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LiFePO4 Series and Parallel: Comprehensive Guide
LiFePO4 Features and Applications
Advantages: Lithium iron phosphate (LiFePO4) batteries are known for their long cycle life, stable structure and reliable safety,
Applications: In electric vehicles, renewable energy fields, material handling, golf carts, marine and ESS fields.
Why LiFePO4 needs to be connected in series and parallel
LiFePO4 batteries are connected in series and parallel to achieve voltage and capacity in various applications.
· Series connection: Multiple batteries are connected end to end to increase the total voltage.
· Parallel connection: Multiple batteries are connected side by side to increase capacity and current output.
By properly utilizing the series and parallel connection of LiFePO4 batteries, users can customize the battery configuration to meet the needs of specific devices.
1.LiFePO4 series connection
A. LiFePO4 Series Operation
• LiFePO4 battery cells are connected end to end, with the positive terminal of one cell connected to the negative terminal of another cell.
• By connecting in series, the capacity remains unchanged, and the total voltage increases to the sum of all individual cells.
• The nominal voltage of LiFePO4 batteries is usually 3.2V, for example, 4 3.2V batteries connected in series can get a 12.8V battery pack, so series connection is essential for applications that require higher voltages.
B.Series Connection Advantages
Connecting LiFePO4 batteries in series has several advantages, including:
• Higher voltage output：Multiple cells in series increase the overall voltage output of the battery pack, making it suitable for applications requiring higher voltages. With four sets of 12V batteries connected in series, they can provide a total of 48V.
• More efficient energy storage：The cells in a series battery pack share the load equally, ensuring that each cell charges and discharges at the same rate. As a result, there is a higher efficiency in overall energy storage.
• The series connection is ideal for applications requiring high voltages, such as electric vehicles and solar power systems. In addition to enabling efficient energy storage, it ensures even charging and discharging within the battery pack.
C. Disadvantages Series Connection
LiFePO4 batteries connected in series have some disadvantages as well, including:
• Overcharge Risk: Different battery cells in a series battery pack may discharge at different rates, resulting in an unbalanced voltage in the battery pack. The battery pack can be shorted in life if some battery cells are overcharged.
• Lower capacity：Batteries in series have the same capacity as single cells in a series pack. Battery packs with serial connections do not have a greater total capacity.
Battery capacities and ages must be similar in a series battery pack in order to avoid these problems. Furthermore, properly charging the battery pack and monitoring its voltage are essential for preventing overcharging and ensuring its efficiency.
D. Series Considerations
Series Connection Problems
Cell Imbalance:
In a series connection, it is critical to ensure that all cells have similar characteristics, including capacity and internal resistance. If there is a severe imbalance between cells, one or more cells may be overcharged or over-discharged, resulting in performance degradation and potential damage.
Charge/Discharge Control:
LiFePO4 series batteries require careful management of the charging and discharging processes. It can be detrimental to the overall performance and life of a battery system if differences in charge or discharge rates between cells are not properly controlled.
Provide Solutions
Balanced Charging:
It is possible to solve the problem of unbalanced cells in series by implementing a balanced charging system. By balancing the charge to each cell, the cells are prevented from being overcharged or overdischarged. Balancing can be achieved through active circuits or passive methods, such as resistance-based methods.
Battery Management System (BMS):
For series LiFePO4 batteries, BMS are highly recommended. Each cell is monitored and controlled by the BMS to ensure that it operates within a safe range during charging and discharging. This prolongs the battery’s life and optimizes its performance by preventing overcharging, overdischarging, and extreme temperatures.
Balanced charging and a BMS can effectively mitigate problems with series connections in LiFePO4 battery systems. As a result, the battery system will perform optimally, have a longer life, and be safe.
2.LiFePO4 parallel connection
A. LiFePO4 Parallel Operation
• LiFePO4 battery cells are connected side by side, with all positive electrodes connected together and all negative electrodes connected together.
• In this method, the total capacity of the battery is increased by adding the capacity of all connected batteries, while the voltage remains unchanged.
• For example, 2 100ah batteries connected in parallel can get a 200ah battery pack. Parallel connection should be adopted when more energy storage or longer discharge time without increasing voltage is required.
