LiFePO4 (LFP) batteries: What are they, the benefits, and what makes them better than other Li-ion batteries?
In this article, we will tell you everything you need to know about these types of batteries.
Li-Ion, LiFePo4, LiPo Batteries
Lithium-ion (Li-ion), lithium polymer (Li-Poly, Li-Po) and lithium iron phosphate (LiFePo4, LFP) batteries are today’s lightweight and powerful batteries for all kinds of equipment.
So, where are these batteries used and what are the main differences between these batteries?
What is LiFePo4, LFP Battery?
Lithium-iron-phosphate or lithium-ferum-phosphate (LiFePo4) batteries have found their application in uninterruptible power supplies, as well as their use in moto and car segment as a replacement for regular starter lead-acid batteries.
Such use is primarily due to its higher thermal and chemical stability, and the ability to receive and output a higher current compared to Li-Ion, Li-Po, and lead-acid batteries. The operating voltage of LiFePo4 batteries has a very small range, resulting in an almost constant discharge voltage.
The combination of these factors makes LiFePo4 a promising replacement for conventional lead-acid batteries in almost every possible industry. But so far the price is the main discouraging factor.
Typical applications of LiFePo4 batteries are traction batteries for electric cars, golf carts, electric scooters and bicycles, starter batteries for motorcycles and cars, as well as applications in uninterruptible power supplies/equipment demanding voltage stability.
Best LiFePo4 Batteries 100Ah
- Expert Power Lithium Iron Phosphate 100Ah 12V.
- Renogy Smart LiFePO4 100Ah Battery.
- HQST Lithium Iron Phosphate 100Ah Battery.
- Lossy Lithium Iron Phosphate 100 Ah Deep Cycle Battery.
- Battle Born LiFePO4 12V 100Ah Battery.
- Ampere Time LiFePO4 12V 100Ah Battery.
Expert Power Lithium Iron Phosphate 100Ah 12V
ExpertPower is a Los Angeles-based energy storage provider. ExpertPower has earned a reputation as one of the most reliable battery companies on the market.
In recent years, ExpertPower has been a mainstay for battery power with its advanced and innovative products.
Expert Power Lithium Iron Phosphate 100Ah Specifications
This battery is ideal for Camper, RV, solar, marine, and land-based stations.
The battery’s lithium chemistry more than halves the weight of a traditional lead-acid battery while providing a significant increase in performance and capacity.
The batteries are designed not only for simple energy storage, but also to provide long-lasting performance at home, at work, or outdoors.
Technical details
- Brand: ExpertPower
- Battery weight: 22.6 lbs.
- Product dimensions: 13 x 6.8 x 8.4 inches
- Voltage: 12.8 volts
- Power: 1280 watts
LiFePo4 Batteries Specifications
- The working voltage of LiFePo4 -3V-3.6V. Discharge as low as 2.8V is possible, but further voltage reduction leads to irreversible battery damage.
- The nominal voltage of LiFePo4 is 3.2-3.3V.
- Fully charged LiFePo4 battery – 3.6V fully discharged – 3V.
- A Group of 4 cells would have a voltage of 12.8V to 13.2V
- The typical shelf life of such batteries is 2000 IEC cycles or 5-7 years from the production date.
Li-ion and Li-Poly Batteries
These types of batteries have found their application mainly in rechargeable batteries for cell phones, cameras, radio-controlled toys, in portable power sources like power banks.
Often they are used in starters for starter batteries because of their low cost. Batteries of this type cannot deliver much current.
Li-Ion, Li-Poly (LiPo) Batteries Specifications
- The working voltage of Li-Ion, Li-Po – 3V-4,2V. Discharge as low as 2.8V is possible, but the further reduction in voltage leads to irreversible damage to the battery.
- The nominal voltage of Li-Ion, Li-Po – 3.6-3.7V.
- Fully charged Li-Ion, Li-Po battery – 4.2 V, fully discharged – 3 V.
- A Group of 3 cells would have a total voltage of 10.8V – 11.1V, a group of 4 cells – 14.4-14.8V
- The typical shelf life of such batteries is 1000 IEC cycles or 3 years from the production date.
