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 of 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.
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Industry-leading charge-discharge cycles, half the capacitance to achieve the same electrical performance compared to lead-acid, high-current fast charging and stable discharge voltage, automatic parameter control are the advantages lithium iron phosphate batteries. A wide range of these products manufactured by the company EEMB, used in power supply systems of cellular base stations and automatic weather stations, solar power systems, emergency power systems, power supply for industrial electric drives and electric transport.
In recent years, the issue of improving mobile energy sources is more relevant than ever. Even 10-15 years ago it was not so acute. But the best is the enemy of the good, and with the increase in the mobility of the city dweller, i.e. With the transition from desktop to laptop, from a simple mobile phone to a smartphone, the demand for mobile energy sources has increased dramatically.
With the miniaturization of consumer electronics, consumer electronics designers must keep up with the general trend by reducing the size of power supplies while increasing their capacity. However, the question arises of changing not only the capacity of the batteries, but also the speed of their recharge and durability. After all, if the battery will restore the charge almost instantly, then it is no longer so critical how many hours the device can operate without recharging.
Battery capacity, as well as its ability to be recharged many times, is also important for:
- autonomous devices focused on long-term operation without maintenance - weather stations, hydroposts, soil stations;
- alternative energy systems - solar and wind generators;
- electric transport - hybrid cars, loaders, electric cars.
In almost all of these cases, batteries are operated in conditions that are far from ideal: at low temperatures, suboptimal or incomplete charge cycles, and a high probability of deep discharge.
Among modern batteries, lithium occupies a special place. Lithium has a huge energy storage resource, so the use of lithium-ion batteries as energy storage devices for solar power plants and other renewable energy sources is the most profitable compared to lead-acid batteries or other types of batteries. A special place among batteries based on lithium ions is occupied by lithium iron phosphate batteries (LiFePO4).
LiFePO4 was first used as a cathode for a lithium-ion battery in 1996 by Professor John Goodenough of the University of Texas. This material interested the researcher because, compared to traditional LiCoO2, it has a significantly lower cost, is less toxic, and more thermally stable. But its disadvantage is its smaller capacity. And only in 2003 the company A123 System under the guidance of Professor Jiang Ye-Ming, she began researching lithium iron phosphate batteries (LiFePO4).
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 is enough than for lead-acid batteries (including lead-helium). 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 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 | Absent | 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) | No | |
| The need to maintain the battery in a charged state |
No | 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, °C | -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 | ||
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. The 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 relevant, 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 supply 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.
Literature
- http://www.eemb.com.
- http://www.eemb.com/products/rechargeable_battery/lifepo4_battery/lifepo4_battery.html.
What is LiFePO4 battery
LiFePO4 is a naturally occurring mineral of the olivine family. The date of birth of LiFePO4 batteries is considered to be 1996, when the use of LiFePO4 in the battery electrode was first proposed at the University of Texas. The mineral is non-toxic, relatively cheap and occurs naturally.
LiFEPO4 is a subset of lithium batteries and uses the same power generation technology as lithium batteries, however they are not 100% lithium (lithium ion) batteries.
Due to the fact that the technology appeared relatively recently, there is no single standard for assessing the quality of LiFEPO4 batteries, as well as direct analogies with lead-acid batteries that we are used to.
Due to the lack of a single standard for LFTP batteries, there are many varieties of LFP cells on the market and batteries using them with different characteristics and chemistry inside, they are all called LFP or lithium batteries, but they work in different ways. Without trying to embrace the immensity, we will focus on what our batteries are guaranteed to be able to do.
Aliant Lithium Iron Phosphate batteries offer the following practical benefits:
- dimensions - batteries are 3 times smaller than lead analogues, so only 3 batteries cover the entire model range of motorcycles
- the battery self-discharges less than 0.05% per day, i.e. can safely stand on the shelf for a year without recharging and, without losing its characteristics, start the engine and then charge to a state close to 100%
- can be in a discharged state without serious consequences for subsequent performance, the discharge threshold is 9.5V, as long as the voltage at the battery terminals does not fall below 9.5V - the battery can be charged and returned to its original state
- uniform charge of all 4 cells inside using a BMS (Battery Management System - Battery Management System) controller built into the battery. Inside the battery there are 4 cells connected in series, each 3.3V, the nominal voltage is 13.3V, however, the battery is charged through 2 terminals. This charging method is suitable for lead batteries, but not suitable for LFP - the internal cells are always undercharged, which increases the likelihood of their failure, in order for LFP cells in a series connection to be charged evenly, an electronic circuit is built into the battery that distributes the charge coming to 2 terminal by 4 cells inside the battery evenly
a huge number of recharge cycles, more than that of lithium-ion batteries and lead batteries,
The battery withstands 3000 charge cycles from 70% discharged and 2000 charge cycles from 80% discharged state, which provides a battery life of up to 7 years, we provide an unconditional 2 year warranty on ALIANT batteries. On average, the battery is rated for 12,000 starter starts.
