How to charge LiFePO4 battery at freezing temperature?

Charging LiFePO4 battery at freezing temperatures can be challenging as the low temperature can affect the performance and lifespan of the battery. (Why You Cannot Charge LiFePO4 Battery Cell Under 0°C(32°F)?)

Here are some general guidelines to follow when charging a LiFePO4 battery at freezing temperatures:

Check the manufacturer’s recommendations: Before charging a LiFePO4 battery at freezing temperatures, it is essential to check the manufacturer’s recommendations. Some manufacturers may have specific guidelines on how to charge the battery at low temperatures.
Use a suitable charger: Make sure to use a charger that is designed to charge LiFePO4 batteries at low temperatures. Some chargers are equipped with temperature sensors that can adjust the charging process based on the battery temperature.
Warm up the battery: Before charging the battery, warm it up to room temperature. This can be done by placing the battery in a warmer environment for a few hours.
Charge at a lower rate: Charging a LiFePO4 battery at freezing temperatures can increase the risk of overcharging, which can damage the battery. To avoid this, charge the battery at a lower rate than the recommended charging rate.
Monitor the battery temperature: During charging, monitor the battery temperature closely. If the temperature starts to rise too quickly, stop the charging process and let the battery cool down before resuming.
Avoid overcharging: Overcharging can damage the battery, especially at low temperatures. Make sure to monitor the charging process closely and stop the charging process once the battery is fully charged.
Store the battery properly: After charging, store the battery in a dry and cool place, away from direct sunlight and other sources of heat. This will help to preserve the battery’s performance and lifespan.

How the BMS heated battery pack function works

The function of a BMS with a heating system is to regulate the temperature of a battery pack by applying heat to the cells. The BMS will monitor the temperature of the battery pack and activate the heating system when the temperature drops below a certain threshold.

The heating system typically consists of a heating element, such as a resistor or a heater pad, and a temperature sensor that measures the temperature of the battery pack. The heating element is connected to the BMS and is controlled by a microcontroller that adjusts the amount of heat applied to the battery pack based on the temperature reading from the temperature sensor.

The BMS with a heating system can work in a few different ways:

Passive heating: Some BMS systems use passive heating, which means that the BMS does not actively apply heat to the battery pack but instead relies on the heat generated by the battery’s internal resistance during charging or discharging. This can be less effective in very cold temperatures.

Active heating: Active heating involves using a heating element that is controlled by the BMS to apply heat to the battery pack. The BMS will turn on the heating element when the temperature drops below a certain threshold and will turn it off when the temperature reaches the desired level.

Preheating: Some BMS systems will preheat the battery pack before use, such as before starting an electric vehicle, to ensure that the battery pack is at an optimal temperature for performance and safety. The BMS will heat the battery pack using the heating system before the vehicle is started.

Overall, the BMS with a heating function is designed to regulate the temperature of the battery pack to ensure optimal performance and safety, especially in cold weather conditions. The specific functions and operation of the BMS heating system will depend on the manufacturer and the type of BMS used.

Which BMS models have a active heating function

Some of the new models of JK BMS have heating function and take active heating (JK-B1A20S15P/JK-B1A24S15P/JK-B2A24S15P/JK-B2A24S20P/JK-B1A8S20P/JK-B2A8S20P). Compared with other models, they have added a special heating port. In conjunction with the user’s heating device (such as a car heating pad), they can form a heating system for the battery pack.

This is a 7PIN socket and JK is equipped with a wiring harness. PIN1-PIN5 connects to the negative terminal of the heating pad, PIN6 is the positive charge detection terminal and PIN7 is the negative charge detection terminal. The maximum current supported by this port is 3A.

When the BMS detects that the battery pack temperature is below the low temperature charge cutoff value (which you can set in the app), charging will be turned off and at the same time, the heating circuit will be turned on. The heating pad starts to warm up.

When the BMS detects that the battery pack temperature is higher than the Charing Low Temperature Recovery, the heating port turns off the heating pad and the BMS turns on charging again.

The JK BMS uses this to help the battery pack warm up above freezing temperature and charge the pack properly.

It is important to note that this heating method will consume some of the remaining charge in the battery pack and may accelerate the loss of battery pack charge when the internal charge of the battery pack is low.

Other heating methods

If you have external power available, can build a beating system that works foever with a thermostat + heating pad.

There are many options for thermostats, such as the Inkbird All-Purpose Digital Temperature Controller.

This way can keep the battery pack above 0 degrees Celsius at all times.

Summary

Charging LiFePO4 and other types of lithium batteries at temperatures below freezing can damage the battery pack. You may not feel it in a short time, but if you do it often, the life of the battery pack will be reduced or even damaged. So you should try to avoid charging the battery pack at low temperature.

If you need to charge a battery pack at low temperatures, it is best to have a battery pack heater. A simple heater can be formed by using a BMS with a heating function (e.g. JK BMS) and an heating pad. Or when you have an external power source available, a stable heating system can be set up with a thermostat and a heating pad.

Energiepanda can currently deliver JK BMS quickly to customers in North America, Europe, Australia, Asia and South Africa.