Charging of Li-ion, Li-Poly, and LiFePo4 batteries with an external battery charger
Using an analogy with a car generator it’s easy to guess that using an ordinary battery charger for Li-Po and Li-Ion batteries is dangerous because, for an assembly of three batteries, the charging voltage (14.4V) will exceed the allowable voltage of the battery group of 12.6V. When charging an assembly of four batteries, the charge will not be complete because such a group must be charged to 16.8V.
LiFePo4 battery, unlike Li-Po and Li-Ion batteries, can be charged with an external charger because its characteristics are almost exactly the same as those of lead-acid batteries (in terms of charging voltage and nominal voltage).
However, there are a couple of nuances:
- Many LiFePo4 batteries have Lithium Ion written on them, without any indication of LiFePo4, which is misleading. If in doubt as to what type your battery is, check the full battery specifications on the manufacturer’s website.
- LiFePo4 batteries are charged through a special battery cell monitoring system built into the battery. This system is called BMS (Battery Management System).
LiFePO4 (LFP) batteries
What are they, the benefits, and what makes them better than other Li-ion batteries?
LiFePO4 batteries (referred to as “LFP”) are a type of rechargeable lithium-ion battery that uses a lithium-iron-phosphate cathode (the material is structured in the nanometer range) and a graphite anode with a metal substrate as the main component.
Read on to find out what makes LFP technology the ideal choice for electric vehicles, energy storage systems, and industrial devices, despite its drawbacks.
Hereinafter in the text LiFePO4, lithium-iron-phosphate, lithium-iron-phosphate, and LFP mean the same thing – used as synonyms.
As a scientific justification for all the theses mentioned in the article, we took a joint paper [published on ScienceDirect] by the National Center for Scientific Research of the University of Montpellier (France) and the Shanghai Research Center for Electrochemical Energy Devices (China).
Why have lithium-iron-phosphate batteries become so popular?
LiFePO4 batteries are growing in popularity amid falling costs [source BusinessWire]. The industry is now experiencing an era of increasing mass production of components to assemble off-the-shelf batteries.
Lithium-iron-phosphate batteries have a number of advantages over traditional electrochemical systems like lead-acid and nickel-cadmium:
- Higher energy density,
- Longer life,
- Virtually no self-discharge
- Some of the best safety performance.
Synthesis Processes for LiFePO4
Ford, Volkswagen, and Tesla have shown the greatest interest in the technology. To create less expensive electric cars with up to 10 years longer battery life, they are abandoning NMC chemistry.
The price and reliability of LiFePO4 are much better suited for this purpose than conventional Li-ion cells. But this change has the disadvantage that range suffers. LFPs hold much lower energy than the common cobalt (LCO) or nickel-manganese (NMC) Li-ion cells of comparable size.
History of the emergence of LiFePO4
Where did LiFePO4 batteries come from?
Lithium iron-phosphate battery technology came about through the efforts of John B. Goodenough and Arumugam Mantiram. They were among the first to define the use of materials in lithium-ion batteries.
One of the most important limitations of Li-ion is that their anode materials are not ideal because they tend to short-circuit as quickly as possible.
Scientists have made a discovery that makes it possible to change the stability and conductivity of a Li-ion battery by altering the surface materials of the cathode. By acting on the cathode, it is possible to improve (and deteriorate) many of the battery’s properties.
Thus, when the possibility of making the cathode of LiFePO4 was discovered, the lifetime of the cell was increased, and its tendency to go into a short circuit was significantly changed (i.e. to raise the degree of safety). It was also possible to get rid of expensive cobalt, which, however, provides one of the best energy capacities in the electrochemical industry (you always get less capacity than the battery in a smartphone or laptop of the same size).
For self-study, check out another study on the characteristics of lithium-iron-phosphate batteries: “Experimental Measurements of LiFePO4 Batteries” [PDF Document] from the State University in Waterloo, Canada.
What is inside LiFePO4 batteries?
LFP batteries themselves are cells of different shapes (we told you what they are in general in our article). They are made of lithium-iron-phosphate material, which is non-toxic and does not harm the environment.
