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The LiFePO4 battery DIY guide is the ideal starting point for beginner considering DIY and bulid high-quality LiFePO4 batteries project.
LiFePo4 Battery Cells 101
The LiFePO4 Battery 101 is the ideal starting point for anyone considering a DIY and building quality Li-Ion battery project. Learn the basics of LiFePO4 batteries and get tips for incorporating this abundant clean energy source into your home.
Before your DIY battery project, you should know the following:
What are Lithium Iron Phosphate (LiFePO4, LFP) Batteries?
Lithium iron phosphate (LiFePO4 or LFP) is the safest of the mainstream lithium-ion (Li-Ion) rechargeable battery types. Compared to more traditional cobalt-based lithium-ion batteries, they have the advantage of increased power output, faster charging, lighter weight, and longer life. The battery also has better safety features and will not explode under extreme conditions.
LiFePO4 batteries use LiFePO4 as the positive electrode and graphite as the negative electrode. The nominal voltage of the battery is 3.2V, it is worth mentioning that the nominal voltage of the lead-acid battery is 2.1V, and in many cases, the LiFePO4 battery is a perfect replacement for the lead-acid battery.
Further reading: LFP Battery & AGM Battery
Common LiFePO4 Battery Shapes
There are currently three common shapes of LiFePO4 batteries: cylindrical, prismatic, and pouch. Different shapes of batteries will have a certain impact on performance. At present, the most suitable battery DIY enthusiasts are the prismatic LiFePO4 batteries, which are very suitable for both performance and operational difficulty.
Benefits of LiFePO4 Batteries
The benefits of LiFePO4 batteries are many:
1. With a service life of up to 10 years and more than 4000 cycles.
2. Lighter weight and smaller size.
3. The overall cost over the service life is low.
4. Support high-speed charging and discharging.
5. Allow 80% DOD or more discharge.
6. No memory effect.
7. Low self-discharge rate.
8. Very environmentally friendly and safe, and requires little maintenance.
9. High-temperature performance is guaranteed.
Important Components Related to LiFePO4 Batteries
The battery management system (BMS) is a very important battery protection system. By preventing battery overcharge/overdischarge/overcurrent/overheating, it can cut off the power in time when the battery is in some dangerous situation, and at the same time, it can provide a partial balancing function to help the LiFePO4 battery run longer.
BMS is essential to prevent damage to large lithium-ion battery packs. At the same time, as a device to protect the battery, the BMS is also very safe.
Balancer is another important device in the LiFePO4 battery pack. The balancer can maintain the charge balance of each cell in the battery pack for a long time, ensuring that the battery pack can be used normally for a longer period of time.
Busbars are connection accessories for connecting different cells. The connection between each LiFePO4 cell should use suitable busbars, which can maximize the performance of the battery. Generally, when referring to busbars it includes washers/nuts/studs.
Further reading: LiFePO4 Battery DIY Related
Connection of LiFePO4 Battery
There are two basic types of connections:
One is series connection (S). The way of connecting the positive and negative electrodes of two different cells is called series connection. As a result, the voltage of the battery pack will increase while the capacity remains the same.
The other is parallel connection (P), where the positive and positive electrodes of two different cells are connected in parallel. The result is that the capacity of the battery pack increases while the voltage remains the same.
Of course, pure series and parallel connections are only applicable to small LiFePO4 battery packs, and large LiFePO4 battery devices are often both connected in series and in parallel. It should be noted that mixing batteries is not recommended. Only when the chemical properties and voltages are the same can be considered for mixing batteries. Some extreme situations can only be mastered by senior electricians, and beginners must not imitate them.
Balancing and Compression of LiFePO4 Battery Cells
The balance and compression of LiFePO4 batteries is a very important part.
The purpose of battery balancing is to balance the amount of charge between each cell to ensure consistent performance across the battery pack, allowing the battery pack to maintain performance and operate more safely for longer. Generally, the battery balance can be manually balanced or balanced by a balancer.
Further reading: LiFePO4 cell balancing
Battery compression refers to the use of certain tools to tightly combine each cell. The purpose of this is to prevent the cells from swelling during operation, thereby affecting the performance of the battery pack. Similarly, it is not difficult to compress the battery. It is generally recommended to use a sponge or insulating plate to fill the gaps of different cells, and add an insulating shelf or insulating container to the outermost layer of the entire battery pack.
Further reading: LiFePO4 battery compression
Storage Conditions and Operating Temperature of LiFePO4 Batteries
The storage of LiFePO4 batteries requires attention:
Since the self-discharge rate of LiFePO4 batteries is about 3% per month, it should be stored at a SOC of about 50%, and it needs to be stored in a place with low humidity and ventilation. Also, make sure there is no load during storage.
