Mastering Power: Connecting 18650 Batteries in Series – A Comprehensive Guide


In the realm of DIY electronics and power solutions, the 18650 lithium-ion High Performing Battery has become a staple for its compact size and impressive energy density. For those seeking to amplify voltage output, connecting 18650 batteries in series offers a powerful solution. In this guide, we’ll delve into the intricacies of this process, providing a comprehensive step-by-step approach to successfully connect 18650 batteries in series.

Understanding the Basics:

Before embarking on the series connection journey, it’s crucial to grasp the fundamentals of the 18650 battery. These cylindrical cells, commonly found in laptops and power tools, boast a nominal voltage of 3.7V. Connecting them in series involves linking the positive terminal of one cell to the negative terminal of the next, effectively stacking the voltages to create a higher output.

Tools and Materials:

  1. 18650 cells (matching capacities and voltages)
  2. Battery holder or spot-welding equipment
  3. Multimeter
  4. Soldering iron and solder
  5. Insulating materials (heat shrink tubing, electrical tape)
  6. Wire stripper and cutter

Step-by-Step Connection Process:

  1. Safety First: Begin by ensuring a well-ventilated workspace and wearing appropriate safety gear. Lithium-ion cells can be volatile if mishandled.
  2. Cell Selection: Test each 18650 cell using a multimeter to verify their voltage and capacity. It’s crucial to use cells with identical specifications to ensure optimal performance and longevity.
  3. Parallel Connection (Optional): If you desire increased capacity, start by connecting cells in parallel. Solder the positive terminals together and the negative terminals together. This configuration maintains the nominal voltage while adding up the capacities.
  4. Series Connection: To stack the voltages and create a higher output, connect the cells in series. Solder the positive terminal of one cell to the negative terminal of the next, repeating this process until you achieve the desired voltage. Insulate each connection using heat shrink tubing or electrical tape to prevent short circuits.
  5. Testing: Before finalizing the series connection, use a multimeter to check the voltage across the entire setup. Ensure it aligns with the expected output, taking into account the nominal voltage of each 18650 cell.
  6. Battery Holder or Spot-Welding: Once satisfied with the series connection, secure the cells in a battery holder or use spot-welding for a more robust and permanent assembly.
  7. Insulation: To prevent any accidental shorts and ensure the safety of your setup, thoroughly insulate the entire battery pack. This can be achieved using heat shrink tubing or multiple layers of electrical tape.

Tips for Success:

  1. Consistent Cell Specifications: Use 18650 cells with the same capacity and voltage ratings to ensure uniform performance and longevity.
  2. Proper Soldering Techniques: Exercise caution during the soldering process to avoid overheating the cells. Use minimal heat and ensure secure connections.
  3. Testing at Each Step: Verify the voltage at each step of the connection process to catch any issues early on and prevent potential damage to the cells.
  4. Labeling: Clearly label the positive and negative terminals of your battery pack to avoid confusion during future use.

Applications and Considerations:

Connecting 18650 batteries in series opens the door to various applications, from powering DIY projects to creating custom battery packs for electronic devices. However, it’s essential to consider the total voltage and ensure compatibility with the intended use.


Mastering the art of connecting 18650 batteries in series is a valuable skill for DIY enthusiasts and electronic hobbyists. By understanding the basics, employing proper safety measures, and following a meticulous step-by-step process, you can harness the combined power of these compact lithium-ion cells. Whether you’re crafting a high-voltage and High Performing Battery for a specific project or exploring the versatility of series connections, this guide equips you with the knowledge to elevate your DIY power solutions. So, gather your materials, exercise caution, and empower your projects with the amplified voltage of series-connected 18650 batteries.

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