LFP cells are assembled into batteries to obtain the desired voltage and capacity to the specifications of the application where they are to be used (electric car, electric scooter, uninterruptible power supply, or even just a flashlight). The assembly is performed by spot welding and retrofitting the control system (BMS, Battery Management System – we will tell you about it a little bit below).
The BMS ensures that the battery stays within safe voltage and current limits. It actually protects, monitors, and controls the battery within operational limits. With it, you can be assured that the device is safe and that the service life will be as long as possible.
To delve deeper into the understanding and principles, take a look at an example of a battery management system device in LiFePO4 [page on ResearchGaet with a link to a PDF document].
Safety of lithium-iron-phosphate batteries
LiFePO4 batteries are considered safe because they have the lowest probability of thermal runaway and combustion. The lower operating voltage results in lower internal resistance and higher charge/discharge rates. Their chemical composition is more stable than other lithium-ion chemicals, making them less likely to explode or emit harmful gases in the event of damage (such as an accident or fire).
Because LFP cells offer a longer lifespan than other lithium-ion cells, they are preferred as a safer option where long-term storage is required (the same uninterruptible power supplies or solar energy storage).
LiFePO4 cells are better able to withstand various modes of operation and loads than the common cobalt or nickel-manganese lithium-ion cells. However, they are still prone to overvoltage during charging. Moreover, they have stricter upper voltage limits than conventional Li-ion cells – 3.65 V maximum versus 4.25 V (we’re not talking about LiHV, which can be as low as 4.4 V).
This situation reduces the performance and capacity of the LiFePO4. If you deviate from this limitation and still charge the LFP cell to 4.2 V instead of 3.65 V, the material used for the cathode could potentially deteriorate and lose its stability. The BMS adjusts the power output of each cell and ensures that the maximum battery voltage is maintained so that nothing like that can happen.
Electrode materials deteriorate for a variety of reasons, including aging. That’s a fact.
And since lithium-ion technology “doesn’t like” voltages below 3V, storing LiFePO4 discharged becomes a serious problem on old cells. If the voltage of any cell drops below a certain threshold (usually 2.5 V), the BMS disconnects the battery from the circuit in the name of safety. It also serves as an overcurrent backstop and opens the circuit during a short circuit.
What is a BMS?
BMS (Battery Management System) battery system and charging by an external charger.
A BMS is an electronic device that controls the charging and discharging current of a battery. This device is already built into the battery and can have simple logic or more complex logic. The simple logic of operation is to turn off charging when a given voltage (full charge) is reached, the more complex logic is to continuously monitor the state of the battery, the voltage in each cell, and the temperature, including can record the log of the battery.
A sophisticated BMS system can shut down the battery by overheating, overcharging, and similar events. The BMS system can have deep discharge protection, which blocks charging when the voltage drops below the threshold (2.8V-3V per cell) – UVP (under-voltage protection).
Thus, in case the BMS system is triggered by the deep discharge protection, a conventional charger will not be able to unlock the BMS and charge the battery. For this purpose, specialized chargers for LiFePo4 batteries capable of unlocking the BMS are used.
In addition, the charger profile must be CC/CV (Constant Current/Constant Voltage): charging with constant current, and then at constant voltage, the current decreases. Current pulses and voltage increases up to 16V or higher are not acceptable for LiFePo4 batteries. The use of desulfation chargers is prohibited.
The vehicle’s generator has a classic CV profile so charging from the generator is possible as long as the battery is not deeply discharged and the protection is not triggered.
When charging a LiFePo4 battery with triggered protection you must be extremely careful and monitor the battery voltage and temperature throughout the charging process, because it is essentially a process of restoration of a deeply discharged and possibly already defective LiFePo4 battery.
Modern LiFePo4 battery chargers have a BMS reset function, can automatically monitor the battery temperature, reduce the current as necessary and stop charging if the battery shows no signs of life during the charging process, which makes the recovery and charging process absolutely safe.
Frequent questions about LiFePO4 batteries
Some people may be looking for information on how to use LFP in their projects, while others may be wondering if LFP is a good choice for off-the-shelf electronics. Whatever the reason, it’s always good to know the answers to common questions before making any decisions about battery technology.
