How to Wake Up a LiFePO4 Battery: A Step-by-Step Guide

LiFePO4 batteries (lithium iron phosphate batteries) are a popular type of lithium battery, widely used in electric vehicles, solar energy storage systems, and portable devices due to their high safety, long lifespan, and environmental benefits. However, in some cases, LiFePO4 batteries may enter a deep discharge state, causing the battery to fail to start or charge properly. In such situations, certain measures need to be taken to "wake up" the LiFePO4 battery. This article provides practical steps to help you "wake up" a non-functional or deeply discharged LiFePO4 battery.

Before proceeding, it's important to understand why a battery may enter a "sleep mode," as this can help us find better ways to wake it up.

LiFePO4 batteries are typically equipped with an internal Battery Management System (BMS) designed to protect the battery from overcharging or deep discharging. When the battery voltage drops to a certain low level (around 2.0V), the BMS cuts off the battery's output to prevent damage. If the battery remains in a deep discharge state for an extended period, it may enter a "sleep mode" and fail to restart. Deep discharge doesn't necessarily mean the battery is beyond repair. With certain methods, the battery can sometimes be "woken up" and returned to normal operation.

First, Check the Battery Status and Voltage

Before attempting to wake up the battery, it's important to check the battery's voltage. Use a multimeter to measure the battery voltage and see if it is below the normal voltage range. For LiFePO4 batteries, the charging voltage should typically be between 3.2V and 3.65V, while the discharge voltage should not go below 2.0V.

If the battery voltage is below 2.0V, it indicates that the battery may have entered a deep discharge state, and the BMS has cut off the battery's power output.

If the battery voltage is above 2.0V but below 3.0V, there is still some remaining charge, and the battery may recover during the charging process. This brings us to the next step: waking up the LiFePO4 battery through charging.

It is important to note that when reviving a deep-discharged LiFePO4 battery, low-current charging should be used. This is because rapid charging of deeply discharged LiFePO4 batteries may damage the battery or cause the Battery Management System (BMS) to fail to recognize the battery's state. Therefore, it is recommended to charge at a low current to gradually restore the battery's voltage.

You can follow these steps:

1. Choose the Right Charger: Use a charger that is compatible with your LiFePO4 battery. Ensure the charger's output voltage and current are suitable for your battery. If your charger has adjustable current settings, it is recommended to set the current between 0.1C and 0.3C (for example, for a 100Ah battery, the charging current should be between 10A and 30A).

2. Connect the Charger: Connect the charger to the battery and begin charging. During the process, monitor the battery temperature and avoid overheating.

3. Slowly Increase the Voltage: Initially, the charging voltage may be low and might only restore the voltage to around 2.5V to 2.8V. If the battery gradually recovers and shows a charging response, continue to charge at low current until the battery voltage rises above 3.2V.

4. Monitor the Charging Process: Regularly check the battery voltage and temperature to ensure there is no overheating or voltage abnormalities. Be extra cautious during charging to avoid overcharging or short circuits.

Example:

One of our staff members worked with a LiFePO4 battery that had a voltage of 1.8V, which had entered a deep discharge state. At this point, they used a charger with an adjustable output current of 1A and adjustable voltage to begin the charging process. During charging, the staff observed whether the battery voltage gradually rose to around 2.5V. As the battery began to recover, they continued the charging process.

Now, you might be wondering, what if the battery doesn't recover during the charging process? In that case, you can follow the next solution we provide—Resetting the Battery Management System (BMS)

Resetting the Battery Management System (BMS)

If the battery fails to recover during the charging process, it could be because the LiFePO4 battery's BMS has entered protection mode due to deep discharge, preventing normal charging. To restore the battery's normal function, we recommend resetting the BMS. 

Below are several common methods for resetting the BMS:

1. Disconnect the Battery from the Load: First, disconnect the battery from all loads (such as power tools, vehicle systems, etc.) and the charger, ensuring the battery is in a completely powered-off state.

2. Short the Battery’s Positive and Negative Terminals: Use a wire or appropriate tool to short the battery’s positive and negative terminals. This process will help reset the Battery Management System (BMS). Please be cautious during this operation to ensure the connections are secure and there is no short circuit.

3. Wait a Few Minutes Before Disconnecting the Short: After waiting for about 5 to 10 minutes, disconnect the shorting wire and reconnect the battery to the charger.

4. Try Charging Again: At this point, the BMS should recognize the battery again and allow the charging process to resume.

If you are unsure how to perform these steps safely, we recommend consulting our professionals for guidance to avoid any accidents during the process.

Replacing the BMS or the battery

If you are unable to wake up the LiFePO4 battery after following the above methods, we recommend replacing the BMS or the battery. This is because if the battery voltage cannot be restored, the BMS may be damaged.

If the battery is still under warranty, contact the manufacturer for repair or replacement. If the warranty has expired, or if you prefer a more convenient solution, you can contact us. We have professional technicians who can help you attempt to replace the BMS, but please make sure the new BMS is compatible with the battery.

Although you can wake up a LiFePO4 battery using the methods mentioned above, to extend the battery's lifespan and avoid deep discharge, we recommend the following preventative measures:

1. Charge Regularly: Do not wait until the battery is completely drained before charging. Ideally, keep the battery charge between 20% and 80%.

2. Use a Suitable BMS: Ensure that your Battery Management System (BMS) can promptly cut off the power to the battery to prevent over-discharge.

3. Avoid Extreme Temperatures: High or low temperatures can negatively impact battery performance, especially when the battery is exposed to these conditions for extended periods.

(※ For more specific maintenance guidelines, please follow the operating instructions and precautions provided by the LiFePO4 battery manufacturer.)

Waking up a LiFePO4 battery is not impossible, but it requires proper procedures and some patience. By gradually restoring the battery voltage, resetting the BMS, and charging at the right time, many non-functional LiFePO4 batteries can be revived. However, prevention is always better than cure. Proper maintenance, regular charging, and correct usage can effectively prevent the battery from entering a deep discharge state and extend its lifespan. If you encounter difficulties during the process, seeking professional help is always a wise choice.