What’s the wiring difference between batteries in series and parallel?

Connecting lithium batteries in series or parallel is an essential skill when building customized battery systems for various applications. Whether you’re powering electric vehicles, solar systems, golf carts, or marine equipment, knowing how to link batteries properly can enhance power output, extend runtime, and increase system efficiency.

In this guide, Lítio Yibai explains the differences between batteries in series and parallel, how to wire them correctly, the precautions you should take, and how to charge them safely.

What Does Battery Series and Parallel Mean?

When you connect two or more batteries together, you can do so in series or parallel depending on whether you want to increase voltage, capacity, or both.

• Series connection increases the voltage while maintaining the same capacity.

• Parallel connection increases the capacity while keeping the voltage constant.

Let’s dive deeper into each method.

Parallel Connection of Lithium Batteries

What Happens in a Parallel Connection?

In a parallel connection, the positive terminals of all batteries are connected together, and the negative terminals are connected together as well. This type of connection keeps the voltage the same while increasing the amp-hour (Ah) capacity of the system.

Example: Connecting four 12V 100Ah batteries in parallel results in a 12V 400Ah battery bank.

⚙️ How to Connect Batteries in Parallel

To connect Lítio Yibai batteries in parallel:

1. Connect the positive terminal of Battery 1 to the positive terminal of Battery 2.

2. Connect the negative terminal of Battery 1 to the negative terminal of Battery 2.

3. Repeat until all batteries are connected.

4. Use thick, high-quality cables to ensure proper current distribution.

Advantages of Parallel Connection

• Increased runtime

• Lower internal resistance

• More stable operation under heavy loads

Series Connection of Lithium Batteries

What Happens in a Series Connection?

In a series connection, you link the positive terminal of one battery to the negative terminal of the next. This raises the voltage while keeping the amp-hour capacity unchanged.

Example: Connecting four 12V 100Ah batteries in series gives you a 48V 100Ah battery bank.

How to Connect Batteries in Series

To wire Lítio Yibai batteries in series:

1. Connect the positive terminal of Battery 1 to the negative terminal of Battery 2.

2. Continue this pattern until all batteries are linked.

3. The system voltage is the sum of all battery voltages.

Important Note

All batteries must have the same voltage and capacity ratings to avoid imbalance and damage.

Internal Configuration: Series-Parallel Inside Battery Packs

Most LiFePO4 battery packs from Lítio Yibai are internally connected in both series and parallel. For example:

A 12.8V 300Ah LiFePO4 battery is built using a 4S3P configuration:

• 4S = 4 cells in series (3.2V x 4 = 12.8V)

• 3P = 3 cells in parallel per series group (100Ah x 3 = 300Ah)

This internal structure is critical to delivering consistent performance and stability.

Precautions When Connecting Lithium Batteries

To ensure battery longevity and safety, observe the following rules:

1. Use the Same Chemistry

Never connect batteries of different chemistries. The weaker battery will degrade quickly and damage the entire system.

2. Avoid Mixing New and Old Batteries

Do not combine new batteries with old ones. Differences in internal resistance and capacity will lead to:

• Overcharging of newer batteries

• Undercharging or over-discharging of older ones

• Leakage, zero voltage, and premature failure

3. Use Matched Batteries

Batteries should have:

• Voltage difference ≤ 10mV

• Internal resistance difference ≤ 5mΩ

• Capacity difference ≤ 20mAh

This ensures balanced performance and uniform charging/discharging cycles.