A LiFePo4 battery is currently the most convenient and efficient way to store electricity.
The storage of electricity has always been a scientific and technical challenge.
Let’s look at the characteristics of the perfect LFP battery:
- Ready for quick charging/discharging
- Cost effective
LiFePo4 batteries are performing quite well in all the above categories. They are the best choice for many applications, ranging from solar batteries for off-grid systems, to long-range electric vehicles.
In this article, you’ll discover the technology behind the Lithium Iron Phosphate battery. (LiFePO4), also called LFP battery.
You’ll also find out how LFP batteries are used as well as their major advantages.
Some frequently asked questions about LiFePO4 batteries will follow.
Finally, the myth that lithium batteries are expensive will be debunked and you’ll find out how you can even earn money with your LFP battery pack.
What Is A LiFePO4 Battery?
A LiFePO4 battery is a reversible electricity storage system – LiFePo4 being one of the battery parts. It has the ability to be charged (storage) with electricity when connected to a power source, and to be discharged (release of electricity) when a power load is applied.
LiFePo4 batteries mainly compete against Lead-acid AGM and GEL batteries, but they have advantages in all categories ranging from energy and power density, compacity, and life duration.
LiFePo4 batteries only supply and accept DC (direct current). One LFP battery is the assembly of multiple prismatic LiFePo4 cells of 3.2V.
Therefore, a 12V LiFePo4 battery is made of 4 prismatic battery cells in series. A 24V LiFePo4 assembles 8 prismatic cells.
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 into more detail at the LiFePO4 battery cell.
It is made of these 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 which in the end stores 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 would highly recommend this free article – it gives a good in-depth explanation.
Is LiFePO4 The Same As Lithium-Ion?
Yes, LiFePO4 is a lithium-ion battery.
Lithium-ion is a generic name 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+).
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. Some other types of lithium-ion batteries are:
- LiCoO2 – LCO
- LiNiMnCoO2, NMC
- LiNiCoAlO2, NCA
Chemists and materials scientists are making multiple variations of the lithium oxide to find the best lithium-ion battery. 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. On the negative side, it is not as safe as LFP batteries and is more expensive.
NMC lithium-ion batteries, as well as 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, we cannot just rely on the buying price of the battery (up-front cost). We have to take into account the total energy in kWh that the battery can store and release (a charge/discharge cycle) during its lifetime. Then, we divide the upfront cost by this value.
You will get the LCOS or Levelized Cost Of Storage in USD/kWh.
This number is interesting when used to compare different energy storage systems. Indeed manufacturers are now giving long warranties on their products (up to 10 years and 5000 cycles).
Levelized Cost Of Storage For A 24V LiFePo4 Battery
Let’s calculate the levelized cost of storage (LCOS) for a 100Ah, 24V lithium battery. The current upfront cost (buying price) is 909 USD and this battery comes with a 10 years warranty. Let’s assume 1 full charge/discharge cycle per day for a total capacity of 2.4 kWh per cycle.
Over 10 years, you will store/release a total of 8,760 kWh.
Therefore, the LCOS of this battery is 0.103 USD/kWh. Compared to an average price of 0.112 USD/kWh for retail electricity in the US.
- In South California, the average cost of electricity is 0.25 USD/kWh and can climb up to 0.66 USD/KWh during peak time in summer (4pm to 9pm). 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 are cheap!
But wait, there’s more.
Can I Save And Earn Money From A LiFePo4 Battery?
You can actually earn money with an Energy Storage System (ESS). An ESS is a plug-and-play box that combines an inverter, solar charger, and battery storage. It can be connected to a domestic solar panel array and to the electricity grid.
With no solar panels, you could charge your ESS during off-peak hours at 0.25 USD/kWh, then sell it back at a higher price to the grid during peak hours.
Let’s do the math:
0.25+0.16= 0.41 USD/kWh and you sell it for 0.66 USD/kWh, your profit is 0.25 USD/kWh.
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 Are LiFePO4 Batteries Used For?
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.
- 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, thanks to safety equipment, LiFePo4 batteries are extremely safe. 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 Default:
LiFePo4 batteries are manufactured by the hundreds of millions and there is a tiny chance of battery failure. It was calculated to be 1 in 10 million, quite small compared to the chance of being hit by lightning (1 in 13,000).
2. LiFePo4 In Contact With External Heat (More Than 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.
What Is The Average Price Of A LiFePO4 Battery?
Driven by the electric vehicle industry, the price of a LiFePo4 battery is going down year after year.
From 2010 to 2020, the price per kWh dropped by 89% with a 13% decrease from 2019 to 2020.
On average, the current price of a LiFePo4 battery pack was 137 USD/kWh in 2020. It is forecasted to reach 100 USD/kWh by 2023 while EV makers reach mass production, with a goal of 50 USD/kWh by 2030.
Those prices are only accessible for larger systems. In practice, and for domestic use, expect to pay somewhere around 300 to 400 USD/kWh for your battery.
But, remember that this is the upfront cost of your battery. Most of the recent LiFePo4 batteries come with a 10-year warranty, therefore it is better to consider the LCOS to determine the real cost of your lithium battery.
How To Get A Cheap LiFePo4 battery?
To drastically reduce the price of your LiFePo4 battery, our solution is DIY.
Thanks to their technology you could DIY your own LiFePo4 battery.
In short, for a 12V 200Ah battery (2.4 kWh), you’ll need:
The total cost is less than 300USD/kWh.
We will release a more in-depth DIY LifePo4 battery article in the near future, stay tuned.
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 in 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.
Charging profile LiFePO4, stage 1: Constant Current
During the first stage, the charging current is the highest, 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% 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 that 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 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.
Make sure that the temperature of the battery never falls below 32°F as it could cause irreversible damage to the lithium battery.
Is LiFePO4 The Best 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 LTO (Lithium Titanate Oxide) might be the best alternative to LFP.
LTO are capable of working from -40°F to 140°F, they have incredible charging and discharging speeds, up to 15C (15 times their rated current) that allow full charge in 15min. On top of that, their life duration is huge with more than 15’000 cycles.
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, there are still some necessary improvements that 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.