high starter current, at -18C the battery provides the starter with a power corresponding to the average new lead battery, but at +23C the power that the starter can supply is twice that of a lead battery. High power output is immediately felt when starting the engine, the starter rotates quickly, like on the freshest lead battery
weight - ALIANT batteries are 5 times lighter than lead
fast charge - on average, batteries are charged by 50% during the first 2 minutes, 100% charge within 30 minutes, which means that after 30 minutes of driving - the battery is 100% charged, i.e. in fact, your battery is always 100% charged
stable discharge voltage - during discharge, the battery keeps the voltage close to 13.2V until the last, then, after the discharge, there is a sharp drop in voltage, - a battery in which 40% of the charge remains will quickly turn the starter
stable discharge voltage - during discharge, the battery until the last holds a voltage close to 13.2V, then, after discharge, a sharp drop in voltage occurs
work at ultra-low temperatures. We have put special emphasis on battery performance at ultra-low temperatures, some experienced riders who have used LFP batteries from other manufacturers have noticed that the performance of LFP batteries drops sharply with temperature. So at +3 degrees, there is no more vigorous rotation of the starter, and at minus, the battery "falls asleep" and wakes up only after warming up, as energy is returned. Due to special chemistry our batteries are free from this shortcoming. Although the power given off by the batteries at -18C drops by almost 2 times, it is still enough to vigorously turn the starter. The battery is designed to operate at temperatures up to -30C, at temperatures from -3 and above, the batteries have excess power. In the temperature range from -18 to -30C, the battery will turn the starter, but it will feel like a half-discharged lead battery.
works in any position, the batteries do not contain liquids, it can be used in any position, just like gel batteries
wide temperature range - from -30С to +60С
Fundamental physical differences between LiFePO4 batteries and lead analogs
As mentioned earlier, LiFePO4 batteries and lead batteries have different chemistry, and to understand your battery, you need to know what the differences are.
the main difference concerns capacity. You can understand the differences in batteries using an example: if you connect the starter to a LiFEP04 battery and to a lead battery and start turning it, then in the same time the LiFEPO4 battery will turn the starter almost 1.5 more, practically without reducing the rotation speed than a lead-acid battery, if If you have previously used a lead battery, then you will have the impression that there is a lot of charge left in the battery, but the battery, in fact, may already be almost discharged, the drop in rotational speed will not occur smoothly, as in the case of a lead battery, but will occur abruptly after voltage drops below 12v. If we take a lead battery of 7A / h and a LiFEPO4 battery of similar capacity, then the number of rotations of the starter (in fact, the load) until it is completely depleted in the first 10 minutes of LiFEP04 will be much larger, but over the next 5 minutes the battery will be depleted, while the lead battery will be able to turn the starter up to 20 minutes. Thus, in all practical cases of life at temperatures from -18C LiFEPO4 battery outperforms lead batteries, except when the generator is out of order. In this case, without a generator, a lead battery can last longer than LiFePO4.
overvoltage. When the charge voltage exceeds the allowable limit, LiFEPO4 and lead-acid batteries behave differently. The lead-acid battery begins to boil. Irreversible chemical reactions take place in LIFEPO4 batteries. There is no motorcycle on the market that would give a voltage capable of destroying a LIFEPO4 battery, however, in very rare cases, when the regulator relay fails in such a way that the voltage at the battery terminals is in the range from 15 to 60V - a LIFEP04 battery will damaged.
temperature. LIFEP04 batteries do not like low temperatures, in our batteries we use special cells capable of operating at temperatures up to -30C, however, after -18C, the performance of LIFEPO4 batteries drops in such a way that the lead battery produces more power than ours. If it were not for the special chemistry in the cells, then at +4 degrees LIFEPO4 the battery would lose performance.
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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
Characteristics:
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 you need to make a pass for 7-10 days (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?
Modern equipment is becoming more complex and powerful day by day. The high standards of technology place increased demands on batteries, which must now combine high performance, energy efficiency and have an increased supply of electricity.
The introduction of new types of electrical equipment into production, the acceleration of the technological process - all this increases the requirements for electricity sources, and modern batteries can no longer always satisfy them. To solve this problem, manufacturers have taken the path of improving lithium-ion technology. This is how lithium-iron-phosphate was born, which is the ideological descendant of Li-ion batteries.
Historical reference
LiFePO4, or LFP, a natural mineral of the olivine family, was first discovered in 1996 by University of Texas scientist John Goodenough, who was looking for ways to improve Li-ion power sources. It was noteworthy that this mineral had less toxicity and higher thermal stability than all electrodes known at that time.
In addition, he met in the natural environment and had a lower cost. The main disadvantage of electrodes based on LiFePO4 was a small electrical capacity, which is why the lithium-iron-phosphate battery was no longer developed.
Research in this direction was resumed in 2003. A team of scientists worked on the creation of fundamentally new batteries that would replace the most advanced Li-ion batteries at that time. Large companies such as Motorola and Qualcomm became interested in the project, which hastened the appearance of batteries with LiFePO4 cathode cells.
