Home » Solar Batteries » LiFePO4 battery (Expert guide on lithium iron phosphate)
Romain Metaye Ph.D. in Chemistry, École Polytechnique Feb 10, 2023
Ph.D. in Chemistry, École Polytechnique
Feb 10, 2023
Lithium Iron Phosphate (LiFePO4) batteries continue to dominate the battery storage arena in 2023 thanks to their high energy density, compact size, and long cycle life.
You’ll find these batteries in a wide range of applications, ranging from solar batteries foroff-grid systemsto long-rangeelectric vehicles.
Despite them being available for some time, questions about LiFePO4 batteries still remain:
- How much do they cost?
- Are they safe?
- Are they the best for solar applications?
Whether you’re looking to integrate LiFePO4 batteries or simply someone who wants to know more about the latest advancements in battery technology, this article will provide comprehensive answers to these questions and more.
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What is a LiFePO4 battery?
LiFePO4 batteries are a type of rechargeable lithium-ion technology that uses a LiFePO4 cathode and a graphite anode. However, they differ from traditional lithium-ion batteries in their chemistry and construction.
LiFePO4 batteries are known for their high energy density, making them a popular choice for various applications, including electric vehicles, renewable energy systems, and consumer electronics.
Additionally, they are known for their long cycle life, with the ability to last for thousands of charge and discharge cycles. This makes them a cost-effective choice for applications that require frequent battery replacement.
Compared to traditional lithium-ion batteries, LiFePO4 batteries have a lower nominal voltage of 3.2V, making them safer and more stable. They are also less prone to overheating and are less likely to catch fire due to their excellent thermal stability.
Furthermore, these batteries offer fast charging capabilities, a high discharge rate, and a wide operating temperature range, making them ideal for high-performance applications in various environments.
The main competitor of the LiFePO4 battery
Lithium-ion batteries continue to compete against their lesser lead-acidcounterparts. As such, you’ll find LiFePO4 batteries up against AGM and Gel batteries in the marketplace.
That said, LiFePO4 batteries also face competition within their own ranks —lithium-titanate (LTO) batteriescome to mind.
Moreover,hydrogen fuel cells are beginning to compete against lithium batteries for use in EVs.
How do LiFePO4 batteries work?
From a scientific point of view, LiFePO4 batteries are reversible electrochemical storage systems. In other words, they convert electricity into charged chemical particles, called ions, in a reversible process.
Let’s look at the LiFePO4 battery cell in more detail. It’s made of the following 8 essential components:
|Positive electrode (cathode)||Lithium metal oxide (LiFePo4)|
|Negative electrode (anode)||Graphite|
All lithium-ion batteries (LiCoO2, LiMn2O4, NMC…) share the same characteristics and only differ by the lithium oxide at the cathode.
Let’s see how the battery is charged and discharged.
Charging a LiFePO4 battery
While charging, Lithium ions (Li+) are released from the cathode and move to the anode via the electrolyte. When fully charged, the anode stores more lithium than the cathode.
Discharging a LiFePO4 battery
The opposite reaction occurs if a power load is applied to the battery. Lithium ions flow from the anode to the cathode, ultimately storing more lithium than the anode.
Finally, this movement of lithium ions inside the battery creates an electron flow between the two electrodes, generating an electric charge outside the battery.
If you’d like to know more about the electrochemical equations and material science behind the LiFePO4 battery, we highly recommend this free article — it gives a good in-depth explanation.
Is LiFePO4 the same as lithium-ion?
Lithium-ion is a label that describes a certain type of battery based on lithium technology. All lithium-ion batteries take advantage of the electrochemical properties of Lithium as an ion (Li+). In other words, yes, LiFePO4 is a lithium-ion battery.
They only differ by the material used in their electrodes, which is lithium oxide for all of them (LiCoO2, LiMn2O4, LiFePo4).
Therefore, LiFePO4 is one of the many different lithium-ion batteries that exist. Some other types of lithium-ion batteries include:
- LiCoO2 (LCO)
- LiNiMnCoO2 (NMC)
- LiNiCoAlO2 (NCA)
- Li2TiO3 (LTO)
Chemists and materials scientists continue to make multiple lithium-oxide variants to create the best lithium-ion battery possible. So far, LiFePO4, created in 1996, is their greatest discovery.
The second most popular lithium-ion battery is the NMC battery, based on Lithium Manganese Cobalt Oxide. Compared to LiFePO4, it has a higher energy density (better storage capacity) and power. It also allows for several thousand cycles and accepts quick charge/discharge. Unfortunately, it’s less safe than LFP batteries and is more expensive.
NMC lithium-ion batteries and NCA (nickel-cobalt-aluminum oxide) are predominantly used in the electric vehicle industry.
