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. Indeed, the perfect solar battery should be:
- light weight,
- ready for quick charging/discharging,
- and ultimately cheap
LiFePo4 batteries are performing quite well in all the above categories. They are the best choice for many applications, ranging from solar battery for off-grid systems to long range electric vehicles.
In this article, I will first describe the technology behind the Lithium Iron Phosphate battery (LiFePO4), also called LFP battery.
Then, I will show how LFP batteries are used and their major advantages are.
Secondly, I will answer all the most frequently asked questions about LiFePO4 batteries, such as safety concerns.
Finally, I will debunk the myth that lithium batteries are expensive and demonstrate how you could even earn money with your LiFePo4 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 the 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 now look into more details at the LiFePo4 battery cell.
It is made of three 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 now 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 is the movement of Lithium ions inside the battery that 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, I would highly recommend this free article giving 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 batteries 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 a 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 material 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 more expensive.
NMC lithium-ion batteries as well as NCA (nickel-cobalt-aluminum oxide) are mainly 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 could 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 to compare different energy storage systems, indeed manufacturers are now giving long warranty 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 920 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 0.105 USD/kWh. Compared to an average price of 0.132 USD/kWh for retailed electricity in the US.
- In South California, the average cost of electricity is 0.23 USD/kWh and can climb up to 0.54 USD/KWh during peak time in summer (4pm to 9pm). In addition, electricity prices are continuously increasing (1.5% per year on average, over the last ten years).
I guess you now see my point, 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 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 0.23 USD/kWh, then sell it back at higher price to the grid during peak hours.
Let’s do the math:
0.23+0.16= 0.39 USD/kWh and you sell it for 0.54 USD/kWh, your profit is 0.15 USD/kWh.
Bear in mind that this is only a rough estimate and a more accurate calculation should be performed, but this how cheap LiFePO4 batteries are in reality!
What are LiFePO4 batteries used for?
Thanks to their high specific power (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 batteries.
They are sealed in an airtight aluminum case, specificallydesigned to withstand temperature, pressure variations, punctures and impacts.
Therefore, they are maintenance free, and in addition they all include a BMS (battery management system).
A 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 multiple 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 two situations in which a LiFePo4 could explode:
LiFePo4 factory default:
LiFePo4 batteries are manufactured by the hundreds of millions and there is a tiny chance of a battery failure. It was calculated to be 1 in 10 million, quite small compared to the chance of being hit by lighting (1 in 13’000).
LiFePo4 in contact with external heat (more than 200°C):
Several studies were conducted to asses the effect of overheating different lithium batteries. It was proven that LiFePo4 are 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 an objective of 50 USD/kWh by 2030.
Those prices are only accessible for larger systems. In practice, 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, my answer is DIY.
Indeed, thanks to their technology you could DIY your own LiFePo4 battery.
In short for a 12V, 200Ah battery (2.4 kWh), you’ll need:
Total cost is less than 300USD/kWh.
We will release a more in-depth DIY LifePo4 battery article in the near future, stay tuned.
I guess that if you read this article till the end, you might ask yourself is LiFePo4 the best battery battery?
In my opinion, I would say that this is the best battery available and you should not hesitate between LiFePo4 and Lead-Acid. The LiFePo4 battery technology could be considered 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 improvements in sight, regarding their energy density, charging speed and durability. And for certain applications it already has a strong competitor: the hydrogen fuel cell.