Top-Balancing in Lithium Iron Phosphate Battery Packs


In this article, we will explore the crucial aspect of top-balancing lithium iron phosphate battery before using them to build a battery pack. Whether you’re working with brand-new batteries or second-hand ones, ensuring an initial balance is essential. This process helps bring all the batteries to the same state of charge, ensuring accurate results during capacity tests and optimizing the performance of your battery pack.

Why Top-Balance Lithium Iron Phosphate Battery?

One might wonder why we need to top-balance lithium iron phosphate battery. The answer lies in the unique characteristics of this chemistry. Unlike some other battery types, lithium iron phosphate batteries exhibit a relatively flat charge and discharge curve. This means that batteries with the same voltage might have varying states of charge. Relying solely on voltage to determine their state of charge is unreliable for this chemistry.

To illustrate the importance of top-balancing, let’s consider a scenario where you have batteries with identical voltage readings on your meters. These batteries could still be slightly off in terms of their state of charge. Failing to achieve a solid initial balance can lead to inaccurate capacity test results. In cases where one battery’s state of charge is too high or too low, it may trigger your Battery Management System (BMS) to disconnect due to high or low voltage, further skewing your capacity results.

If you encounter balancing issues with your battery pack, whether it’s a new or used one, simply slapping on active cell balancers is not the solution. The first step should always be to perform an initial balance and check if it resolves the problem. It’s a common misconception that adding active balancers can address imbalances. Instead, the process involves a systematic approach of initial balancing, capacity testing, and monitoring batteries under heavy loads to detect variations in internal battery resistance.

The Balancing Process

Balancing lithium-iron phosphate batteries is a straightforward process. Below are the steps to achieve a top balance:

Prepare Your Batteries: Ensure that your batteries are in good condition and that you have taken proper safety precautions.

Parallel Connection: Connect the batteries in parallel, meaning the positive terminals are on one side and the negative terminals are on the other.

Use Bus Bars: Connect the batteries with the bus bars. It’s essential to wear safety glasses when dealing with battery terminals.

Additional Bus Bars for Charging: Add two more bus bars at the end to attach a charger.

Charging: Use a power supply to charge the batteries up to 3.65 volts. Set the voltage and current settings accordingly. You may need to wait until the current drops to near zero or 0.1 amps, indicating that the batteries are in the same state of charge.

Equalization: The process may take some time, especially if the batteries are at a low charge. If you want to expedite the process, consider creating individual 4S batteries and charging them with a 12-volt charger before connecting them in parallel.


Top-balancing lithium iron phosphate batteries is critical in building a reliable and efficient battery pack, especially for solar energy storage. It ensures that all batteries are at the same state of charge, optimizing the accuracy of capacity tests and enhancing the longevity of your battery system. While this process may seem simple, it is of utmost importance, and it eliminates the need for active balancers in most cases.

Remember that a properly balanced and healthy battery system requires periodic maintenance and monitoring. If a battery exhibits abnormal behavior, such as differing internal resistance under heavy loads, it’s advisable to replace it. By following these steps, you can create a robust and efficient battery pack for your energy storage needs.


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