Why are LiFePO4 batteries so expensive?
LiFePO4 batteries are known to be expensive, but are they really?
When it comes to energy storage, you cannot just rely on a battery’s retail price. You must also account for the total energy in kWh that the battery can store and release (charge/discharge cycle) during its lifetime.
Diving a battery’s retail price by this value will help you get its levelized cost of storage (LCOS) in $/kWh. This value helps compare the real value of different energy storage systems.
Levelized cost of storage for a 12V LiFePO4 battery
Let’s calculate the levelized cost of storage (LCOS) for using Li Time’s 100Ah, 12V LiFePO4 battery.
Note to our readers: If you’d like to view more quality batteries like the one mentioned above, check out our article discussing the 7 best storage batteries for solar panels in 2023.
The current retail price for this battery is $309.99. Over a 10-year lifespan, the battery is capable of 6,000 charge/discharge cycles at 80% DOD.
Let’s assume one full charge/discharge cycle per day at a total capacity of 1.2 kWh per cycle.
Using the above information, we can determine that the battery will be able to store/release a total of 5760 kWh over a 10-year period. Therefore, the LCOS for this battery will be 0.05 $/kWh. This is substantially cheaper than the average U.S. residential electricity price (0.156 $/kWh).
In California, the average cost of electricity is 0.26 $/kWh. In addition, electricity prices are continuously increasing (1.7% per year on average over the last ten years).
Can you see what we are getting at? LiFePO4 batteries actually end up being incredibly cost-effective!
Can I save and earn money from a LiFePO4 battery?
You can actually earn money with an Energy Storage System (ESS). An ESS, such as the Tesla Powerwall, is a plug-and-play box that combines an inverter, solar charger, and battery storage. You can connect these systems to a domestic solar panel array — with monocrystalline panels, of course — and to the electric grid.
Our article discussing the 7 best Tesla Powerwall alternatives shows that the Fortress Power eVault Max has one of the lowest LCOS at 0.12 $/kWh.
Even without solar panels, you could charge your ESS during off-peak hours at 0.26 $/kWh, then sell it back — via net-metering — at a higher price to the grid during peak hours.
Let’s do the math: 0.25+0.16= 0.38 $/kWh. You sell it for 0.66 $/kWh. Your profit is 0.28 $/kWh.
You could even earn more if you generate your electricity using solar panels, thanks to solar energy being the cheapest source of electricity.
Bear in mind that this is only a rough estimate, and a more accurate calculation should be performed, but this is how cheap LiFePO4 batteries are in reality.
What applications use LiFePO4 batteries?
Thanks to their high power specs (W/kg), energy density (Wh/kg), and extended life duration (up to 10 years), LiFePo4 batteries have many applications. They are safe enough to be used for both stationary and mobile applications.
Below, I have listed some of the many applications of LiFePO4 batteries:
- Energy Storage systems (ESS), like the Fortress Power Evault.
- Solar batteries, along with solar panels.
- Portable solar generators for camping and DIY systems.
- EV batteries An application that requires high power, storage capacity, and durability. LiFePo4 batteries can provide strong pulses of current during car acceleration.
- Solar water pumping systems.
- Electric bikes and scooters.
Is a LiFePO4 battery safe indoors?
LiFePo4 batteries are the safest type of lithium battery.
They are sealed in an airtight aluminum case, specifically designed to withstand temperature, pressure variations, punctures, and impacts.
Therefore, they are maintenance-free, and in addition, they all include a BMS (battery management system).
They come with safety equipment that monitors and controls each individual battery cell. It protects them from overcharging/discharging against short circuits and abnormal temperature fluctuations by disconnecting the affected battery cells. It also balances the battery voltage for an even charging/discharging level.
Can my LiFePO4 battery explode?
As previously explained, LiFePo4 batteries are extremely safe thanks to safety equipment. During normal operations, there is no danger of explosion or ignition, and no chemical leakage will occur.
However, there are 2 situations in which a LiFePo4 could explode:
1. LiFePO4 factory defects
Millions upon millions of LiFePO4 batteries have been made. Naturally, there is a tiny chance of battery failure. It was calculated to be 1 in 10 million — rather small compared to the chance of being hit by lightning (1 in 13,000).
2. LiFePO4 in contact with external heat (over 200°C):
Several studies were conducted to assess the effect of overheating different lithium batteries. It was proven that LiFePo4 is the safest of all lithium-Ion batteries as their temperature rise is minimal. In addition, they will not propagate the fire to other batteries due to the highest thermal runaway.
LiFePo4 batteries will not burn until temperatures above 270°C are reached.
Do LiFePO4 batteries need a special charger?
