A guide to charging lifepo4 batteries

1. The chemical process of charging lifepo4 batteries

Batteries are one of the best ways to store and carry energy in chemical form. You can find many ranges of batteries based on various technologies in the market nowadays. Among these, lifepo4 (lithium iron phosphate battery) is the most common and widely used model because of its low toxicity, excellent performance, extended stability, and long cycle life.

Because of these qualities, they are extensively used in drones,UPS,golf cart, RV, low-speed electric vehicles and so on to provide them with the required electric energy. If you want to know more about the batteries used in golf cart and RV, you could read the articles golf cart batteries and RV battery in our website. Periodic charging lifepo4 batteries with the proper method and source is vital to maintain the long life of such batteries.

2. Charging mode of lifepo4 batteries

The charging mode of the Li-ion battery is CC-CV. 

● Constant charging (CC) - In this process, a safe, constant current is used to charge the battery. At the same time, the voltage of the battery is continuously increasing as the charging process progresses. Generally speaking, in the process of charging and discharging, the battery voltage changes with the capacity.

The minimum voltage of the lithium iron phosphate battery after being fully discharged is 2v, and the voltage after being fully charged is 3.65v. The sources supply the charges to the battery until a particular voltage level is met. During charging lifepo4 batteries, the current and temperature are the factors that influence the charging speed and aging of the battery.

● Constant voltage (CV) - In this process, a predefined constant voltage is regulated while charging the batteries, and the amount of current received will decrease when charging is in progress and increase the level of charges. The most prominent benefit of choosing this method is safe charging while ensuring a healthy and long battery life.

3. How to charge lifepo4 batteries?

It is always recommended to charge a lifepo4 battery using a lifepo4 charger. These are optimized to charge these batteries safely and quickly without damaging the overall life span. But for this, a proper examination of the charger should be carried out. Make sure the wire used in the charger is properly insulated. Also, the metal connector at either end should be free from any rust or dust.

Once everything seems fine, plug the charger into the socket and mate the connector to the battery. Ensure a tight and proper connection to avoid shock or any other damage. During the charging process, be careful not to overcharge or fully charge, and unplug the charger in time. It is recommended to keep the power of the lithium-ion battery at 20%-80%, which is the best for the life of the battery. And charge the lithium-ion battery in a dry and cool place.

4. Can I charge a lifepo4 battery with a normal charger?

It is advised to use only a lifepo4 charger to charge the battery. No charger for other lithium-ion batteries is recommended to charge a lifepo4 battery. Using such chargers can be hazardous as they are manufactured to work at a higher voltage than the required level of lifepo4 batteries. Similarly, other battery chargers, such as lead acid battery chargers, cannot charge lithium iron phosphate batteries.

5. Ways for charging lifepo4 batteries

① Charging lifepo4 batteries in parallel

While charging lifepo4 batteries in parallel, you must keep the voltage value of the terminals of all batteries under a particular value. This practice can help avoid any chances of imbalance between the batteries. The following charging parameters must be maintained while charging lifepo4 batteries.

For ideal charging, you must use 14.6V, charging voltage 3.65V*4=14.6V, to charge a 12V lifepo4 battery. At the same time, 24V batteries of the same kind should have a charging voltage of 29.2V. And for 36V lithium batteries, the optimal voltage is 43.8V.

These values are applicable for both CC-CV charging methods. Make sure your charger does not exceed the given parameters; However, a lower charging voltage can undercharge the battery.

② Charging lifepo4 batteries in series

Before charging lifepo4 batteries, make sure to keep voltage difference per cell below 0.05V or 50mV. In doing so, it can prevent any imbalance while charging the battery. If you have more batteries with imbalanced charging problems, they must rectify before charging. In such cases, each battery should be charged at a common level and can be balanced once again.

③ Charging lifepo4 batteries with solar

Like any other regular charger, lifepo4 batteries can be easily charged using solar panels. One particular device would be required to carry out the process successfully, i.e., a charge controller. These controllers are of two types: Pulse Width Modulation (PWM) controller and Maximum Power Point Tracking Controller (MPPT).

PWM is cheaper than the second one but is not as efficient as the other. However, the controllers' job is to regulate the amount of current being transferred. It checks the possibility of overcharging the battery and avoids overcharging. The role and function of this controller can get diversified with the varying models. Hence, using a solar panel for charging lifepo4 batteries, accompanied by a controller, is entirely safe.

④ Charging lifepo4 batteries with a generator

A generator or alternator can also use for charging lifepo4 batteries. It is basically a device used to convert mechanical energy to electrical energy. The current produced by the generator is alternating, which is later converted into direct current by a rectifier. It is a device that is attached to the generator. The same technique is also used to charge the car starting batteries, which act as a power source to start the vehicle's engine.

The DC charger plays a crucial role in the whole process. As lifepo4 is free to draw any current from the generator, a device is required to limit its energy consumption due to its lower internal resistance. A DC/DC charger acts and regulates the power and alters the current, thus, saving batteries from overheating and overcharging.

⑤ Charging lifepo4 batteries with BMS

A battery management system is an ideal and convenient way of managing and maintaining a battery pack. The system is useful and easy to use. Generally, regular lithium-ion battery products will have built-in bms. Being a significant part of lifepo4 batteries, proper care of bms should be taken while charging lifepo4 batteries. Coming to the charging part of BMS, they control the charging and discharging process of lifepo4 battery packs.

Moreover, another primary duty of this system is to monitor the working and charging of the batteries. If any unusual upsurge is observed in the current, voltage, or temperature, the circuit is broken by BMS. However, at first, the system will try to balance out the charging level of batteries. If you want to know more details about BMS, you can read the article Top 5 energy storage BMS companies on our website.

6. What voltage should charge lifepo4 batteries?

As already mentioned, three factors are crucial while charging a lifepo4 battery, temperature, voltage, and current. Voltage is directly proportional to the current, and the amount of current flowing through the charger can generate heat. Therefore, all three factors are interconnected.

To ensure safe charging, you must maintain a proper system voltage parameter. For a 12V battery, the charging parameter should 14.6V, while for 24V, it should be 29.2V. A 36V battery would require 43.8V of charging voltage.

7. Precautions for charging lifepo4 batteries

● Lithium-ion batteries have no memory effect and can be used at any time, so there is no need to wait until fully discharged to recharge. Generally, it is recommended to discharge to 20% before charging.

● To charge the battery pack fully and efficiently, ensure the terminals of the battery and the charger are cleaned. No dust or oil from the user's hand should be on it.

● Once the battery is charged, do not forget to pull the charger plug from the socket. Switch off the button and do not touch the prongs for at least 10 seconds.

8. How do you know when a lifepo4 battery is fully charged?

To check whether the battery is fully charged, you must check the voltage of the battery. You can do it by using a voltage meter. Just place the voltage meter's cathode and anode terminal to the corresponding terminal of the battery. During the checking, you can read the voltage display on the meter.

Cross check the reading with the voltage value in your user manual of the battery. The figures should be approximately equal. If the purchased battery has a Bluetooth function or a display, the battery management system will also display the status information of the battery in real time.

9. Conclusion

All the provided information are imperative while using and charging lifepo4 batteries to keep it efficient and maintain its capacity. So, these were some critical aspects one should keep in mind while charging lifepo4 batteries. Also, do not overcharge the battery as its effect can be directly observed on the life span of the battery. Proper care and adhering to the technicalities can undoubtedly deliver the best result from a lifepo4 battery.

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