batteries are based on Li-ion technology, which allowed them to absorb all the advantages of these power sources, and at the same time get rid of their inherent disadvantages.

Among the main advantages are:

Durability - up to 7,000 cycles.
High charge current, which reduces the time of replenishment of energy.
Stable operating voltage that does not drop until the charge is completely exhausted.
High peak voltage - 3.65 Volts.
High nominal capacity.
Light weight - up to several kilograms.
Low level of environmental pollution during disposal.
Frost resistance - work is possible at temperatures from -30 to + 60 ° C.

But batteries also have disadvantages. The first one is the high cost. The price of an element for 20 Ah can reach 35 thousand rubles. The second and last drawback is the difficulty of assembling a battery bank with your own hands, unlike lithium-ion cells. Other obvious disadvantages of these power sources have not yet been identified.

Chargers and how to charge LiFePo4

Chargers for LiFePo4 batteries are practically no different from conventional inverters. In particular, you can record a large output current - up to 30A, which is used to quickly recharge the elements.

When buying a ready-made battery pack, there should not be any difficulties with charging them. Their design has built-in electronic control, which protects all cells from complete discharge and oversaturation with electricity. Expensive systems use a balancing board, which evenly distributes energy between all cells of the device.

It is important not to exceed the recommended current when recharging if you are using third-party chargers. This will reduce battery life by several times per charge. If the battery heats up or swells, then the current strength exceeds the allowable values.

Where are LiFePo4 batteries used?

LFP batteries are of great importance to the industry. They are used to maintain the performance of devices at weather stations, hospitals. They are also being introduced as a buffer to wind farms and used to store energy from solar panels.

12v batteries are beginning to be used in modern cars instead of the usual lead-acid cells. LiFePo4 designs are installed as the main power source on electric bicycles and ATVs, motor boats.

Widely their value in everyday life. They are built into phones, tablets, and even screwdrivers. However, such devices differ significantly in price from their less technological counterparts. Therefore, it is still difficult to find them on the market.

Rules for storage, operation and disposal of LiFePo4

Before sending the LFP battery for long-term storage, it is necessary to charge it to 40-60% and maintain this charge level throughout the conservation period. Keep the battery in a dry place where the temperature does not fall below room temperature.

During operation, the manufacturer's instructions must be followed. It is important not to overheat the battery. If you notice that the battery heats up unevenly during operation or recharging, then you should contact the repair center - perhaps one of the cells is out of order, or there are malfunctions in the control unit or balance board. The same should be done with the appearance of swelling.

For proper disposal of a battery that has completely exhausted its life, contact an organization specialized in this. So you will not only act as a conscientious citizen, but you will also be able to earn money on it. However, if you just send the battery to a landfill, then nothing bad will happen.

The main properties of lithium iron phosphate batteries

Lithium iron phosphate (LiFePO4) batteries are a type of lithium ion battery that uses iron phosphate as the cathode. Without exaggeration, they can be called the pinnacle of power battery technology. This type of batteries in some parameters, in particular, in the number of charge-discharge cycles, surpasses all others.

Unlike other lithium-ion batteries, LiFePO4 batteries, like nickel ones, have a very stable discharge voltage. The output voltage during discharge remains close to 3.2 V until the battery is fully charged. This can greatly simplify or even eliminate the need for voltage regulation in circuits.

Due to the constant output voltage of 3.2 V, four batteries can be connected in series to obtain a nominal output voltage of 12.8 V, which approximates the nominal voltage of six-cell lead-acid batteries. This, along with the good safety characteristics of lithium iron phosphate batteries, makes them a good potential replacement for lead acid batteries in industries such as automotive and solar energy.

With repeated charge / discharge cycles, there is no memory effect at all
Lithium iron phosphate batteries have a long service life (over 4600 cycles at a depth of discharge of 80%)
They have a high specific energy intensity: the energy density reaches 110 Wh/kg)
They are characterized by a wide temperature range of operation (-20 ... 60 ° C)
These batteries are maintenance free
It is possible to quickly charge the batteries: in 15 minutes - up to 50%
Reliability and safety of lithium iron phosphate batteries are confirmed by international certificates
They are highly efficient: 93% at startup 30…90%
Allowed high discharge current up to 10 C (ten times the rated current)
These batteries are environmentally friendly and do not pose a danger to humans and the environment when disposed of.
Unlike lead batteries, lithium iron phosphate batteries are twice as light with the same capacity

Disadvantages compared to lead acid batteries:

higher cost;
the need for a special charge-discharge control circuit.