Q: “How much longer do LiFePO4 batteries last compared to smartphone Li-ion and Li-Polymer batteries?”
Conventional lithium-ion batteries on a cobalt cathode (as in mobile gadgets) provide an average of 500-1000 charge-discharge cycles. This is enough for capacities of up to 5000 mAh at 3.7V for about 4 years of service, if the manufacturer has bothered with the sparing parameters of the depth of charge (DoD) when the range does not exceed 90%.
In the same mode, lithium iron phosphate batteries will last 4500-5000 charge-discharge cycles. Considering that they are not used in mobile electronics, but in large devices like UPSs or electric cars, the depth of charge can be less than 60% (like in electric cars, for example), which will further increase the service life up to 10,000 cycles.
Q: “Why aren’t LiFePO4 used in smartphones, since they last so long?”
LiFePO4 is not used in smartphones because they are not as efficient as lithium cobalt in terms of electrical energy capacity. Yes, this leads to a reduction in overall battery life of up to 2-4 years (depending on the intensity of use). However, mobile gadget manufacturers put exactly the same lifespan into the product itself, after which it is supposed to be replaced with a new, more modern product.
Q: “Tell me simply – LiFePO4 or Li-ion, which is better?”
LiFePO4 is what Li-ion is, as one type of its electrochemical system. It is often meant by “Li-ion” in the context of a comparison with the LiFePO4 system of cobalt and nickel cathodes.
In that case, there is no unequivocal answer as to which is universally better. The same applies to the question of which is better – lithium titanate or iron phosphate. All options have advantages and disadvantages that are applicable in different applications.
Q: “How much cheaper is LiFePO4?”
Compared to traditional lead-acid battery-based energy storage systems, the economic model of lithium-iron-phosphate batteries is much more efficient (a combination of factors: price + life + maintenance + maintenance + charge principles). More on this was the article: Comparison of lithium and lead batteries, which provides formulas and calculations for uninterruptible power supplies. We must also take into account the current reality when lead-acid batteries have increased in price.
Compared to 3.7-volt electrochemical NMC (electric vehicles) and LCO (mobile electronics) systems, more 3.2-volt LFP cells are needed to get the same capacity. It is more expensive (less profitable) when cells are purchased. But in long-term operation, the costs are recouped at a certain calculation point, when the NMC and LCO wear out (age and lose capacity) and the LFP continues to work.
Q: “How is LiFePO4 better than lead-acid batteries?”
Lead-acid batteries are cheaper, but they need to be replaced regularly to maintain their capacity, keep them charged, and monitor their temperature, otherwise they will wear out quickly. That is, they are more expensive to maintain for long periods of use. A LiFePO4 battery will last 2-4 times longer without any maintenance at all.
Q: “What makes LiFePO4 batteries better than gel batteries?”
Gel batteries, while relatively expensive, require regular and proper charging; they must be disconnected as soon as fully charged to avoid degradation. LiFePO4 doesn’t require all that, and they hold even more power and handle peak loads better.
Q: “What makes LiFePO4 batteries better than AGM batteries?”
An AGM battery loses capacity irrevocably when discharged to 50% or less, which is difficult to keep track of because they have a high self-discharge. LFP cells retain capacity at full discharge without risk of damage, with one of the lowest self-discharge in electrochemical systems.
Q: “Where is the most profitable use of LiFePO4?”
- Water transport (from fishing boats and sailing boats to kayaks);
- Mobile electric transport (from electric scooters and segways to electric motorcycles);
- Solar panels and wind turbines (energy storage and reserve);
- Uninterruptible power supplies;
- Industry (robots, tools, forklifts, hoists);
- Medical equipment;
- Flashlights;
- Electronic cigarettes;
- Emergency lighting;
- Radio equipment and so on.
Q: “Will lithium-iron-phosphate batteries someday have the same capacity as smartphone cobalt batteries?”
It looks like it. Right now, LFP cells have up to 75% of the capacity of LCO and NMC technology.
There are no commercial products with this density yet, but apparently in the future LiFePO4 will approach the capacity of Li-ion in smartphones and electric cars of yesteryear.