B. Advantages of Parallel Connection
There are several advantages of connecting LiFePO4 batteries in parallel, including:
• Increased capacity: When multiple batteries are connected in parallel, the overall capacity of the battery pack increases, making it suitable for high-power applications. If four 12.8V 100AH batteries are connected in parallel, the voltage remains the same, but the capacity increases to 400Ah.
• Reduced risk of overcharging: The batteries in the parallel battery pack charge and discharge independently, reducing the risk of overcharging. Therefore, the entire battery pack is safer and has a longer service life.
• Application: Efficient energy storage through uniform charging and discharging of the battery pack is very suitable for off-grid and backup power systems for solar power generation systems.
C.Disadvantages Parallel Connection
LiFePO4 batteries connected in series have some disadvantages as well, including:
• Overcharge Risk: Different battery cells in a series battery pack may discharge at different rates, resulting in an unbalanced voltage in the battery pack. The battery pack can be shorted in life if some battery cells are overcharged.
• Energy storage efficiency is low：Batteries in series have the same capacity as single cells in a series pack. Battery packs with serial connections do not have a greater total capacity.
Battery capacities and ages must be similar in a series battery pack in order to avoid these problems. Furthermore, properly charging the battery pack and monitoring its voltage are essential for preventing overcharging and ensuring its efficiency.
D.Parallel Considerations
Parallel connections and potential issues
Uneven Charge/Discharge:
LiFePO4 batteries connected in parallel may experience uneven charging or discharging. There can be differences in internal resistance and capacity that cause batteries to charge more or discharge faster than others due to imbalances. Battery performance and life can be affected by this.
Temperature Control:
Temperature control can also be a challenge with parallel connections. The overall temperature of the battery system can be affected if one or more of the batteries in the parallel connection generate excessive heat during charge or discharge. Consequently, efficiency may be reduced, aging can be accelerated, and safety risks may arise.
Providing Solutions
Balanced Discharge:
LiFePO4 battery systems with parallel charging or discharging can benefit from a balanced discharge system. In this case, a battery management system (BMS) is used to monitor and control the discharge process, ensuring that each battery contributes proportionally to the load. In addition to preventing overdischarge of individual batteries, it promotes equal utilization of battery capacity.
Temperature Monitoring Systems:
To ensure proper temperature control in parallel LiFePO4 battery systems, a temperature monitoring system is essential. The temperature of each battery is continuously monitored by temperature sensors on these systems. It is possible to reduce the charge/discharge rate or provide adequate cooling if a battery exceeds safe temperature limits.
Balanced discharge and temperature monitoring systems can effectively address potential problems with parallel connections in LiFePO4 batteries. In addition to maximizing battery capacity, these solutions ensure proper temperature management, thereby optimizing performance, life, and safety.
3.LiFePO4 battery series VS parallel connection
Similarities:
① Improve battery performance:
LiFePO4 batteries can be connected in series and parallel to improve their overall performance, with series connection enhancing voltage output and parallel connection enhancing capacity.
② Wide range of uses:
There are many applications for series and parallel connections, including RVs, ships, and solar homes. In addition to electric vehicles, they can also be used as off-grid power sources.
Differences:
①Voltage output:
Battery pack voltage output is increased by connecting LiFePO4 batteries in series. A battery pack with four 12V batteries connected in series will produce 48V when the batteries are connected in series. In contrast, parallel connection of LiFePO4 batteries increases the overall capacity of the battery pack, but the voltage output remains the same.
② Capacity:
The total capacity of the battery pack can be increased by parallelizing lithium iron phosphate batteries, for example, 4 100Ah batteries connected in parallel yield 400Ah. However, parallelizing lithium iron phosphate batteries will only increase the voltage output of the battery pack, not its total capacity.
③ Efficiency:
Due to the ability to charge and discharge each cell or battery pack independently, LiFePO4 batteries are usually more efficient in parallel than in series. The battery pack will not be affected by the failure or damage of one cell or battery pack. In contrast, if one cell or battery pack in a series battery pack fails or is damaged, it will affect the whole pack’s performance.
④ Cost:
Due to the additional wiring and hardware needed to ensure the proper operation and safety of the battery pack, paralleling LiFePO4 batteries is generally more expensive than connecting them in series. Some applications, however, may justify the added cost due to the increased capacity and efficiency.
