Can LiFePO4 Batteries Be Connected in Series?

By Matthew Joseph Nandirio •  Updated: 10/22/22 •  6 min read

How you connect and charge your batteries becomes a crucial question while working with one or more battery packs. People with LiFePO4 batteries often ask whether they can connect batteries in series for charging. 

In this write-up, I will discuss everything about the series connection of LiFePO4 batteries. So, let’s get right in. 

Series connection is not ideal for LiFePO4 batteries. However, you can connect some 12V LiFePO4 batteries to 4 pieces with special integrated BMS in a series circuit. But you can’t connect 24V or 48V batteries in series. 

Before we get into more details, here are some key facts about connecting LiFePO4 batteries in series. 

  • You can only connect 4 12V LiFePO4 batteries with advanced Power adopter and special BMS in series mode. 
  • A battery bank of 4 12V LiFePO4 batteries connected in series has to have a nominal voltage of 51.2V and a maximum operating voltage of 58.4V. 
  • The main reason series connection is not ideal for LiFePO4 batteries is the PCM or BMS configuration of these batteries. 
  • While charging LiFePO4 batteries connected in series, you must use a multi-bank battery charger that charges each battery individually. 

What Is the Charging Method Of LiFePO4 Batteries In Series Connection? 

Most of the LiFePO4 batteries are not suitable for series connection. Some manufacturers provide advanced Power adopters and special BMS so that they can connect in series circuits. 

But the cardinal question is how LiFePO4 batteries are charged in a series connection. But to understand that, you have to know how LiFePO4 batteries work. 

Charging Chemistry of LiFePO4 Battery
Charging Chemistry of LiFePO4 Battery

Lithium iron phosphate cells are provided with a configuration to create a larger battery cell. They often come with an integrated battery management system wired into the battery that balances the charge and discharge of individual cells. 

According to a study conducted at National Formosa University, “charging LiFePO4 batteries installed in series connection, the BMS constantly controls the charge of the battery cells.” 

It does not allow them to overcharge and balance them to ensure batteries are well maintained. When the batteries become fully charged, BMS goes open circuit to prevent overcharging. 

If these batteries are connected in series, the charging circuit is open and does not allow the charger to charge the batteries. 

The first battery in the connection will become fully charged, but others will not. They won’t get any further charge from the charger since the first one has gone open circuit.

However, if you want to charge them in series, you have to use one BMS over all your LiFePO4 batteries, which will control the charging of all batteries. Most importantly, it’ll ensure that all the BMSs go open circuit simultaneously so that all your batteries get enough charge. 

Pros And Cons of Series Connection Charging for LiFePO4 Batteries? 

Advantages of Series Circuit Charging 

Here are the advantages of Series connection for LiFePO4 batteries. 

  • Generally, a series connection is easy to understand, and you can build it quite easily. 
  • A series circuit will be a better choice if you have large applications that require large voltages.
  • You will get higher system voltage and lower system current when your LiFePO4 batteries are connected in a series circuit. As a result, you will have fewer voltage drops in your system. 
  • When your batteries are connected in series, they won’t become overheated quickly. 
  • You can use thin wires to connect your LiFePO4 batteries in a series circuit. 
  • In a series connection, all your batteries will have the same amount of current. 

Disadvantages of Series Circuit Charging 

Now, let’s check out the disadvantages of series connection for LiFePO4 batteries. 

  • Without using an additional controlling BMS over the batteries, LiFePO4 batteries won’t charge in a series circuit. 
  • If one point of a series connection fails, your entire LiFePO4 battery pack will stop charging. 
  • You cannot charge more than 4 12V batteries in a series connection. 
  • Larger voltage LiFePO4 batteries like 24V and 48V won’t work in a series connection. 
  • Since a series connection increases the battery voltage, you won’t get a lower voltage from your battery pack without using a converter. 

If you wonder about the ins and outs of parallel charging of LiFePO4 batteries to understand more, then refer to our mentioned article above.

How Do You Charge LiFePO4 Batteries in Series Circuit? 

Now it’s time to see the process of connecting 4 12V LiFePO4 batteries in a series circuit for charging. But before that, you have to know the components required for the connection. 

4 12V LiFePO4 Batteries Jumper Cables 
A BMS A LiFePO4 Battery Charger 

Here’s a step-by-step process of connecting LiFePO4 batteries in series for charging. 

Step 1: Choose Your System

The first step of connecting LiFePO4 batteries in series is to select your battery. Since you can only connect 12V LiFePO4 batteries, so you have no other choice. But use the same amps of batteries for the series connection. 

Note that- if all of your batteries are 12V and 100 amps, in this series connection, you will get 4 X 12V = 48V. But the amperage will remain the same, which is 100 amps. 

Step 2: Connect The Battery

Now, take a jumper cable and attach it to the negative terminal of one battery. And then, attach the other end of the jumper cable to the positive terminal of your second battery. Similarly, connect all your batteries in a series circuit. 

A Battery Bank In Series Circuit
A Battery Bank In Series Circuit

You can connect up to four LiFePO4 batteries in a series connection. You will know the positive and negative terminals by the (+) and (-) signs beside the terminals. 

Step 3: Connect A BMS Over Your Battery 

LiFePO4 batteries generally come with integrated BMS. But for a series connection, you will have to use another BMS over all your batteries to ensure each one is fully charged. 

Step 4: Connect Charger to Your Battery 

Finally, it’s time to connect the charger to your battery. Take your LiFePO4 battery charger and connect the positive output in red color to the open positive terminal of your battery. 

Charging Battery In Series Circuit
Charging Battery In Series Circuit

Then, connect the negative output of your charger in black color and connect it with the open negative terminal of your battery. The charger is connected to your LiFePO4 battery pack in a series circuit. Now, you can charge your battery as required. 

Final Thoughts 

Connecting LiFePO4 batteries in a series connection is not ideal. But looking at the advantages, you can still go for it. Just make sure the batteries are compatible with the series connection. 

References

1. W. Sen-Tung et al. (2019). A Fast Charging Balancing Circuit for LiFePO4 Battery. 

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Matthew Joseph Nandirio

Matthew Joseph Nandirio is the Founder of walkingsolar. After graduating from the University of Houston in 2002, matt started working as an electrical and electronic engineer for several multi-national solar energy companies. He has a wide range of experiences including solar system requirement analysis, planning, maintaining, debugging and even solar device development through research. He now shares his 20 years of expertise through his articles on the walkingsolar website. Further, he is also the author of two books on Solar Technology, “Solar Power for Villages” and “DIY Solar System for Dummies”.

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