Do I need a special charger for LiFePO4 batteries?

TLDR; Short answer is no, you do not need a special charger with LiFePO4 batteries.
But, it’s recommended to always use a charger designed for your chemistry.

This is a very common question, and a very good question to be asking.

Our batteries come with a built-in Battery Management System (BMS) that protects the battery from under and overcharging. You can think of the BMS as the brains of the battery, and these brains have the sole purpose of keeping the battery safe, always on watch 24/7, and never taking a break. You can watch a short LiFePO4 BMS video we made discussing all the settings available on our 50Ah and up batteries.

So, let’s say you hook up a 24V charger on accident, to one of our 12V batteries, the BMS would detect high voltage, go into “overvoltage protect” and shut off the charge path to prevent damage to the battery cells. Pretty cool right?

So, you can see why you don’t need a “special” charger for our LiFePO4 batteries with built-in BMS.

What about charging LiFePO4 batteries with a lead-acid charger?

The problem with lead-acid chargers is that they run a “charge profile” and vary amperage based on the voltage of the battery. If the voltage is low, they go into “bulk” charge mode, which means the charger sends max amps. Then as the voltage increases the charger will begin to send fewer amps to the battery, this is called the “absorption” phase. Finally, once the charger gets near a predetermined voltage of about 13.1 volts, the charger will transition into a “float” stage where it just barely keeps any amperage on the battery to keep it “topped off”.

Due to these steps down in charging amps, the first problem arises, that is that LiFePO4 batteries are being charged much more slowly than they could be. A lead-acid charger will typically charge a LiFePO4 battery 4-5 times slower. That is obviously a huge disadvantage of using a lead-acid charger on LiFePO4 batteries.

You’re next question might be “Isn’t it better to charge slower?” No, not with LiFePO4, there are no negative effects of charging at high charge rates on LifePO4 batteries.

The next issue is that even at 13.1 volts, a LiFePO4 is not fully charged. A fully charged LiFePO4 sits around 13.6 volts. Between 13.1V and 13.6V is a pretty good bit of power and worth noting that you won’t get 100% of your available power if charging with lead-acid chargers. The total amount of capacity varies based on your charger and what the float voltage is set to.

Summary

No, you do NOT need a “special” charger to charge a LiFePO4 battery, the BMS will protect itself at all times. However, you will have significantly longer charge times and decreased total capacity using lead-acid chargers.