To charge a LiFePO4 battery, you need a dedicated charger with a charging profile (voltage limits) designed for lithium batteries.
However, you can also use a lead-acid battery charger, as the voltage limits are within the acceptable range of a lithium battery.
The charging profile of a LiFePO4 battery is divided into two steps:
- Stage 1: Constant Current
- Stage 2: Constant Voltage
These two stages are similar to the charging profile of GEL and AGM batteries. The main difference is the charging speed. Whereas lead-acid only accept charging speeds of 0.1-0.3C (10 to 30% of their max current capacity), LiFePO4 batteries can charge up to 0.3C-1C (30 to 100% current capacity).
For example, a 12V–100AH lithium battery accepts charging power up to 1000W. The same battery – AGM or GEL technology only accepts charging power of 300W.
Let’s have a closer look at the charging stages of a lithium battery.
Related reading: 4 Best ways to charge a LiFePO4 battery
Charging profile LiFePO4, stage 1: constant current
During the first stage, the charging current is the highest, and the LFP battery will recover up to 90% of its capacity in 1 to 2 hours.
Charging profile LiFePO4, stage 2: constant voltage
The second stage will help recover the remaining 10% of capacity. It can take around 20min to complete stage 2.
If your battery charger delivers enough current, your lithium battery can be fully charged in 2 to 3 hours. This is much faster than GEL or AGM batteries which need 10 to 12 hours for a full charge.
Note: Fast chargers are hard to find. Currently, the most powerful domestic chargers rarely exceed 400W, such as the Victron battery charger.
The best option to fast charge a lithium battery is solar energy. With solar, currents of up to 100 Amps can be pulled in the depleted battery.
How to store a LiFePO4 battery
LiFePO4 batteries should be stored in a dry and temperate environment (around 77°F) at 60-80% capacity.
The self-discharge rate is around 2-3% per month.
Ensure the battery’s temperature never falls below 32°F, as it could cause irreversible damage to the lithium battery.
Is LiFePO4 the best for a solar battery?
Currently, LiFePO4 is the best solar battery. It is more compact, stores more energy, and lasts much longer than any other type of battery.
Moreover, it is perfectly suited for solar energy as it accepts fast charging/discharging.
The main limitation of LiFePO4 technology is its degradation at low temperatures (below 32°F), which makes it unsuitable for cold climates.
A modified lithium battery called lithium-titanate oxide (LTO) might be the best alternative to LFP.
LTOs are capable of working from -40°F to 140°F. They have incredible charging and discharging speeds, up to 15C (15x their rated current), allowing a full charge in 15min. On top of that, their life duration is huge, with more than 15,000 cycles.
LTO cells are currently available on Amazon under the brand YinLong.
It’s safe to say that the LiFePO4 battery is the best battery available.
The LiFePo4 battery technology could be viewed as the biggest technological improvement in electricity storage since the invention of the lead-acid battery more than 100 years ago.
It is paving the way for a revolution in clean energy storage.
However, some necessary improvements still need to be made regarding their energy density, charging speed, and durability. And for certain applications, it already has a strong competitor: the hydrogen fuel cell.
What is the best voltage to charge LiFePO4 battery? ›
In the case of LiFePO4 chemistry, the absolute maximum is 4.2V per cell, though it is recommended that you charge to 3.5-3.6V per cell, there is less than 1% extra capacity between 3.5V and 4.2V. Over charging causes heating within a cell and prolonged or extreme overcharging has the potential to cause a fire.What is the best charging current for LiFePO4 battery? ›
A recommended charging current no greater than 0.5C will help to maximize the lifespan of the LifePO4 battery.What is the best float voltage for LiFePO4? ›
Float charging is only required for an SLA battery, recommended around 13.8V. Based on this, a charge voltage range between 13.8V and 14.7V is sufficient to charge any battery without causing damage.What is the optimal temperature for LiFePO4? ›
The typical operational temperature of the cells (at the surface) is at 0°C to 40°C (max 60°C). The internal temperature under load should not exceed the maximal limit (<85°C) that is why the surface temperature of the cell should be kept within a limit of 40°C (to 60°C).Should you fully charge a LiFePO4 battery? ›
If LiFePO4 batteries are not fully discharged, they do not need to be charged after each use. LiFePO4 batteries do not get damaged when left in a partial state of charge (PSOC). You can charge your LiFePO4 batteries after each use or when they have been discharged up to 80% DOD (20% SOC).How long does it take to charge a 100ah LiFePO4 battery? ›
A 100-amp hour LiFePO4 battery can take 2 hours to charge with a 50-amp charger. Charging time may depend on the used charger for your lithium batteries. For example, a 500AH battery needs 5 hours to charge with a 100-amp charger.Is it OK to charge LiFePO4 to 100%? ›
Leaving LFP at "100%" and not connected to anything "active" is where things are not so good and this is where damage can happen. Storing LFP for Longterm is best at no more than 50% charge or 3.200 +/- 0.100 per cell.When should I stop charging LiFePO4? ›
No matter what charge mode the battery is in, stop charging once the cell temperature exceeds the absolute charge temperature range. No matter what charge mode the battery is in, stop charging once the cell voltage exceeds the absolute charge voltage.Which is better LiFePO4 vs lithium ion battery? ›
Is LiFePO4 better than lithium ion? The LiFePO4 battery has the edge over lithium ion, both in terms of cycle life (it lasts 4-5x longer), and safety. This is a key advantage because lithium ion batteries can overheat and even catch fire, while LiFePO4 does not.How do I increase my LiFePO4 battery life? ›
Charge and discharge the batteries properly: Lifepo4 batteries should be charged and discharged within the recommended voltage range to ensure optimal performance and longevity. Overcharging or deep discharging the batteries can damage the cells and reduce their lifespan.
