Introduction: DIY 12V Lithium-Ion Battery Pack | Multi-Voltage Output | Battery Holder + Voltmeter

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About: 👋 Hi, I’m Regal Choudhary! I’m a passionate electronics hobbyist, DIY maker, and content creator from India. I love building innovative projects using Arduino, sensors, displays, robotics kits, and more. Wheth…

🔋 How to Build a 12V Lithium-Ion Battery Pack with Multi-Voltage Outputs | DIY Power Solution for Makers 🔋

Are you a DIY enthusiast looking for a compact and reliable power solution for your projects? Whether you're into Arduino, RC cars, robotics, or portable gadgets, this custom-built 12V lithium-ion battery pack is a must-have. In this tutorial, I’ll guide you through the complete process — from components and features to step-by-step assembly and testing.


🌟 Why This Battery Pack Is Awesome

This isn't just a basic battery pack. Here’s why it stands out:

  1. ✅ Multi-Voltage Outputs: Get 3.7V, 7.4V, and 12V outputs from a single pack.
  2. ✅ Built-In Voltmeter: Monitor battery status in real time.
  3. ✅ Modular Design: Easy-to-replace cells using 1S battery holders — no spot-welding needed.
  4. ✅ High-Quality PCB Integration: Clean, safe, and efficient power delivery.
  5. ✅ Perfect for Multiple Projects: RC, robotics, power banks, and more

🧠 Applications of This Battery Pack

This custom battery pack is super versatile and can be used in:

  1. Arduino and Raspberry Pi projects
  2. RC cars, drones, and boats
  3. Robotics and IoT devices
  4. Portable LED lighting setups
  5. Custom power banks

Supplies

Components Required

  1. 3x 3.7v 2000maH 18650 Lithium Ion Cell
  2. 3x Single Cell 3.7v 18650 Battery Holder
  3. 3 Cell 40A BMS Board
  4. Mini Digital Voltmeter
  5. 2x 4 Pin Male JST Connector
  6. 4 Pin Male JST Connector
  7. 4x Crocodile Clips
  8. Universal PCB Mount Connector
  9. Screws & Spacers
  10. Prototype PCB Board

Buy All Components From Here - Buy Now

Step 1: Create Circuit Diagram

Before assembling any physical components, it's essential to design a clear and accurate circuit diagram. This step helps you plan your connections, identify components, and avoid mistakes during the actual build.

Attachments

Step 2: Add BMS Board and Solder

First we have to attach the 3S 40A BMS Board with the PCB then we will assamble rest of the components.

  1. Put the BMS Board to their desired mark on the back of the PCB
  2. Now solder the BMS with the board
  3. If you are unable to solder the BMS board directly to the PCB then you can use jumper wires to connect it.

Step 3: Add All Components and Solder

What to Add:

  1. The mini digital voltmeter
  2. Output terminals (Male JST Connectors )
  3. All Battery holders with PCB
  4. And rest of the parts

Why This Step Matters:

It ties everything together — the voltmeter, holders, and outputs — and ensures your battery pack is modular and functional.

Step 4: Add Spacers and Mount the Second PCB

Adding a second PCB or a protective layer ensures the internal wiring and components are shielded from damage or shorting.

How to Do It:

  1. Use plastic or metal PCB spacers or standoffs to elevate the second board.
  2. Secure it with screws or glue depending on your enclosure type.
  3. This layer gives the professional look to the battery.


Step 5: Create the Output Connector Setup

What to Use:

  1. A JST 4-pin female connector
  2. Banana plugs or other output types based on your needs

Instructions:

  1. Solder wires from the 3.7V, 7.4V, and 12V points to the appropriate pins of the 4-pin connector.
  2. Add banana connectors or bullet plugs to make connecting to external loads easy.

Tip:

Label the voltages on the connector or color-code them for safety.

Step 6: Insert Batteries and Test Voltages

Caution:

Make sure all connections are correct before inserting batteries.

Steps:

  1. Insert the 3 x 18650 cells into the holders.
  2. Use a multimeter to measure voltages from:
  3. Cell 1 (3.7V)
  4. Cell 1 + Cell 2 (7.4V)
  5. Full pack (12V fully charged)
  6. Verify that the voltmeter display is working and showing the correct value.

Step 7: Test the Battery Pack With Real Loads

Try Powering:

  1. LED strips
  2. Motors
  3. Microcontrollers like Arduino, ESP32, Raspberry Pi
  4. Portable fans, mini amplifiers, or other 12V-compatible gadgets

This is the real-world proof that your battery pack works as intended.

🧪 Final Testing & Safety Tips

  1. Make sure there is no heat buildup during operation.
  2. Secure all components using hot glue or insulation tape for durability.
  3. Always balance-charge lithium-ion cells using a proper charger.
  4. Add fuse protection or a BMS (Battery Management System) for extra safety in production versions.

Step 8: How to Charge

Yes, you can charge this pack using a 12V DC adapter or another 12V battery, as long as:

  1. You charge through the BMS-protected charging port (P+ and P-) Or Just Connect a 12v adopter with it.
  2. The 12V source provides constant voltage, preferably via a 12.6V CC/CV lithium charger

DO NOT:

  1. Charge directly through the battery terminals
  2. Use unregulated or unsafe power sources

Safe Charging Options:

  1. 12.6V lithium battery charger
  2. Solar panel with charge controller
  3. Any 12V Adopter

Step 9:

📝 Conclusion

Building your own lithium-ion battery pack is not only fun but also incredibly useful. With multiple output voltages, modular battery replacement, and a built-in voltmeter, this pack offers flexibility and functionality for makers of all levels.

Have any questions or want to showcase your version? Leave a comment or tag me on social media — I’d love to see your builds!