Lithium battery is now the most trending battery technology, especially, LiFePO4 batteries.
It is widely used not only in Electric Vehicles but also in energy storage and other power appliances.
This post is going to tell you not only the advantages, but also the shortage, and also some other things you have to know about LiFePO4 battery packs.
The Biggest Advantage – Super Long Cycle Life
For a lot of people who choose LiFePO4 battery, is because of its super-long cycle life.
In my opinion, this is the biggest advantage of LiFePO4 battery. The cycle life of LiFePo4 batteries is not only a lot more than lead-acid batteries but also 50% more than other lithium-ion batteries.
If at a reasonable setting, the LiFePO4 battery can reach 6000 cycles. If one cycle a day, it can be working for about 20 years.
So, it is best used in applications with more than one cycle a day. Such as residential and commercial solar systems, low-speed vehicles, and other deep discharge applications.
Not Allowed to Charge Under 0 ℃
The old lead-acid battery is not limited by the cold temperature, even the usable capacity can be really low if under 0℃.
But for all lithium batteries, it is not allowed to charge below 0℃.
Lithium ions can be crystalized while charging under 0℃. This crystallization will reduce the battery capacity, and even worse, it can cut through the battery separator, causing an internal short circuit.
In one word, charging under 0℃ can damage the battery, or even possibly, burn it.
That is also why CATL considers adding sodium battery cells into the EV car battery packs.
Solium batteries can be working at a low temperature very well, they can support the EV cars in northern China.
So, for those areas the temperature can reach under 0℃, you will need to consider how to charge while under 0℃.
One solution is the self-heating BMS, it can heat up the battery pack with a heating film inside. It will support the temperature low to -20℃.
Another solution is to switch to another lithium battery type with a special electrolyte, which supports working even under -20℃.
Safe Lithium Ion Technology
Now the lithium technology is matured, and also the battery management system. It is now safe, but still, a lot of people think it is dangerous.
LiFePO4 battery is safest in chemical structure, there is no thermal runaway. In the simple understanding of Thermal Runaway, it is self-burning or explosion.
NMC lithium battery will burn at the temperature of 200℃, while LiFePO4 battery only burns at 500℃.
This is needle test to create the internal short circuit, and let’s see what will happen.
As you can see from the name of LiFePO4 battery, Lithium, Ferro, P, are all common elements on the earth, no harmful metal.
Unlike a lead-acid battery, lead is heavy metal. or NMC lithium battery, cobalt needs special treatment.
Renewable energy is to protect the earth, it is also important for the battery not to harm the earth.
The Nominal Voltage
One single cell of LiFePO4 is 3.2V.
Now there are a lot of energy storage systems that are 48V, while mini ones are 12V and 24V.
LiFePO4 Battery packs are compatible with most inverters and charge controllers (12V, 24V, 48V), and also other devices 12V, 24V, 36V, 48V, 72V, etc.
The High Constant Power, and the Max Current Cut Off
For lead-acid batteries, the recommended constant discharge current is always 0.1C. While most of the LiFePO4 battery packs are 1C or more.
For most of the high current applications, the energy storage type LiFePO4 battery has already covered the demands.
For high rate discharge, such as for UPS, 5C grade cells can be chosen.
Yes, this kind of cell costs a lot, and also the battery system. But to many UPS systems downtown, LiFePO4 battery can save a lot of space.
Compared to the extremely high cost in the buildings & room, the high battery cost is also worthy.
Even though the discharge current of the LiFePO4 battery is high, it still needs protection.
While the current is over the limit, BMS will cut down the circuit, so it is very important to choose the appropriate batteries.
Must Be Protected by BMS
LiFePO4 technology is safe, but still, protections are mandatory.
There is one friend, who only limits the voltage, with no problems while the battery working in the solar system.
But you have to know that, there is the cost of risk. In case something bad happens, you will pay too much more unexpectedly.
All lithium batteries are sensitive to over-voltage, under-voltage, over-current.
These conditions can easily lead to capacity loss, battery cell inflation, damage, even worse, possibly flamming, explosion.
BMS is mandatory for lithium battery packs.
Battery Cell Balance – Top Balance
Even now the technology of LiFePO4 battery cells is advanced, there are still minor differences between the batteries.
So, before the battery cells are assembled into packs, it is recommended to do the top balance.
Our BMS also has a function of internal balance, after cycles of use, the battery cells can keep balanced.
This is helpful to keep all the cells at similar status, prolong the battery life, and work at better performance.
Different Grade of LiFePO4 Battery Cells
LiFePO4 batteries are widely used in a lot of different industries, and they are not exactly the same.
For energy storage, discharge current under 1C.
For power applications, sometimes the current can be 2C or higher.
For Electric Vehicles, a high rate is required for charge and discharge. It can be 5C grade cells.
The Different Shapes of LiFePO4 Battery Cell
There are also different shapes of LiFePO4 battery cells.
Prismatic cells (square cells) are now widely used for energy storage and electric vehicles. In the year 2020, prismatic cells accounted for 40% of the EV battery market. It is also considered as the safest cell.
BYD launched Blade Cell with a needle test, it is really impressive. Then the demand for LiFePO4 batteries in the entire EV market grew very fast.
For large energy storage systems, low-speed vehicles, and also electric vehicles, prismatic cell is always the first choice.
The cylinder cell (round cell) is the oldest manufacturing technique, and the round shape of the shell allows the pressure to be equal on every side, it is a very stable structure.
The size of cylinder cell is very small. So it is ideal to be used in small devices, such as electric toys, rechargeable LED lights, hand power tools, and portable mobile power banks.
Well, it is also possible to build a huge battery pack, such as TESLA.
There is a very specific case, TESLA uses cylinder cell as the EV battery pack in Model 3. It is a quite huge battery pack, which holds hundreds of kWh of energy.
Well, Tesla has a really powerful battery management system and cooling system to implement the entire EV battery pack. Or it will not be a good idea to use cylinder cells to make up a big battery pack.
The pouch cell (polymer cell) can be customized to any size, it can fit into a variety of limited spaces. So it is very common in smartphones, drones, wearable devices, and other mobile, space-intensive applications.