What is a high temperature environment for LiFePO4? ›
Good high-temperature performance
Generally speaking, the working environment of LiFePO4 batteries is between -4℉ to 140℉.
You should never attempt to charge a LiFePO4 battery if the temperature is below 32°F. Doing so can cause lithium plating, a process that lowers your battery's capacity and can cause short circuits, damaging it irreparably.What voltage is a full charge LiFePO4? ›
Individual LiFePO4 cells have a nominal voltage of 3.2 volts. They are fully charged at 3.65 volts and fully discharged at 2.5 volts. You can buy individual LiFePO4 battery cells online. They're best used for making your own lithium batteries.What is the bulk voltage for LiFePO4 battery? ›
To summarize this, a bulk/absorb setting between 14.2 and 14.6 Volt will work great for LiFePO4! Lower is possible too, down to about 14.0 Volt, with the help of some absorb time. Slightly higher Voltages are possible, the BMS for most batteries will allow around 14.8 – 15.0 Volt before disconnecting the battery.What should I set my float voltage to? ›
Float mode is where the voltage on the battery is maintained at approximately 2.25 volts per cell, or 13.5 volts for a 12V battery. This voltage will maintain the full charge condition in the battery without boiling our electrolyte or overcharging the battery.What are the best LiFePO4 charging parameters? ›
The charge voltage of LiFePO4 battery is recommended to be 14.0V to 14.6V at 25℃, meaning 3.50V to 3.65V per cell. The best recommended charge voltage is 14.4V, which is 3.60V per cell. Compared to 3.65V per cell, there is only a little of the capacity reduced, but you will have a lot more cycles.How far can you drain a LiFePO4 battery? ›
LiFePO4 batteries can be continually discharged to 100% DOD and there is no long-term effect. However, we recommend you only discharge down to 80% to maintain battery life.How many years do LiFePO4 batteries last? ›
LiFePO4 batteries, also LFP batteries, are designed to last a maximum of 10 years. They can last about 5,000 cycles at 80% depth of discharge, which is much longer than lead-acid batteries. Thanks to the long lifespan of LFP batteries, many people will choose to use them in many applications.Is it OK to leave a lithium-ion battery on the charger overnight? ›
Most power banks use lithium-ion batteries, which are safe to leave plugged in and charging overnight.Is it better to have 2 100ah lithium batteries or 1 200ah lithium battery? ›
A: As far as capacity goes it's the same. However, 2 100 ah batteries would be better than 1 200 ah battery.
Can you use a trickle charger on a LiFePO4 battery? ›
It is important to note that trickle charging is not acceptable for lithium batteries. "Trickle charging" means that a certain current is forced into the battery even when full.What is the state of charge voltage of LiFePO4? ›
Battery Monitoring - Our LiFePO4 batteries are equipped with two methods of monitoring battery State of Charge (SOC). This is important because unlike lead acid batteries, LiFePO4 batteries maintain a nearly constant voltage between 13 and 13.4 volts so a volt meter is of limited value for measuring SOC.What is the BMS cutoff voltage for LiFePO4? ›
To summarize this, a bulk/absorb setting between 14.2 and 14.6 Volt will work great for LiFePO4! Lower is possible too, down to about 14.0 Volt, with the help of some absorb time. Slightly higher Voltages are possible, the BMS for most batteries will allow around 14.8 – 15.0 Volt before disconnecting the battery.What is the resting voltage of a 12V LiFePO4 battery? ›
The charging voltage and resting voltage of a completely charged 12V LiFePO4 battery is 14.6 and 13.6 volts, respectively.