LiFePO4 batteries can be connected serially or parallelly depending on the application. Whenever high voltage output is required, series connections are the best option. Parallel connections are best if high capacity is required. Despite their respective advantages and disadvantages, both configurations are capable of improving overall battery performance in a variety of applications, such as RVs, ships, and solar homes. The cost, efficiency, and voltage output of a configuration must also be considered to determine which configuration is best for your needs.
4. Parallel and Series Considerations
To ensure optimal performance and safety when connecting LiFePO4 batteries in parallel, consider the following points:
Consistency:
Parallel connections require cells or battery packs with the same specifications, including voltage, capacity, and age. When the cells are not matched, charging and discharging can be unbalanced, increasing the risk of battery failure.
Balance:
Maintaining balance and preventing overcharging or undercharging of each cell or battery pack requires monitoring the charge state of each cell or battery pack. This way, the battery pack has a longer and safer life.
Wiring:
Parallel connections must be wired correctly for the battery pack to operate efficiently and safely. Wiring errors can cause short circuits and other dangerous conditions.
The following points should be considered when connecting LiFePO4 batteries in series:
Consistency:
When connecting in series, it is important to use cells or battery packs with the same specifications, including voltage, capacity, and age. Due to the unbalanced voltage distribution, overcharging or undercharging of individual cells or battery packs can occur when the cells are not matched.
Charging:
Overcharging can occur in a series connection when one cell or battery pack finishes charging before the others. To avoid this, it is recommended to use a battery management system (BMS) to monitor the voltage of each cell or battery pack.
Safety:
Electric shock is more likely to occur when connected in series because the total voltage output increases. For safety reasons, the battery pack should be properly insulated and grounded.
In addition, it is not recommended to connect new and old batteries (purchased within 3-6 months) together because they may have different internal resistances, which will affect the overall performance of the battery pack. It is also important to use lithium-ion batteries with consistent performance and never mix lithium-ion batteries of different brands, capacities, or types. Finally, ensure that the polarization of the batteries is correct to prevent voltage drop.
5. Series and Parallel Connection Cases
Electric Vehicles:
In order to meet voltage and capacity requirements for efficient propulsion, electric vehicles (EVs) often use series and parallel connections. LiFePO4 batteries are connected in series to achieve high voltage, while parallel connections are used to increase power output and capacity.
Solar Storage Systems:
Series and parallel connections are often used in solar storage systems to optimize energy storage and utilization. In series connections, higher voltage levels are achieved for efficient energy storage, whereas in parallel connections, more solar panel energy is stored.
Explore the reasons and consequences of use
Electric Vehicles:
Power output and performance of EVs are improved by series connections, which enable higher voltages. The result is higher speeds and a longer driving range for EVs. Parallel connections, however, increase the capacity of the battery pack, enabling longer driving times and continuous power supply. By combining parallel and series connections, EVs achieve optimal voltage, capacity, and power output, balancing performance and range.
Solar Energy Storage Systems:
It is essential to have series connections in solar energy storage systems to achieve the higher voltages required for efficient energy storage. It improves inverter compatibility and maximizes energy conversion efficiency. In contrast, paralleling can increase the total capacity of the energy storage system, allowing more solar energy to be stored. Systems that utilize series and parallel connections can efficiently store and supply solar energy, reducing grid dependency and promoting self-sufficiency.
Optimizing voltage, capacity, and power output of LiFePO4 battery systems with series and parallel connections can result in improved performance, longer operating times, and improved energy storage. As a result, electric vehicles have been able to reach higher speeds and drive for longer ranges, and solar energy storage systems have been able to store more energy and provide reliable power during peak times.
Conclusion
Parallel and series connection of LiFePO4 batteries can improve the overall performance and are commonly used in various applications. For optimal performance and safety, it is important to take some precautions when connecting these batteries.
Parallel connection requires uniformity, balance, and correct wiring, while series connection requires uniformity, charging, and safety.
In addition, it is important not to connect old and new batteries, use batteries with stable performance, and pay attention to their polarity. When we follow these precautions, our LiFePO4 battery pack can operate efficiently and safely.
If you have any battery-related questions, please feel free to contact our battery experts.