Lithium iron phosphate batteries (LiFePO4) are slightly inferior to lithium polymer batteries in terms of energy intensity (Figure 1). But one of the strengths is the stability of the material, which allows you to create batteries that can withstand many more discharge / charge cycles (more than 2000), and fast charging. Due to these features, these batteries are optimally used in electric vehicles.

In the Russian market, a special place among the suppliers of batteries based on lithium ions is occupied by the company EEMB. It produces several groups of lithium iron phosphate batteries (Figure 2), which differ from each other in electrical and design parameters:

modular battery systems;
accumulators for telecommunication devices;
energy sources for "smart home";
traction batteries for electric vehicles.


a) modular battery systems	b) batteries for telecommunications equipment	c) batteries for systems emergency power supply and autonomous power supply systems	d) traction batteries for electric transport

Lithium iron phosphate batteries, when discharged, have a very stable output voltage until the cell is completely discharged. Then the voltage decreases sharply.

Figure 3 shows the discharge curves of the battery, taken at various discharge currents (0.2 ... 2C) under normal temperature conditions. As can be seen from the graph, a feature of a lithium iron phosphate battery is a weak dependence of the capacity on the magnitude of the discharge current. When discharging with a low current (0.2C) and when discharging with an increased current (2C), the battery capacity practically does not change and remains equal to 10 Ah (the nominal capacity of the specified battery).

It is very important not to allow the cell to discharge to a level of less than 2.0 V, otherwise irreversible processes will occur that will lead to a sharp loss of nominal capacity. For this, the discharge controller is used. EEMB manufactures batteries with or without protection circuitry. The presence of a protection circuit against discharge and overcharge voltage is encoded in the name by the abbreviation PCM at the end, for example, LP385590F-PCM.

Consider the dependence of the number of "charge-discharge" cycles on the magnitude of the discharge current and the depth of the discharge. Figure 4 shows the experimental data. It can be seen from them that with a full discharge, a 20% loss in battery capacity occurs with a number of cycles of at least 2000 (discharge current 1C). If the depth of discharge is limited to the level of 80% in each cycle, then during approximately 1500 such cycles, there was practically no decrease in the battery capacity from the initial value (discharge current 0.5C).

The latest generation of EEMB lithium iron phosphate batteries, unlike existing lead acid batteries, does not require frequent replacement and maintenance. As a rule, a lithium-iron phosphate battery is a modern battery that can withstand more than 2000 charge-discharge cycles, absolutely insensitive to chronic undercharging modes. In most cases, it has a built-in battery management system (Battery Management System). The charge is carried out by constant voltage and constant current without stages.

Table 1 shows the main parameters of EEMB single cell lithium iron phosphate batteries. The nominal capacity of this type of batteries is in the range of 600 ... 36000 mAh (weight - 15 ... 900 grams, respectively). Single-cell Li-FePO4 batteries are most often used in self-powered devices. These batteries allow high current discharge up to 10C. After 2000 charge-discharge cycles with a current of 1C, the residual capacity is about 80%.

Table 1. EEMB Single Cell LiFePO4 Batteries

Name	Voltage, V	Capacity, mAh	Weight, g
	3,2	600	15
		1250	31,25
		2000	50
		3500	87,5
		5000	125
		5000	125
		7000	175
		9000	225
		22000	500
		36000	900

Using modular systems with individual cells with increased capacity, the parameters of which are given in Table 2, it is possible to assemble a battery pack of the required capacity and output voltage.

Table 2. Main parameters of Li-FePO4 modular systems

The modular systems are also equipped with a power management system (BMS), which allows high power discharge and has many control and protection functions. Modules with an integrated monitoring system provide a high level of security for the entire system and the environment. Recommended applications:

emergency and uninterruptible power supply systems;
base stations.

Telecommunication power systems require batteries to be small in size, light in weight, have a high number of recharge cycles, high specific capacity, wide operating temperature range, and ease of maintenance. Lithium iron phosphate batteries meet these requirements quite well. Table 3 shows the main parameters of EEMB batteries for telecommunication systems.

Table 3. Batteries for telecommunications power systems

Name	Voltage, V	Capacity, Ah	Weight, kg
	12	50	6
	12	100	22
	48	100	40
	48	200	78

An example of a nomenclature entry: 4P5S - four parallel-connected assemblies (each assembly consists of five batteries connected in series), P - Parallel, parallel connection, S - Serial, serial connection.

These batteries are mainly used in:

DC power systems;
uninterruptible power supplies (UPS);
high-voltage DC power systems (240/336 V).

Characteristics of rechargeable batteries for uninterruptible power supplies and systems for "smart home" (UPS / UPS) are shown in Table 4, and the appearance is shown in Figure 3c.

