LiFePO4  battery is one of the safest types of batteries in the world. It is reflected in the fact that there is no safety risk due to high temperature runaway in case of abnormal battery conditions. This article gives a brief guide on how to handle the LiFePO4 battery.

One of the significant qualities of the LiFePO4 battery is the energy density ratio. In a typical lead-acid battery, the energy density ratio is close to 40Wh/KG of Lead. However, the LiFePO4 cells of Ampere Time provides over 150Wh/KG of Lithium. Therefore, most of the higher capacity LiFePO4 batteries are quite light compared to lead-acid batteries. Since Lithium has a high energy density, the manufacturers can reduce the cell sizes further to suit different lightweight applications.

Charging Information

Take Ampere Time 12V 100Ah LiFePO4 battery as an example, generally recommend battery charger that support lithium iron phosphate (LiFePO4) battery charging. And to fully charge the battery, the DC charging voltage should be between 14.2V~14.6V, and charging current less than 100A.

Here is a list of voltage levels that the LiFePO4 battery will reach at different charging stages. (The following are all examples of 12V 100Ah LiFePO4 battery)

LiFePO4 Cell Voltages

Nominal cell voltages

12.8V

Peak cell voltage

14.6V

Over-charge voltage

15V

Discharge voltage

8.8V

 Charging a LiFePO4 battery involves two steps to raise the state of charge (SOC) level to 100%. The first step is the constant current charging. In this step, the charge applies a constant current to the LiFePO4 battery. The voltage level floats until it reaches 14.6V. Until this stage, The charger charges the battery at a constant current. But when the voltage reaches 14.6V, the charger will lock in on the voltage and keep it constant. At this stage, the SOC level of the battery is approximately 90%. Here onwards, the charger will output a decreasing current into the battery while keeping the voltage constant at 14.6V. When the SOC level reaches 100%, the charger will automatically disconnects and no longer charges the battery.

Full Battery Protection

In Lithium batteries, over-discharge occasionally occurs. The lowest value of the voltage that you can discharge a LiFePO4 battery is 8.8V. Ampere Time LiFePO4 battery has built-in BMS to protect it from overcharge, over-discharge, overcurrent, and short circuit with excellent self-discharge rate. Without BMS protection, if you discharge the battery even a bit below this voltage will make the whole battery scrap. It cannot be recovered afterward. If you discharge the battery lower than 8.8V, the damage would be permanent.

Therefore, it is important to stop using the battery before it reaches this deadline. This requires a BMS board to be connected in series with the battery's internal circuitry to protect the battery in the event of over-discharge. 

Effects of Temperature

The temperature has a strong connection with the battery characteristics. The lower the temperature, the lower the available capacity. At a temperature below 0 degrees, Lithium batteries cannot be charged at all.

Long-term Storage

  • Temperature

The battery can be operated in temperature of -20℃ to 60℃， and a temperature between 10℃ to 35℃ is ideal for long-term storage. Store in a fireproof container and away from children.

  • Capacity

For a longer- lasting product, it is best to store your battery at 50% charge level and recharge every three months if it is not going to be used for a long period of time.

So, these are the main points you need to have in mind when using a LiFePO4 battery. As mentioned at the beginning, LiFePO4 batteries have many advantages over Lead-Acid batteries. However, make sure that LiFePO4 has a suitable environment to work in to reap the benefits it offers.