How To Charge LiFePO4 with Power Supply?

By Matt •  Updated: 09/17/22 •  6 min read

You might be wondering how you can charge LiFePO4 with a power supply. In this write-up, I’ll discuss that and other ways to charge a LiFePO4 battery pack.

Should I Charge the LiFePO4 Battery with External Power Supply?

Many seem to say, charging a LiFePO4 battery pack with an external power supply is an excellent way. Before I tell you about the best ways of charging, let’s clear this dilemma.

Solar Inverter
Solar Inverter

LiFePO4 battery pack requires a controlled condition while charging. Inconsistent voltages or currents, specifically high voltage and current, can damage the battery pack or even cause fires in the worst-case scenario. 

Having said that, you can use an external power supply to charge your battery pack only if you can ensure that your power supply is compatible with your battery pack’s specifications. But you have to keep it under a close monitor.

The Best to Charge LiFePO4 with Power Supply?

You can only charge your LiFePO4 battery with a power supply if the specification matches from both ends.

You will need the following components to charge your LiFePO4 battery pack with a power supply:

  • LiFePO4 Battery Pack
  • A Power Supply
  • An Amp Meter

Here’s a step-by-step process to charge a LiFePO4 battery pack with a power supply:

  1. Firstly, calculate the C rate of your battery pack. [watch the video]
  2. Then, set the limit of your power supply [limit the current].
  3. Now, figure out the charged voltage of your battery. It’s generally 3.2V per cell for the LiFePO4 battery.
  4. Finally, connect the battery to the power supply with an amp meter connected in series. When the indicator drops to zero, your battery pack is fully charged.
How to check the C-rate of Lithium batteries

There are two stages of charging the LiFePO4 battery. In stage 1, the charger provides a constant current, and the voltage increases gradually. It generally takes 1-2 hours.

In stage 2, the voltage reaches 14V (if your battery nominal rate is 12V), and the battery is 90% charged. At this moment, the voltage becomes constant until full charge, and the current is decreased to 5% to 10% of the battery’s amp-hour rating.

LiFePO4 battery charging stages graph
Stage 1 & Stage 2 of Charging LiFePO4 Battery (source = power-sonic)

LiFePO4 batteries do not discharge as fast as other batteries like lead acid. So, you won’t need float charging for the LiFePO4 battery pack. So, ensure you do not have a float charging option in your power supply.

But even if it does, do not forget to switch it off. If you can’t do that, at least ensure the power supply cannot reach more than 13.6V for a 4-cell LiFePO4 battery pack.

Here’s a list showing the voltage requirements of each system voltage.

System VoltageCharging parameters
12V14V – 14.2V
24V28V – 28.4V
36V42V – 42.6V
48V56V – 56.8V
Charging voltage parameters for LiFePO4 batteries

Things to Maintain While Charging LiFePO4 Battery

According to a study by MDPI, You have to consider three things while charging a LiFePO4 battery.

Here are the things you must do before and while charging.

Inspection of Charger

Before using a LiFePO4 battery charger, you have to check whether its cables are properly insulated and do not have any breakage. Ensure the charger’s connectors are clean and properly attached to the battery terminal.

That’s how you will be sure you have a good connection and optimum conductivity. Check your battery’s datasheet to ensure that everything is by the book.

Temperature While Charging

The safe charging temperature for the LiFePO4 battery is 0° to 45°C. However, this battery pack does not require any temperature compensation for voltage in a cold or hot environment.

Make sure you are charging your LiFePO4 battery within this temperature range. Otherwise, the integrated BMS might stop working due to low or high temperatures. In that case, you will have to warm up the battery or cool it down to reconnect the BMS.

Guidelines For Charging

You must follow the manufacturer’s guidelines to charge your LiFePO4 battery pack to ensure a smooth charging cycle. You do not have to recharge your battery pack after each use if it’s not fully discharged.

Charge the battery pack either after every use or when it’s up to 80% discharged. However, leaving it at any particular stage won’t damage the battery pack.

But, if you are going to store them for a longer period, then I suggest you fully charge them accordingly.

What Are Other Ways to Charge LiFePO4 Battery?

Now, you will find many ways to safely charge your LiFePO4 battery pack. But I will show you the best 4 ways to charge your battery pack. So, let’s get into it.

A Smart Charger

The most basic way to charge your LiFePO4 battery is by a smart charger. This charger matches the battery chemistry and has all the requirements in the correct amount for your battery.

Because of its optimized charging technology, you will get better performance for a longer period. Most importantly, you can program a smart charger to deliver customized charging specifications according to your battery pack.

A Lead Acid Battery Charger

If you have a lead acid battery charger, you can use it for charging your LiFePO4 battery pack. Most lead-acid battery chargers are compatible with LiFePO4 batteries. But here also, the charger’s specification has to be acceptable to your battery pack.

Again, you won’t need any equalizer or temperature compensation. If you cannot disable these options from your lead-acid battery charger, then stay away from using it to charge your LiFePO4 battery pack.

An Alternator

An alternator is a generator that turns mechanical energy into electrical energy and can generate Alternating Current. An Alternator is a pretty good way to charge your LiFePO4 battery.

A Solar Panel

A Solar Panel is a great way to charge your LiFePO4 battery. That’s because the current does not come from other sources but sunlight. As a result, it’s a reliable and safe way to charge your LiFePO4 battery.

However, you can’t just connect your solar panel directly to your LiFePO4 battery. You will be needed a charge controller as well.

Final Thoughts

Although you can charge your LiFePO4 battery pack with a power supply, I would highly suggest you use a specific charger designed for this battery pack. The power supply won’t damage your LiFePO4 battery, but a specific charger will help the battery perform better and last longer.

References

1. W. Andrezej., M. Wieslaw. (2021). Analysis of the Charging and Discharging Process of LiFePO4 Battery Pack.

Matt

I’m Matt, a computer and electronic embedded system developer. Currently, working as an electronic engineer. In my leisure time, I do love to blog about technology stuff. Specially, new advance high tech devices. Portable solar systems are one of topic that I love to investigate. They are becoming more powerful day by day which keep me alert.

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