Table 4. Smart Home UPS Batteries

Name	Voltage, V	Capacity, Ah	Weight, kg
	12	10	1,3
	12	20	2,5
	12	30	3,5
	24	20	4,5
	14,4	4,5	0,7
	14,4	7	0,9
U1	48	10	4

EEMB Super Energy SLM Lithium Iron Phosphate batteries completely replace conventional lead-acid and gel batteries. They are maintenance-free, 80% lighter and five times more durable than lead-acid batteries and their equivalents.

Traction batteries for electric vehicles are a rechargeable battery for installation in electric vehicles. The key features of electric vehicle batteries are light weight, compact size and high energy capacity, which reduces the weight of the electric vehicle itself and enables fast charging.

EEMB offers a range of batteries for electric vehicles of various categories (tables 5, 6).

The main parameters of lithium iron phosphate batteries used in golf cars and similar batteries of the GOLF CART series are shown in Table 5. These batteries allow parallel and series connection of cells, so that you can easily change the nominal capacity and voltage of the battery.

Table 5. Parameters of GOLF CART batteries

Name	Voltage, V	Capacity, Ah	Weight, kg
	6,4	10	0,5
	9,6	20	1,5
	12,8	30	3
	12,8	40	4
	25,6	10	2
	25,6	60	12

The parameters of Li-FePO4 batteries for electric bicycles (E-bike series) are shown in Table 6.

Table 6. E-bike series battery parameters

Name	Voltage, V	Capacity, Ah	Weight, kg
	24	10	2,5
	24	20	4,5
	24	40	9
	36	10	3,5
	36	20	6,5
	36	30	10
	48	20	9

Other options can be made according to the requirements of the client under the order. These series of batteries are also available in assemblies, where single cells are connected in series or parallel-series. Overall dimensions of one assembly element of this series are 9.1x67.5x222 mm.

Table 7 shows the parameters of lithium iron phosphate batteries for electric scooters and power tools. E-scooter series batteries are small in size, have a high allowable discharge current, long service life, high energy density, no memory effect, which makes these batteries popular in devices of suitable power, where it is necessary to autonomously power electric motors.

Table 7. E-scooter series battery parameters

Name	Voltage, V	Capacity, Ah	Weight, g
	9,6	1,4	150
	16	1,4	250
	19,2	7	1500
	22,4	8,4	2100

Table 8 shows the parameters of lithium iron phosphate batteries for E-motorcycle series electric scooters. The rated voltage of all batteries in this series is 48 V. The minimum nominal capacity is 9 Ah with a weight of 4 kg. The maximum capacity value is 90 Ah with a weight of 40 kg. The dimensions of one element are 7.5x67x220 mm.

Table 8. E-motorcycle series battery parameters

Name	Voltage, V	Capacity, Ah	Weight, kg
	48	9	4
	48	36	16
	48	54	24
	48	90	40

Comparative characteristics of LiFePO4 batteries

At small power facilities in constant cycling modes, lithium iron phosphate batteries, due to the possibility of deep discharge and a large number of charge-discharge cycles, provide tangible advantages in servicing the facility.

Battery modules have built-in protection against overvoltage, low charge, high currents. They are compatible with all devices, including inverters and chargers that work with lead-acid batteries. Initially, the price of lithium iron phosphate batteries seems quite high. However, when calculating the battery capacity for operation in the cycling mode, it turns out that in the case of using LiFePO4 batteries, a battery of approximately 2 ... 2.5 times less capacity than for lead-acid batteries (including lead-helium) is sufficient. This is possible due to the fact that lithium-iron phosphate batteries allow charging with higher currents than lead-acid batteries (1C versus 0.1 ... 0.2C typical for lead-acid batteries). As a result, an array of solar panels, for example, with the same output current of the array and the required charge time, can be loaded on a less capacious than lead-acid, lithium iron phosphate battery. The lower capacity per discharge will be compensated by faster charge cycles, especially since the resource for charge-discharge cycles is on average an order of magnitude greater. Added to this is a much slower drop in capacity during recharge cycles.

Consider an example. If we previously used a lead-acid AGM / GEL 150 Ah battery in cycling mode, then a LiFePO4 battery with a capacity of 60 Ah will be enough to replace it without loss of performance. With a correct calculation of 1 to 2.5, the cost of a LiFePO4 battery is only 25 …35% more than lead-acid batteries. At the same time, lithium-iron-phosphate batteries will, on average, have better performance characteristics in comparison with lead-acid batteries.

In the mode of accumulation and subsequent discharge at the same discharge currents, lithium iron phosphate batteries can provide a capacity advantage of 2.5 times, which is easy to show by example.

As a rule, the battery capacity is selected based on the possible time of absence of the main energy and the power consumption of the load.