Battery based on LiFePO4
This type uses the same technology for generating electricity as the lithium-ion cells that are familiar to us. However, there are also a number of significant differences between them. Firstly, it is the use of its own type of BMS - a control system that protects electric batteries from overcharging and severe discharging, increases the service life and makes the energy source more stable.
Secondly, LiFePO4, unlike LiCoO2, is less toxic. This fact made it possible to avoid a number of problems associated with environmental pollution. In particular, to reduce emissions of cobalt into the atmosphere in case of improper disposal of batteries.
Finally, due to the lack of unified standards, LFP elements have different chemical composition, which causes the variation in the technical characteristics of models over a wide range. In addition, the maintenance of these power supplies is more complex and must follow certain rules.
Specifications
It is worth saying that 48 Volt, 36 Volt and 60 Volt lithium-iron phosphate batteries are manufactured by connecting individual cells in series, because the maximum voltage in one LFP section cannot exceed 3.65 V. Therefore, the technical indicators of each battery can significantly differ from each other - it all depends on the assembly and the specific chemical composition.
To analyze the technical characteristics, we present the nominal values of one individual cell.
The best implementation of the capabilities of each individual cell has been achieved in Everexceed batteries. Everexceed Lithium Iron Phosphate batteries have a long service life. In total, they are able to withstand up to 4 thousand charge-discharge cycles with a loss of capacity of up to 20%, and replenishment of the energy reserve occurs in 12 minutes. Given this, we can conclude that Everexceed batteries are one of the best representatives of LFP cells.
Advantages and disadvantages
The main advantage that distinguishes a lithium-iron-phosphate battery from other battery representatives in a favorable light is durability. Such an element is able to withstand more than 3 thousand charge-discharge cycles when the level of electricity drops to 30%, and more than 2 thousand - when it drops to 20%. This results in an average battery life of about 7 years.
A stable charge current is the second important advantage of LFP cells. The output voltage remains at 3.2V until the charge is completely depleted. This simplifies the wiring diagram and eliminates the need for voltage regulators.
Higher peak current is their third advantage. This property of the battery allows them to deliver maximum power even at ultra-low temperatures. This property has prompted automotive manufacturers to use the lithium iron phosphate battery as the primary energy source for starting gasoline and diesel engines.
Along with all the advantages presented, LiFePO4 batteries have one significant drawback - a large mass and size. This limits their use in certain types of machinery and electrical equipment.
Operation features
If you buy ready-made lithium phosphate batteries, then you will not have any difficulties with maintenance and operation. This is due to the fact that manufacturers build BMS boards into such elements that do not allow overcharging and do not allow the element to be discharged to an extremely low level.
But if you purchase separate cells (AA batteries, for example), then you will have to monitor the charge level yourself. When the charge falls below a critical level (below 2.00 V), the capacity will also begin to drop rapidly, which will make it impossible to recharge the cells. If, on the contrary, you allow overcharging (above 3.75 V), the cell will simply swell due to the gases released.
If you use a similar battery for an electric car, then after 100% charge you need to disconnect it. Otherwise, the battery will swell due to oversaturation of electric current.
Operating rules
If you plan to use lithium phosphorus batteries not in a cyclic mode, but in a buffer mode, for example, as a UPS power source or in conjunction with a solar battery, then you need to take care to lower the charge level to 3.40-3.45 V. Cope with this task is assisted by "smart" chargers, which in automatic mode first fully replenish the energy reserve, and then lower the voltage level.
During operation, you need to monitor the balance of the cells or use special balancing boards (they are already built into the battery for an electric car). Cell imbalance is a condition when the overall voltage of the device remains at the nominal level, but the voltage of the cells becomes different.
A similar phenomenon occurs due to the difference in the resistance of individual sections, poor contact between them. If the cells have different voltages, then they are unevenly charged and discharged, which significantly reduces the battery life.
Commissioning batteries
Before using lithium-phosphorus batteries assembled from individual cells, care must be taken to balance the system, since the sections may have different levels of charge. To do this, all components are connected in parallel to each other and connected to a rectifier, charger. Cells connected in this way must be charged to 3.6 V.
Using a lithium-iron-phosphate battery for an electric bike, you probably noticed that in the first minutes of operation, the battery produces maximum power, and then the charge drops rapidly to a level of 3.3-3.0 V. Do not be afraid of this, because this is normal battery operation . The fact is that its main capacity (about 90%) lies precisely in this range.
Conclusion
The efficiency is 20-30% higher than other batteries. At the same time, they serve 2-3 years longer than other sources of electricity, and also provide stable current throughout the entire period of operation. All this highlights the presented elements in a favorable light.
However, most people will continue to ignore lithium iron phosphate batteries. The pros and cons of batteries pale in front of their price - it is 5-6 times more than that of lead-acid cells that are familiar to us. Such a battery for a car costs about 26 thousand rubles on average.
