Modern equipment is day by day becoming more complex and powerful. High standards place high demands on batteries, which combine high performance, energy efficiency, and have increased the supply of electricity.
The Introduction of new types of electrical equipment in production, acceleration of technological process – all this increases the requirements for energy sources, and modern batteries are not always able to satisfy. To solve this problem, manufacturers have gone the way of improvements to lithium-ion technology. So was born the lithium-iron-phosphate battery (LiFePO4), which is the ideological descendant of the Li-ion batteries.
LiFePO4, or LFP, – the natural mineral family of olivine, was first discovered in 1996, scientists from the University of Texas by John Goodenough, who was looking for ways to improve Li-ion energy sources. Notable was the fact that this mineral had a lower toxicity and a higher thermal stability than anything known at the time the electrodes.
Besides, he met in a natural environment and had a lower cost. The main drawback of LiFePO4 electrodes at the base was a small capacity, causing the lithium-iron-phosphate battery no longer developed.
Research in this direction was renewed in 2003 at the Massachusetts Institute of technology. A team of scientists worked to create a radically new battery that would replaced the most progressive at that time Li-ion batteries. The project became popular, large companies such as Motorola and Qualcomm, which brought the advent of batteries with LiFePO4 cathode elements.
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This type of batteries uses the same technology for producing electricity, that familiar to us the lithium-ion cells. However, between them there also some significant differences. First, is the use of a private type, BMS-control system, which protects the electric batteries from overcharge and low discharge, increases service life and makes an energy source more stable.
Secondly, LiFePO4, in contrast to LiCoO2, is less toxic. This fact helped to avoid certain problems related to environmental pollution. In particular to reduce emissions of cobalt to the atmosphere if not properly disposed of the battery.
Finally, due to the lack of uniform standards LFP elements have different chemical composition, what determines the variation in technical characteristics of models in a wide range. In addition, maintenance of these power sources is more complex and should be carried out following certain rules.
It is Worth saying that lithium iron phosphate batteries 48 Volts, 36 Volts and 60 Volts produced by the serial connection between individual cells, because the maximum voltage in one LFP section may not exceed 3,65 V. Therefore, the technical performance of each battery can differ significantly between themselves – it all depends on the Assembly, and specific chemical composition.
For performance analysis we give the nominal value of a single cell.
The Best implementation capacities of each individual cell was achieved in a battery Everexceed. Lithium-iron-phosphate batteries Everexceed provide a long service life. Only they are able to withstand up to 4 thousand cycles of charge-discharge loss of capacity to 20%, and replenishment of energy reserves occurs in 12 minutes. Given this, it can be concluded that the batteries of Everexceed are one of the best representatives of the LFP elements.
The Main advantage in a favorable light emit lithium-iron-phosphate battery among the other members of AKB, is the durability. Such an element is able to withstand more than 3 thousand cycles of charge-discharge at falling of level of electricity to 30%, and more than 2 thousand-in the fall up to 20%. Due to this the average battery life is about 7 years.
Stable charge current is a second important advantage of the LFP elements. The output voltage remains at 3.2 V until then, until the charge is completely exhausted. This allows to simplify the wiring diagram, eliminates voltage regulators.
Higher peak current-third of their advantage. This property AKB allows them to produce maximum power even at very low temperatures. This property has prompted automakers to use lithium-iron-phosphate battery as the primary energy source when you run petrol and diesel engines.
Along with all the presented advantages, LiFePO4 battery have one significant drawback-a large mass and dimensions. This limits their use in some types of machinery and equipment.
If you buy ready-made lithium-phosphate batteries, the difficulties with maintenance and operation, you will not have. All thanks to the fact that manufacturers build in such elements of the Board BMS that prevents overcharging and not allowed to discharge the element down to the lowest level.
But if you purchase individual cells (penlight batteries, for example), then you will have to monitor the charge level on their own. In the fall of the charge below the critical level (below 2.00) will start to plummet and capacity, making it impossible to recharge the elements. If you, instead, allow overcharging (above 3.75 In), the cell will just swell due to the evolved gases.
If you use such a battery for the electric vehicle, then after 100% charging, you must unplug the charger. Otherwise, the battery will swell due to saturation by an electric current.
If you plan to use lithium-phosphate batteries are not in cyclic mode, and a buffer, for example, as a power source UPS or in conjunction with a solar battery, then you need to take care of the downgrading of the charge to 3.40 to 3.45 V. to Cope with this problem help “smart" charger, which automatically first fully replenish energy, and then lower the voltage level.
During the operation you need to monitor the balance of cells, or to use a special balance Board (in the battery for the electric vehicle they are built). Imbalance of cells call this condition, when the total device voltage remains at the nominal level, but the voltage of the cells becomes different.
A Similar phenomenon occurs due to differences in resistance of individual sections of the poor contact between them. If the cells have different voltage, and they are unevenly distributed charge-discharge, which significantly reduces the battery life.
Before using lithium-phosphate batteries collected from individual cells, it is necessary to take care of the balancing system, because the sections can have different level of charge. For this purpose all the components are connected in parallel and connected to the rectifier charger. United therefore, the cells need to charge to 3.6 V.
Using the battery of lithium iron phosphate for electric bikes, you probably noticed that in the first few minutes of operation, the battery gives the maximum power, and then charge rapidly drops to 3.3 and 3.0 V. don't be afraid, it's normal battery life. The fact that the bulk of its capacity (about 90%) lies in this range.
The efficiency of lithium-phosphate batteries is 20-30% higher than other batteries. They serve for 2-3 years longer than other sources of electricity and provide stable current for the entire period of operation. All of this highlights the elements in a favorable light.
However, most people will ignore a lithium-iron-phosphate batteries. The pros and cons of battery pales in front of them – it is 5-6 times more than usual for us lead-acid elements. A battery for a car on average costs about 26 thousand rubles....
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Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."
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