For example, if we need to power a load of 2 kW for 1 hour, then, accordingly, we need an energy reserve of at least 2 kWh. It is necessary that this system can function normally for more than 6 months in a cyclic mode (charge during the day, in the evening - rank). For a battery or set of batteries with an output voltage of 48 V, the required design capacity will be approximately 42 Ah. The discharge current will be approximately 1C (42 A). However, it should be noted that in our example, the discharge should be considered not as a constant current, but as a constant power, while when the battery is discharged, the discharge current will increase. In the discharge mode with a constant power (2 kW), a lead-acid battery (48 V / 40 Ah) can work for no more than 30 minutes (with a deep discharge - up to 40.8 V).

In order for the load to work confidently for one hour on a lead-acid battery, its capacity will be approximately twice that originally calculated - about 85 Ah. On the other hand, discharging an iron-phosphate battery with a current of 1C or higher does not lead to a significant decrease in its capacity - it remains at nominal level (Figure 3). From this it can be seen that a difference in capacity of two types of batteries by a factor of two can be achieved. It is also necessary to take into account that when a lead-acid battery is operated in cycling mode, its capacity will decrease by 20% already at 150 ... It turns out that the conditions of the previously set task will be met during the first 6 months with a lead-acid battery capacity of 102 Ah. between two types of batteries is about 2.5 times.

Lithium iron phosphate batteries easily accept a powerful charging current. Therefore, by loading them with a three times more powerful (relative to lead-acid batteries) array of solar batteries, you can charge them in a short time equal to 2 ... 4 hours. And taking into account the insensitivity to deep discharge and chronic undercharging, these batteries are indispensable in winter, especially given the fact that lithium iron phosphate batteries have a higher efficiency of 95% (as opposed to 80% for lead-acid batteries), and this means that in cloudy and rainy weather these batteries charge faster (table 9).

Table 9. Comparison of lithium iron phosphate and lead acid batteries

Parameter	Lithium iron phosphate power supply system	conventional system with lead batteries deep discharge	Benefits of LiFePO4
Operating number of effective cycles	> 6000 at 80% discharge	~500	The number of cycles is much higher
Cell balancing system	Present when charging and discharging	Missing	Automatic control of the state of each cell
Cell level overcharge/deep charge protection	100% multi-level control
Battery protection in case of system failure	100% (disable charge and discharge current)
Accurate calculation of the energy reserve in the battery based on data from voltage, current, temperature and cell resistance sensors	Constant real-time calculation
Fast charging capability	Yes (about 15 minutes)	Not
The need to maintain the battery in a charged state	Not	Yes, otherwise - plate sulfation	No need to maintain charge, saving on maintenance
Estimated service life with daily full cycling of 70% for LiFePO4 and 50% for lead batteries (under ideal conditions), years	15	~4	At least 4 times higher
Operating temperature range, °С	-20…60	Recommended temperature: 20°C	It is possible to install a power supply system in unheated rooms
Influence of elevated temperature (30°C and above)	Permissible operation up to the upper limit of the operating temperature range	Rapid degradation	Battery cells withstand significantly higher temperatures
Calendar life (buffer mode or hold mode)	Is not limited	Limited as plates degrade anyway	Significant win
Ability to add capacity to an existing accumulation unit	Yes	Not recommended as it will lead to imbalance	Possibility of gradual modernization and scaling without extra costs
Possibility to replace one/several damaged cells in the battery assembly	Yes, because there is a balancing system	Not recommended as it will lead to imbalance

Conclusion

In cycling modes, the use of lithium-iron-phosphate batteries is more beneficial, since approximately two times less capacity than lead-acid batteries is sufficient to achieve energy and operational parameters. Equally valuable are insensitivity to undercharging, increased efficiency and accelerated charging with high currents.

Lithium iron phosphate batteries are recommended for use in solar power systems operating in short daylight hours, which is especially important for central Russia, northern regions, and mountainous regions. Long service life (a large number of "charge-discharge" cycles) of lithium-iron phosphate batteries can significantly reduce the cost of their maintenance and replacement, which is important, for example, for automatic weather monitoring stations and emergency power systems for cellular communication base stations. Extending the time between scheduled battery changes results in savings in maintenance crew salaries as well as travel costs (especially if the equipment is installed in hard-to-reach locations). The lower maintenance overhead will more than offset the relatively high cost of a lithium iron phosphate battery.

Batteries of this type can also be successfully used in telecommunications technology (basic telecommunications equipment and mobile devices), uninterruptible power supplies, emergency power supply systems, power systems for electric drives and electric vehicles.

The battery manufacturer, EEBM, maintains rigorous product quality control and is able to make custom battery assemblies according to customer requirements.

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