1. What Is a Series Connection in a Battery Pack?

A series connection is created by connecting the positive terminal of one battery cell to the negative terminal of the next cell.

The main purpose of connecting cells in series is to increase the total voltage of the battery pack, while the amp-hour capacity remains the same.

For example, if four lithium-ion cells are connected in series, each with a nominal voltage of 3.6V and a capacity of 3000mAh, the resulting battery pack will have:

• Total Voltage: 14.4V

• Total Capacity: 3000mAh (3Ah)

• Total Energy: 43.2Wh

The configuration is commonly referred to as 4S, meaning four cells connected in series.

Series connections are widely used in applications that require higher operating voltages, such as electric bicycles, cordless power tools, and other battery-powered equipment.

2. What Is a Parallel Connection in a Battery Pack?

A parallel connection is created by connecting all positive terminals together and all negative terminals together.

Unlike series connections, parallel connections increase the overall capacity and current capability of a battery pack while keeping the voltage unchanged.

For example, four lithium-ion cells, each rated at 3.6V and 3000mAh, connected in parallel will provide:

• Total Voltage: 3.6V

• Total Capacity: 12,000mAh (12Ah)

• Total Energy: 43.2Wh

This configuration is called 4P, meaning four cells connected in parallel.

Parallel connections are useful when a battery pack needs longer operating time or greater current output without increasing its voltage.

They are commonly found in portable power stations, electric mobility products, and various energy storage applications.

3. Key Differences Between Series and Parallel Connections

Understanding the differences between these two configurations helps battery designers select the right setup for different applications.

In practical battery pack designs, series and parallel connections are often combined to achieve the required voltage, capacity, and power output.

4. What Should You Consider When Designing a Battery Pack?

Selecting the correct series and parallel configuration is only one part of battery pack design. Several other factors should also be considered.

1. Cell Capacity

Choose cells with suitable capacity to meet the required operating time and energy demands.

2. Discharge Rate

For high-power applications, select cells with sufficient continuous discharge capability. High-discharge cells are commonly used in power tools and electric mobility equipment.

3. Cell Consistency

Cells in the same battery pack should have compatible capacities, voltages, internal resistance, and aging characteristics. Proper cell matching helps improve pack performance and reliability.

4. Battery Management System (BMS)

A suitable BMS is essential for monitoring cell-group voltages, current, and temperature. It provides protection functions such as overcharge, over-discharge, overcurrent, and overtemperature protection, depending on its design.

5. Thermal Management

Heat generation should be considered during battery pack design. Appropriate cooling methods and structural design help maintain stable operating temperatures.

6. Safety and Assembly Quality

Proper insulation, reliable electrical connections, suitable protection devices, and professional assembly procedures are important for battery pack safety.

Battery packs should be designed and assembled according to the cell manufacturer's specifications and applicable safety standards.

5. How to Choose the Right Battery Configuration?

The ideal battery configuration depends on the voltage and capacity requirements of the target application.

Here are some general considerations:

• Electric Scooters: Often require series-parallel configurations to achieve the required voltage and driving range.

• Power Tools: Usually require suitable voltage and high discharge capability to support demanding loads.

• Portable Power Stations: Often use parallel and series-parallel configurations to achieve higher energy capacity.

• Home Energy Storage: Requires carefully designed battery configurations to meet system voltage, energy capacity, and power requirements.

Before selecting a configuration, calculate the required voltage, capacity, energy, and maximum discharge current. Always verify that the selected cells and BMS are compatible with the intended application.