In addition, LiFePO4 batteries need to be stored in a suitable temperature environment (preferably 15 ° C ~ 25 ° C), too low temperature is not good for LiFePO4 batteries.
LiFePO4 Battery Charging
LiFePO4 battery charging requires the use of a dedicated charger for charging.
Be careful not to use a lead-acid battery charger for charging, as this will cause the LiFePO4 battery to not be fully charged.
Also, it is important to note that LiFePO4 batteries are not allowed to charge at temperatures of 0°C (32°F) and below, which can damage the battery.
Further reading: LiFePO4 Battery Charging FAQ
The difference between LiFePO4 Battery and NMC/NCA Battery
LiFePO4 batteries (LFP) are quite different from NMC/NCA batteries, but they are both lithium-ion batteries.
LFP battery: The nominal voltage of the single unit is 3.2V, the life span can reach more than 10 years, the number of cycles is more than 4000 times, and the safety is extremely high, but the energy density is relatively weak, most of which are 120~160Wh/kg, and some can reach 180Wh/kg. Suitable for use in the field of energy storage.
NMC/NCA battery: The nominal voltage of the single unit is 3.7V, the life span is about 3-5 years, and the number of cycles is about 2000-4000 times. The safety is worse than that of the LFP battery, but the energy density is very high, which can reach more than 250Wh/kg, some can reach 350Wh/kg. Suitable for use as a power battery (electric vehicle).
Further reading: LFP Battery VS NMC Battery
Safety Precautions Section of the LiFePO4 Battery
There is no doubt that the LiFePO4 battery is a very safe lithium-ion battery. Even if it is punctured or knocked hard, it will not explode, which is an important reason why LiFePO4 batteries are so trusted.
Despite this, the installation and maintenance of LiFePO4 batteries still need to be carried out by professional technicians, and relevant safety regulations must be strictly followed during use. Non-professionals are not allowed to install and maintain the battery alone, let alone abuse is beyond the scope.
When operating on batteries, pay attention to:
1. It is strictly forbidden to touch the positive and negative poles of the battery box with both hands at the same time.
2. Wear protective equipment such as rubber gloves when operating the battery.
3. It is strictly forbidden to use external force to manually impact, puncture, disassemble the battery and damage the battery system.
4. It is strictly forbidden to use or place the battery in high temperatures (in the hot sun or in a very hot car), strong magnetic fields, and strong corrosive environments.
5. If the battery leaks or the electrolyte gets into your eyes, please do not rub it, rinse your eyes with clean water, and send it to a doctor immediately, otherwise your eyes will be hurt.
6. If the battery emits odor, heat, discoloration, deformation, or any abnormality during use, storage, or charging, immediately remove the battery from the device or charger and stop using it.
7. In case of fire, please use carbon dioxide or dry powder fire extinguisher to put out the fire.
Further reading: LiFePO4 Battery Safety
LiFePO4 Battery Damaged
Of course, LiFePO4 batteries may also be damaged. These include shipping damage, design damage, and man-made damage. Human damage is the main reason, we should keep the battery healthcy and not use the battery abnormally.
Further reading: LiFePO4 Battery Damaged
LiFePO4 Battery Recycling
As an environmentally friendly battery, LiFePO4 battery is undoubtedly recyclable. LiFePO4 batteries contain substances such as copper, cobalt and nickel, as well as rare earths, of which up to 96% can be recycled. While reducing the burden on the environment, chemicals can be reused.
The benefits of recycling LiFePO4 batteries are numerous:
1. Effective protection of non-renewable resources
2. Lower overall manufacturing costs
3. Reduce the amount of material that goes into landfill
4. Reduction of associated environmental hazards
5. Avoid potential fire hazards
6. Create new jobs
The recycling of LiFePO4 batteries is also simple.
Start by covering the battery terminals with non-conductive tape, then head to a lithium battery recycling point. These places can generally be searched through the Internet, and every city will have them. In addition, some electronic hardware stores/government offices/lithium battery specialty stores will also have facilities dedicated to battery recycling.
How to prevent being deceived?
This is a very important question. LiFePO4 battery is a very popular battery at present, both experienced people and rookies want to buy batteries and do DIY. This has attracted the attention of many unscrupulous merchants. There are many counterfeit products on the market today, and we must prevent being deceived.
Excellent LiFePO4 batteries are generally referred to as Grade A batteries. And most of them have clear QR codes and corresponding specifications. The voltage/resistance/capacity will also remain the same as the specification or slightly higher.
In addition, it is not recommended to buy LiFePO4 batteries that are too cheap, and the probability of being fooled is greater than the chance of luck.
Further reading: How to stay away from Fake LiFePO4 Battery?